Fundamentals of Yarn Winding (2013)

Fundamentals of yarn winding

Fundamentals of yarn winding

Milind Koranne

WOODHEAD PUBLISHING INDIA PVT LTDNew Delhi l Cambridge l Oxford l Philadelphia

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First published 2013, Woodhead Publishing India Pvt. Ltd.© Woodhead Publishing India Pvt. Ltd., 2013

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Contents

Preface ix

Acknowledgements xi

1 Winding as a weaving preparatory process 1

1.1 Weaving introduction 1

1.2 Quality requirements of warp and weft threads 3

1.3 Weaving preparatory processes 4

2 Basics of package building 12

2.1 End packages produced on winding machines 12

2.2 Some definitions related to cross wound packages 14

2.3 Traverse acceleration 16

2.4 Building a cross wound package 18

3 Principles of winding systems 34

3.1 Basic modes of winding 34

3.2 Random winding 34

3.3 Precision winding 39

3.4 Positive and negative aspects of random and precision 42 winding

3.5 Step-precision winding 44

3.6 Winding systems with flexibility in package building 48

4 Winding package parameters 66

4.1 Winding system at various stages of yarn processing / production 66

4.2 Main parameters related with a winding package 69

4.3 Various end uses of wound packages 70

4.4 Yarns with diverse properties subjected to winding 71

4.5 Winding package parameters and criteria of their 71 selection according to end-use requirements for a given yarn

4.6 Yarn waxing 97

5 Yarn tension during winding 100

5.1 Necessity of yarn tension during winding 100

5.2 Various supply packages on winding/rewinding machines 100

5.3 Unwinding tension from packages 101

5.4 Yarn tensioning devices 104

5.5 Measures/devices to minimize tension fluctuations 110

5.6 Expression of tension 119

5.7 Amount of tension 119

6 Yarn clearing and clearing devices 121

6.1 Introduction to yarn faults 121

6.2 Objectionable and allowable yarn faults 123

6.3 Types of yarn clearers 124

6.4 Instrumental measurement of yarn faults 132

6.5 Basic yarn clearing with electronic yarn clearers 136

6.6 Additional yarn clearing 140

6.7 Assessment of clearer performance 143

6.8 Methods of yarn joining 144

7 Package driving and yarn traversing 159

7.1 Direct and frictional package drive 159

7.2 Frictional or surface drive with drum 160

7.3 Methods of yarn traversing 163

vi Contents

8 Winding package faults and remedies 174

8.1 Stitches or ‘jali’ on cones/cheeses (winding packages) 174

8.2 Soft nose or base (wrinkles) 176

8.3 Yarn sloughs 177

8.4 Wild yarn 177

8.5 Yarn entanglement on package 177

8.6 Snarls 177

8.7 Chaffed yarn 178

8.8 Patterning or ribboning 178

Index 185

Contents vii

Preface

Phenomenon of winding delivered yarn is observed at various stages of textile production such as winding at weaving preparation, soft dye package winding, rewinding of soft dye packages/ left over packages from warping creels, assembly winding prior to twisting, winding at unconventional spinning machines for taking up spun yarn, yarn singeing, single end sizing, take up winding at spinning lines of synthetic yarns, yarn texturising, sewing thread finish winding, winding of string wound filter cartridges etc. Technical developments in winding systems are taking place to offer new possibilities in package building. Efficient utilization of such technologies demands thorough understanding of various winding related aspects. This book intends to highlight on fundamental aspects of yarn winding in a broader perspective. The book contains eight chapters focusing on a range of topics on yarn winding. The first chapter introduces yarn winding as a weaving preparatory process. Basics of building winding packages are explained in second chapter clarifying frequently used winding related terminologies like random winding, patterning, precision winding, gain, open wind, close wind, head wind, after wind etc. Principles of various random, precision and step precision winding systems are covered in third chapter along with basic mathematics involved. The part of mathematics of Chapter 3 is based on author’s fundamental understanding, research experience and interaction with the industries. There are diverse end uses of wound packages, each having its specific requirements. These can be achieved through optimal selection of various parameters related to package build which are discussed in Chapter 4. Chapter 5 is dedicated to various measures on winding machines employed to maintain optimum yarn tension during winding. Significance of yarn clearing and various yarn clearing devices are discussed in Chapter 6. The same chapter includes a detailed note on yarn splicing. Chapter 7 describes various methods of package driving and yarn traversing on winding machines. Various winding package faults and their remedies are discussed in Chapter 8. For ease of understanding, the text is supplemented by various self explanatory labeled diagrams and photographs. Main features of the latest

generation of winding systems of leading manufacturers are also included in the book. It is hoped that this book will prove to be a useful reference for students, academicians, textile technologists as well as persons from other engineering disciplines like chemical, mechanical, electrical, electronics, instrumentation and computer dealing with winding systems. I apologize in advance for any errors and omissions in the content and hope that there would be an opportunity later to rectify them.

Milind KoranneEmail: [email protected]

Acknowledgements

My sincere gratitude and thanks are due to all individuals and organizations that have directly or indirectly supported me in publication of this book. I would express my sincere gratitude to the following: Mr. Jean-Claude Alleman, Head, Textile Technology, SSM, readily shared his expertise and vast experience; and took pains to reply all my queries on various aspects of winding. Interaction with Mr. Jean-Claude Alleman has immensely helped in enriching the book content. Mr. Horst Luechinger, Director Sales Asia and Mr. A. T. Narayanan, General Manager, India, of SSM provided the necessary help. Mr. Thomas Elsener, Marketing Service of SSM took pain to provide me with all photographs I asked for. Dr.-Ing. Ansgar Paschen, Manager, Research & Development Textile Technology and Mr. Peter G. Gölden, Senior Manager, Textile Technology of Oerlikon Schlafhorst, Germany furnished valuable information on technical aspects of their range of Automatic winding machines. Mrs. Heike Scheibe provided with a wide range of photographs related to Oerlikon Schlafhorst range of products I required. Mr. Umang Kothari, National Manager (Service) and Mr. A. T. Kumar, Manager (Product Management) from Oerlikon Textile (India) Pvt. Ltd. readily interacted with me regarding various aspects of their range of products. Mr. K. C. Panchal. Assistant Manager (Service) of the same company provided required information source of Schlafhorst range of winding machines and discussed various technical aspects personally. Mr. S. J. Chokshi, General Manger CSS of Loepfe brothers provided information about Loepfe range of products. Mr. Nellaiappan, Head – Product Support, from Uster Technologies (India) Private Limited provided the necessary information about Uster range of products. Mr. Bhargav Patel, Executive director, Mr. R. G. Yadav, GM (mfg), Mr. Ashok Singh, Dy. Mgr. (Electronics) and Mr. Anthony Francis Dy. Mgr. (Design) of Peass Industrial Engineers Pvt. Ltd. were always eager to extend me all kind of support and necessary information about products of their company. Mr. Pankaj Desai, General Manager, Fadis India helped in getting all necessary photographs of range of Fadis make machines along with necessary permission. Mr. Mrunal

Kansara, MD of NIF Mechanical Works Pvt. Ltd. permitted to publish the photographs and information of various winding drums manufactured by his company. I am extremely thankful to all other individuals/ organizations that have provided required photographs along with necessary permission. My wife Seema Koranne and daughter Trusha Koranne have always supported me during write up of this book. I have been able to write this book due to encouragement and support from my Professors, colleagues and technical staff at Textile Engineering Department of Faculty of Technology and Engineering, The M.S. University of Baroda. I am aware that it has not become possible to acknowledge full list of individuals and organizations due to space constraint.

Milind Koranne

Yarn winding is an integral part of many textile production activities such as spinning, weaving, synthetic yarn manufacturing, etc. This chapter describes various weaving preparatory processes very commonly practiced where yarn winding is involved at some stages.

1.1 Weaving introductionIn a woven fabric the lengthwise yarns forming the basic structure of the fabric are called the warp threads or ends and the widthwise threads are called the weft threads or picks or fillings. A woven fabric is produced through repeated cyclic process of shedding, picking and beating (Fig. 1.1).

1Winding as a weaving preparatory process

Figure 1.1 Weaving cycle

For weaving the fabric, usually weaving machine (also known as loom) is required to be supplied with a weaver’s beam which consists of thousands of warp threads wound on a weaver’s beam in sheet form. Weaver’s beam may be supplied to loom with warp threads which are already drawn through the heald shafts and dented through reed (with drop wire warp stop motions threading through drop wires may be additionally required) as shown in Fig. 1.2.

2 Fundamentals of yarn winding

Form of weft supply on loom depends upon picking system. (a) For shuttle looms weft is wound on pirns. The pirn fits into a shuttle.

The shuttle is projected into the shed. So, supply of weft is in the form of pirn wound with weft as shown in Fig. 1.3.

Figure 1.2 Warp supply on loom

Figure 1.3 Pirn in a shuttle

Figure 1.4 Weft supply packages in creel of a shuttle-less loom (Courtesy: Picanol)

Winding as a weaving preparatory process 3

(b) For shuttle looms fitted with “Unifil” loom winder, pirn winding is done by a special mechanism on loom itself. So supply of weft is in form of packages such as cones or cheeses.

(c) For looms in which insertion of weft is carried out without the use of the shuttle are called shuttle-less looms. In these looms (generally) weft insertion takes place from one side of the loom. The weft is withdrawn from the packages such as cones or cheeses and inserted into the shed by some carrier (gripper, rapier, air jet or water jet). Figure 1.4 shows a shuttle-less weaving machine with weft supply packages.

Weaving productivity is influenced by quality of warp and weft supplied to loom. Poor quality of warp and weft causes frequent breakages which hampers fabric quality and loom productivity. Better performance in weaving cannot be realized with poor quality of warp and weft.

1.2 Quality requirements of warp and weft threads Broadly, a quality warp fulfils the following requirements: (1) To produce fabric of uniform quality, the tension of warp threads

across the width of the cloth as well as along the weaver’s beam should be as uniform as possible.

(2) Warp threads should be free from places which are likely to cause breakages during weaving or hamper fabric appearance, such as

• a weak place can cause breakage during weaving. • a thick place can cause breakage (Fig. 1.5) and give bad

appearance in fabric. • A thin place can cause bad appearance. Particularly, thinner

place continuing over a long length, say 1m or 2m, will give bad appearance; as in that portion a fine crack-like appearance would be seen.

(3) During weaving warp threads are kept under considerable tension and are subjected to the abrasive action of the healds, reed, and other moving parts and also of the neighboring warp threads. At heald eye an end is subjected to bending (flexing) and rubbing. To and fro movement of reed causes abrasion of reed dents with warp threads. At beat up the warp threads are subjected to sudden stress. Shed formation causes strain on warp threads.

Therefore the warp threads should be strong enough to resist these actions without breaking.


Broadly, quality weft fulfils the following requirements. As explained earlier, pirns or packages such as cones or cheeses can be weft supply packages. These packages should be built so as to give trouble-free unwinding during weaving. The weft thread should also be free from any places which are likely to cause break during weaving or hamper fabric appearance.

1.3 Weaving preparatory processesThe yarn received from spinning department is usually in the form of ring frame bobbins. To weave this yarn on loom, it must be converted into required form, i.e. warp and weft. The intermediate processes between spinning and weaving on loom employed to convert the yarn received from spinning department into suitable form that is required for weaving are called weaving preparatory processes. The processes converting yarns from spinning department into suitable warp form are called warp preparatory processes and into required weft form are called weft preparatory processes.

1.3.1 Warp preparatory processesThe sequence of processes depends upon the type and quality of yarns, the type of fabric to be produced, and also on the equipment and other facilities

Figure 1.5 Harm caused by thick places


Figure 1.6 Warp preparatory processes

available in the mill. The process flow chart is shown in Fig. 1.6 which shows the various stages of warp preparation. The solid lines indicate the basic process most commonly used and the dotted lines indicate some additional processes required for different types of fabrics. In winding, yarn from a number of ring frame bobbins or hanks is transferred in a long continuous length onto bigger packages such as cones or cheeses (Fig. 1.7). Some places in the yarn are likely to cause breaks in subsequent processes or hamper fabric appearance which are called yarn faults. Winding machine carries yarn clearer that breaks yarn at yarn faults. Faulty yarn portion is cut away and the yarn ends are rejoined. To introduce colored threads in warp or weft, it becomes necessary to dye yarn. Yarn dyeing can be done in any one of these three forms: hank/muff, package (cone/ cheese) or warper’s beam. If hanks are acquired from spinning department, they can be taken for hank dyeing. If ring frame bobbins are supplied from spinning department, usually yarn is wound onto bigger packages (cones/cheeses) eliminating yarn faults. Subsequently, hanks are obtained from these bigger packages on a reeling machine. Figure 1.10(a) shows photograph of a hank reeling machine. These hanks are dyed. A muff is


Figure 1.8 Package dyeing (Courtesy: Ashima)

Figure 1.9 Beam dyeing (Courtesy: Ashima)

Figure 1.7 Autoconer X5 winding machine (Courtesy: Oerlikon Schlafhorst)

also a loose package like a hank without any supporting tube. This form of the package is used mainly for yarns with high shrinkage during dyeing. A muff is produced on a special winding machine. Dyed hanks/muffs are taken to a hank/muff to cone winder to obtain dyed cones/cheeses. For package dyeing, yarn from ring frame bobbins is usually wound onto bigger packages (cones/ cheese) eliminating yarn faults. These bigger packages are taken to a soft dye package winder which produces soft packages suitable for package dyeing. These soft packages are subjected to dyeing (Fig. 1.8). These packages being soft are not suitable for high speed unwinding.


Therefore, they are taken to a rewinding machine to produce compact packages suitable for subsequent processes. Yarn may be dyed in beam form, which is produced on direct warping machines. Figure 1.9 shows beams dyed in a beam dyeing machine. The object of direct warping (Fig. 1.10b) is to collect yarns from number of single end packages (winding packages from which a single thread is delivered on unwinding) mounted on a warping creel, convert into sheet form with ends uniformly spaced, and wind a specified length onto warper’s beam. The warper’s beam so obtained is a multi-end package (multiple ends are delivered on unwinding). The warper’s beams for beam dyeing are soft wound and smaller in diameter with perforations to allow dye liquor flow.

Figure 1.10 (a) Hank reeling machine (Courtesy: Fadis)

(b) Direct warping machine (Courtesy: Prashant Gamatex)

In sectional warping hundreds of warp threads are collected from creel. These threads are passed through a reed to form a narrow warp sheet with warp spacing closer to what is required on weaver’s beam. Several sections of predetermined length of this sheet are wound on a large diameter drum (which is usually tapered at one end) side by side. Figure 1.11 shows a


sectional warping machine. Subsequent stage is beaming in which ends from all sections are collected and wound onto a weaver’s beam. Thus, at the end of the process, weaver’s beam is obtained which may be sent to loom or for drawing-in. Warp threads are subjected to considerable stresses, strains, flexing and rubbing action during weaving. So warp threads are impregnated with size, whose main constituent is an adhesive substance. The size binds the constituent fibres in the yarn as well as forms a coating on yarn surface so

Figure 1.11 Sectional warping machine (Courtesy: Prashant Gamatex)

Figure 1.12 Sizing machine (Courtesy: Prashant Gamatex)


that it can withstand stresses, strains, flexing and rubbing actions of weaving without breaking. At the back of sizing machine, warp sheets from number of warper’s beams are combined to obtain a single sheet containing required number of ends for weaving. This sheet is impregnated with size, dried and wound on a weaver’s beam. When beam from sectional warping is a supply package on sizing machine, it is called beam to beam sizing. Figure 1.12 shows a sizing machine. Thus, at the end of sizing, weaver’s beam is obtained which may be sent for drawing-in and denting or directly to loom for end-to-end joining. The process of drawing in and denting consists of passing ends of warp sheet of weaver’s beam through heald eyes of the heald shafts and through dents of reed, respectively. With drop wire stop motions additional operation of pinning may be involved. Figure 1.13 shows manual drawing in and denting. Automatic drawing in and denting machines are also available and used. On loom, if exactly the same fabric is to be reproduced after a weaver’s beam is exhausted, warp threads of the new sheet are joined end by end with the old sheet. This operation is called tying-in or twisting depending upon the method of joining. Knotting machines are available to join the ends of exhausted beam and new beam one by one (Fig. 1.14). Thus, this process needs only weaver’s beam wound with warp as a warp supply. But if other

Figure 1.13 Manual drawing in and denting


variety of fabric is to be produced, a weaver’s beam with warp threads drawn and dented is required. Old beam with its heald shafts and reed are removed and a new beam with its heald shafts and reed are reset on the loom.

Figure 1.14 Warp tying machine for end to end joining (Courtesy: Jaytex)

Figure 1.15 Weft preparatory processes


1.3.2 Weft preparatory processesFigure 1.15 shows flow chart of weft preparatory processes. Flow chart is the same up to winding/rewinding. (In olden days, the end packages of weft ring spinning frames were directly used in the shuttle where no additional weft preparatory process was involved. This type of weft is known as direct weft). The yarn from bigger packages (cone/cheese or warper’s bobbin from which objectionable faults are removed/ may be dyed) is wound on to pirns on pirn winding machines. These pirns are supplied to shuttle looms. The winding packages (cone/cheese) are supplied to automatic shuttle looms fitted with Unifil loom winder and shuttle-less looms (such as gripper, air jet, water jet or rapier). Unconventional spinning machines like OE spinning produce bigger packages which may be directly supplied as weft on shuttle-less weaving machines.

Yarn winding is basically a process of deposition of delivered yarn to form a suitable package that can meet requirements of its subsequent process. This chapter discusses some basic aspects related to package building.

2.1 End packages produced on winding machinesWinding packages, which are very commonly used, can be divided into two groups:• Parallelwoundpackages• Crosswoundpackages

2.1.1 Parallel wound packagesParallelwoundpackagesaredouble-flangedbobbins,alsoknownaswarper’sbobbins (Fig. 2.1a). Yarn is wound on these packages in such a way that the laid coils are almost parallel to one another. These packages were widely used in olden days. These packages may be built with parallel faces (Fig. 2.1b) or withbulgingfacesformingabarrel-shapedbobbin(Fig.2.1c).Figure2.1alsoshowsawindingmachinewithdouble-flangedbobbins.Flangesareneededoneithersidetosupportparallellaidcoils.Withoutflanges,coilsatthetwoendswouldcollapse.Forgivendimensionsofabarepackage,barrel-shapedbobbin accommodates more yarn. To withdraw the yarn from these packages, usually package has to be rotated by pull of yarn. Hence, high unwinding speed leads to excessive unwinding tension causing yarn break. When unwinding is stopped, the package continues to rotate due to its inertia and, therefore, yarn may continue to come out from package. Hence, this package is not suitable as a supply package where high speed unwinding takes place. These packages are usually used for yarns which do not form a stable cross wound package, like monofilamentyarns.

2Basics of package building

Basics of package building 13

2.1.2 Cross wound packagesTo build a cross wound package, the supporting tube required is usually cylindrical or conical. The yarn is laid on the package in form of helices which reverse at extremes. Figure 2.2 shows how yarn is laid in form of helices on cylindrical or conical packages.

Figure 2.1 Parallel wound packages (Courtesy: Fadis)

Figure 2.2 Cross winding on packages


In this type of winding, the yarn wraps cross one another and therefore these packages are called cross wound packages. Because of reversal of helices at the extremes, usually there is no possibility of yarn coils collapsing atthetwoextremes.Hencethesepackagesdonotneedflanges.Thecylindricalcross wound package is commonly known as a cheese and the conical one as a cone.

The yarn is usually withdrawn from cone and cheese over end (also known as nose unwinding). In over end unwinding, package remains stationary and yarn is pulled though a stationary yarn guide located on the package axis. The over end withdrawal allows unwinding at high speeds. As rotation of package during unwinding is not essential, yarn stops leaving the package almost at the same instant when withdrawal is stopped. Figure 2.3 shows over end withdrawal or nose unwinding from a cone and a cheese. Over end withdrawal adds or subtracts one twist from the delivered yarn which is not desired for some yarns. These packages are also suitable for side unwinding which is carried out for such exceptional cases.

2.2 Some definitions related to cross wound packagesIt is very essential to understand some definitions related to cross woundpackages before understanding the basics of yarn laying.

(a) Cone taper or semi-vertical angle Cone taper or semi-verticle angle is defined as the angle between the sideof the coneand its axis as shown inFig.2.4.Cone tapergenerally rangesbetween0°(cylindricalpackage)and9°15’.

Figure 2.3 Over end withdrawal

Figure 2.4 Cone taper


(b) Wind Windisdefinedasthenumberofcoilslaidonapackageinasingletraverse(i.e. winding of the yarn from one end to other). As shown in Fig. 2.5(a), duringtraversefromlefttoright,i.e.frompointAtoC,1.25coilsarelaid.

Hence wind at that diameter of the cheese is 1.25 i e or. . 114

54

.

Figure 2.5 Package wind and traverse ratio

(c) Traverse ratio / crossing ratio / winding ratio Traverseratio/crossingratio/windingratioisdefinedasthenumberofcoilslaid on the package during double traverse of the same wind point. As shown in the Fig. 2.5(b), yarn laying fromA toC completes one single traverse.MovingfrompointCtoEcompletesadoubletraverse.Duringthis,2.5coilsarelaidduringadoubletraverse[(A–B=1coil)+(B–C=1/4coil)+(C–D

=1coil)+(D–E=1/4coil)]andhencetraverseratiois2.5 i e or. . 2 12

52

.

(d) Coil angle or angle of windItisdefinedastheangle‘f’betweeninstantaneousdirectionofyarnlaidonthe package and any plane perpendicular to package axis (Fig. 2.6a). This angle would be taken as coil angle in this book and would be used. (In some literatures, this angle is also called helix angle or winding angle).

(e) Complimentary angle It is the angle (90 – f), i.e. angle between instantaneous direction of yarn laid on the package and any plane parallel to package axis. Sometimes this angle isdefinedasthecoilangle.

(f) Crossing angleItistheangleatwhichyarncoilscrosseachother.Crossingangleistwicecoilangle (Fig. 2.6 b).


(Aunique terminology anddefinitionof angle atwhichyarn is laid isnotusedinallliteratures.Therefore,itsdefinitionmustbeunderstoodbeforegoing through any literature).

2.3 Traverse accelerationIn case of a cheese, the surface area available for winding the yarn is same across the width of package due to uniform diameter. In case of cone the situation is different. The surface area available to wind the yarn decreases from base to nose as shown in Fig. 2.7(a). If two strips of same width at different diameters on cone are taken (Fig. 2.7b), and yarn is wound with same coil angle at both the strips then length of yarn crossing both the strips would be the same. Length wound across both the strips is same but area of strip towards base of the cone is greater than area of strip towards nose of the cone. So, taking into account amount surface area available, quantity of yarn deposited on strip towards nose is greater than that towards base. Upon continuing winding this way, the package diameter would build at greater rate towards nose than at base as

Figure 2.6 Coil angle and crossing angle

Figure 2.7 Winding on a conical package


package.Thisleadstonon-uniformbuildupforconeasshowninFig.2.7(c)which is not desirable. To achieve uniform built up of cone, the length of yarn laid in given region of cone should be proportional to the area available to accommodate theyarn.If‘A1’and‘A2’areareasofstripsattwolocationsalongthelengthoftheconeand‘L1’and‘L2’areyarnlengthscrossingthesestripsrespectively,then,

LL

1

2 =

AA

1

2

\ L2 = L A

A1 2

1 To shorten the length of yarn crossing the strip towards nose of the cone, coil angle should be kept greater than that at strip towards the base of the cone (Fig. 2.7d) so as to achieve uniform build up of cone (Fig. 2.7e). Speed of yarn traverse in relation to rotational speed of the package at given diameter influencescoilangle.Fasterthetraversespeedgreateristhecoilangleandvice versa. In cheese winding as same coil angle is to be kept across the length of the package at given diameter, yarn need to be traversed at uniform speed from one end of the package to the other, i.e. acceleration is not involved. But in case of cone winding, to achieve uniform build up, coil angle should be increasedfrombasetonose.Puttingthisinsimpleterms,yarntraversespeedmust be increased from base towards nose and vice versa. Thus acceleration is involvedinyarn traversespeedwhichiscalled‘accelerated traverse’. Inthis way an accelerated traverse is required for cone winding, especially, with higher cone taper. Cone is preferred over cheese due to greater freedom of withdrawal.Because of conical shape, yarn can leave the package during unwinding with greater ease due to lesser chances of yarn getting dragged over the surface of the cone. But if the freedom of withdrawal of a full cone and an empty cone is compared, it is obvious that the chances of yarn dragging over the face of the cone are greater at bigger cone diameter than at smaller one (Fig. 2.8a). The phenomenon of yarn ballooning, i.e. yarn leaving the package is thrown away

Figure 2.8 Foster cone


from the package surface, reduces the chances of yarn getting dragged against face of the package. But the intensity of ballooning depends upon unwinding speed and yarn linear density. At higher unwinding speeds and with coarser yarns, as yarn leaves the package, it is thrown away from the surface with higher intensity than that at very low unwinding speeds. Therefore, there are more chances of yarn getting dragged with the face of the package at slower unwinding speeds than that at higher speeds of unwinding. In an application like knitting, unwinding speeds are lower and an intense balloon is not formed. It is desired that yarn should leave the package with same freedom at all diameters of package. To maintain same ease of withdrawal, cone may be built purposefully in such a way that cone taper keeps on increasing from an empty to full cone. Hence during winding, yarn is laid in such a way that length of yarn laid in comparison with the area availability is more towards base than nose. So cone taper keeps on increasing as the cone builds up (Fig. 2.8b). To build such cone, yarn would be traversed much slower at base and faster at nose compared to uniform build up of cone. Hence acceleration involved in traverse would be greater. Therefore, traverse for cone for uniform build is calledhalf-acceleratedtraversewhilethatwithincreasingtaperiscalledfullyaccelerated traverse.Aconebuilt upwith increasing taper is called ‘fostercone’.

2.4 Building a cross wound packageFor building cross wound packages, two approaches can be thought:• Buildingapackagekeepingconstant traverseratio throughoutpackage

build• Buildingapackagekeepingconstantcoilanglethroughoutpackagebuild. For ease of understanding, winding of only cylindrical packages is discussed here.

2.4.1 Building a package with constant traverse ratio throughout package build

Let a package be built with constant traverse ratio of 2 throughout its build. As shown in Fig. 2.9(a), one coil is laid in a single traverse moving from left to right and the other coil is laid while moving from right to left. Therefore, at the end of the double traverse, yarn arrives at the same point from where the laying was begun. If winding is continued, the yarn coils of second double traversewould be overlapped on coils of first double traverse. Onfurther continuing winding, successive warps of double traverse will be laid


exactly on top of one another and will form a thick ribbon or pattern. This phenomenon is called patterning or ribboning. The yarn will not be uniformly distributed on the surface of the package and therefore a satisfactory package would not be obtained. Thus, with constant traverse ratio of two, a satisfactory package would

Figure 2.9 Package building with same traverse ratio

not be built. Let us take case of package winding with a constant traverse ratio 3 (Fig. 2.9b). In this case too, the starting point of yarn after a double traverse comes out to be at the same place after a double traverse leading to pattern formation with yarn coils wrapping over one another. With traverse ratio of 2.5, the wraps of yarn will be laid on top of each other after completion of two double traverses as shown in Fig. 2.10 (a). Figure 2.10(b) shows coils viewed from side of the package. In this case yarn coils of every alternate double traverse would get overlapped on one another forming ribbons.

Figure 2.10 Winding with traverse ratio 2.5

Thus, a constant traverse ratio of 2.5 is also not suitable for winding.

The situation of winding with constant traverse ratio of 2.25( 2 14

) is shown

inFig.2.11(a).Ifwindingisstartedatsaypoint‘A’atleft,yarnreachesthe

rightendatpoint‘B’laying1.125(118

) coil. From right side it reaches on left

sideatpoint‘C’attheendoffirstdoubletraverse.Thus,startingpointofyarn


on a face shifts through 14rotation(fromAtoC,i.e.though90°).Withshift

of 14

rotation every double traverse, yarn would reach the same place after

4 double traverses, i.e. every 1st, 5th, 9th.... wraps of double traverses would be laid on top of one another. Similarly every “2nd, 6th, 10th ….”, “3rd, 7th, 11th ….” and “4th, 8th, 12th ….” wraps of double traverses would be laid on top of

one another. There would be only four starting points on the circumference on each side.

With traverse ratio of 2.33 ( 2 13

), starting point on a face shifts by 13

rotation (120°) and it would come to same place after three double traverses, i.e. every 1st, 4th, 7th.... wraps of double traverse would be laid on top of one another (Fig. 2.11b).

For traverse ratio of 2.40 ( 2 25

), starting point on a face shifts by 25

rotation (72°)and itwouldcome tosameplaceafterfivedouble traverses,

i.e. every 1st, 6th, 11th.... wraps of double traverse would be laid on top of one another. Yarn starting point would come to same place after 5 double traverses, i.e. every 1st, 6th, 11th.... wraps of double traverse would be laid on top of one another (Fig. 2.11c).

2.4.1.1 Relation between traverse ratio and number of double traverses after which yarn comes to same place

Figure 2.11 Winding with different traverse ratios


Table 2.1 shows some traverse ratios and number of double traverses after which yarn come to same place.

Table 2.1 Traverse ratios and number of double traverses after which yarn come to same place

S.No.

Traverse ratio

Traverse ratio

expressed as a

fraction in

form of xy

Value of numerator,

i.e. x

Value of denominator,

i.e. y

Traverse ratio

expressed in decimal

Number of double traverses

after which yarn comes to

same place

1 221

2 1 2.00 1

2 2 12

52

5 2 2.50 2

3 2 12

73

7 3 2.33 3

4 2 14

94

9 4 2.25 4

5 2 15

115

11 5 2.40 5

Some important conclusions can be derived from Table 2.1 as

• Iftraverseratioisexpressedinformof xy

, where x and y are natural

numbers without any common factors except 1, y indicates number of double traverses after which yarn comes to same place.

• Thetraverseratioswithsmallvalueofy(whenexpressedasafractionin form of x

y) would cause pattern formation. The most severe

patterns would be formed for whole numbers as traverse ratios, e.g. 2, 3, 4, … etc. for which value of y is 1.

2.4.1.2 Building a satisfactory package with constant traverse ratio throughout package

A smaller value of y (for a traverse ratio of xy

, where x and y are natural


numbers without any common factors except 1) causes yarn to come to same

place after fewer number of double traverses that leads to pattern formation and yarn is not laid across the entire package area. A traverse ratio of say 4 would not be suitable as successive wraps of yarns would be overlapped. What could be a suitable traverse ratio closer to number 4 to build a satisfactory package?

Number 4 can also be expressed as an equivalent fraction, say 40001000

. If

numerator is reduced marginally then we can get fractions like 39931000

, 39911000

,

39971000

, 39791000

… etc. If winding is carried out with these traverse ratios, end

point of a double traverse would lie before its starting point and overlapping can be avoided as the coils of next double traverse would get displaced as shown in Fig. 2.12(a). As value of denominator of traverse ratio is a larger number 1000, patterning would be avoided. The numbers 3993

1000, 3991

1000, 3997

1000, 3979

1000

arelittlelesserthan4.Differencebetweenthesenumbersand4 is highest for 39791000

[4−39791000

],i.e.itisthehighestamongall.Thereforedisplacement of

yarn after a double traverse would be the greatest. This displacement would be

the least for 39931000

. This displacement has to be at least equal to yarn diameter

to avoid overlapping. Instead of taking numbers little less than 4, numbers exceeding it can also

be taken, i.e. numbers such as 40111000

, 40131000

, 40171000

, 40191000

… can be taken.

Figure 2.12 Winding with constant traverse ratio without overlapping


With these numbers at the end point of a double traverse would lie beyond itsstartingpointasshowninFig.2.12(b).Differencebetween 4011

1000, 4011

1000,

40171000

, 40191000

and 4 is the highest for 40191000

and therefore the shifting of coils

of next double traverse from previous one would be the highest. For 40111000

,

the difference is least and therefore the shifting of coils of next double traverse from previous one would be the least. Thus suitable traverse ratios for building a package with same traverse ratio throughout the package can be obtained by incrementing or decrementing a traverse ratio that would form patterns (with smaller value of y) in such a way that patterning is avoided and yarn coils shifts adequately at the end of pattern repeat. The traverse ratios with a smaller value of y leading to pattern formation

are called “nominal traverse ratios”, like 4 14

( ) , 4 12

92

( ) , 6 13

193

( ) , 5 25

275

( ) ,

8 14

334

( ) and 4 34

194

( ) which if expressed as decimal numbers are 4.00, 4.50,

6.33, 5.40, 8.25 and 4.75, respectively.

With a nominal traverse ratio expressed in form of xy

, where x and y are

natural numbers without any common factors except 1, y indicates number of double traverses after which yarn comes to same place or it shows after how many double traverses pattern of laying repeats. Thus, for a traverse ratio of 92

pattern of laying repeats after two double traverses and for a traverse ratio

of 113

it repeats after 3 double traverses.

Traverse ratios suitable for building satisfactory packages are obtained by suitably incrementing or decrementing nominal traverse ratios which are called actual traverse ratios.

2.4.1.3 Gain and precision windingTraverse ratios for building satisfactory packages are obtained by suitably incrementing or decrementing nominal traverse ratios so that the yarn coils at the end of pattern repeat displace adequately. Minimum displacement should be at least equal to diameter of the yarn at the end of pattern repeat so


that there is no overlapping. For example, for a nominal traverse of 6 (y = 1, i.e. pattern repeats after every double traverse), coils of subsequent double traverses should displace at least equal to diameter of yarn and for a nominal traverse of 10

3 (y = 3, i.e. pattern repeats after three double traverses), coils

of a double traverse should displace at least equal to diameter of yarn from coils starting after 3 double traverses. The amount of shifting depends upon difference between actual traverse ratio and nominal traverse ratio. Gain is the measure of amount of displacement of yarn at the end of pattern repeat. Gain is expressed either as linear gain or revolution gain. Let‘A’bethestartingpointofadoubletraverseonfaceofapackageand‘B’bethestartingpointafterpatternrepeatasshowninFig.2.13(a)and(b).Lineargainisthedistancebetweenpints‘A’and‘B’expressedintermsofunitof length, say mm. Revolutiongainisrevolution(rotation)frompoint‘A’to‘B’.

Revolution gain = AB(linear gain)

2pr(circumference)

or Revolution gain = ∠BOA( )degrees

360

or Revolution gain = ∠BOA radians( )

2π

or Revolutiongain=Differencebetweenactualtraverseratioand nominal traverse ratio Inpractice‘revolutiongain’isthebetterknownquantity. Figure2.13(c)showsyarncoil‘A’of1stdoubletraverseandcoil‘B’ofadoubletraversebeginningaftertheendofpatternrepeat.Coils‘A’and‘B’are

Figure 2.13 Gain in winding


laid adjacent to each other, i.e. just touching each other. Figure 2.13(d) shows enlarged view of these coils. LM = diameter of yarn LN = minimum shifting of yarn at the periphery of the package at the end of double traverse or in other words it is linear gain, thus LN = linear gain ∠LNM = Ø = coil angle

sin f = LMLN

\ LN = LM dsin

'sinφ φ

= , where d′ is yarn diameter

Thus, if coil angle and yarn diameter are known, minimum linear gain can be calculated. If package radius = r,

Revolution gain (minimum) = Linear gaincircumference

d

rdr

= =

'sin '

sinφπ π φ2 2

When an entire package is wound with same suitable traverse ratio, revolution gain remains the same throughout the package. Therefore, displacement of yarn at the end of pattern repeat remains same though out winding in terms of revolution gain and usually it appears as if yarn is systematically and orderly laid throughout the package. Hence, such winding is called precision winding. Thus, a precision wound package is a package wound with a suitable constant traverse ratio throughout its build up.

2.4.1.4 Head wind, after wind, close wind and open wind in precision winding

When actual traverse ratio is less than nominal traverse ratio, the end point of

yarn when pattern repeats, lies before its starting point. For example, if 113

is

nominal traverse ratio and 1093300

is actual traverse ratio then the point at the

endof threedouble traverseswould liebefore thepointof startingoffirstdouble traverse. Such wind is called head wind. When actual traverse ratio is greater than nominal traverse ratio, the end point of yarn when pattern repeats, lies beyond its starting point. For example,

if 113

is nominal traverse ratio and 1109300

is actual traverse ratio then the


point at the end of three double traverses would lie beyond (after) the point of startingoffirstdoubletraverse.Suchwindiscalledafterwind. Gain determines the displacement of yarn coils at the end of pattern repeat. If gain is selected in such a way that coils of yarn after pattern repeat lie adjacent to one another, this winding is called close precision winding and the traverse ratios used are called close winding traverse ratios. Gain in a close winding traverse ratio is usually taken to displace yarn 1 to 1.5 times its diameter at the end of pattern repeat. Therefore, a given close traverse ratio is calculated for a specific yarn diameter and thereby for a particular yarnlineardensity(count/Tex/denier).Closewindingtraverseratioforaparticularlinear density of yarn builds a compact package with high density. If a close traverseratiowhichissuitableforlowlineardensity(finer)yarnisemployedfor winding a high linear density (coarser) yarn, it would cause over riding of yarnattheendofpatternrepeat.Conversely,ifaclosetraverseratiowhichis suitable for high linear density yarn is employed for winding a low linear density yarn, it would cause gap between yarns at the end of pattern repeat, leading to a package with less compactness. If gain is selected in such a way that coils of yarn after pattern repeat lie away from one another (displacement is much greater than yarn diameter), a package with more openness (lesser compactness/density) is formed and therefore this precision winding is called open winding and traverse ratios used are called open winding traverse ratios. Thus, gain is one of the important parameters influencing packageproperties. Instead of gain, “yarn distance” is also used to express yarn displacement. It is yarn to yarn distance of coils of a double traverse and those after a pattern repeat. Yarn distance of zero indicates that yarn coils of a double traverse and one after a pattern repeat are just touching, i.e. laid adjacent to one another. Figure 2.14(a) shows relation between yarn distance and package density for a precision wound package wound with cotton yarn. Theoretically, zero yarn distance would give the highest density. However, it leaves the possibility of overriding of yarns at the end of pattern repeat. It can be seen in the graph that initially there is not a great change in package density with increase in yarn distance. Therefore, it would be advantageous to avoid absolute minimum, i.e. zero yarn distance.

2.4.1.5 “Fish bone” pattern in close windingWhen a package is precision wound with a close winding traverse ratio, typical diamond patterns are formed as shown in 2.14(b) that gives “picturesque”


Figure 2.14 Close precision wound packages with picture winding (Courtesy: SSM AG)

appearance to package and it looks attractive. The diamond formation creates aso-called“fishbone”patternonpackage. For close winding, number of diamonds along a row circumferentially and along a row lengthwise can be counted. If nominal traverse ratio of close winding is x

y, where x and y are natural numbers without any common factors

except 1, then number of lengthwise diamonds along a row = x2

and along a

row circumferentially = y. As shown in Fig. 2.15, if 4 12

diamonds are seen

along a row lengthwise and 1 diamond along a row circumference wise, then

nominal traverse ratio is 2 4 51

91

9( . )= = .

It follows from this that numerator of nominal traverse ratio of a close precision wound package is twice number of diamonds counted along a row of diamonds lengthwise and numerator is obtained by counting number of diamonds along a circumferential row.

2.4.1.6 Relation between traverse ratio, coil angle, traverse length and package diameter for a cylindrical package

Let‘T’betraverseratio,‘D’bepackagediameter,‘L’betraverselengthand‘Ø’becoilangle.


Figure 2.15 Number of diamonds in pattern or picture winding

‘T’coilsarelaidduringyarntraverseof‘2L’,

Therefore traverse per coil would be 2LT

,

As shown in Fig. 2.16(a), if surface of one coil of package is enveloped, it becomes a rectangle for which,

f = tan( )

( )tan− −=1 1

22

LTD

LT Dπ π

… (2.1)

Figure 2.16 Coil angle variation in precision winding


While building a cylindrical precision winding package with same traverse lengththroughoutpackagebuild,coilangle‘f’wouldkeepondecreasingaspackage diameter decreases. Thus, coil angle keeps on decreasing as package diameter increases for a precision wound package (Fig. 2.16b). With bare package diameter of 20 mm, traverse length of 80 mm (Table 2.2) shows variation in coil angle at various package diameters, for given traverse ratios. Decreaseincoilanglewithincreaseinpackagediameteristhemajordrawbackofprecisionwinding.Packageatlargerdiametersbecomesunstabledueto decrease in coil angle. Moreover, package density tends to increase with increasing package diameter due to reduction in coil angle.

Table 2.2 Variations in coil angle at various package diameters, for given traverse ratios

Packagediameter in mm

Coil angle in degrees

(For traverse ratio 5.9987)



20 25.539 17.668 14.295

25 20.919 14.296 11.522

30 17.669 11.989 9.641

35 15.272 10.316 8.284

40 13.436 9.049 7.261

45 11.989 8.058 6.461

50 10.820 7.261 5.820

55 9.857 6.607 5.294

60 9.050 6.061 4.855

2.4.1.7 Conceptual questions related to precision windingIdentify nominal traverse ratio for the given actual traverse ratios and also identifywhetheritisahead-windorafter-windtraverseratio. (a) 6.9916, (b) 5.4015, (c) 5.393, (d) 6.0504 Actual traverse ratio 6.9916 is close to 7. Therefore, nominal traverse ratio is 7. As actual traverse ratio is less than nominal traverse ratio, it is a head-windtraverseratio. Actual traverse ratio 5.4015 is close to 5.4. Therefore, nominal traverse ratio is 5.4. As actual traverse ratio is greater than nominal traverse ratio, it is after-windtraverseratio.


Actual traverse ratio 5.393 is close to 5.4. Therefore, nominal traverse ratio is 5.4. As actual traverse ratio is less than nominal traverse ratio, it is a head-windtraverseratio. Actual traverse ratio 6.0504 is close to 6. Therefore, nominal traverse ratio is 6. As actual traverse ratio is greater than nominal traverse ratio, it is after-windtraverseratio. Find number of lengthwise and circumferential diamonds for the following close winding traverse ratios (a) 4.993, (b) 5.497 For actual traverse ratio 4.993, nominal traverse ratio is 5. Nominal

traverse ratio 5, expressed in form xy

is 51

. Therefore, number of lengthwise

diamonds is 52

and circumferential diamonds equals 1.

For actual traverse ratio 5.497, nominal traverse ratio is 5.5 5 12

112

, . .i e

.

Therefore, number of lengthwise diamonds is 112

5 5= . and circumferential diamonds equals 2. Find revolution gain for the given traverse ratios. (a) 4.4977, (b) 6.0504 Nominal traverse ratio for 4.4977 is 4.5. Therefore, revolution gain is 4.5 − 4.4977 = 0.0023.Nominal traverse ratio for 6.0504 is 6.Therefore,revolutiongainis6.0504−6=0.0504. What would be the main difference in precision winding between traverse ratios 5.422 and 7.422? The two traverse ratios differ mainly in terms of first digit.At givenpackage diameter, coil angle with traverse ratio 5.422 (lower traverse ratio) would be greater than that with 7.422 (higher traverse ratio). Arrange given traverse ratios in ascending order of gain. 5.417, 5.411, 5.423, 5.421 (b) 5.987, 5.983, 5.991, 5.989 5.417, 5.411, 5.423, 5.421 are after winding traverse ratios with nominal traverse of 5.4, where greater is the traverse ratio more the gain. Therefore, traverse ratios arranged in ascending order of gain is 5.411, 5.417, 5.421, 5.423. 5.987, 5.983, 5.991, 5.989 are head winding traverse ratios with nominal traverse of 6, where smaller is the traverse ratio more the gain. Therefore traverse ratios arranged in ascending order of gain is 5.891, 5.989, 5.987, 5.983.


2.4.2 Winding with same coil angle throughout package build

Other approach of building a cross wound package is keeping same coil angle throughoutpackagebuild.Letacylindricalpackagewithtraverselength‘L’bewoundwithconstantcoilangle‘Ø’,thenfromEq.(2.1)

tan f = ( )

( )

22

LTD

LT Dπ π

=

\ T = 2L

Dπ φtan

Figure 2.17 Traverse ratio variation

This equation shows relation between traverse ratio ‘T’ and diameter‘D’ofpackage.Astraverselength‘L’andcoilangle‘f’areconstant,thereis inverse relation between traverse ratio and package diameter. Therefore traverse ratio would keep on decreasing with an increase in package diameter (Fig. 2.17). With package length of 152 mm and bare package diameter of 30 mm, change in traverse ratio for a range of package diameters is shown in Table 2.3. If winding is started from a 30 mm bare package with 11° coil angle, traverseratiowouldchangegraduallyfrom16.594to2.489.Duringthis,thetraverse ratio would reach whole numbers (16, 15, 14 …. 3), half numbers (16.5, 14.5, 13.5 …. 2.5) as well as other fractions (one third, one fourth, onefifth,etc.)duringwhichpatternformationwouldtakeplace.Mostseverepatterns would be formed with whole number traverse ratios.


Table 2.3 Change in traverse ratio for a range of package diameters

Pkg. dia.

in mm

Traverse ratios for various coil angle in degrees

10º 11º 12º 13º 14º 15º 16º 17º 18º

30 18.2929 16.5940 15.1750 13.9713 12.9369 12.0379 11.2488 10.5503 9.9272

40 13.7197 12.4455 11.3812 10.4785 9.7027 9.0284 8.4366 7.9127 7.4454

50 10.9758 9.9564 9.1050 8.3828 7.7622 7.2227 6.7493 6.3302 5.9563

60 9.1465 8.2970 7.5875 6.9857 6.4685 6.0189 5.6244 5.2751 4.9636

70 7.8398 7.1117 6.5036 5.9877 5.5444 5.1591 4.8209 4.5215 4.2545

80 6.8599 6.2227 5.6906 5.2393 4.8514 4.5142 4.2183 3.9563 3.7227

90 6.0976 5.5313 5.0583 4.6571 4.3123 4.0126 3.7496 3.5168 3.3091

100 5.4879 4.9782 4.5525 4.1914 3.8811 3.6114 3.3746 3.1651 2.9782

110 4.9890 4.5256 4.1386 3.8104 3.5283 3.2831 3.0679 2.8773 2.7074

120 4.5732 4.1485 3.7937 3.4928 3.2342 3.0095 2.8122 2.6376 2.4818

130 4.2214 3.8294 3.5019 3.2242 2.9854 2.7780 2.5959 2.4347 2.2909

140 3.9199 3.5558 3.2518 2.9939 2.7722 2.5795 2.4105 2.2608 2.1273

150 3.6586 3.3188 3.0350 2.7943 2.5874 2.4076 2.2498 2.1101 1.9854

160 3.4299 3.1114 2.8453 2.6196 2.4257 2.2571 2.1091 1.9782 1.8613

170 3.2282 2.9283 2.6779 2.4655 2.2830 2.1243 1.9851 1.8618 1.7519

180 3.0488 2.7657 2.5292 2.3286 2.1562 2.0063 1.8748 1.7584 1.6545

190 2.8884 2.6201 2.3960 2.2060 2.0427 1.9007 1.7761 1.6658 1.5675

200 2.7439 2.4891 2.2762 2.0957 1.9405 1.8057 1.6873 1.5825 1.4891

Ribboning or pattern formation is the major drawback of winding with constant coil angle. As traverse ratio changes with yarn diameter, displacement of yarn coils is not precise, but keep on varying. Instead of a precise, orderly lay of yarn, a random kind of lay is seen on the package and therefore, the packages wound with constant coil angle are called random wound packages and its winding is called random winding.


Figure 2.18 Traverse ratio and coil variation with package diameter for random winding traverse length 152 mm

Figure 2.19 Traverse ratio and coil variation with package diameter for precision winding traverse length 80 mm

Duringrandomwindingonacone,coilangledoesnotremainconstantfrom base to nose but varies. However, traverse ratio reduces with increasing package diameter in a similar manner as with a cylindrical package. Figures 2.18 and 2.19 show relation between traverse ratio and coil angle with package diameter for random and precision winding, respectively.

In Chapter 2, we have discussed two basic approaches of laying yarn on cross wound packages: winding with constant coil angle (random winding) and winding with constant traverse ratio (precision winding). In Chapter 3, principles of actual winding systems for random, precision and other better modes are discussed in this chapter. For simplicity of understanding, systems are explained taking case of only cylindrical packages. For conical packages also, basic principles remain the same.

3.1 Basic modes of windingThree basic modes of cross winding are very common in winding systems. 1. Random winding 2. Precision winding 3. Step-precision winding or hybrid winding

3.2 Random winding The principle of random winding system is shown in Fig. 3.1. Winding package is rotated through frictional contact with rotating drum. This type of drive is also called surface drive. Two methods of yarn traversing are usually employed:

3Principles of winding systems

Figure 3.1 Random winding

Principles of winding systems 35

Thefirstoneiswindingsystemwithgrooveddrumtraverse(Fig3.1a)inwhich a drum carries spiral slots or grooves. Yarn follows the grooves cut on drum surface and is moved to and fro to traverse yarn across package length. Figure 3.2 shows close-up view of a random winding system with grooved drum. Figure 3.4 shows a winding machine with grooved drum traversing system. The second is winding system with a plain face drum for rotating package and cam traverse in which a yarn traversing guide that follows a grooved cam moves yarn to and fro across the length of the package (Fig. 3.1b). Figure 3.3 shows close-up view of a winding system with plain face drum to drive the winding package and traverse with a separate thread guide.

Figure 3.2 Close-up view of grooved drum winding system (Courtesy: SSM AG)

Figure 3.3 Close-up view of winding system with plain face

drum and separate thread guide traverse (Courtesy: SSM AG)

Figure 3.4 Rewinding machine with grooved drum winding system (Courtesy: SSM AG)


3.2.1 Package surface speed and traverse speed in random winding

Drum is driven by a motor. If rpm (revolutions per minute) of motor remains constant, drum rpm would also remain constant. Therefore, surface speed of drum (speed at which drum surface moves which equals ‘pDN’, where ‘D’ is drum diameter and ‘N’ is package rpm) also remains constant. The package is driven through frictional contact with the drum; hence, surface speed of package equals that of the drum (Fig. 3.1c). In case of grooved drum traverse, if drum rpm remains constant, traverse speed also remains constant [refer appendix at the end of this chapter]. In case of cam traverse, with constant motor rpm, cam rpm also remains constant and therefore traverse speed remains constant.

3.2.2 Package characteristics of random wound packagesPackage characteristics of random winding systems are as follows: 1. Yarn winding velocity is the vector summation of surface velocity

(which is perpendicular to package axis) and traverse velocity (which is parallel to package axis; Fig. 3.5).

2. In this case, as the surface speed and traverse speed remains constant, winding speed as well as coil angle ‘f’ remains constant at all diameters of package.

tan f = vv

t

s

f = tan−1 vv

t

s

As ‘vt’ (traverse speed) and ‘vs’ (surface speed) are constant, coil angle ‘f’ will remain constant throughout package and entire package is wound with constant coil angle.

3. As discussed in section 2.4.2, when a package is wound with constant coil angle, traverse ratio keeps on decreasing with increase in package

Figure 3.5 Winding velocity as a vector sum


diameter. This phenomenon can be understood the other way also. The package rpm reduces as diameter increases. But traverse speed remains constant. So traverse ratio reduces as package diameter increases. At smaller diameter, package rotates faster but traverse speed remains constant; hence, more coils are laid in a double traverse i.e. traverse ratio is more. At larger package the package rotates slowly so less coils are laid in a double traverse, i.e. traverse ratio is reduced.

4. Decreasing traverse ratio leads to pattern formation at definitediameters.

5. Displacement of yarn keeps on changing due to varying traverse ratio. Therefore, revolution gain keeps on changing throughout winding and an ‘orderly lay’ on package is not seen.

3.2.3 Mathematical calculations related to random winding

3.2.3.1 Case of grooved drum windingIt is necessary to understand definition of number of turns or number ofcrossings on the grooved drum, which is defined as the number of drumrotations per single traverse. For a cylindrical package, let ‘L’ be traverse length, ‘K’ be number of turns on the drum, ‘D’ be drum diameter and ‘d’ be diameter of winding package. Referring to Fig. 3.1(a), if ‘N’ is motor rpm, surface speed of drum = pDN, Therefore, surface speed of package = pDN Drum rotates at ‘N’ rpm and ‘K’ revolutions of drum completes a single traverse, i.e. causes traverse of length ‘L’,

Therefore traverse speed = LNK

Therefore, winding speed = ( ) ( )πDN LNK

2 2+

All parameters determining winding speed remains constant for given drum and motor rpm and therefore winding speed remains the same at all diameters of the package.

Coil angle, f = tan( )

( )tan− −=1 1

LNKDN

LK Dπ π

During winding a cylindrical package with given drum, values of ‘L’, ‘K’ and ‘D’ remain constant and therefore coil angle remains constant.


Traverse ratio ‘T’ would be number of package rotations in ‘2K’ rotations of cam which equals to,

T = 2KDd

, where ‘d’ is package diameter.

As ‘K’ and ‘D’ remain constant with a given drum, traverse ratio ‘T’ varies in inverse proportion to ‘d’.

3.2.3.2 Case of plain face drum with separate thread guideReferring to Fig. 3.1(b), let ‘D’ be drum diameter, ‘N’ be motor rpm, ‘Z’ be number of cam revolutions per single traverse, ‘L’ be traverse length, and ‘x’ be number of teeth of gear on drum shaft driving other gear on cam shaft with teeth ‘y’. Surface speed of package = pDN in meters per minute if ‘D’ is in meters.

RPM of cam = Nxy

‘Z’ revolutions of cam give traverse length of ‘L’,

Therefore Nxy

revolutions of cam would give traverse of NxLyZ

Thus NxLyZ

gives traverse speed in meters/ minute if ‘L’ is in meters.

Winding speed = ( ) ( )πDN NxLyZ

2 2+

Coil angle f = tan( )

( )tan− −=1 1

NxLyZDN

xLyZDπ π

For a given system x, y, L, Z and D remains constant and therefore coil angle ‘f’ remains constant throughout package build. Traverse ratio ‘T’ would be number of package rotations in ‘2Z’ rotations of cam which equals to

T = 2 2Z yx

Dd

ZyDxd

= , where ‘d’ is package diameter

As ‘Z’, ‘x’, ‘y’ and ‘D’ remain constant for a given system, traverse ratio ‘T’ varies in inverse proportion to d. Theoretical curve of package diameter versus coil angle is given in Chapter 2. Practically, to avoid pattern formation, traverse ratio is continuously disturbed during winding (which is discussed later) due to which actual coil angle on package keeps on varying over a narrow range. Extent of coil angle variation depends upon magnitude of disturbance. Therefore, practical curve of package diameter versus traverse


ratio for random winding becomes a thick line or a narrow band within which coilanglefluctuates.

3.3 Precision windingA precision winding machine builds precision wound packages. Conventionally, in a precision winding machine, package is directly driven by mounting it on a spindle. Therefore, these winders are also called spindle driven winders. The principle of precision winding is as shown in Fig. 3.6(a). The package is driven by mounting it on a spindle which is positively driven from motor. Traversing cam is driven from spindle shaft through a train of gears. A yarn traversing guide that follows traversing cam traverses yarn. Let ‘Z’ be number of cam revolutions per single traverse. For given cam, number of cam revolutions per single traverse of cam remains constant. With constant motor rpm, spindle rpm and thereby package rpm will be constant. If motor rpm remains constant, cam rpm would also be constant and therefore, traverse speed will remain constant.

Figure 3.6 Principle of precision winding

The ratio of cam rotation and package rotation would remain constant irrespective of package diameter. Therefore, a package with constant traverse ratio would be produced in which coil angle reduces with increasing package diameter as discussed in Chapter 2. With suitable selection of traverse ratio, patterning can be avoided.

3.3.1 Package characteristics of precision wound packages 1. Referring to Fig 3.6(a), if motor rpm remains constant, cam rpm

would also be constant. Surface speed of package is proportional to package diameter. Therefore, surface speed of package would keep on increasing as package diameter increases. However, traverse speed would remain constant.

Winding speed = ( ) ( )Surfacespeed Traversespeed2 2+


Due to increase in surface speed with package diameter, winding speed would also increase. Increase in winding speed causes increase in yarn tension which is not desirable for most of the winding applications. Therefore suitable means must be provided to keep yarn tension/winding speed constant. Winding speed can be kept constant by reducing package rpm progressively with increasing package diameter.

For the set up shown in Fig. 3.6(a), let motor rpm = ‘N’, number of cam rotations per single traverse = Z, winding speed = W, package diameter = d and (A, B, C, D) be number of teeth of gears of gear train. Then,

Surf ace speed of package = pDN

Cam rpm = NDBCA

Traverse speed = NLDBZCA

Winding speed = W = ( ) ( )πdN NLDBZCA

2 2+

= N d LDBZCA

( ) ( )π 2 2+ (3.1)

It is clear from the Eq. (3.1) that with constant ‘N’, winding speed would keep on increasing with increase in package diameter. Winding speed can be kept constant by reducing package rpm as package diameter increases. RPM of package at diameter ‘d’ of the package to maintain constant winding speed is given by,

N = W

d LDBZCA

( ) ( )π 2 2+

Let DBCA

= G , i.e. gear ratio or between spindle shaft and cam shaft

OR rotational speed ratio between spindle shaft and cam shaft speeds,

i.e. rpmof spindlerpmof cam

,

Therefore, N = W

d LGZ

( ) ( )π 2 2+


To reduce the spindle rpm, required system is principally shown in Fig. 3.6(b). Spindle speed can be decreased by shifting belt as package diameter increases. As spindle speed is decreased, cam rpm would also decrease proportionately but ratio of spindle speed and cam speed does not change and therefore traverse ratio is not affected.

From Fig. 3.7, Vw = Vs sec f, i.e. winding speed is the product of surface speed and sec f. Some precision winding systems work with constant surface speed. With such winding systems, there would be reduction in winding speed (with decreasing coil angle, sec f keeps on reducing).

Figure 3.7

2. Coil angle, i.e. f = tan tan( )

( )tan

( )

( )tan ( )

(− − − −= = =1 1 1 1v

v

NLDBZCA

dN

LDBZCA

dLGt

s π π ZZ dπ )

Equation shows that coil angle ‘f’ reduces with increase in package diameter.

3. Traverse ratio = number of coils laid on package in double traverse = number of rotations of package in double traverse = number of

rotations of package in ‘2Z’ rotations of cam = ( ) ( )2 2ZACBD

ZG

=

Traverse ratio remains constant irrespective of package diameter. Theoretical curve of traverse ratio versus package diameter is discussed in Chapter 2. If actual winding system manages to build entirepackagewithoutanyminorfluctuations(maybecauseddueto reasons like play in drive transmission) in traverse ratio, actual curve of traverse ratio versus package diameter would be a thin line. For winding system shown in Fig. 3.6, desired traverse ratio can be obtained for given cam by taking suitable number of teeth of gears A, B, C and D. For example, if number of cam rotations per single traverse, i.e. Z = 4 and desired traverse ratio is 7.9887,


( ) ( . ) ( . )ACBD Z

= =7 9887

27 9887

8= 0.99857

Values of gears found are [( ) ( )( ) ( )

]36 1937 38

.

Teeth of gears A, B, C and D are 18, 37, 39 and 19, respectively. If gears 18 and 19 prove to be smaller, teeth of A and D may be doubled

[ ( ) ( )( ) ( )

]36 1937 38

.

3.4 Positive and negative aspects of random and precision winding

3.4.1 Positive aspects of random winding 1. Owing to constant coil angle, a stable package is produced. Package

propertiesareinfluencedbycoilangleselectedforwinding. 2. Constant winding angle leads to package of uniform density.

Moreover, there are no restrictions on building packages with greater diameters.

3. The basic winding mechanism is simpler in construction, especially with grooved drum winding. As the yarn winding speed remains constant, no regulating device is required to keep winding speed constant. Economical winding systems are possible with random winding. Maintenance and operation can be simpler and easy.

3.4.2 Negative aspects of random winding 1. At certain diameters during package build up, patterning occurs

(unless an effective method is provided to avoid it). These pattern zones become problematic during unwinding, as yarn may get caught at ribbons and break. Yarn breakages tend to increase at pattern zones during unwinding. Package density increases pattern zones which is problematic for an application like dyeing.

2. When grooved drum winding is employed, the yarn remains in the groove of the drum. Therefore, point at which yarn is laid on the package does not remain at nip between drum and the package but remains away from it as shown in Fig. 3.8. The distance between nip and the laying point keep on increasing as the package diameter builds up. This leads to reduction in effective traverse of yarn on package. Therefore, instead of parallel side faces, somewhat ‘convex’ side faces tend to be formed which is disadvantageous for certain end-use applications like TFO twisting.


Figure 3.8 Package side flanks in grooved drum winding

3. Package density achievable with random winding is about 20–25% lower than precision winding.

3.4.3 Positive aspects of precision winding 1. Due to avoidance of patterning, packages exhibit good unwinding

properties. 2. By selecting close traverse ratio, a package with high density can

be built. Precision winding offers possibility of building packages with the highest density. Similarly open traverse ratios produce open packages with lesser density. Desired properties of a package can be obtained by selecting appropriate traverse ratios.

3.4.4 Negative aspects of precision winding 1. As the coil angle decreases with an increase in package diameter,

it may lead to a fragile package at higher diameters. Therefore, precision wound packages can be built up to limited diameters only. Precision wound packages become problematic when package diameter exceeds traverse length. Such packages are called “over-squared cones. Changing coil angle is disadvantageous for certain end-use applications.

2. The change of coil angle with package diameter causes change in density from empty to full package. The density tends to increase from bare towards full package.

3. The mechanism is usually required to reduce package rpm as diameter of package increases on winding which puts an additional cost in machine construction.

4. Changing coil angle causes effective reduction in traverse length


on package at bare package which keeps on increasing as package grows. As shown in Fig. 3.9, the traverse guide moves between two extremes ‘L’ and ‘R’ throughout winding. Due to higher coil angle at bare package, the extreme points up to which yarn reaches remain nearer to package centre (Fig 3.9A). Due to lesser coil angle towards full package, the extreme points up to which yarn reaches move away from package centre. Moreover, at reversal points yarn tends to slip towards package centre and reduce effective traverse on package. At higher coil angle this slippage would be greater causing greater reduction in effective traverse stroke on package. Therefore, a precision wound cylindrical package is not built with parallel side flanksbutwithsideflanksasshowninFig.3.9(B).Figure3.10showsa side flank of a precision wound package. Such package shapebecomes problematic in certain end-use applications. As effective traverse length on package tends to increase with increasing package diameter overthrown ends may be observed especially towards bare package.

5. Higher coil angle towards bare package may be problematic for end-use application like TFO twisting.

3.5 Step-precision windingRandom winding has the main drawback of pattern formation, and precision winding has the main drawback of reducing coil angle with growing package

Figure 3.9 Package shape in precision winding

Figure 3.10 Side flank of a precision wound package


diameter. To overcome drawbacks of random and precision winding, a new system of winding called step-precision winding is developed which combines positive characteristics of random and precision winding to build a package that is free from patterning (positive characteristic of precision winding) with almost constant coil angle (positive characteristic of random winding). As step-precision winding is a combination of positive characteristics of random and precision winding; it is also sometimes called hybrid winding. As the name implies, step-precision winding is basically precision winding. Principle of step-precision winding is shown in Fig. 3.11. Package is directly driven through a motor as in precision winding. The drive from spindle shaft to cam shaft can be taken through any one of series of gear combinations A, B, C, D each suitable for precision winding (i.e. each traverse ratio would give pattern free package). Gear combination ‘A’ would give the highest traverse ratio whereas ‘E’ would give the least. During winding any one of the gear combinations would be in action with the others in neutral position. Instantaneous shifting from one gear combination to the other can take place at desired package diameter, i.e. traverse ratio can be instantaneously changed. In step-precision winding, entire package is produced in precision mode, but traverse ratio for the entire package does not remain the same but is varied in steps instantaneously. Coil angle does not remain constant during build up but varies over a narrow range. Build up of step-precision wound package can be understood from Fig. 3.11. Let ‘Ø’ be the desired angle at which a cylindrical package is to be wound. If ‘d’, ‘L’ and ‘Z’ are bare package diameter, traverse length and cam rotation per single traverse, respectively; traverse ratio ‘T1’ that would give coil angle ‘Ø’ can be found by,

Figure 3.11 Principle of step-precision winding


T1 = 2L

dπ φtan A traverse ratio ‘Ta’ very close to ‘T1’ calculated mathematically is to be taken that would not lead to pattern formation. Gear combination ‘A’ should be taken such that it would give this traverse ratio ‘Ta’. Thus, precision winding would be carried out starting from bare package diameter ‘d’ with traverse ratio ‘Ta’. Starting coil angle would be almost ‘Ø’. With increase of package diameter, coil angle would keep on decreasing. Let allowable coil angle decrement be 1º. Package diameter ‘d1’at which coil angle becomes ‘Ø−1’wouldbegivenbyformula,

d = 2

1L

Taπ φtan( )− When package diameter increases to ‘d1’,coilangledecreasesto‘Ø−1’.At this time, coil angle decrement can be stopped and can be brought back to ‘Ø’ by decreasing traverse ratio instantaneously, which can be calculated as,

T2 = 2

1

Ldπ φtan

Actual suitable traverse ratio to be taken should be ‘Tb’ which should be very close to ‘T2’. Thus, at diameter ‘d1’, traverse ratio is instantaneously decreased to value ‘Tb’. Gear combination ‘B’ should be such that it would give traverse ratio ‘Tb’. At diameter ‘d1’ gear combination ‘B’ should be instantaneously brought in action and gear combination ‘A’ would be discontinued. This would bring coil angle almost back to ‘Ø’. Thus at diameter ‘d1’, precision winding continues but with new traverse ratio ‘Tb’. On continuing winding, coil angle again would keep on decreasing. A diameter ‘d2’ can be calculated at which coil angle decrements by one degree,i.e.itbecomes(Ø−1).Anewlowervalueoftraverseratio‘Tc’ can be determined that would bring the coil angle back to value very close to ‘Ø’. At diameter ‘d2’, an instantaneous switch over should be made to gear combination ‘C’ that gives traverse ratio ‘Tc’ so as to reach coil angle ‘Ø’. Similarly at further diameters ‘d3’, ‘d4’, ‘d5’ ….. , instantaneous transitions to traverse ratios ‘Td’, ‘Te’, ‘Tf’ ….respectively, would maintain change in coil angle variation within a narrow range. In this way, step-precision wound package is precision wound but with decreasing traverse ratio in steps in which coil angle varies over a narrow range. The package consists of several concentric layers, each wound with different traverse ratio. Figure 3.12 shows graph of traverse ratio v/s package diameter for step-precision winding. If traverse ratios Ta, Tb, Tc, Td …. are taken as close traverse ratios, built step-precision wound package would be


Figure 3.12 Step-precision wound package

denser and if these traverse ratios are taken as open traverse ratios, built step-precision wound package would be open, i.e. with lesser density. This description of step precision winding just highlights basic principle. Other approaches are also possible. For example, if a series of suitable traverse ratios are predetermined, switch over to subsequent one may be done at calculated diameter that increases coil angle back to the required one. With greater number of suitable available traverse ratios, a package with minimal changes in coil angle can be produced. Actual winding systems do not have gearsystemforchangingtraverseratio,butflexiblesystemswhoseprinciplesare discussed later in this chapter.

3.5.1 Positive aspects of step-precision winding 1. The package is free from pattern zones and therefore offers

several advantages like good unwinding properties, better dyeing performance.

2. Package properties can be ‘engineered’ through suitable selection of coil angle and traverse ratios that keep on reducing stepwise.

3. Step-precision wound cylindrical package is built with parallel side faces, which is advantageous for some end-use applications like TFO twisting and package dyeing.

3.5.2 Negative aspects of step-precision winding 1. Cost of winding system becomes high. 2. Winding at a particular diameter starts with a certain traverse. During

this build, effective traverse length gradually increases due to reduction in coil angle as discussed in section 3.4.4. At subsequent certain greater diameter, when traverse ratio is instantaneously decreased,


coil angle increases suddenly. This tends to instantaneously decrease effective traverse length. Therefore, instead of planar side faces, some steps may be observed.

3.6 Windingsystemswithflexibilityinpackagebuilding

Conventionally, random winders are surface driven winders whereas precision and step-precision winders are spindle-driven winders. Some winding systems like take-up winders of synthetic yarn production may be with spindle drive or surface drive, and any one of the yarn traversing system like grooved cam traverse / belt traverse / counter rotating blade traverse / levertraverse.Thesesystemsmayoffergreatflexibilityinselectingamongvarious modes of winding to user, i.e. random, precision or step-precision winding. In such systems, package and yarn traversing mechanisms are driven by separate motor drives. These systems are provided with various sensors for online determination of parameters like package rpm, cam rpm, package diameter, etc. Highly sophisticated drive systems, sensors and suitable (e.g. computer/microprocessor) control system offer several possibilities in package building. Such systems may also offer other additional feature like building a package with gradually increasing or decreasing coil angle within preselected range of package diameter. Pattern zones are taken care of with greater effectiveness while winding with random winding mode. Traversing systems like one with a yarn guide mounted on a belt moved to and fro using a programmable stepper motor systems permit programmable variation of traverse stroke length which gives additional possibilities in package building like building bi-conical packages, effective hard edge prevention, building packages with rounded edges advantageous for package dyeing, etc. Principle of some of these winding systems is discussed.

3.6.1 Winding systems with spindle (direct) drive with grooved cam traverse

Figure 3.13 shows principle of winding system with spindle (direct) drive to package. Motor ‘A’ drives a spindle on which package is mounted. Motor ‘B’ drives traversing cam. Instantaneous rotational speeds of both the motors can be changed though a suitable drive system. A press roll applies pressure on package for compact winding. Press roll is driven by winding package through surface contact (In some winding systems like take up winding, press roll is also positively driven to minimize drag on yarn, especially at package


Figure 3.13 Flexible winding system with spindle drive

doffing). From rotational speeds of press roll and package, instantaneouspackage diameter can be determined. As package diameter increases, press roll has to move away from package axis. Relative position of press roll with respect to package axis can also be an indication of instantaneous package diameter.

3.6.1.1 Random winding with spindle drive with grooved cam traverse

For random winding the user chooses the coil angle at which the package is to be built. Consider ‘N’ as rpm of spindle motor, ‘n’ as traverse motor rpm, ‘X’ as press roll rpm, ‘Y’ as press roll diameter, ‘d’ as package diameter and ‘L’ as traverse length. Let ‘Z’ be traverse system revolution per double traverse, ‘f’ be coil angle, ‘Vt’ be the traverse speed, ‘Vs’ be the surface speed and ‘Vw’ be the winding speed at which package is to be wound. Package diameter ‘d’ at any instant may be determined by sensing rpm of press roll.

Press roll rpm, X = NdY

As press roll is surface driven by package, surface speed of press roll and package is same. With increase in package diameter press roll rpm would tend to increase. If spindle rpm is decreased in such a way that press roll rpm remains constant, constant surface speed of package would be achieved.

Traverse speed = V VLnZt w= =sinφ

2

∴ =n

ZVL

w sinφ2

This equation determines cam rpm. For given situation Vw, Z, L and Ø are constant. Therefore cam rpm remains constant. Traverse ratio ‘T’ is the number of revolutions made by package in double traverse, i.e. in ‘Z’ revolutions of traverse system. In ‘Z’ revolutions of traverse


system traverse of length ‘2L’ is given. Let ‘S’ be the surface movement of package during ‘Z’ evolutions of traverse system. As coil angle is constant, this surface movement per double traverse would remain the same during build up of entire package.

tan f = 2 2LS

S L,tan

∴ =φ

Traverse ratio is the number of package rotations to cause its surface movement equal to ‘S’. Number of package rotations to cause its surface

movement equal to ‘S’ would be Sd

Ldπ π φ

=2tan

Thus traverse ratio T = Sd

Ldπ π φ

=2tan

(3.2)

(This equation is the Equation 2.1 of Chapter 2) Equation (3.2) shows that traverse ratio is inversely proportional to package diameter. During pattern zone arrival, traverse ratio can be disturbed by changing tan f to break pattern formation. More effective measure is instantaneous switching over to other coil angle. Such principle on Barmag take up winders is called ‘Ribbon Free Random Wind’ (RFR).

Principle of Ribbon Free Random Wind Referring to Fig. 3.14(a), if a package is random wound with coil angle ‘f1’, traverse ratio keep on reducing with increase in package diameter. During its build up, it passes through several traverse ratios where pattern formation takes place. Suppose package diameter is building up and is reaching a diameter ‘dp’ where traverse ratio would be 5. Better picture of

Figure 3.14 Ribbon free random wind


thissituation isshowninmagnifiedview.Beforereachingdiameter‘dp’, if coil angle is instantaneously changed to suitable coil angle ‘f2’, traverse ratio instantaneously starts following values of curve of coil angle ‘f2’. There is no pattern formation at and around diameter ‘dp’ on this curve. When package is built beyond diameter ‘dp’, winding is switched over back to coil angle ‘f1’. Thus, pattern zones are skipped by instantaneous switch over to other coil angle. Figure 3.14(b) graphically shows how whole number traverse ratios can be skipped. Using same principle, fractional values of traverse ratios (halves, one-thirds, one-fourths, etc.) can also be skipped. For winding at constant winding speed, instantaneous switch over to other coil angle requires instantaneous change in surface speed as well as traverse speed.

3.6.1.2 Precision winding with spindle drive with grooved cam traverse

Let ‘T’ be the traverse ratio selected by the user. To wind the entire package with constant traverse ratio ‘T’: In ‘Z’ rotations of traverse system package should always make ‘T’ revolutions, Therefore in ‘n’ revolutions of traverse system package should make nT

Z

revolutions Therefore, for ‘n’ rpm of traverse motor, spindle rpm ‘N’ would be nT

Z,

i.e. N = nTZ

\ n = NZT

Traverse speed would be 2LnZ

, as n = NZT

, traverse speed would be 2LN

T Surface speed is pdN

\ VW = ( ) ( )πdN LNT

2 22+

If spindle rpm ‘N’ is kept constant, winding speed will increase as package diameter ‘d’ increases. To keep winding speed constant, spindle speed must be reduced.

VW = N d LT

( ) ( )π 2 22+

\ N = V

d LT

w

( ) ( )π 2 22+

(3.3)


As package diameter increases, spindle motor rpm can be determined from Eq. (3.3) so as to maintain constant winding speed. Corresponding change in cam rpm should be brought using equation n

NZT

= .

tan f = traverse speedsurface speed

=

=

22

LNTdN

LT dπ π

\ f = tan−

1 2LT dπ

(3.4)

Coil angle during package build up can be determined using Eq. (3.4). It is discussed in 3.4.4 that actual traverse length obtained on package in precision winding is usually much less than traverse length of traversing system which leads to problems like curved side faces and over thrown ends. Therefore,withflexiblewinding system, during precisionwinding, initialwinding is normally started with higher traverse ratio (low coil angle) for predetermined length that gives longer initial effective traverse on package. For example, if a package is to be precision built with traverse ratio of 4.434, initial traverse ratio would be 6.434 till predetermined length is wound..

3.6.1.3 Step-precision winding with spindle drive with grooved cam traverse

In step-precision winding, package is wound with almost constant coil angle. The user selects the coil angle ‘f’ atwhich thepackage iswound.Let ‘α’be the angle within which coil angle deviation is to be allowed.” ‘Vw’ is the desired winding speed. At bare package diameter ‘d’, the desired initial coil angle is ‘f’. At start, to find traverse ratio ‘T1’ that would give coil angle ‘f’, an approximate traverse ratio ‘T1A’ is to be determined initially using equation

T1A = 2Ldπ φtan

‘T1A’ may not be a satisfactory traverse ratio for package build up. Therefore, suitable closest traverse ratio ‘T1’ should be taken that would give satisfactory winding. Thus at bare package diameter ‘d’, winding should be begun in precision mode with traverse ratio ‘T1’.

RPM of spindle motor at start, N = V

d LT

w

( ) ( )π 2

1

22+

As the package diameter increases, spindle motor rpm should be increased


as discussed in section 3.3.1. Corresponding values of traverse motor rpm can be determined using equation n = NZ

T1

Winding with traverse ratio ‘T1’ should be continued till coil angle reduces to (f – a). Diameter ‘d1’of winding package when coil angle reduces to (f – a) is given by,

d1 = 2

1

LTπ φ αtan( )−

At diameter ‘d1’ traverse ratio should be instantaneously reduced to ‘T2’ so that coil angle restores back to ‘f’. It would be necessary to determine an approximate traverse ratio ‘T2A’ that would restore same coil angle.

T2A = 2

1

Ldπ φtan

‘T2A’ may not be a satisfactory traverse ratio for package build up. Therefore, actual traverse ratio ‘T2’ that is to be taken should be the closest odd traverse ratio that would give satisfactory winding. At diameter ‘d1’ there should be instantaneous transition from traverse ratio ‘T1’ to ‘T2’. At diameter ‘d1’, winding with traverse ratio ‘T1’, spindle motor rpm would be

N = V

d LT

w

( )π 12

1

22

+

For instantaneous transition to lower traverse ratio ‘T2’ at diameter ‘d1’, spindle motor rpm should be instantaneously changed to

N′ = V

d LT

w

( )π 12

2

22

+

As T T2 1 , spindle rpm will have to be decreased instantaneously.

Before transition traverse motor rpm n NZT

=1

and after transition

n N ZT

' '=

2

where [n] and [n’] are traverse motor rpm before and after

transition respectively and [N] and [N’] are spindle motor rpm before and after transition, respectively.

nn

N TN T

' '= 1

2

, Here N N and T T' 2 1


For further winding, there would be instantaneous transitions at subsequent higher diameters to lower traverse ratios to keep coil angle deviation within a narrow range.

3.6.1.4 Winding with varying coil angle Most of the winding systems employ any one among the three modes of winding, i.e. random, precision and step-precision winding. Winding with varying coil angle is an additional possible feature with flexible windingsystems, where coil angle can be progressively increased or decreased. It is possible to build a package with progressively increasing or decreasing coil angle between two diameters with either random mode or step-precision mode.

Winding with varying coil angle in random modeAs shown in Fig. 3.15, let a package be wound with increasing coil angle from ‘f1’ to ‘f2’ from diameter ‘d1 ’ to ‘d2’. Coil angle ‘fb’ at an intermediate diameter ‘db’ can be determined using equation

φ φ φ φ

φφ φ

φb

bb bd d d d d d

d d−−

=−−

∴ =−−

−

+

1

1

2 1

2 1

2 1

2 11 1( ) (3.5)

Instantaneous value of ‘db’ can be determined from spindle rpm ‘Nb’,

press roll rpm ‘Np’ and press roll diameter ‘Dp’ using equation dN D

Nbp p

b=

VS = V d NW b b bcosφ π=

\ Nb = V

dW b

b

cosφπ

,

VT = V LnZ

bW bsinφ =

2

Figure 3.15 Winding with varying coil angle


Figure 3.16 Variation of surface and winding speeds

Tb = 2Ldπ φb btan

During package build up from ‘d1’ to ‘d2’; values of both, ‘db’ and ‘fb’ keep on changing and therefore traverse ratio ‘Tb’ also changes. It may reach values leading to pattern formation. Suitable measures must be taken to avoid pattern formation. Referring to vector diagram in Fig. 3.16, it can be understood that during package build up from ‘d1’ to ‘d2’ for constant ‘Vw’; if φ φ2 1 , surface speed will keep on decreasing and traverse speed will keep on increasing but if φ φ2 1 , surface speed will keep on increasing and traverse speed will keep on decreasing. With constant surface speed winding, with φ φ2 1 , traverse and winding speed keep on decreasing whereas with φ φ2 1 , traverse speed and winding speed would keep on increasing. Patterning can be avoided while winding with random mode using principle of ribbon-free random wind discussed in section 3.6.1.1.

Winding with varying coil angle with step-precision mode Winding with varying coil angle with step-precision mode is basically similar to one discussed in the above section “Winding with varying coil angle in random mode”. As shown in Fig. 3.15, let a package be wound with increasing coil angle from ‘f1’ to ‘f2’ from diameter ‘d1’ to ‘d2’ with step-precision mode. Coil angle ‘fb’ at an intermediate diameter ‘db’ can be determined using equation

fb ̀= φ φ

φ2 1

2 11 1

−−

−

+d d

d d( )b (3.6)

At diameter ‘d1’, winding is to be begun in precision mode with traverse ratio ‘T1’ so that initial coil angle is ‘f1’. Diameter ‘d2’ is to be determined when coil angle decreases to f1 – a. At this diameter ‘fb1’ is to be determined


using Eq. (3.6). Traverse ratio is changed instantaneously to ‘T2’ so as to switch over to coil angle ‘fb1’. This way instantaneous transition to traverse ratios is carried out so that coil angle changes from ‘f1’to ‘f2’ from diameter ‘d1’ to ‘d2’.

3.6.2 Winding with spindle drive with reciprocating element involved in traversing mechanism

Figure 3.17 shows principle of winding system for a cylindrical package with surface drive to package and traverse with yarn guide mounted on a belt/wire. Motor ‘A’ drives package and stepper motor ‘B’ moves belt/wire to and fro carrying yarn traversing guide. The traversing system permits programmable change in traverse frequency and stroke during package build up.

3.6.2.1 Random winding with spindle drive with reciprocating element involved in traversing mechanism

Let ‘Ø’ be coil angle at which the package is to be built and ‘Vw’ be desired

winding speed. Vs = Vw sin f

For winding at constant coil angle, traverse and surface speeds should remain constant. Surface speed = VS = pdN, where ‘d’ is package diameter and ‘N’ is rpm of motor ‘A’.

\ N = V

dV

dS w

πφ

π=

cos (3.7)

If ‘N’ is constant, surface speed will increase with increase in package diameter. Therefore, to maintain constant surface speed, ‘N’ should be varied

Figure 3.17 Direct drive with a reciprocating guide moving on a belt


in inverse proportion to ‘d’. Value of ‘N’ at any diameter can be determined using Eq. (3.7). Traverse speed = 2LF, where ‘F’ is traverse frequency in oscillations/minute and ‘L’ is traverse stroke length. If a package is wound with constant traverse length, i.e. constant ‘L’, then traverse frequency should be kept constant. If traverse length is varied, traverse frequency should be changed to maintain product ‘LF’ constant. For example, for building a bi-conical package where traverse length is decreased as package diameter increases, traverse frequency should be increased so that ‘LF’ remains constant. Frequency ‘F’ for given stroke length can be determined using equation

F VL

= T

2, but V V F V

LT WW= ∴ =sin sin

φφ

2

Now, T Ld

=2

π φtan, where ‘T’ is traverse ratio and ‘d’ is package diameter.

With constant traverse length ‘L’, traverse ratio varies in inverse proportion to package diameter.

Building a bi-conical random wound packageWhile building a bi-conical package, traverse length decreases with increase in package diameter. Let ‘b’ be taper angle of bi-conical package, i.e. angle between side face and package axis as shown in Fig. 3.18.

Referring to Fig. 3.18, tan ,β = =−

= −BCAC

BC d d r rbut b eb e2

\ AC = r rb e−tanβ

L L AC L r r L d db e e

b ee

b e= − = −−

= −

−

2 2

tan tanβ β (3.8)

Figure 3.18 Bi-conical package winding


(‘de’ is diameter of bare package, ‘db’ is instantaneous package diameter during its build up, ‘Le’ is traverse length at bare package and ‘Lb’ is instantaneous traverse length at package diameter db)

F VL

V

L d dbW

b

W

eb e

= =−

−

sin sin

tan

φ φ

β2

2

,

Fb is traverse frequency during build up at package diameter ‘db’.

V d N L Fw b b b= +( ) ( )π 2 22

Substituting value of ‘Lb’,

V d N F L d dw b b e

b e= + −−

( )

tanπ

β2

2

2 (3.9)

Equation (3.9) determines winding speed during build up of a bi-conical package. Pattern zones can be skipped using principle of ribbon free random wind discussed in above section “Principle of Ribbon Free Random Wind”.

T = 2Ld

b

bπ ϕtan

\T ∞ Ld

b

b (Traverse ratio is proportional to ratio of ‘Lb’ and ‘db’)

3.6.2.2 Precision winding with spindle drive with reciprocating element involved in traversing mechanism

For precision winding, traverse ratio ‘T’ is selected by the user which should

remain constant. During time ‘1F ’ minutes (minutes per double traverse),

package should make ‘T’ revolutions, i.e. motor A should make ‘T’ revolutions.

In time 1F minutes motor A makes ‘T’ rotations

Therefore in 1 minute, motor A makes ‘TF’ rotations.

\ N TF i e F NT

T NF

= = =, . . ,

Vw = ( )surface speed) + (traverse speed2 2

= ( ) ( ) ( ) ( )π πdN LF dN LNT

2 2 2 22 2+ = +

\ Vw = N d LT

( ) ( )π 2 22+ (3.10)


As package builds up, ‘d’ keeps on increasing. With constant ‘N’, ‘Vw’ would keep on increasing.

To maintain constant winding speed, ‘N’ should be varied using Eq. (3.11).

Now, N = V

d LT

w

( ) ( )π 2 22+

(3.11)

Now, N = TF

\ TF = V

d LT

w

( ) ( )π 2 22+

\ F = V

T d LT

w

( ) ( )π 2 22+

\ F = V

dT Lw

( )π 2 22+ ( )

With constant ‘Vw’ and ‘L’, traverse frequency decreases with increase in package diameter. Traverse speed = 2LF Surface speed = pdN

\ tan f = traverse speedsurface speed

= =2 2LFdN

LdTπ π

( )FN T=

1

Thus, tan f = traverse speedsurface speed

= =2 2LFdN

LdTπ π

(3.12)

As ‘L’ and ‘T’ are constant, coil angle decreases with increase in package diameter. Equation 3.12 is the basic equation for a cylindrical cross wound package.

Building a precision wound bi-conical packageDuring build up of a bi-conical package, traverse length decreases with increase in package diameter. From Eq. (3.10),

\ Vw = N d LT

( ) ( )π 2 22+

Substituting values of diameter during package build up and traverse length (from Eq. 3.8) for a bi-conical package,


Vw = N dL d d

T( )

(tan

)π β

b

eb e

2

2

+−

−

Vw = ( ) ( )πd N L Fbb b2 22+

= ( )tan

πβ

d N F L d db b e

b e22

2+ −−

Similarly, tantan

, . . tantan

φβ

πφ

β=

−−

=−

−

−2 2

1L d d

d Ti e

L d de

b e

b

eb e

πd Tb

(3.13) Equation (3.13) gives coil angle at any diameter during build up of a precision wound bi-conical cylindrical package. Reduction in traverse length also causes reduction in coil angle which would reduce gain.

3.6.2.3 Step-precision winding with spindle drive with reciprocating element involved in traversing mechanism

In step-precision winding, the user chooses the coil angle and winding speed at which the package is wound. Winding system manufacturer usually determines the angle within which the coil angle deviates. Let this angle be ‘a’. At bare package diameter ‘d1’, the desired initial coil angle is ‘f’. Atstart,tofindtraverseratio‘T1’ that would give coil angle ‘f’,firstlyanapproximate traverse ratio ‘T1A’ is to be found using equation

T1A = 2

1

Ldπ ϕtan

‘T1A’ may not be a satisfactory traverse ratio for package build up. Therefore, actual traverse ratio ‘T1’ that is to be taken should be the closest odd traverse ratio that would give satisfactory winding. Thus at bare package diameter ‘d1’, winding should be begun in precision mode with traverse ratio ‘T1’.

\ Vw = N d LT

( ) ( )π 12

1

22+


\ N = V

d LT

w

( ) ( )π 12

1

22+

(3.14)

Equation (3.14) gives initial spindle motor rpm. As the package diameter increases beyond ‘d1’ on package build up, spindle rpm should be reduced to maintain constant winding speed, which is also given by substituting instantaneous value of package diameter in Eq. (3.14). Corresponding values of traverse frequencies can be determined using equation

F = NT1

Using these winding conditions, package from bare package diameter ‘d1’ should be wound with constant traverse ratio ‘T1’, till package reaches diameter ‘d2’ when coil angle reduces to (f – a).

d2 = 2

1

LTπ φ αtan( )−

At diameter ‘d2’, there should be instantaneous transition to a lower traverse ratio ‘T2’ so that coil angle is restored back to ‘f’. First, an approximate traverse ratio ‘T2A’ should be determined from equation

T Ld2

2

2A =

π φtan, Substituting d2 =

2

1

LTπ φ αtan( )−

,

T2A = T1 tan( )tanφ αφ−

Actual traverse ratio ‘T2’ that is to be taken should be the closest odd traverse ratio to ‘T2A’ that would give satisfactory winding. To switch over to this new traverse ratio, corresponding value of spindle rpm ‘N’ is

\ N = V

d LT

w

( ) ( )π 22

2

22+

Substituting this value of ‘N’, corresponding traverse frequency can be

determined with equation F NT

=2

.

Similarly, beyond diameter ‘d2’, winding would be carried out with constant traverse ratio ‘T2’ till diameter ‘d3’ is reached when coil angle again drops to (f – a) and so on till desired diameter is reached.


3.6.3 Winding systems with surface driveVariouspossibleflexiblewinding systemswith surfacedrive are shown inFig. 3.19. Figure 3.19(a) shows a system with grooved cam traverse. Figure 3.19(b) shows a system having traverse system in which a yarn traversing guide mounted on a belt/wire, moved to and from by a servomotor traverses yarn. System shown in Fig. 3.19(c) is with a traversing lever having a fork at top through which yarn passes. Traversing lever is given angular movement by a motor to traverse yarn. The commercial systems usually employ system to sense package rpm instead of that of drum. Drum motor speed regulation regulates package speed via drum. Basic equations related to winding are principally similar to those discussed with direct drive systems and therefore are not discussed.

Figure 3.19 Surface driven flexible winding systems

AppendixA.3.1 Surface speedThe amount of surface movement (with respect to a reference point) per unit time is called surface speed. For a cylindrical roller of diameter ‘d’, its circumference would be ‘pd’. If this roller is rotated by one revolution, its surface movement equals to its circumference. In one revolution of wheel of bicycle, bicycle moves forward equal to circumference of its wheel. Let a cylinder rotate at ‘N’ rpm (i.e. in one minute it makes ‘N’ rotations). In 1 rotation its surface movement equals ‘pd’. Therefore in ‘N’ rotations, its surface movement becomes ‘pdN’ meters/min, if ‘d’ is in meters (Fig. A.3.1).

A.3.1.1 Surface speed in case of surface driveSurface speed of a cylindrical drum of diameter ‘D’ rotating at ‘N’ rpm is ‘pDN’ (Fig. A.3.2). The drum drives a package of diameter ‘d’. The surfaces


Figure A.3.1 Surface speed

of drum and package are in contact with each other and there exists a frictional force between the surfaces of drum and package in contact with each other. As the drum is rotated, the surface of the drum drags the surface of package; hence, package also rotates. If attention is focused at point of contact between the drum and package, it can be appreciated that the surface movement of drum and that of the package remains the same (assuming no slippage between the two surfaces). If drum rotates by one rotation then its surface movement equal to its circumference ‘pD’. So, surface movement package would also be ‘pD’. This can also be understood the other way. Let drum circumference be 100 cm. There are packages of different circumference 10 cm, 25 cm, 50 cm and 100 cm. Package of circumference 10 cm package would make 10 rotations in one rotation of the drum. Therefore surface movement of package per drum rotation would be 10 times its circumference i.e. (10 × 10) cm = 100 cm.

Figure A.3.2 Surface speed in case of surface drive


Similarly with package circumference of 25 cm, 50 cm and 100 cm, package rotation per drum rotation would be 4, 2 and 1, respectively, and therefore corresponding package surface movements would be 100 cm for each package (25 × 4 = 50 × 2 = 100 × 1 = 100). Thus, surface movement of package per drum revolution remains constant irrespective of package diameter; and therefore surface speed of the package is same as that of the drum irrespective of package diameter.

A.3.2 Winding speed in case of parallel windingLet a package of diameter ‘d’ be rotating at ‘N’ rpm (Fig. A.3.3a). Package circumference is pD. Let the package be rotated by one revolution and yarn be wound. One coil will be wound. The length of this coil very nearly equals to circumference of the package = pD, and the surface movement of package also equals to ‘pD’ in one rotation. Thus amount of surface movement of package and length of yarn wound will be same in case of parallel winding.Winding speed is equal to surface speed of the package for parallel winding.

Figure A.3.3 Winding speed for parallel winding and generation of helix

Figure A.3.4 Winding speed determination


A.3.3 Winding speed in case of cross windingA roll of paper has diameter ‘d’ (Fig. A.3.3b). It is rotated at uniform speed and simultaneously a pen is moved in a straight line at uniform speed parallel to the roll axis touching the paper. In one rotation of paper roll, let ‘L’ be the displacement of pen. This will generate a helix on paper that completes one turn. Now cut the roll of sheet along line of movement of pen (Fig. A.3.4a). On unfolding, the paper roll becomes rectangular in shape. The line of helix becomesdiagonal‘AD’ofarectangleABCD.AC=BD=πd(circumference)and AB = CD = L (movement of pen). The length of diagonal (i.e. length of

spiral), AD = (AB) + (AC)2 2 = ( ) ( )πd L2 2+ The laying of yarn on the package takes place in the similar manner. If a cylindrical package of diameter ‘d’ is taken and yarn is wound on it by traversing at uniform speed through displacement ‘L’ per rotation of the package (Fig. A.3.4b), then the yarn will also follow a spiral path.

Length of yarn wound per revolution of package becomes ( ) ( )πd L2 2+ , where ‘d’ is package diameter and ‘L’ is length of traverse in one rotation of package. If package rotates at ‘N’ rpm, winding speed becomes

( ) ( )πdN LN2 2+ meters/ minute if ‘d’ and ‘L’ are in meters. But, ‘pdN’ is package surface speed in meters/ minute and ‘LN’ is traverse speed in meters minute. Therefore, winding speed = ( )Packagesurfacespeed) + (Traversespeed2 2

From Fig. A.3.4, tanφπ

=Ld

Multiplying and dividing by N, i.e. package rpm, tanφπ

=LNdN

But ‘pdN’ is surface speed and ‘LN’ is traverse speed and therefore,

tan Traverse speedSurface speed

φ =

It is essential to build a winding package that suits the best requirements of its subsequent end use. Parameters opted in building a package on a winding machine influence its performance. This chapter discusses various parameters associated with a winding package and criteria for their optimization.

4.1 Winding system at various stages of yarn processing / production

Broadly, yarn winding is a process in which delivered yarn(s) is/are wound on a package. Yarn winding system finds its presence at various stages of yarn processing/production. The main objective of a machine with yarn winding system may be yarn winding. For example, the winding machine that winds yarn from ring frame bobbins onto bigger packages is mainly intended for yarn winding. Yarn winding system is one of the elements in some machines whose main purpose is not solely yarn winding. For example, winding system provided on an unconventional spinning machine or a take-up winder of a synthetic yarn production line winds the yarn that is spun. Winding system provided on a yarn singeing machine winds yarn from which protruding fibers are burnt away by passing it through a flame at high speed. Thus, main purpose of a singeing machine is processing yarn in terms of burning away of protruding fibers. Similarly, winding system on a texturising machine winds textured yarn whereas single-end sizing machine winds sized single end. Rewinding machines simply transfer yarn from one package to the other. A dye package rewinding machine winds yarn supplied from soft-dyed packages which are not suitable for high speed unwinding to form a stable package. An assembly winder assembles yarns from two or more packages to wind them onto a single package. A filter winder winds materials like yarn or roving onto filter packages. Thus, phenomenon of yarn winding finds its presence at various stages of production in textile industry.

4Winding package parameters

Winding package parameters 67

Examples of some machines with yarn winding as the main purpose are as follows: • Yarn winding machine in spinning or weaving mill that winds yarn

from ring frame bobbins onto bigger packages. • Rewinding machines used to rewind soft dyed packages, leftover

packages from warping machine creel. etc. • Filter winders used to wind yarn or roving on perforated tubes. Examples of some machines provided with yarn winding system to wind spun/modified/finished yarn are as follows: • Yarn singeing machine that burns protruding fibers from a spun yarn • Yarn texturising machine imparts bulk to yarn • Single-end yarn sizing machine in which a yarn is singly sized • Take-up winding system of a synthetic yarn production line winds

yarn spun through spinneret • Unconventional spinning machines like open-end spinning • Sewing thread finish winding machine where yarn is applied with a

lubricant and wound on package forms which can be sold as sewing thread packages

• Assembly winder assembles two or more yarns together and winds onto a winding package. This assembled package subsequently becomes a supply package on a TFO twister where assembled yarn is twisted to produce a ply or a cable yarn.

Figure 4.1(a) and (b) shows a dye package winding/rewinding machine and a yarn singeing machine, respectively. Figure 4.2 shows some winding

Figure 4.1 (a) Dye package winder; (b) Yarn singeing machine

(Courtesy: SSM AG)


machines with various elements. Figure 4.2(a) shows a grooved drum winding/rewinding machine. Figure 4.2(b) shows a precision winding machine with grooved cam traverse. Figure 4.2(c) shows a hank to cone grooved drum winder with supply package as a dyed hank. Figure 4.2(d) shows a precision soft package winder.

Figure 4.2 Various winding machines (Courtesy: Peass Industrial Engineers Pvt. Ltd.)


4.2 Main parameters related with a winding packagePackages produced on winding machine/machine with winding system are put to various end uses. A winding package should be built with suitable parameters so as to satisfy its end-use requirements. Main parameters related to a winding package are the following: • Cone taper • Bare package length and diameter • Bare package material and its construction • Coil angle • Gradual coil angle variation • Traverse ratio • Mode of winding, i.e. random, precision or step-precision winding • For random and step-precision winding, it is required to select suitable

coil angle. • For precision winding suitable traverse ratio is to be selected. • Traverse length variation – For prevention of formation of hard

edges at package side faces, traverse length of successive traverses is changed so as to stagger reversal points.

For building packages such as bi-conical packages or pineapple cones, traverse length is shortened with buildup of the package.

Traverse length may be decreased, especially towards full package so as to form packages with rounded edges.

In some cases traverse length may not be varied during package build but packages with reduced shorter lengths are produced. For example, 6” traverse length may be reduced to 4” over the entire package.

• Traverse position variation – For some packages such as king spools traverse length may remain same throughout package build but its position relative to winding package may be varied.

• Traverse acceleration – A cone may be built with half accelerated traverse for uniform cone build up or with fully accelerated traverse to build a cone with increasing taper.

• Dynamic traverse acceleration. • Selection between ‘p’ and ‘q’ wind – Winding packages on a winding

machine may be wound with ‘p’ wind or ‘q’ wind. • Building package with varying yarn winding tension and/ or pressure

between package and support roll/ drum/ press roll. Parameters such as winding tension, pressure between winding

package and drum/press roll also influence package properties. Some winding systems allow manipulation of winding tension and or pressure between winding package and drum/press roll/support roll which also influences winding package built up.


• Package density • Yarn length on full package/full package diameter During winding yarn may be applied with wax, some finishes like anti-static oil, lubricant, etc., depending upon end-use requirements. Knitting yarns are waxed. Some filament yarns are applied with anti-static oil. Sewing threads are applied with lubricant. Smart package appearance is also a requirement for end-use application like sewing thread.

4.3 Various end uses of wound packagesWound packages are subjected to various end uses. Expected performance of a wound package depends upon its end use. Various end uses of wound packages are the following: • Warping – During warping yarn is unwound continuously at high

speed. Yarn should unwind from entire package with minimum breakages and tension fluctuations. Figure 4.3 shows a warping creel.

• Pirn winding – During pirn winding, unwinding is continuous at lower speeds. Yarn should unwind from entire package with minimum breakages and tension fluctuations.

• Weft supply package on a shuttleless weaving machine – During shuttleless weaving, yarn may be unwound intermittently at high speed from a weft supply package. Yarn should unwind from entire package with minimum breakages and tension fluctuations.

• Dyeing – Winding package intended for yarn dyeing should be open that allows uniform dyeing across entire package. Uniformity of dye uptake is the prime requirement of a dye package. Figure 4.4 shows a column of packages being prepared for package dyeing.

• Knitting – Unwinding speeds in knitting are lower. Withdrawal with ease is the main requirement from the winding package meant for knitting.

• TFO twisting – Unwinding speeds are lower during TFO twisting. To minimize downtime of doffing, TFO feed packages should occupy maximum possible volume of pot and should be compact.

• Rewinding – Dye packages are soft wound and not usually suitable for unwinding in subsequent processes. These packages are subjected to rewinding mainly to build stable packages suitable for subsequent processes. Such winding is called rewinding as the yarn already subjected to winding once is rewound. Left over yarn on packages from warping creel is also rewound to utilize yarn.

• Sewing/embroidery – Unwinding speeds are lower during sewing. A sewing package should ensure the best seam performance. Accommodating maximum yarn in a given volume is usually prime consideration for a sewing/embroidery thread package. A smart and attractive package appearance is also desired.


• Filter cartridge package – Layers of yarn/roving wound on a filter package serve as a filter media. Efficient filtration becomes prime consideration while building a filter package.

4.4 Yarns with diverse properties subjected to winding

Yarns with diverse mechanical properties are subjected to winding. Yarns vary with regard to their linear densities as well as other properties such as frictional property, elasticity, yarn structure, rigidity, hairiness, etc. Various types of yarns are monofilament yarn, multifilament yarn, textured yarn, spun yarn, cotton yarn, silk yarn, jute yarn, woollen yarn, worsted yarn, glass yarn, carbon fiber yarn, stainless steel yarn, ring spun yarn, compact yarns, rotor spun yarn, air jet spun yarn, DREF yarn, fancy yarn, single yarn, ply yarn, cable yarn, etc. In some cases roving or braid are also subjected to winding. Yarn fineness, type and its properties also play decisive role in determining winding package parameters.

4.5 Winding package parameters and criteria of their selection according to end-use requirements for a given yarn

4.5.1 Cone taperIt is desired from a winding package that breakages in its end-use application should be minimum. There are two major reasons for yarn breakages during

Figure 4.3 Packages on a warping creel (Courtesy: Ashima)

Figure 4.4 Columns of packages being prepared for package dyeing

(Courtesy: Ashima)


unwinding from a package – tension peaks and slough off. Tension peaks would be generated during unwinding from a package due to lack of freedom for yarn to leave the package. Slough off occurs when several coils on the package come out instantaneously. The steeper the cone taper the greater the freedom of withdrawal and therefore reduced tension peaks. However, chances of slough off increases with increasing cone taper. With higher cone taper, during yarn unwinding, yarn leaving the package contacts package surface only at one point which is advantageous as described later in section 4.5.8. Chances of slough off are also dependent on withdrawal speeds. For a given package, slough off chances tend to increase with increased withdrawal speeds. Steeper cone tapers offer some disadvantages. Initial layers are not securely wound on the bare package. In this case the surface finish of the bare package becomes very important. Only securely wound initial layers give firm base for building up of the remainder of the package, and also gives a trouble-free change over from emptying package to new package in case of magazine creels (creels in which end of running package is tied with starting yarn of waiting package). With a smooth surface of bare package, last layers of the running package tend to slough off which can lead to breakage during transfer as shown in Fig. 4.5(a). Higher cone taper tends to make package fragile (layers may slip) and hence package transportation can become problematic. Due to conicity, winding rate on the package keeps on fluctuating; it is higher towards base than nose. This introduces error in measuring fault length in case of electronic yarn clearing as length is taken from pulse measurement from drum that drives the package. Shorter fault length will be recorded than actual at base and the longer at nose. In knitting the yarn speed is low and uniform; hence, sloughing off is not a problem and maximum consideration can be given to the reduction in tension by increasing freedom of withdrawal by opting for greater cone taper. In olden days 9° 15’ cones were widely used for knitting of spun yarns. Switch over to 5° 57’ cones took place due to disadvantages associated with steeper cones. With weft supply packages for shuttleless weaving, withdrawal of yarn is intermittent, abrupt and at high speed. An optimum taper which leads to minimum stoppages should be opted. Figure 4.5(b) shows a hypothetical curve illustrating determination of optimum cone taper for a weft supply packages for shuttleless weaving. Curves ‘A’ and ‘B’ in Fig. 4.4(b) shows stops due to slough off and tension peaks, respectively. Stops due to slough off would be least with 0° cone taper and would keep on increasing with increased cone taper whereas stops due to tension peaks would be highest with 0° cone taper and would keep on decreasing with increasing cone taper. Curve ‘C’ shows


total stops, which is the sum of stops due to slough off and tension peaks. Best cone taper would be one that gives least stoppages. In this hypothetical curve it lies between 2° and 3°. Same logic holds to determine optimum cone taper for every application, e.g. warping. A cylindrical feed package for TFO twisting for spun staple yarns is preferred to occupy optimum volume of TFO pot. Cylindrical packages are the optimum packages for package dyeing. With conical packages an optimum packing of dye vessel cannot be achieved as some space of remains unoccupied. With conical packages dye flow is not uniform across the package as shown in Fig. 4.5 (c) for a typical case for 5 inches traverse 4° 20’ cone. Cylindrical packages can offer even resistance to flow of dye liquor along package axis, and therefore allow uniform flow of dye liquor over the entire package giving better dye uniformity. Cylindrical packages can give straight and parallel side faces to ensure an optimum sealing between the packages to avoid any by-passing of the dye stuff. Yarn/roving wound filter packages are also cylindrical as flow of liquid to be filtered would flow uniformly over the entire length of the package.

4.5.2 Package length and diameterFor optimum continuity of yarn supply in the processes subsequent to winding, the longer package with the greater diameter would undoubtedly serve the turn. Along with optimum continuity in subsequent process, it is also necessary to take into account unwinding behavior of the package under unwinding conditions in the subsequent process. For example, yarn tension tests made on a 38 tex cotton yarn withdrawn intermittently at a speed encountered in a weaving machine, and employing cone tapers of 0° and 5°57’ and package diameters of 50, 130 and 230 mm, together with a yarn traverse of 76 and 152 mm, revealed that cylindrical package with shorter traverse and larger diameter gives lower tension picks. With conical package of 5°57’ with

Figure 4.5 Cone as a package


152 mm traverse length and 130 mm diameter gave lower tension peaks than those at smaller or larger diameters. As package diameters decrease, these tension peaks are said to increase in both frequency and magnitude, so that some shuttleless weaving machine manufacturers recommend large cores for filling packages, tube cores of 105 mm diameter and 5°57’cone cores of 90 mm diameter. Uniform flow of dye liquor across the entire package and thereby achieving uniform dyeing would be the main criterion for determining optimum dimensions of a dye package. A sewing thread package for domestic use requires smaller quantity of yarn content and therefore it is with smaller dimensions, whereas the same for a garment industry would be bigger for optimum continuity. Winding mode also influences package dimensions. Figure 4.6 is a graph of traverse ratio v/s package diameter for random winding for 152 mm traverse, 10° coil angle. The graph shows the package diameters at which traverse ratio become whole number, i.e. severe patterning occurs. It can be observed that starting with a smaller bare package diameter, patterning would occur frequently. Therefore, it is advantageous to take a larger bare package diameter with random winding to reduce occurrence of pattern formation. In precision winding coil angle reduces with increasing package diameter. Hence, it is advisable to build precision wound package only up to certain maximum diameter till it remains a stable package. Generally package exceeding traverse length becomes problematic. Beyond this diameter, package becomes fragile due to extent of coil angle reduction. Thus, in precision winding, reduction in coil angle imposes limitations on full package diameter.

Figure 4.6 Consideration for bare package diameter for random winding


4.5.3 Bare package material and its constructionThe packages for winding are made from various materials such as paper, impregnated compressed paper (impregnated with oil or synthetic resin), plastics, wood, metal, etc. It is essential to use appropriate bare package taking in to consideration factors like type of yarn to be wound and its linear density, subsequent process, winding speeds, etc. High machine speeds, such as take-up winders, impose stringent requirements on the strength, concentricity, surface properties and dimensional tolerances. Packages made from paper are non-returnable, i.e. the consumer of the subsequent end use does not return it back to winder for reuse. The reusable packages have to be strong enough to withstand various stresses during winding as well as material handling. The packages used in the man-made fiber industry have to withstand relatively heavy duty as extremely high speeds are used and the yarn pressure imposed by shrinkage is extremely high. Packages for finer yarns as well as filament yarn must be smooth enough to prevent yarn or filament adhering to package surface at the same time sufficiently rough to avoid slough-off of the first wound layers. Packages which are subjected to heat treatment under conditions of pressure and humidity have to be dimensionally stable during processing. Plastic packages offer advantages like – • Convenience in producing packages in different colors for the

identification of the lot • Very narrow tolerances of mass and weight • Sealed pore-free surface • Good recovery from deformation • Non-damaging to the friction elements for the package drive • Relatively good chemical resistance • Low sensitivity to damp and other climatic influences The surfaces of packages made from paper may be smooth, sand papered, embossed, flocked or knurled to modify its surface. Embossing is used for coarse and lively yarns. This surface provides extra resistance to slippage. However, fine embossing surface is provided for medium counts and for the threads where bold embossing hinders unwinding. This surface holds wound yarn coils, yet permits free delivery to knitting or sewing machines. Velvet finish is ideal for cotton yarns and prevents damage to delicate filament yarns. Flocked surface is found suitable for winding rayon, nylon and other low-twist filament yarns. Flocked finish may be applied on entire package surface or may be provided at critical areas. The extent of flocking can be controlled according to the twist, denier and number


of filaments. This surface also provides barrier to minimize absorption of coning oil by the paper. Dyeing packages are made from plastics, aluminum alloys and stainless steel. Amongst plastic materials, polypropylene is particularly suitable as it meets the requirement of heat and pressure resistance. Dye packages are perforated to allow flow of dye liquor. However, for better dye uniformity, dye springs (Fig. 4.7b) and flexible dye tubes are developed as these packages permit maximum permeability of dye liquor. Dye packages on dye springs are wound with lower densities. Dye package column is pressed axially that may smoothen axial irregularities. Pressing increases density that increases utilization of dye equipment. However, disadvantages like difficulty in handling of soft packages with spring tubes, change in density with flow reversal, density variations due to inaccuracy in pressing, increased yarn hairiness due to displaced yarn layers, poor unwinding behavior after dyeing, etc., are associated with pressing. Moreover, pressing becomes an additional process after winding. King spools (Fig. 4.7b) are special packages with a conical base and top cylindrical portion with a slight taper which are used mainly for sewing and embroidery packages. Due to its broader base it can be conveniently placed in erect position. As yarn reversal points do not lie in same vertical plane, hard edges formation is reduced. Tapered portion at package tip helps in imparting stability to the package even with slippery yarns wound at smaller coil angles. King spools are also called Y cones or vi-cones.

4.5.4 Mode of winding The choice among three modes of winding, i.e. random, precision and step-precision winding for a particular end use should be made looking at their merits and demerits.

Figure 4.7 (a) Winding on a dye spring [Courtesy: Ashima]; (b) A king spool


Random winding offers lower winding machine costs but suffer from problem of patterning. Pattern zones lead to uneven package density and breakages during unwinding. Random winders with grooved drum winding give cylindrical packages with convex faces which are undesirable for certain end uses. Density of the random wound packages is usually approximately 20 –25% lower than precision wound packages. Thus, roughly 20–25% less weight (and length) is obtained on random wound packages as compared to precision wound packages. Cost of a precision winding system would be generally higher than a random winding system. In precision winding, package properties can be flexibly altered through selection of a suitable traverse ratio. Highest package densities are achievable in precision winding through close traverse ratios. Decreasing coil angle with increasing package diameter is the main draw back associated with precision winding. Decreasing coil angle leads to increasing package density from bare to full package. Decreasing coil angle limits upper diameter of a built package. ‘Concave’ kind of side flanks of precision wound cylindrical packages are not desirable for certain end-use applications like dyeing. Cost of step-precision winding system would be the highest among all. Achievable maximum package density through step-precision winding is higher than random winding but lower than precision winding. Step-precision wound package is free from patterning with almost constant coil angle and therefore gives cylindrical packages with parallel side faces. Pattern zones in random wound packages lead to unwinding problems for end-use applications like warping, pirn winding and weft supply package on a shuttleless loom; whereas in dye packages they cause uneven dyeing. From dyeing point of view, a step-precision wound package is the best choice as it is free from patterning with almost constant coil angle. By selecting open traverse ratios, a package suitable for dyeing can be obtained in precision winding, but variations in package density due to coil angle variation is an obvious disadvantage. As parallel package faces are not achieved on grooved drum winders as well as and precision winders, uniform column density of package column in dyeing machine cannot be achieved which can lead to uneven dyeing. Step-precision wound packages with parallel side faces are advantageous from this point of view also. Filter packages are mostly precision wound. Desired filtration performance of a filter package can be achieved mainly by manipulating traverse ratio. A compact assembly wound TFO feed package reduces frequency of doffing and increases productivity; and therefore random wound packages are not preferable from this point of view as a compact package can not be achieved. Precision winding proves


to be a better choice. During TFO twisting, flyer rotational speed is different while unwinding from top to bottom and bottom to top. This leads to tension fluctuations. This difference widens with increase in coil angle. Due to coil angle variation in a precision wound package, this difference is the lowest at full package and the highest near bare package; and therefore, fluctuations in tension varies from full to empty package. From this point of view random wound and step-precision wound packages are advantageous due to uniformity in coil angle. For sewing thread, embroidery and like applications, a compact package reduces volume of a package and offers advantages like reduced transportation costs, reduced space requirement for storage, etc. For these applications precision winding is preferred. Figure 4.8 shows a sewing thread finish winder. Precision winding can give smart and attractive appearance to packages.

4.5.5 Coil angleOptimum coil angle is to be selected with random and step-precision winding. In precision winding coil angle reduces with increasing package build up.

Figure 4.8 Sewing threads finish winder (Courtesy: SSM AG)


Selected traverse ratio determines range of variation of coil angle from empty to full package. Coil angle influences various package characteristics like package density, ease of unwinding (and thereby occurrence of tension peaks), chances of slough off, saddle formation at the sides, etc. In general, lower coil angle leads to higher package density, less ease of withdrawal (and therefore increased chances of tension peaks) and decreased tendency of slough off. Therefore, lower coil angles lead to greater stability of the package with reduced chances of slough off but increases chances of occurrence of tension peaks, whereas higher coil angles lead to increased chances of slough off but reduced occurrence of tension peaks. Lower coil angles result in to greater package compactness and thereby increased package density, whereas higher coil angles decrease package compactness and thereby decreased package densities. It must be kept in mind that one cannot reduce the coil angle to an extent that will sacrifice the firm, self-supporting characteristics of the cross-wound package when wound is at high tension and pressure. Coil angle also influences extent of hard edge formation. Intense hard edge formation would take place if a coarse yarn is wound with very low coil angle. This would lead to saddling at sides that may adversely affect package unwinding properties. Moreover, problems may arise in transportation of package. Ideally, depending upon priorities of an end-use application, coil angle should be optimized for given yarn. With most low-speed applications, coil angle is not critical but knitting cones are an exception. Low unwinding speeds during knitting do not form a prominent balloon leading to increased chances of yarn dragging with cone surface. Therefore, knitting cones should be wound with relatively higher coil angle to reduce dragging of yarn with cone surface and increase ease of withdrawal. Dyeing packages should be wound with relatively higher coil angles to form an open package with reduced density required for dyeing. Assembly wound TFO feed packages could be wound with relatively lower coil angles to achieve a compact package to reduce frequency of doffing. Moreover, difference between flyer rotational speed while unwinding from top to bottom and vice versa reduces with reduced coil angles; and therefore tension fluctuations occurring due to it are minimized. Figure 4.9 shows an assembly winding machine to produce TFO feed packages. Packages for high speed warping as well as weft supply on shuttleless looms wound with relatively lesser coil angle offers advantage of reduced frequency of sloughing off. In grooved drum winding, coil angle for given traverse length depends upon number of turns on the drum of a given diameter. For a drum with given diameter and traverse length, coil angle reduces with increase in number of


turns. For given turns on the drum and traverse length, smaller drum diameter leads to higher coil angle. [For a drum for cylindrical package, coil angle

= tan−1 traverse length(drum diameter) (drum turns)π

]

In order to switch over to an appropriate coil angle, it becomes necessary to replace the grooved drum which is time consuming and also demands an inventory of large number of drums. On Oerlikon Schlafhorst PreciFX winding system with drum-less traverse required number of turns (mean pitch) and thereby coil angle is to be input by the user on “informator” (computer) of the machine. Range of number of turns that can be input is from 1 to 4 with an increment of 0.1. Thus, user can select optimum coil angle from a wide range offered. SSM step-precision soft dye package winding systems permit coil angle selection between 10° to 18°.

4.5.6 Coil angle variationSome flexible winding systems with programmable individual drive to package and traverse mechanisms like Barmag take-up winding system facilitate gradual transition from one coil angle to the other during built of package from one diameter to the other to improve package build.

Figure 4.9 Assembly winding machine (Courtesy: SSM AG)


4.5.6.1 Coil angle variation to prevent overthrown endsOn Barmag take-up winders with counter rotating blade traverse system, traverse stroke remains the same through out packager build. Initial effective traverse on the bare package tends to be lesser than the traverse given by traverse system, as yarn coils at the extremes tend to shift towards package centre. Therefore, situation arises where least-effective traverse is obtained on bare package which keep on widening as package builds up. This leads to the problem of overthrown ends at initial stage of package formation. To prevent this, CBC (Core Bicone) winding system is provided on Barmag take-up winding system. In CBC winding system, winding begins on a bare package at lesser coil angle which keeps on gradually increasing the initial stage of package formation. As shown in Fig. 4.10(a), at bare package diameter ‘d1’ winding is initiated with coil angle ‘Ø1’ which gradually decreases to ‘Ø2’ at diameter d2. Therefore, highest effective traverse length is obtained at bare package which keeps on reducing during initial package build up leading to formation of a bi-conical core. This formation prevents overthrown ends. This system is suitable for very critical conditions, e.g. fine deniers and fine dpf, deep-matte yarns, slick spin finishes, etc. This winding can be combined with the random wind, ribbon-free random wind and step-precision winding systems.

Figure 4.10 Barmag CBC and Helicont systems

4.5.6.2 Coil angle variation to build a stable packageHelicont feature of Barmag take-up winding systems provides a feature of building a stable package with good unwinding properties through changing coil angle. The user has to input values of required coil angles at any desired eight package diameters. Referring Fig. 4.10(b), initially starting from a bare package diameter at lower coil angle, the coil angle gradually increases [point 1 in Fig. 4.10(b)] with an aim to build a bi-conical package at start to prevent over-thrown ends and widen the operating window. Thereafter, package


builds with a constant coil angle. During further build, the coil angle is made to gradually decrease. Decreasing coil angle increases hold of the yarn on the package which avoids slippage of layers. An inadequate hold of yarn can lead to layer slippage especially during handling. Figure 4.10(c) shows a polyester POY package with layer slippage.

4.5.7 Traverse ratioIn precision winding desired package characteristics can be achieved mainly through selection of an optimum traverse ratio. In close precision winding traverse ratios, selection of gain giving spacing of 1 to 1.5 times diameter of yarn between successive coils laid after pattern repeat results into a compact package. Open precision traverse ratio (in which gain gives spacing of substantially more than the diameter of yarn) results into an open package with reduced density. For end-use applications like sewing threads, embroidery yarns and TFO twisting, close precision winding is used. Close precision winding traverse ratio depends upon yarn diameter, and therefore they have to be selected according of yarn diameter. Suitable close winding traverse ratio is dependent on yarn linear density. An open precision winding traverse ratio can be used for a range of yarn counts. Some typical recommended traverse ratios for dyeing cones are 4.434, 4.422, 4.631, etc. For assembly winding it is recommended to use close precision winding with head wind. For weaving mill/ knitting, open precision winding in after-wind version is recommended. For filter packages, desired filter characteristics can be manipulated by using optimum traverse ratio. Filter packages are wound with close- as well open-traverse ratios to achieve desired performance from the filter cartridge. In case of step-precision winding, if all stepwise changing traverse ratios are open traverse ratios; an open package would be formed. On the contrary if they are close winding traverse ratios, a compact package would be formed. For an end-use application like package dyeing, it would be appropriate to opt for open winding traverse ratios, whereas for TFO feed packages it would be appropriate to use close winding traverse ratios.

4.5.8 Traverse length variation

4.5.8.1 Traverse length variation for hard edge preventionDuring cross winding, it is practically difficult to achieve sharp yarn reversal. Therefore, at reversal points, some portion of yarn is wound with 0° coil angle


due to which package density increases at package extremes and its edges tend to be hard. Hard edges are not desirable as they would adversely affect uniformity of yarn dyeing and increased abrasion between package edges and drum/ press roll/ support roll of winding machine. With coarser yarns and high stretch/elastic yarns, hard edges lead to bulging of package at side faces. To minimize hard edges formation, quick yarn reversal at traverse extremes is desirable. Moreover, yarn guide and yarn laying point on package should be located as close as possible. Hard edges can be prevented by scattering reversal points at the extreme. With grooved drum traverse, either drum or package cradle is given few millimeters (e.g. between 1 and 8 mm) continuous to and fro motion along axis parallel to drum to scatter reversal points as shown in Fig. 4.11(A). With a separate guide traverse, traverse stroke of a guide is continuously varied by few millimeters due to which traverse guide does not every time reverse from the same point as shown in Fig. 4.11(B). Winding machines with programmable traverse variation offer greater flexibility in hard edge prevention. On SSM winding machines the user has to input three values related to hard edge prevention. Maximum possible staggering of reversal points is over a width of 25 mm whose % input determines width over which reversal points are scattered. For example an input of traverse variation of 40 % scatters reversal points over a width of 10 mm (40% of 25 mm) as shown in Fig. 4.13(a). Second input is of traverse variation cycle time in minutes that determines time cycle for completion of a traverse variation cycle. Traverse variation cycle consists of 36 reversal point locations within scattering width which the user can customize. Some fixed traverse variation cycles are also available for the user to select. Staggering of reversal points should be optimum. Excessive staggering may lead to packages with soft edges which are prone to both overthrown ends and physical damage.

4.5.8.2 Production of bi-conical packages through traverse length variation

Filament yarns are usually slippery. Cylindrical cross wound packages with filament yarns may lack stability and yarn may collapse at edges. This problem can be solved by gradually reducing the traverse length with increase in diameter of the package. This traverse length reduction forms packages with tapered side faces. Such cylindrical cross wound packages are called bi-conical packages. Pineapple cones are the cones produced with progressive traverse length reduction. With the faster rate of traverse length reduction,


flatter side faces are developed and vice versa. Machines are usually provided with arrangement of adjusting steepness of side faces. Figure 4.11(C) shows a bi-conical cylindrical package. The conicity of side faces is to be adjusted to achieve a stable package. Volume of yarn content in a bi-conical package would obviously be lesser than that of a cylindrical package obtained without traverse length reduction for same full package diameter. Bi-conical packages are advantageous as reversal points are prevented from lying in same plane which helps in minimizing hard edges formation and thereby serious package bulging problem associated with some yarns. Figure 4.12 shows a winding machine for filament yarns producing bi-conical packages. Automatic winding machines with grooved drum traverse do not permit production of bi-conical packages. However, Schlafhorst PreciFX automatic winding machines with drum-less traverse permit production of packages with improved unwinding characteristics. These machines have traverse length of 6” (150 mm). It is known that shorter traverse length packages (3”, 4”) give reduced breakage rates than 6” package. Unwinding problems tend to occur in the larger diameter range, depending upon factors like yarn or packages build. Unwinding problems occurring at higher diameters can be reduced by reducing traverse length, especially at higher diameters. Thus, a package initially may be built with 6” traverse up to certain diameter and then traverse length decrease may be started so as to initiate tapering of package. Reduced traverse length at higher diameters would improve unwinding properties and also allow package build to larger diameters. Bi-conical packages are expected to reduce breaks in end-use applications like warping and weft supply package on a shuttle-less weaving machine. Machine permits freely selectable traverse length shortening within desired range of package diameter individually on either side.

Figure 4.11 (A) and (B) Traverse length variation (C) A bi-conical package (Courtesy: SSM AG)


4.5.8.3 Traverse length variation to produce dye packages with rounded edges

Yarn traversing mechanisms with yarn guide on belt move to and fro or on a traverse lever, driven by servomotor (e.g. Oerlikon Schlafhorst Autoconer X5 PreciFX winding system, Barmag ATT take up on texturising machine) facilitate programmable variation in stroke of yarn traversing guide which allows production of packages for optimum package dyeing. Edges at side package flanks act as “dead zones” during package dyeing where lesser dye liquor flows (Fig. 4.13b). Therefore, a dye package with rounded side flanks is desirable. With conventional winding systems, packages without rounded edges are formed. Through mechanical process of pressing or rolling, “dead zone” portion is broken to get rounded edges (Fig. 4.13c). However, this impairs the package build and deterioration of the unwinding behavior due to shifting of yarn layers. Traversing mechanisms facilitating programmable stroke alteration allow winding of dye packages with rounded flanks of desired rounding radius (Fig. 4.13d). With such systems, programmed gradual traverse stroke reduction towards full package builds packages with desired radius of curvature at the edges. Figure 4.14 shows dye packages with rounded edges produced on Autoconer X5 PreciFX system.

4.5.8.4 Traverse length variation for shape correctionWhen a cross wound package with parallel side faces is built, side faces tend to bulge out, especially with a coarser yarn and high package density. Bulging leads to curved side faces. When bi-conical filament yarn package

Figure 4.12 Winding machine producing bi-conical packages (Courtesy: Fadis)


is built (which has usually taper angle of 42°), similar phenomenon takes place. Figure 4.15(a) shows expected package with straight side faces and Fig. 4.15(b) shows package with bulged side faces. Packages with straight side faces can be obtained by intentionally winding a package with curved side faces. Figure 4.15(c) shows package winding by varying traverse length in a specific manner along a curve. This curve is to be so shaped that after bulging package side flanks become straight (Fig. 4.15d). SSM winding machines with programmable traverse length variation facilitate programming of the traverse variation curve. The user can select the curve between two extremes through of input % compensation. As shown in Fig. 4.16(a), an input of 0% compensation gives no curvature whereas 100 % compensation gives maximum possible curvature. The form of the curve to be input depends upon factors like type of yarn, fiber, count, etc. On some machines, programmable variation in traverse length can also

Figure 4.13 A dye package with rounded edge

Figure 4.14 Packages with rounded edges produced on Autoconer X5 PreciFX system (Courtesy: Oerlikon Schlafhorst)


be used to correct package shapes. Traverse length can be progressively increased or decreased on any side within a given range of package diameter. For example, if a package with deformation from diameter ‘D1’ to ‘D2’ is produced as shown in Fig. 4.16 [b(i)], its shape can be corrected by reducing traverse length towards cone base side from diameter ‘D1’ to ‘D2’. Figure 4.16 [b(ii)] shows the corrected package shape.

4.5.8.5 Traverse position variation to produce packages with shorter length

Traverse stroke cannot be varied for a given grooved drum, and therefore packages of certain length only can be produced. With Autoconer PreciFX drum-less traverse system, traverse length can be programmed on “Informator”. Therefore, packages with required shorter lengths can be produced. For example, a package with 4” traverse can be wound on a 6” tube at desired position. As shown in Fig. 4.16[b(iii)], a cone with a shorter stroke is produced with winding positioned near the base of the cone. Such stroke reduction may

Figure 4.15 Traverse variation curve

Figure 4.16 Traverse length variation for package shape correction


be required for certain end-user applications, e.g. clip cone packages with 3” or 4” width used for twisting as well as “sun cheeses” (packages with short traverse length built to very large diameters which are found advantageous as weft packages) can be conveniently produced with this feature.

4.5.8.6 Traverse position variation for king spoolsWhile winding king spools (Fig. 4.7), it becomes necessary to shift relative position between king spool and traverse as the package builds up.

4.5.9 Traverse accelerationTraverse acceleration is discussed in principle in section 2.3. A cone with same taper throughout is built with a half-accelerated traverse. Fully accelerated traverse builds a cone with increasing taper which is advantageous for knitting. Due to fully accelerated traverse, yarn can be withdrawn from the package with lesser drag with cone face even at greater diameters. Cones with taper up to 5° to 6° can be wound on fully accelerated, half-accelerated or uniform traverse depending upon end-use application. Uniform traverses are normally used in winding packages up to 4° 20’. A grooved drum for a cylindrical package is with same groove angle from one end to the other whereas groove angle keeps on increasing from base towards nose for a drum for a conical package which is to lay desired yarn length per unit area across the length of the package. Distance of successive crossings of grooves for a cylindrical package remains the same for a cylindrical package, whereas for a conical package crossing distances towards base side is lesser than that towards base. Therefore, a drum for a cylindrical package is called “symmetric drum” and that for a cone is called “asymmetric drum”. With grooved drum traverse, traverse acceleration remains the same throughout package build. Autoconer PreciFX winding system provides facility of selecting “symmetry ratio”, e.g. 1.2, 1.4, 1.6, 2, 2.5, etc. Higher is the symmetry ratio greater the traverse acceleration. Symmetry ratio of 1 indicates linear traverse. As discussed in section 4.5.5, the system permits selection of drum pitch which principally allows selection of mean coil angle. Suitable selection of drum pitch and symmetry ratio permits build up of an optimum package. A cone during uniform build up is shown in Fig. 4.17 where L, M, N and O shows cone during its progressive build up. ‘A1’ and ‘B1’ are two strips of equal width at nose and base of the cone at initial build up stage L. Area of strip ‘B1’ is substantially greater than A1. It can be appreciated that during subsequent


cone build up stages (i.e. M, N and O) the proportionate difference between

strip areas and nose and base keep on narrowing ( B

ABA

BA

BA

1

1

2

2

3

3

4

4 ).

Therefore, to lay same yarn length per unit area, difference between coil angle at towards nose and base must be reduced as cone builds up. Autoconer PreciFX winding system provides an option of “dynamic symmetry ratio” where traverse acceleration is reduced as the cone builds up. However, the benefit of this feature in improving package performance is still under study and it is advised not to select this option.

4.5.10 Selection between ‘p’ wind and ‘q’ wind on a winding machine

A winding machine may be with ‘p’ wind or ‘q’ wind. Figure 4.18(a) shows a machine with ‘p’ wind. With ‘p’ wind, the base of the cone lies towards right side looking from front. When this cone is withdrawn over end, English alphabet ‘p’ is seen looking at yarn from nose side. Figure 4.18(b) shows a machine with ‘q’ wind where base of the cone is towards left looking from front. When this cone is withdrawn over end, English alphabet ‘q’ is seen

Figure 4.17 Dynamic symmetry ratio

Figure 4.18 ‘p’ and ‘q’ winding


looking at yarn from nose side. It is also important to select between ‘p’ wind and ‘q’ wind while procuring a winding machine. This wind influences addition or subtraction of twist on overhead unwinding. During over end unwinding, each revolution of yarn adds or subtracts one twist. How much twist is added or subtracted per meter depends upon package diameter. At small package diameter, this can create as good as five twists per meter of yarn. Especially for fine yarn counts with a certain level of hairiness, this additional twist flows towards the yarn being unwound from the package and can “spin” the protruding hairs of other layers with the yarn leaving the package (Fig. 4.19a). Due to this, the yarn leaving the package tends to “stick” with the other layers and an end break can be created. The worst case happens, when a prominent balloon is not formed or a balloon collapses. At this time, yarn “grinds” with the package surface and therefore, the added twist has the greatest chances of “spinning” with the protruding hairs on package surface to cause a break (Fig. 4.19b). Finer yarns do not develop a prominent balloon and therefore, they are most likely to exhibit this phenomenon of “sticking” due to twist addition. Yarns coarser than 20s Ne develop a prominent balloon and therefore even if the twist adds, “sticking” problem does not occur. In order to reduce this tendency, spinners should wind the yarn so that the twist reduces (twist is subtracted rather than added). For this reason, ‘S’ twisted yarn should usually be wound in ‘q’ and the ‘Z’ twisted yarn should be wound on ‘p’ machines. For the same reason, the sewing threads which are generally twisted ‘S’ should be wound ‘q’. With greater conicity of the package contact between unwinding yarn and package surfaces would be generally at one point and that can also minimize “sticking” problem. In olden days packages with higher conicity of up to 9° 15’ were used. But due to problems associated with higher conicity (as discussed in

Figure 4.19 Yarn breakage due to twist addition


section 4.5.1 of this chapter) their use declined. In case of a cylindrical package wound with given twist in a yarn, whether twist is added or subtracted depend upon how the package is put in creel in subsequent process. Figure 4.20 shows a cheese is wound on a machine. When it is put in the creel of subsequent machine, either ‘p’ wind or ‘q’ wind may be obtained depending upon package orientation with respect to its guide eye. Hence, if proper care is not taken in putting packages with defined orientation in creel of subsequent machine, twist may be added or subtracted. Some machines are provided with an arrangement to lay transfer tail wind at the beginning of the package. In the creel of subsequent process, e.g. a shuttleless loom, this tail is joined with starting end of next waiting package to have uninterrupted supply of yarn. With transfer tail, package is always

Figure 4.20 ‘p’ and ‘q’ wind for a cheese

put in the creel of the subsequent machine so as to keep transfer tail opposite to guide eye. Some machines are provided with facility to program laying of transfer tail on any desired side, i.e. on left or right. Therefore, with transfer tail on left side, ‘q’ wind is obtained (Fig. 4.21a) and transfer tail on right side ‘p’ wind is obtained (Fig. 4.21b). Transfer tail must be put on appropriate side to obtain desired wind. With machines provided with facility of lay transfer tail only on one side either ‘p’ or ‘q’, wind becomes possible. Diamond pattern formation in close precision winding is discussed in

Figure 4.21 Transfer tail position and wind (‘p’ or ‘q’)


section 2.4.1.6 of Chapter 2. The diamonds formed on the package have raised portion as shown in Fig. 4.22. This raised portion has arrow-shaped section. This arrow-shaped section points in the direction of rotation of package for head wind and opposite to package rotation for after wind. Figure 4.23 shows raised section arrow shape on a precision wound package with ‘p’ head wind.

Figure 4.22 Raised section arrow-shaped direction

Figure 4.23 Raised arrow-shaped portion

4.5.11 Manipulation of winding tension and/or pressure between package and support roll/ drum/ press roll

Along with other parameters (winding mode/ coil angle/ traverse ratio), package density is influenced by yarn tension and pressure between package and support roll/ drum/ press roll. With a simple winding system, pressure between package and support roll/ drum/ press roll may be adjusted through dead weight on a cantilever cradle or a spring force. As package grows, its weight increases which would tend to increase pressure between package and support roll/ drum/ press roll which in turn would tend to build a package with gradually increasing density from empty to full package. For most cases, it is desirable to maintain pressure between package and support roll/ drum/ press roll constant. Mechanical systems have been incorporated on some winding systems attempting to maintain constant pressure between package and support roll/ drum/ press roll throughout build up of package.


Outer layers of a winding package exert radial pressure on inner layers towards package axis. A layer nearer to bare package experiences greater pressure from outer layers as compared to that away from bare package. This factor can also contribute to radial density variations. A package with defect of “wrinkles” may be formed. While winding elastic yarns, side faces tend to bulge as discussed in section 4.5.8.4. Bulging problem can also be tackled through manipulation of pressure between package and support roll/ drum/ press roll, and/ or yarn winding tension. Some advanced winding systems are provided with systems to wind packages with programmable reduction of pressure between package and support roll/ drum/ press roll as well as yarn tension with package built. Programmed regulation of pressure and yarn tension becomes possible through motorized movement of package cradle and tension regulation systems, respectively. For example “Variopack” feature of Autoconer winding machines is provided to eliminate bulging of side faces especially while winding elastic yarns with elastane fibers in which pressure between drum and package as well as yarn tension are gradually decreased as package build up. Range of variation of pressure and yarn tension is pre-selectable and should be optimized to avoid bulging. For winding systems with surface drive, it must be borne in mind that certain minimum pressure between package and drum is always necessary without which drum would fail to drive the package. Winding systems with direct drive enables winding with

Figure 4.24 Advantage with VariopackFX (Courtesy: Oerlikon Schlafhorst)


very low pressure between the package and press roll/ support roll; provided press roll/ support roll is not used to measure yarn length/ package diameter (as slippage between winding package and roll would give error in length measurement). Figure 4.24 shows advantage with VariopackFX system. S.S.M winding systems (TW2, PW2, DP5, and PS6) also enable programmed reduction of yarn winding tension as well as pressure. The system enables input of desired yarn winding tension at package start up. Amount of yarn winding tension at medium diameter and full diameter is also to be input. During winding, yarn winding tension gradually changes from start-up tension to medium diameter tension to full diameter tension. Minimum on tension required will be 2 cN (especially for very fine monofilament yarns). Below this value, the yarn sensor does not work correctly. This feature is helpful to build a package with good unwinding property/dyeability.

4.5.12 Package density/hardnessPackage density is also an important parameter related to a winding package. With higher package density, greater yarn length can be accommodated in given volume which is usually an advantage. Package density is expressed in grams per cubic centimeter or grams per liter.

Density = Mass of yarn in grams

Volume of yarn in cubic centimeters/liters

To determine package density it is necessary to determine mass of yarn wound on package and yarn volume. Mass of yarn can be determined using a balance. Package volume can be determined from its geometric dimensions. Package density determination through manual measurement of mass and package dimensions and calculating density is a tedious and cumbersome method. Package density measurement systems are available in market for the conical or cylindrical packages produced on winding machines which measures mass of the package electronically and package dimensions by a camera. Computer of the system calculates density from measured mass and package dimensions. The system enables segregation of packages falling out of range with regard to mass, volume or density as defined by the user. Winding package density in general is influenced by pressure between package and drum/ press roll/ support roll as well as winding tension. Moreover, it is also related to parameters related to given winding mode. Coil angle opted for random and step-precision winding influences package density. Lower the coil angle greater the package density and vice versa. With step-precision winding, selection of stepwise decreasing traverse ratios also


influences package density. Close winding traverse ratios would give greater package density whereas open winding traverse ratios would give lesser package density. In precision winding, greater traverse ratio (that would give lower average coil angle) with close wind would give greater package density whereas lower traverse ratio (that would give grater average coil angle) with open wind would give lesser package density. Dye packages are soft wound to allow penetration of dye liquor across the package. Dye package density for cotton yarns usually ranges between 300 and 450 g/L. With dye springs, packages are compressed in making dye column that increases package density by around 20%, and therefore they are wound much softer in comparison with perforated solid packages. With high pressure dyeing equipment, packages densities towards higher side can be opted for. Flow of dye liquor disturbs yarn lay through lesser extent with relatively greater package density. Muffs for dyeing should be wound with density as low as 200–230 g/L, as this form of package is used for yarns giving very high shrinkage during dyeing. Package density influences other package characteristics such as stability, ease of withdrawal, etc. A package which is too soft may get deformed during handling or transportation. Moreover, it is more prone to slough off during high speed unwinding. Density of packages for warping or shuttleless weaving weft packages is kept higher than for knitting. For example, typical density of a warping package is 420 g/L and of a knitting package is 350 g/L. Lower density packages in knitting allow easier withdrawal of yarn with no danger of slough off due to slow unwinding speeds. Higher density in warping packages prevent slough off at high withdrawal speeds. Package compactness is also measured in terms of hardness by package hardness testers. Package hardness of filament take-up packages of polyester usually ranges between 85 and 88 degree shore and of nylon between 65 and 70 degree shore.

4.5.13 Yarn length on full package/ full package diameterSome end-use applications like warping and TFO twisting demand preselected length on winding package. It is ideally desired that all packages in a warping creel should be of exact length so that none of them exhaust or left with any yarn at the end of last beam (in case of direct warping) or section (in case of sectional warping). Packages with inadequate length run out during winding of last beam/ section causing an interruption in warping. Packages with excess length are left with some yarn on the package at the end of last beam/ section. Such packages require rewinding for utilization of left over yarn.


For an end-use application like TFO twisting, optimum utilization of volume of pot is necessary which demands an exact feed package diameter. TFO feed package with excessive diameter does not fit in the TFO pot where as a smaller diameter package would run out earlier. When two packages are put in TFO pot one above the other, they should have equal length so that both exhaust simultaneously. Dye packages should be within tolerance limit with regard to package density, and should be with minimum diameter variations. An excessively soft package in a lot would be of greater diameter, whereas a hard package would be of smaller diameter. Old machines did not have length measuring system but had only diameter stop motion. Required yarn length was indirectly set through package diameter. In this case, packages will have differing yarn lengths because of varying yarn tension conditions from spindle to spindle. To overcome this disadvantage, length measuring systems working on different principles are developed on winding machines. Principles of these systems are discussed below. Length being wound on the package can be measured by passing yarn around a small grooved pulley placed in the passage of yarn. Friction between yarn and pulley causes pulley rotation during winding. Surface movement of disc gives length being wound on the package. By sensing pulley rotations, surface movement of disc can be calculated. However, this method necessitates pulley rotation which is brought about by yarn itself and hence it puts some stress on yarn. This method is not suitable for elastic yarns. A minimum tension level of about 25 grams is necessary during winding without which yarn would fail to rotate the discs. Moreover, pulley becomes an additional element for yarn threading. In case of grooved drum winding, yarn length can be measured by sensing rotations of drum. Drum rotations are associated with length being wound onto the package. With a conical package, surface speeds of the drum and cone are equal only at one point. This point is called slip-free point. Diameter at slip-free point becomes effective driven diameter and determines package rotational speed. This slip-free point initially lies nearer to the base of the cone and does not remain stable at one place during package build up but usually shifts towards cone centre. Therefore, it is difficult to exactly correlate drum rotations with length being wound. Moreover, slippage brought about by anti-patterning also gives some error. Therefore, it is better to sense package rotations along with drum rotations as well as package diameter. Package diameter can be determined through sensing of angular position of package cradle. Drum rotations give traverse length and package rotations with its


diameter give surface movement, which enables determination of yarn length. However, the calculation is not simple and straight forward. Some precision winding systems sense rotations of support roll. Length being wound is taken as the surface movement of support roll. However, yarn being wound is always greater than support roll surface movement due to traverse component. For reducing error, input from traverse component should also be included by sensing traverse strokes (e.g. sensing cam rotations). ‘Ecopack FX’ is a non-contact type yarn length measuring system introduced on Schlafhorst automatic winders which gives variations from package to package below 1%. Principle of this system is shown in Fig. 4.25. Yarn passes through the sensing head of the system placed in the passage of yarn. Yarn passes between a parallel beam of infra red light and two photoelements ‘a1’ and ‘a2’ on which its shadow is formed. The two photoelements are spaced apart through a fixed distance ‘s’. Spun yarn always has an irregular cross-section along its length. An irregularity ‘x‘ arrives at photoelement ‘a1‘ at time ‘t1’ that reaches photoelement ‘a2’ at time ‘t2’. Thus time interval ‘t’ can be recorded for an iregularity to cover a distance ‘s’. Yarn

Figure 4.25 Measuring principle of ‘Ecopack FX’

speed ‘v’ is the ratio of distance and time. Thus, velocity of yarn with time can be known. The real length is the integral value of the time[Length dt]= ∫ v .

4.6 Yarn waxingWinding machines for producing packages for knitting are usually provided with a waxing device that applies wax on yarn surface. The wax is meant to improve the frictional properties of the yarn during the processing on knitting


machines. A low coefficient of friction between yarn and knitting needles becomes advantageous. Coefficient of friction of yarn is reduced by almost 50% on waxing. A wax roll is kept pressed against running yarn in the passage of winding machine. Coefficient of friction of yarn depends upon wax pick up. It is necessary to ensure an optimum wax pick up during winding. For example, only 1 gram of wax is sufficient to wax 1 kilogram of 50s Nm yarn. Too little or too much wax increase coefficient of friction. Wax pick-up on machine is influenced by contact pressure of wax, wax quality and ambient temperature. Higher contact pressure of wax would increase the wax pick up and vice versa. Wax quality may be hard or soft that influences wax pick up with given contact pressure. Ambient temperature also influences wax softness and thereby wax pick up. Too damp bobbins in the creel of winding machines reduce wax pick up drastically. If ring bobbins are conditioned or steamed, the yarn should be made to return to normal moisture regain before winding. It is necessary to select an appropriate wax depending upon the type of yarn, fiber material and the temperature during winding. Storage of waxed packages is also important. If waxed yarn is stored in an unheated room in winter, the temperature of the material is correspondingly reduced. When these packages are brought later into the warmer atmosphere of the production department, vapor condensation on the cooler package results, and in extreme conditions the packages can become saturated with water. With cotton yarns, friction coefficient increases on moisture pick up which can lead to problem in its processing. In summer, if packages are stored in conditions reaching temperature of 50°C or more, the wax may soften and penetrate inside the yarn body losing the benefit of waxing. Quality of wax also influences efficiency of waxing. With excessively hard wax, inadequate wax deposition takes place and too soft wax is easily cut by the yarn. The “penetration” is an important property associated with wax which expresses the hardness of the wax in conjunction with the temperature. In order to allow universal use of wax in summer as well as winter, one must use the waxes which show only small variations in penetration within a temperature range of 20° to 35°. Melting point of wax is also an important property. Both of these values prevent the wax from melting on the winding machine. The crystalline structure of wax gives a guideline with regard to its application for different fibers. The so-called large-crystalline waxes give the best results. The oil content of the wax can be measured. Increased oil content causes an increase in wax pick up on the yarn. However, optimum oil content in the wax is necessary. Excess content does not allow the oil remain bound in the wax, and is sweated out from the wax roll.


Immediately upon exhaustion of a wax roll, it is necessary to place a new wax roll otherwise yarn gets wound on the package without waxing. Some machines are provided with stop motion that stops the spindle on exhaustion of a wax roll. Waxed packages should not be conditioned because it deteriorates running properties of yarn. Figure 4.26 shows waxing system along with wax roll changing on Autoconer X5 automatic winding machines.

Figure 4.26 Waxing system along with wax roll changing on Autoconer X5 winders

(Courtesy: Oerlikon Schlafhorst)

To construct a homogeneous package, it is usually necessary to maintain uniform, desired yarn tension during winding. Yarn tension is influenced by various factors. Optimum yarn tension is maintained on winding machines through suitable systems which are described in this chapter.

5.1 Necessity of yarn tension during windingUsually some optimum yarn tension is necessary during winding to 1. cause a break at weak place. On rejoining the broken ends properly,

the weak place gets eliminated. 2. support yarn sensing device working on mechanical principle. This

device actuates thread stop motion if yarn breaks or bobbin exhausts during winding.

3. help in keeping the yarn in elements of yarn traversing system, e.g. in groove of the groove drum or yarn traversing guide. With an inadequate yarn tension, yarn usually fails to follow yarn traversing system.

4. help in getting a compact winding package. Tension in yarn contributes in forming a compact package.

5.2 Various supply packages on winding/rewinding machines

Various types of supply packages are possible on winding/rewinding machines. Some of them are 1. Mule Cop is a hollow package produced on mule spinning. 2. Ring frame bobbin is produced on ring spinning frame. These

packages are usually cop built. However, they may be roving built or combination built.

3. On some winding machines supply packages are hanks (bundles of yarn containing a certain length). If yarn is dyed or supplied in hank

5Yarn tension during winding

Yarn tension during winding 101

form, a machine is required that winds yarn from these hanks onto cones or a cheeses. Such winders are usually called hank to cone winders. A muff is also a package without any supporting tube which is subjected to dyeing. Muff dyeing is carried out for yarns giving very high shrinkage during dyeing. Dyed muff is not suitable for over end unwinding. It is subjected to side winding.

4. The dyed cones / cheeses can be supply packages on dye package rewinding machines. These supply packages are built h lays on these packages may get disturbed due to liquor flow during dyeing. Yarn layers may tend to stick together due to dyeing. Hence, they may not be suitable for next process involving high speed unwinding. Therefore, they may be rewound on rewinding machines to form a stable package suitable to perform well in subsequent process like weaving/ warping/ knitting etc.

5. The remnants (the cones/cheeses) which are left with some yarn after use, e.g. warping, pirn winding etc. are supply packages on rewinding machines. Basic purpose of such rewinding machine is to gather smaller quantity of left-over yarn from remnants and utilize this yarn.

6. Full (bigger size) packages which are cross-wound, i.e. cones/cheese, produced on unconventional spinning machines (open end spinning, friction spinning etc.) may be subjected to winding for reasons such as elimination of yarn faults or for better package build up.

7. On filter winders cross-wound yarn or roving packages (polypropylene/glass) are supply packages.

8. On assembly winders two or more yarns supplied from cones/cheeses are assembled and wound together onto a single package. The main purpose of assembly winders is to assemble two or more yarns on to a single package. The assembled packages are fed to two for one twister to impart twist.

5.3 Unwinding tension from packagesDuring over end unwinding from a package, unwinding point shifts around the package. Therefore, yarn between yarn guide and unwinding point on the package experiences centrifugal force. Centrifugal force tends to throw yarn away from package due to which characteristic yarn balloon is formed. Rate at which unwinding point shifts around the package depends upon unwinding speed and package diameter. Higher unwinding speeds and lower supply package diameters leads to faster shifting of unwinding point around the package and thereby increased centrifugal force on yarn. Centrifugal force


imparts tension to yarn. Unwinding point also shifts along the length of the package that continuously varies mass of ballooning yarn. Longer traverse lengths would lead to greater variations in mass of ballooning yarn. Rate of variation of mass of ballooning yarn is influenced by coil angle. Higher coil angle will give increased rate of variation of ballooning yarn mass and vice-versa. Ballooning yarn experiences resistance to its motion due to air drag that also imparts some tension to yarn. Air drag on yarn is influenced by yarn structure. Thus, unwinding tension characteristic of a package is influenced by several parameters like taper, coil angle, mode of changes in traverse length, package diameter at the unwinding point, etc. Therefore, when yarn is withdrawn from a package, some tension is generated.

5.3.1 Unwinding tension from a ring frame bobbinThe ring frame bobbins are usually ‘cop built’. The term ‘cop built’ refers to manner of yarn winding during package build on ring frame. To understand the built of the bobbin, the simplified cross-sectional view has been shown (Fig 5.1a). The winding starts from the bottom giving a short length of traverse. This traverse is advanced towards the tip. The cross-section shows how the successive layers are laid and the ring frame bobbin is built in a simplified manner. Except some layers near the base of the bobbin, they are laid along the slope. As the yarn is unwound, the point of unwinding moves along the slope. The portion of least diameter along the slope is called the ‘nose’ and that with the greatest diameter as ‘shoulder’ (Fig 5.1b). Thus, the point of unwinding moves from nose shoulder back to nose and so on. During over end withdrawal from a ring bobbin, unwinding point keeps on shifting around bobbin surface causing yarn rotation. This rotation generates centrifugal force and a characteristic yarn balloon is formed on unwinding.

Figure 5.1 Unwinding tension from a ring frame bobbin


The balloon formed may be a single loop or a multiple loop balloon. The balloon height is divided into loops which are separated by ‘necks’. The balloon portion with maximum loop diameter is called a ‘bulge’. Unwinding tension T, depends on the variable as

T W

N An

Bhr

∞+

2

2

2[( ) ( )]

[‘T’ unwinding tension, ‘W’ winding speed, ‘N’ Indirect yarn count, ‘A’ and ‘B’ are the constants whose values depend upon air drag coil angle, taper of yarn bobbin etc, ‘h’ is the height of a loop and n is the number of loops (h = H/n, where ‘H’ is balloon height) , r = radius of bobbin at the point of unwinding.] The values of number of loops, balloon height and radius of bobbin at the point of unwinding keeps on changing continuously during unwinding of yarn from the beginning to end. Therefore, the unwinding tension also fluctuates from beginning to end. Unwinding tension is lower for a full bobbin and keeps on increasing as bobbin empties. A steep rise in unwinding tension is observed towards the end of the bobbin. With suitable measures, unwinding yarn tension fluctuations can be minimized.

5.3.2 Unwinding tension from over end withdrawal of a cheese

Figure 5.2 shows that unwinding tension from a cheese during over end unwinding fluctuates with a fixed guide distance. With constant withdrawal

Figure 5.2 Unwinding tension from a cheese


speed during unwinding, balloon rpm keep on increasing with decrease in package radius. During unwinding, say starting with single loop, the balloon breaks to two loops/ three loops at certain diameters. Breaking of balloon causes drop in unwinding tension as number of loops increases. Fluctuations in tension are inevitable. With suitable measures, tension fluctuations can be minimized.

5.4 Yarn tensioning devicesSome tension is already generated during over end unwinding. However, if this tension is inadequate, it becomes necessary to employ a yarn tensioning device (also called yarn tensioner) that raises mean thread tension to required level. The most common method of adding tension to a running yarn is to apply frictional retarding force to running yarn. Principle of applying tension to running yarn by applying frictional retarding force is shown in Fig. 5.3(a). A frictional retarding force applied to a running yarn is in the direction opposite to yarn movement, and therefore tension is applied to yarn.

Tensioning devices applying frictional retarding force work on any one of the following two principles or their combination: 1. Multiplicative type of yarn tensioners 2. Additive type of yarn tensioners

5.4.1 Multiplicative type of tensionersThese yarn tensioners work on the principle of friction created by envelopment of running yarn around a surface. Let a running yarn be enveloped round a

Figure 5.3 Tensioning yarn by applying frictional retarding force (Photograph courtesy of Fadis)


surface. Let ‘T1’ and ‘T2’ be incoming and outgoing tensions respectively, and ‘q’ be the angle of envelope then outgoing tension ‘T2’ is given by,

T2 = T1e

µq

As output tension is obtained by multiplying input tension by factor ‘eµθ’, the tensioner working on this principle is called a multiplicative type of tensioner. The most familiar type of tensioner working on this principle is a gate tensioner.

5.4.1.1 Gate-type tensionerFigure 5.3(b) shows a typical gate tensioner which consists of two gates with polished steel rods or porcelain tubes or ceramic coated posts. Generally, one gate is fixed and the other is movable. Out put tension T2 is given by

T2 = T e11 2 3 4 5 6µ θ θ θ θ θ θ( ........)+ + + + + +

where (q1 + q2 + q3 + q4 + q5 + q6 + .........) is total angle of envelop. The required tension can be set by setting angle of envelope. This depends upon the distance between the rows of guide rods. The movable gate is kept in desired position by applying fixed torque by means of a weight or spring. The angle of lap, as shown in Fig. 5.3(b), can be set by a set screw that determines extent of penetration of movable gate with respect to fixed gate. More is the penetration, greater would be the angle of lap and thereby greater would be the tension applied by tensioner and vice versa. Figure 5.3(c) shows a gate-type tensioner.

5.4.2 Additive type of tensionersIn an additive type of tensioner, yarn passes between two surfaces which are pressed against each other. Let ‘R’ be the normal reaction and ‘µ’ be the coefficient of friction between yarn and the surfaces. Each surface applies frictional retarding force equal to ‘µR’ and therefore total frictional retarding force of two surfaces becomes ‘2µR’. Therefore, T2 = T1 + 2µR In this case ‘2µR’ is added to input tension ‘T1’ to get output tension ‘T2’. Therefore the tensioners working on this principle are known as additive type of tensioners. Very commonly used commercial tensioners working on this principle are disc tensioners.

5.4.2.1 Disc tensionersA disc tensioner principally consists of two discs (Fig. 5.4) which are pressed against each other through which yarn passes. Each disc is circular in shape


which has flat portion with curved surface at the periphery. The discs are placed against each other in such a way that their flat faces contact each other. The friction between flat faces and the yarn imparts tension. The peripheral curved portion is to facilitate yarn threading through the discs and prevent yarn contact with disc edges.

Figure 5.4 Disc tensioners

In commercially available tensioners, each disc has a circular hole in the centre. The discs are supported by a pin. A flat circular face whose radius is smaller than diameter of flat faces supports the bottom disc. Washers are placed on the top disc. These washers determine the normal force and thereby tension imparted. A light spring may be kept between top disc and washers. If yarn passage is vertical, a conical spring is used to apply pressure between the two discs. Spring force and thereby the tension applied can be adjusted with a nut with the help of which spring compression can be adjusted (Fig. 5.4). With such disc tensioners, yarn envelopes around the pin of the tensioner which has multiplicative tension component (though this component may be smaller). Figure 5.5 shows a disc type of tensioner used on some winding machines. Yarn passes between two discs. Disc ‘A’ is mounted at the end of a shaft which is driven through a motor. Disc ‘B’ mounted on a separate shaft is freely rotating. Through a suitable system, pressure between the two discs and thereby tension applied can be adjusted. The yarn path is off centre with respect to discs. Disc surface moves in direction opposite to direction of yarn motion. Positive rotation to disc ‘A’ prevent local wearing out of the discs as well as any fluff accumulation between the discs.

Figure 5.5 A disc tensioner with motor drive to disc


5.4.3 Comparison of disc and gate type of tensioners

1. Self-compensating nature of tensionerWith an increase in yarn tension, the movable gate swings outwards that results into decrease in angle of lap and thereby tension imparted by the tensioner. On the contrary, with decrease in yarn tension movable gate penetrates more towards fixed gate that results in to an increase in angle of lap and thereby causes increase in tension applied by tensioner. Thus the gate type of tensioner can act as a self-compensating tensioner. However, this ideal situation would be achieved if corresponding gate movement occurs at the same instant when tension fluctuates. Usually, tension fluctuations occur at high frequency. Therefore, movable gate would fail to respond instantaneously and would fail to act as a self-compensating type of tensioner. Disc types of tensioners are not self-compensating type.

2. Magnification of incoming tension fluctuationsIn case of gate type of tensioners, if average incoming tension is say 10 units and outgoing tension required is 30 units, eµθ would be 3, i.e. T2 = T1 × 3 = 10 × 3 = 30 units. If ‘T1’ fluctuates from 10 units to 20 units (difference of 10 units), then T2 varies from 30 units to 60 units (T2 = 3 × 20 = 60 units). Thus, if coming tension varies from 10 units to 20 units (i.e. doubles), outgoing tension varies from 30 to 60, i.e. doubles. Thus in gate type of tensioners the incoming tension variations are magnified by a multiplying factor ‘eµθ’. An ideal tensioner should maintain outgoing tension the same irrespective of incoming tension. In disc-type tensioner ‘2µR’ is added to incoming tension to get outgoing tension. If incoming tension is say 10 units and outgoing tension required is 30 units, ‘2µR’ would be 20 units, i.e. T2 = T1 + 20 = 10 + 20 = 30 units. If ‘T1’ fluctuates from 10 units to 20 units (difference of 10N), then ‘T2’ varies from 30 units to 40 units (T2 = 10 + 30 = 40 units). If coming tension fluctuates from 10 units to 20 units (i.e. doubles), outgoing tension varies from 30 units to 40 units. Thus, incoming tension fluctuations are not magnified in disc type of tensioners.

3. Sudden rise in out going tension with arrival of a thick placeWhen a thick place passes through gate type of tensioners, it can pass over the enveloping surfaces without any hindrance and output tension is not affected because angle of lap ‘θ’ and co-efficient of function ‘µ’ do not change. When a thick place enters the disc and washer type of tensioner, there is sudden rise in yarn tension. On arrival of a thick place, the upper disc has to be lifted suddenly to create space for thick place to pass through (Fig. 5.6a).


As the yarn speed is high and change in its diameter is sudden, the upper disc has to be lifted up in a very small time. So, upper disc has to be moved up in a short time, i.e. acceleration involved in disc movement would be high.

∴

Acceleration = Change in velocityTime

So, for a thick place to pass through, yarn has to push the mass of upper disc along with washers upwards. The force to be exerted by yarn on upper disc and washers equals product of mass and acceleration. As thick place pushes upper disc along with washers, a reactionary force is exerted by disc on thick place. This becomes an additional reactionary force, i.e. ‘R’ increases and therefore frictional force rises abruptly. Thus, when a thick place passes through a disc and washer type of tensioner, yarn tension increases suddenly. The sudden increase in yarn tension is immediately followed by a tension decrease. While working with very low tension, this phenomenon can be well visible as well as audible. This phenomenon happens so quickly that yarn sustains this tension hike without breakage. Very thick place leads to great rise in tension that may lead to yarn breakage. With a spinning process under control, a thick place would be followed by a thin place.

Figure 5.6 Thick place through a disc tensioner

To overcome the above disadvantage, a light spring is placed between the upper disc and washers as shown in Fig. 5.6(b). When a thick place passes through the tensioner, the upper disc is lifted suddenly and light spring gets compressed. The weights (washers) would remain in the same position due to inertia. Thus, force required exerted by thick place on upper disc is greatly reduced. Therefore, rise in tension on arrival of a thick place is also reduced.

4. Ease of threadingIt is easier to thread yarn through disc type of tensioner. In gate type of tensioner, movable gate is required to be moved to thread the yarn through it. Therefore, threading is simpler in disc type of tensioner as compared to gate type of tensioners.


5. Effect of fluff accumulationAccumulation of fluff between discs of disc type of tensioners reduces normal force of discs on yarn. Therefore, tension imparted reduces. It is necessary to take measures to prevent accumulation of fluff between the discs. The drag exerted by running yarn on disc usually causes discs to rotate. The centrifugal force due to this rotation tends to drive away fluff. This rotation also avoids local wear of discs. Motorized disc drive in a tensioner avoids local disc wear as well as fluff accumulation. In gate type of tensioner, problem of tension reduction due to fluff accumulation does not generally arise.

6. Tensioner interfering with yarn twistAs shown in Fig. 5.7(a), if a twisted ribbon is passed between two fingers, twist would be arrested at fingers. Therefore, the ribbon leaving the fingers would be without twist. Similarly, when twisted yarn is passed through the discs of the tensioners (Fig. 5.7b), twist may be trapped at the discs. If this happens, twist in outgoing yarn would be less as it is trapped at entry. A stage would come when this trapped twist becomes so high that it would escape through the discs. Due to this phenomenon, twist distribution in yarn wound on package would be uneven. Thus, disc type of tensioners interferes with yarn twist. Low twist yarns are more prone to this twist interference. Deviation of yarn path around surfaces in gate type of tensioners also tends to trap twist to some extent.

7. Gradual application of tensionIn a gate type of yarn tensioner, yarn envelopes around many surfaces to impart tension. Therefore, there is gradual rise in tension, i.e. if 20 units total tension is imparted, it increases gradually from one surface to the other. In disc type of tensioner, the tension rise is sudden, i.e. if 20 units tension is imparted, it is imparted in single stage. Therefore, if two disc tensioners are provided one after the other, tension would be imparted in two stages, i.e. say each tensioner imparting 10 units of tension.

Figure 5.7 Twist interference


8. Generation of neps in yarnEach deviation point of yarn around a surface may create neps in spun yarn and deteriorate yarn quality. In gate-type tensioner, yarn deviates around several surfaces and therefore this negative effect on yarn by a gate tensioner is much greater than a rotating disc tensioner.

5.5 Measures/devices to minimize tension fluctuations

Supply packages on winding machines such as ring frame bobbins or cross-wound packages are usually subjected to over end unwinding. As balloon radius and height varies continuously, unwinding tension keeps on fluctuating. Usually, it is desired that although yarn tension at unwinding from supply package may vary, yarn tension should remain as uniform as possible at the point of winding (Fig. 5.8). While unwinding over end from a cheese, balloon height varies periodically whereas balloon radius keeps on decreasing. During over end unwinding from a cone, balloon height as well as balloon radius varies periodically and average balloon radius keeps on decreasing. Through various measures/ devices/ systems, tension fluctuations can be minimized.

Figure 5.8 Unwinding tension from a cheese


Through manipulation of any one or more of the following factors/parameters, fluctuations in yarn tension at the point of winding can be minimized. • Optimizing distance between first yarn guide and supply package • Artificial collapsing of balloon by creating an obstacle between

supply package and first yarn guide • Developing a system that attempts to minimize balloon height

variations • Varying winding speed to regulate tension • Regulating tension by controlling tension applied by yarn tensioner • Regulating tension through positive feed system • Tension regulation by regulating rotational speed of side withdrawn

positively driven supply package

5.5.1 Minimizingballooning tensionfluctuations throughselection of optimum guide distance during over end unwinding from a ring frame bobbin

It is essential that the axis of supply package, i.e. ring frame bobbin passes through centre of the 1st yarn guide. The guide distance i.e. distance between bobbin tip and 1st yarn guide also plays an important role in determining unwinding tension. For minimizing unwinding tension variations, the guide distance should be such that number of balloon loops remains the same from beginning to end, i.e. if a single loop is formed during beginning of unwinding a full ring frame bobbin, at the end also single loop should be formed. It should not happen that a single loop is formed in the beginning and on increase in balloon height as unwinding proceeds; single balloon breaks into two loops. This would give rise to sudden change in unwinding tension. With increase in guide distance (distance between bobbin tip and 1st yarn guide), number of loops formed would tend to increase. Guide distance should be selected in such a way that number of loops remain the same through out unwinding. There would be only one location of yarn guide nearest to bobbin tip where single loop would be formed from beginning till end. Moving beyond this point there would be other definite location where two loops would be formed from beginning till end. If yarn guide is located any where between these locations, a single loop would be formed in the beginning which would break in to double loop subsequently which is not desired. For a given ring frame bobbin, there are definite guide distances ‘G1’, ‘G2’, ‘G3’ ….. where one, two, three…. loops are formed respectively throughout unwinding. If guide is placed at any other point, balloon would


collapse somewhere during unwinding and there would be sudden change in yarn tension which is not desired. Therefore, it is necessary to locate suitable guide distance for a given ring frame bobbin. This is required to be done through trial and error. An empirical formula is given that gives approximate guide distance which is given by, [G = n(L + 25) – L] Where ‘G’ (guide distance) and ‘L’ (bobbin lift) are in mm. ‘n’ is any integer that equals to number of loops that would be formed throughout unwinding. With L = 125 mm and n = 1,2,3 & 4 corresponding values of ‘G’ are 25, 225, 435 & 625 mm respectively. Usually ‘n’ would be taken to be one. Actual value ‘G’ is to be found by trial and error method. Thus, unwinding tension fluctuations can be reduced though selection of a suitable guide distance. However, finding an optimum guide distance is a tedious job. Even with suitable guide distance, ballooning tension fluctuations are not totally eliminated.

5.5.2 Minimizingtensionfluctuationsbyusinganunwinding accelerator (balloon breaker)

Any error, carelessness or inability to select a suitable guide distance can lead to sudden tension fluctuation during unwinding.

T W

N An

Bhr

∞+

2

2

2[( ) ( )]

, therefore with higher value of ‘n’ and lower

value of ‘h’ unwinding tension would reduce.

Figure 5.9 Unwinding accelerator Figure 5.10 Box type unwinding accelerator on Autoconer X5

(Courtesy: Oerlikon Schafhorst)


Unwinding accelerator or balloon breaker is a simple device, in form of a bar, a peg or a box (Fig. 5.9), placed between bobbin tip and yarn guide that obstructs the formation of a single large balloon and splits it into two loops. Due to this ‘h’ (balloon height per loop) decreases and ‘n’ (number of loops) increases artificially. This device reduces unwinding tension considerably and prevents sudden tension fluctuation during unwinding. With the use of unwinding accelerator, the importance of choosing a suitable guide distance diminishes. This device is placed 30–35 mm above the ring bobbin tip. Figure 5.10 shows an unwinding accelerator. Figure 5.11 shows unwinding tension trace from a ring frame bobbin with and without the use of a balloon breaker.

5.5.3 Minimizing tension fluctuations by optimizingballoon formation

5.5.3.1 Minimizing tension fluctuations by optimizingballoonformationwithringframebobbinasasupplypackage

Unwinding accelerator reduces unwinding tension fluctuations from a ring frame bobbin. However, as unwinding proceeds, balloon height keeps on increasing due to which tension fluctuations are not totally eliminated. To further even out tension fluctuations, sensor-based systems are developed which are ‘Balcon’ (Fig. 5.12a) and ‘Speedster FX’ (Fig. 5.12b) systems on Muratec Process Coner and Oerlikon Schlafhorst AC 5/ X5 automatic winding machines, respectively. Figure 5.12(c) shows ‘Speedster FX’ module. Sensor senses extent of unwinding from ring frame bobbin. Taking input from this

Figure 5.11 Unwinding tension trace with and without unwinding accelerator


sensor, as the bobbin unwinds, a balloon controller in form of a hollow tubular body that surrounds ring frame bobbin gradually descends down. Balloon controller of ‘Balcon’ system of Muratec winders attempts to minimize variations of balloon height. In ‘Balcon’ balloon controller moves upto about 60% of bobbin height. In ‘Speedster’ the tube suppresses balloon and does not allow yarn being thrown out due to tangential forces that adds to tension. Moreover, the tube moves till the end of the tube.

Figure 5.12 Sensorbaseddevicesfortoevenoutballooningtensionfluctuations(Courtesy: Oerlikon Schlafhorst)

5.5.3.2 Minimizing tension fluctuations by optimizingballoonformationbyregulatingguidedistancewithcheese/coneasasupplypackage

When yarn is unwound over end from a cheese at constant unwinding speed, package radius keeps on decreasing. Therefore, with a constant unwinding

Figure 5.13 Sensor-based guide distance optimization


speed, balloon rpm keeps on increasing with decreasing package diameter. Increasing balloon rpm increases air drag as well as centrifugal force on yarn. This leads to increase in yarn tension as package unwinds. With a fixed distance between bobbin and first yarn guide, increment in number of loops formed may take place suddenly at intermediate diameters which can lead to abrupt tension fluctuations. These tension fluctuations can be reduced if distance between first yarn guide and supply package is reduced in a specific manner as package diameter reduces. This would reduce length (and thereby mass) of ballooning yarn and avoid rise in yarn tension with diminishing supply package diameter to allow greater winding speeds. SSM winding machines offer feature ‘Tensio’ in which guide distance is optimized with reduction in package diameter as shown in Fig. 5.13. A sensor continuously senses supply package diameter which is input to a control unit. Through control unit, distance between pig tail and supply package is optimized continuously. The advantage of this system depends upon several factors like yarn count, yarn characteristics such as hairiness level, twist, yarn type (ring, OE air jet, compact, singed, etc). With very fine yarns counts (e.g. Ne 60/1), prominent balloon formation does not take place and therefore much advantage is not gained with this system.

5.5.4 Regulating tension through change in winding speed

Schlafhorst Autoconer 238 is provided with feature ‘Autospeed’ in which tension is regulated through speed variation. While unwinding from ring frame bobbin, ballooning tension increases steeply at around last 1/5th portion. For a given yarn, unwinding tension in this zone usually determines upper limit of winding speed. ‘Autospeed’ feature consists of a sensor integrated in yarn path that measures friction temperature in proportion to the yarn tension. The sensor is fixed to a yarn guide eyelet that avoids additional deviation of yarn path. Yarn tension is reflected through friction temperature measured by sensor. When tension rises, winding speed is reduced to regulate yarn tension. Thus, tension is regulated through change in winding speed. This feature allows higher winding speeds while unwinding from upper portion of ring frame bobbin, which otherwise would not be possible while winding at constant speed.


5.5.5 Regulating tension by controlling tension applied by yarn tensioner

This principle of yarn tension regulation is used on Schlafhorst Autoconer 338/ 5/ X5 winders (‘Autotense FX’ feature), SSM winders (‘Digitens’ feature), Savio Polar, etc. An electronic sensor is placed in yarn path after yarn tensioner that continuously senses the yarn tension. Desired yarn tension can be adjusted centrally in a control panel. Input from this sensor is fed to a winding head computer/controller which alters in a closed control loop; tension applied by yarn tensioner by varying pressure between tensioner discs/ wrap angle of a gate tensioner so as to maintain uniform tension. Such device can regulate yarn tension at all stages of winding and prevent an increase in yarn tension especially towards the end of the supply package. When winding is restarted after a stop at gradual acceleration, unwinding tension tends to be low. This is compensated by increasing the tensioner pressure at start up. With deformed ring frame bobbins, tension tends to rise abruptly at the deformed region. Yarn tension is regulated in this region also by sudden drop in tension applied. Figure 5.14 shows principle of ‘Autotense FX’ feature of Autoconers. Figure 5.15 shows yarn tension sensor and yarn tensioner on Autoconer X5 automatic winding machine. It may happen that towards the exhaustion of ring frame bobbin, tensioner discs have been opened up and yarn tension is still rising. Under this situation, ‘Autotense’ feature of Autoconers regulate yarn tension through reduction of winding speed. With presence of ‘Speedster’ along with ‘Autotense’, it becomes possible to regulate tension till the end of the package without any necessity of speed reduction. Figure 5.16(c) shows principle of one of the options (D mode) of ‘Digitens’ feature of SSM winders. In this system, yarn from supply package takes some

Figure 5.14 ‘Autotense’ feature of Autoconers


wraps around feed roll which is positively driven. Feed roll unwinds yarn from supply package and delivers further at constant rate. Taking input from yarn tension sensor, tension applied by tensioner is altered to minimize tension fluctuations.

Figure 5.15 Yarn tension sensor and yarn tensioner on Autoconer X5 winding machine

Figure 5.16 Yarn tension regulation through tensioner pressure and overfeed (Courtesy: Fadis)


5.5.6 Regulating tension through positive over feed system

The over feed device consists of positively driven feed roll. Yarn coming from supply package takes some wraps around feed roll. Positively driven feed roll withdraws yarn from supply package and delivers further for winding. By adjusting feed roll surface speed in relation with winding speed, winding tension can be regulated. Figure 5.16(a) shows a Fadis-make winding machine with over feed device. The over feed device can even out unwinding tension fluctuations from supply package and enable yarn tension delivery from supply package to a very low value (even zero tension). This allows build up of a satisfactory package for yarns with very high elasticity (e.g. Spandex, Lycra). Some yarns lead to very high shrinkage during the dyeing process. Dye packages with such yarns should be wound with extremely low density (200 to 230 g/L). Principle of SSM F-mode of Digitens system is shown in Fig. 5.16(b). Positively driven feed roll unwinds yarn from supply package and delivers for winding. Yarn tension sensor senses yarn tension that is input to controller which regulates rotational speed of feed roll to even out tension variations. Rise in yarn tension requires an increase in feed roll speed and vice-versa. Yarn tensioner discs are not required. This system works only for cylindrical packages with yarn tension lower as 40 cN. With conical packages the system is too ‘lethargic’ in order to compensate the yarn tension difference occurring along the traverse from cone base to nose.

5.5.7 Tension control by regulating rotational speed of side withdrawn positively driven supply package

As discussed in section 4.5.8 of chapter 4, over end withdrawal of yarn may add or subtract twist with every rotation of balloon. If this twist addition or subtraction is not permissible for some yarn, over end withdrawal is desired. A dye package may be too soft with yarn layers sticking together, especially for yarns giving high shrinkage during dyeing, not permitting over end withdrawal. ‘Precitens’ feature of SSM winders is offered for satisfactory and trouble-free side withdrawal of such packages as shown in Fig. 5.17. Supply package is side withdrawn and provided with a positive variable drive. Yarn tension sensor continuously senses yarn tension which is input to a controller. Controller varies rotational speed of package to maintain consistent yarn tension. Yarn winding speed remains constant. Figure 5.17 also shows similar feature on Fadis winding machines.


Instead of cross-wound package, hanks or muffs can also be supply packages and tension is regulated on the same principle. It is important to note that on dyeing, mass distribution in the package does not remain homogeneous. Therefore, rotation of these packages leads to high vibrations due to mass imbalance which has to be properly taken care of in machine building.

5.6 Expression of tensionThe tension is expressed in units of force i.e. Dyne, Newton, etc. However, practically it is also expressed in the units of mass, say grams or grains. Tension of 100 g means tension developed in the yarn when a 100 gram mass is suspended on it. In terms of units of force, 100 g tension equals weight of 100 gram mass which is product of mass and gravitational acceleration. Weight of 100 g mass is [0.1 kg × 9.8 m/s2] 0.98 N.

5.7 Amount of tension

The winding yarn tension should be around 110

th (10% of breaking tenacity)

to 18

th of the breaking strength of a single yarn. Higher winding tension can

make weak places weaker and may cause excessive elongation which reduces yarn elongation at break. This can adversely affect weaving performance. Higher winding tension may lead to increased yarn hairiness. With excellent

Figure 5.17 Tension regulation through controlling unwinding speed of feed package


yarn quality, higher magnitude of yarn tension may be opted for (with risk of adversely affecting yarn quality in terms of hairiness and/or elongation at break). Higher winding tension helps in achieving higher package density. Therefore, some mills tend to keep higher yarn tension, especially in doubling operation, at the cost of yarn quality deterioration. During filament yarn winding, the tension recommended is generally around 0.1 g/denier, so for 100 denier yarn 10 g tension should be applied. Winding yarn tension can be measured using yarn tension meter. Figure 5.18 shows a handy portable yarn tension meter. The running yarn is to be made pass around three pulleys. Pointer indicates yarn tension on dial. Digital yarn tension meters are also available with digital display of tension magnitude.

Figure 5.18 Yarn tension meter (Courtesy: Paramount instruments)

Some faults are usually generated in spun yarn during spinning. It is necessary to eliminate these yarn faults at winding. Yarn clearing refers to the process of fault elimination. Clearing devices are devices employed for fault elimination on winding machines, which are discussed in this chapter.

6.1 Introduction to yarn faults Card sliver contains 20,000 to 40,000 fibers in its cross-section and about 40 to 1000 fibers at the stage of spinning a yarn. It is not possible to keep the number of fibers in the cross-section constant throughout yarn length. Some random variations in mass/ yarn thickness do occur which can be kept within close limits though a well-controlled spinning process. However, some mass/ diameter variations or portions in yarn are required to be eliminated at the winding stage. Such places/portions in the yarn are called yarn faults. A portion in yarn is designated as a yarn fault if • it can hamper quality of fabric produced from it or • it may cause a break in the subsequent processes or • it may hamper quality of fabric produced as well as cause a break in

the subsequent processes. It is necessary to keep online track of the yarn during winding and identify yarn faults. During winding, ideally, each yarn fault should be detected, break must be caused at the yarn fault and winding machine should be stopped. Subsequently, yarn fault portion should be removed from the winding package and yarn ends should be joined to restart winding. Yarn ends are mostly rejoined with a spliced joint which is usually very close in appearance to a regular yarn. The process of removing yarn faults from the yarn is called yarn clearing, and device which is placed in yarn path on a winding machine that breaks yarn on detection of a yarn fault is called a yarn clearer. Yarn faults are generated during spinning due to various reasons such as selection of inferior raw material, carelessness of working of persons working in spinning, poor machine condition, incorrect machine settings, etc.

6Yarn clearing and clearing devices


Some typical yarn faults generated during spinning are as follows:

• SlubsSlubs (Fig. 6.1a) are fish-shaped thick places 1–4 cm long and about 5–8 times larger than the average yarn diameter at the thickest portion. The fiber mass of the slub form an integral part of the yarn but has less twist in it because twist tends to flow less in thick portion than in thinner portion. The slub possesses sufficient strength to withstand its passage through ring spinning and winding. Slubs are formed due to lack of individualization in carding. The loose lint i.e. fiber mass flying here and there in the spinning department may adhere to yarn during spinning and twisted with the yarn.

• CrackersCrackers are the coil-like places produced in the yarn having man-made staple fibers as a component. The fault is generated when a fiber is not cut properly during its manufacture and is longer. Such fiber gets stretched in drafting zone and crackers are produced. When the yarn is stretched at this fault, the thick coil-like fault gets straightened and longer fiber breaks producing a crackling sound.

Figure 6.1 Slubs and spinner’s doubles

• Spinner’s doublesSpinners doubles (Fig. 6.1a) consists of the portion in yarn where it becomes twice coarser and continues over a long length. At spinner’s doubles, fiber mass gets doubled. When this fault is woven in fabric as a warp thread, it appears as a thick line running in warp direction. If it is woven as a weft thread, owing to its longer length, several successive picks would be laid twice coarser. This would produce a thick band of picks running widthwise. Thus, a spinner’s doubles hampers the appearance of the fabric. When two single yarns are twisted to from a ply yarn, if one of them carries a portion with spinner’s doubles, it tends to remain straight due to its coarseness while other normal yarn twist around spinner’s doubles giving a cork screw appearance to ply yarn. The causes of spinners doubles is joining of broken strand on flyer frames with adjacent running roving and twisting with it. This portion

Yarn clearing and clearing devices 123

of roving on ring frame gives rise to yarn with thickness two times greater than normal yarn. The same phenomenon may occur during spinning on ring frame.

• Bad piecingPiecing in ring frame is the process of joining the yarn from ring frame bobbin with the drafted strand coming out of front roller. If piecing is done carelessly, a longer length of drafted roving overlaps with yarn end resulting in a thick place with bad appearance called bad piecing.

• Double gaitingIt is a bad practice on tentor in which at yarn break instead of stopping bobbin and taking end from it, he puts a fresh length of yarn and winds it on rotating bobbin and then pieces it. This causes discontinuity in yarn and so, causes stop in winding and increases yarn waste.

• Slough offIt is a fault in winding package in which coils of yarn slip off from improperly built ring frame bobbin during unwinding. These sloughs may form a three strand loop and pass on to the winding package.

6.2 Objectionable and allowable yarn faults Yarn fault elimination from the spinning package during winding requires interruption in winding, and hence each attempt to eliminate a yarn fault increases winding cost. It is worthwhile to eliminate a yarn fault during winding if benefit obtained through fault removal is greater than the added winding cost in eliminating yarn fault. Yarn faults can be categorized as objectionable faults and allowable faults. Any yarn fault which is likely to cause a break in the subsequent processes should generally be eliminated at winding because a break in the subsequent processes like warping, sizing, weaving, knitting, etc., would incur greater cost than that involved in eliminating it at winding. A yarn fault which may not cause a break in the subsequent process but hampers quality of end product (fabric) should be eliminated if benefit obtained though improvement in quality of end product is greater than cost of elimination of fault at winding. For a spinning mill, meeting yarn specifications of the buyer would be of prime consideration. Looking to this, demarcation should be made between objectionable and allowable yarn faults. Objectionable yarn faults are those yarn faults which need to be eliminated from yarn, and allowable faults are those which may be allowed to remain in yarn.


In conventional system of yarn clearing, yarn clearer breaks yarn on detection of a yarn fault. Faulty portion is removed from the winding package and ends are rejoined (Fig. 6.2a). Modern systems of yarn clearing have moved a step ahead and include an added feature. Sometimes, entire yarn on some ring frame bobbins is unacceptable, e.g. a particular ring frame bobbin may be with excessive hairiness. Modern clearing systems detect such bobbin after sensing some yarn length, and break the yarn. Later, entire bobbin is ejected and replaced with a new bobbin. Initial length of unacceptable yarn that was wound is removed (modern automatic winding systems are provided with suck back facility for this) from the winding package and end from winding package is rejoined with that of new bobbin to resume winding (Fig. 6.2b). Winding machine should have suitable system to ensure that this bobbin does not get into the production again.

Figure 6.2 Elimination of yarn faults

6.3 Types of yarn clearersThe yarn clearers are broadly classified as (1) mechanical yarn clearers and (2) electronic yarn clearers. Electronic yarn clearers are very efficient in eliminating yarn faults and therefore they have almost replaced mechanical yarn clearers. Mechanical yarn clearers are used on rewinding machines as supply package yarn is already cleared or are used as pre-clearers prior to electronic yarn clearer in yarn path.

6.3.1 Mechanical yarn clearersMechanical yarn clearers work on two basic principles: 1. Fixed or parallel blade-type yarn clearer 2. Swinging blade-type or trap clearer


6.3.1.1 Fixed blade or parallel blade type of mechanical yarn clearers

The yarn is passed between two metal blades separated by a narrow gap. The gap between two blades form a slit through which the yarn is made to pass during winding. The thick place in the yarn gets jammed between the blades and yarn breaks. The distance between two blades depends upon the yarn diameter, type of yarn and the degree of clearing required. The optimum setting is about twice the yarn diameter for combed yarns and two-and-half times the yarn diameter for carded yarns. Normally these clearers are designed so that the required gap can be adjusted between the two blades by keeping one of the two blades adjustable (Fig. 6.3a). For proper functioning of these clearers, the two blades must be parallel to each lying in the same vertical plane without slant or bow-shaped faces.

6.3.1.2 Swinging blade-type or trap-type clearerPrinciple of working of swinging blade-type or trap-type mechanical yarn clearer is shown in Fig. 6.3(b) which consists of a pivoted slanting spring loaded blade. The blade remains in slanting position due to a spring. A fixed plate, platform or a rod lies beneath the blade. An adequate clearance lies between blade and platform to pass regular yarn pass through it. A thick place in the yarn pushes the blade and forces it to move in the direction running yarn. This closes the opening between blade and platform for the yarn to pass through to break the yarn. The swinging blade may be with plain or with serrated face. The gap between edge of the blade and platform ranges between 3 and 5.5 times yarn diameter depending upon yarn and type of blade. Mechanical yarn clearers are cheap, robust and easy to maintain. Most of the thick places can get squeezed and pass through the clearer without

Figure 6.3 Mechanical yarn clearers


breaking. As the yarn contacts blade edges it gets abraded with the clearer blade. It can liberate dust, fly, etc., and may increase the yarn hairiness.

6.3.2 Electronic yarn clearers Electronic yarn clearers detect yarn faults using electronic principles and therefore are capable of eliminating a wider spectrum of yarn faults very efficiently.

6.3.2.1 Broader spectrum of yarn faults covered by electronic yarn clearers

Mechanical yarn clearers take into account only thickness of yarn faults. Even thin places may also be objectionable which can never be eliminated by a mechanical yarn clearer. Whether a given mass/diameter deviation (thick or thin) is objectionable or not, also depends upon yarn length over which it continues or extent of its repeated occurrence, i.e. • A marginal increase in yarn mass/diameter is not objectionable

if it is present over smaller length. However, if it continues over a substantially longer length, it becomes a fault because that segment of yarn would be seen as a coarser yarn. A spinner’s doubles is an example of such fault.

• A marginal increase in yarn mass/diameter occurring over a smaller length would not be objectionable singly. However, if this occurs in multiple, at periodic or non-periodic length intervals, fabric appearance is adversely affected and therefore it may be objectionable.

• Decrease in yarn mass/diameter occurring over a longer length is also objectionable as that segment of yarn is seen as a finer yarn.

• If a wrong count bobbin gets mixed in the lot, it is preferable to detect and eliminate it.

Modern electronic yarn clearers take in to account deviations in mass/diameter along with its occurrence along the length of the yarn. A portion of yarn without any diameter or mass deviation may be designated as a yarn fault under following circumstances. • Yarn is contaminated. For example, a foreign fiber, such as human

hair or soiled fiber is spun into the yarn. A rust stain on yarn may be objectionable. It is necessary to detect foreign fiber/ contaminations in yarn and eliminate them as they may adversely affect fabric appearance.


• If synthetic foreign matter like polypropylene or nylon fiber gets into cotton yarn, it cannot be visually traced as it is colorless. This fiber usually comes from packing material for cotton bales. If a piece of plastic bag is mixed with cotton at blow room, it may be fragmented into fibers in card sliver. A polypropylene fiber or fragmented plastic bag into yarn does not pick up dye and is seen as a fault after dyeing. It is necessary to detect polypropylene or fragmented plastic bag pieces and eliminate them from yarn.

• Particular bobbin from lot may have yarn hairiness, imperfections or unevenness beyond tolerance level which should be detected and eliminated from getting on to a winding package.

Thus, criteria for fault determination are much broader in modern clearers.Table 6.1 gives defect matrix for spun yarns.

Modern clearers have major control over elimination of defects in columns 1 and 2 of Table 6.1. For column 1 faults, clearer breaks yarn at a yarn fault, faulty yarn portion is removed and ends are rejoined. For faults of column 2, clearer breaks yarn at a fault, faulty yarn portion is sucked away from the winding package and ring frame bobbin is ejected. For faults of column 3 there is limited control of the yarn clearer where as for faults of column 4, there is no control of the clearer in eliminating them.

6.3.2.2 Sensors for fault detectionAll faults cannot be electronically detected with one sensing principle. Three sensors may be required for detection of entire possible range of faults. Mass deviations are detected using capacitance principle. Alternately, diameter deviations are detected using photo-electric principle. Foreign fiber/ contaminant fiber detection also takes place using photo-electric principle but with different arrangement. Hairiness detection is possible only with optical

Table 6.1 Defect matrix for spun yarns

Defect Matrix

(1) (2) (3) (4)

Neps, slubs, piecing, fluffs, long thick and thin places, bad piecings, count variations, contaminations, colored fibers, polypropylene material, poor fabric appearance, extra long thick and thin places

Hairiness variation, pilling, unevenness variation, imperfections

Barre/ streaks, moiré/ periodic variations

Strength variations, elongation variations twist variation, white spots, weak places


principle. To detect polypropylene fiber, a different sensor e.g. one working on tribo-electric principle may be required. Combined signal from an optical and capacitive sensor also enables detection of polypropylene.

Sensors for detecting mass/diameter deviationTwo principles are used for detection of deviations of yarn diameter/mass: (1) optical and (2) capacitance. In an optical electronic yarn clearer (or photo electric clearer) a photo cell is used. A source of light causes light to be incident on a photocell and generates emf. The yarn is made to pass between the source of light and photocell which interrupts the beam of light and therefore lowers the emf generated. Change in emf indicates variation in yarn diameter. In the capacitance clearer, the yarn passes through an air filled condenser. The capacitance of this condenser changes with the mass of material between the plates. Thus, change in capacitance indicates mass of material passing between the plates of condenser at given instant. Both methods suffer from some inherent sources of error. Their comparative evaluation is as follows: 1. Let the change in mass of the yarn be two times the mean value (Fig.

6.4). Let ‘d’ be mean yarn diameter and ‘D’ be the diameter of thick place where yarn mass is doubled. Take equal length ‘l’ of yarn with mean diameter and increased diameter

Taking ratio of mass of these portions,

Massof length of yarn with diameterMassof length of yarn w

' ' ' '' 'l dl iith diameter ' 'D

mm

= =2

12

Now m = ρπd l2

4 and 2m = ρπD l2

4, (r is yarn density)

Substituting values in ratios of masses m and 2m,

mm

d l

D ldD2

12

4

4

2

2

2

2= = =

ρπ

ρπ

\ D2 = 2d2 or D = 2d Thus, if mass doubles, yarn diameter changes only 2 (1.414)

times. In general if mass increases ‘x’ times diameter increases x times. Therefore, optical sensor needs to be very sensitive capable of detecting minor changes in yarn diameter accurately.

2. In optical method of measurement, the measure is based on criteria which are closer to that appreciated by eye. Out of two portions of yarn; one normal and the other soft spun which is bulky with negligible


mass deviation; bulky portion may be objectionable from visual point of view (Fig. 6.5). This bulky portion would be assessed as an irregularity in optical method but as a regular portion in capacitance method because capacitance principle determines mass and not the diameter.

Figure 6.4 Dimensional change of yarn with mass variation

Figure 6.5 Soft spun bulky portion

3. The deposition of dust or fly on optical component in the vicinity of the thread line can obstruct light and give rise to error in measurement. Therefore, the sensor area should be maintained absolutely clean and free from any deposition to avoid error.

4. The area of shadow cast by a flat elliptical slub depends upon its orientation with respect to direction of beam as shown in Fig. 6.6. If flat portion is oriented along direction of beam of light, area of shadow cast would be less and the slub may escape detection. If faults are scanned from more than one direction, this error can be avoided.

5. The capacitance of the capacitor depends upon the mass of the yarn as well as the dielectric constant of fibers. The dielectric constant of most of the textile fibers is in the range of 1.5 to 8.0. Therefore, with a blended yarn (e.g. a yarn composed of blend of polyester–cotton, polyester–viscous, wool–polyester, etc.) of two fibers say ‘A’ and ‘B’ in the portion 50:50, the resultant dielectric constant of yarn depends upon the constant of its components i.e. ‘A’ and ‘B’. If there is a large difference between the dielectric constant of fibers ‘A’ and ‘B’,

Figure 6.6 An elliptical slub through optical sensor


even in a regular yarn with variations in blend proportion (due to improper homogenization in spinning), different parts of yarn would give different resultant dielectric constant. Hence, this yarn would be sensed as an irregular yarn.

6. Textile fibers are hygroscopic. The absorption of moisture may bring about a large change in dielectric constant because dielectric constant of water is very high, i.e. 81. Therefore, changes in moisture content will be treated as irregularities in yarn even though the yarn may be regular. Thus, capacitance clearers are sensitive to moisture content in the yarn. Capacitive clearer would face difficulties on winding machines using wet splicer in which water particles are incorporated during splicing and yarn becomes wet. This is not so with photoelectric yarn clearers.

7. Optical sensor is capable of simultaneously detect yarn hairiness. With only capacitive sensor, it is not possible to detect yarn hairiness.

Sensors for detecting contaminant fiber detection/ foreign fibersRust stain, dirty fiber, residue of packing material fiber, human hair, vegetable material, etc., are contaminants/ foreign fibers in a yarn which become visually objectionable especially at fabric stage. It is necessary to detect these contaminants/ foreign fibers at winding stage and eliminate them. Yarn clearers employ different principles of sensing to detect contaminants/ foreign fibers. An additional sensor may be required to detect contaminants/ foreign fibers. A contaminant/ foreign fiber may be a darker portion on a lighter background of yarn or a lighter portion on a darker background of yarn (for dyed yarns) as shown in Fig. 6.7. Darker contamination may be due to vegetable matter (e.g. fragments of plant parts in a cotton yarn) or non-vegetable matter. Darker vegetable matter appears in grey yarn. However it is likely to disappear after bleaching and may not be objectionable. Therefore, it is desirable to distinguish between darker vegetable matter (which may be allowed to remain in yarn) and non-vegetable matter (which need to be eliminated).

Figyre 6.7 Yarn contaminants


Principle of detection of yarn contaminationsFigure 6.8 shows principle of contaminant fiber detection which works on optical principle. ‘2b’ and ‘2c’ are light sources on the same side of the photocell ‘1’. Light source ‘2a’ lies opposite to photocell. As shown in Fig. 6.8(A), light from sources ‘2a’ and ‘2c’ reflect from yarn and is received by photocell. Yarn obstructs light from source ‘2a’. With a thicker place, yarn incident on photocell from source ‘2a’ decreases but that due to reflection from sources ‘2b’ and ‘2c’ increases. If yarn is absent (Fig. 6.8B), yarn from light source ‘2a’ reaches photocell without any hindrance whereas light from sources ‘2b’ and ‘2c’ does not reflect and therefore is not received by photocell. The light received by photocell remains the same in presence or absence of yarn or with a thick or thin place. In this principle, yarn is made to ‘disappear’ even if it is present at sensor. On arrival of contaminant fiber, light reflected from yarn from sources ‘2b’ and ‘2c’ reduces and therefore, light received by photo cell decreases. Thus, reduction in emf indicates darkness of contaminant fiber. Green light is used as it gives very good contrast at contamination. Degree of darkness of contamination is measured by this sensor. This principle was invented by CSIRO research laboratory of Australia.

Figure 6.8 Principle of foreign fiber detection

Differentiation between vegetable and non-vegetable contaminationAs vegetable contamination tends to disappear on bleaching, it may be allowed to remain in yarn whereas non-vegetable contamination needs to be eliminated during winding. Through only optical principle, it is not possible to differentiate between vegetable and non-vegetable contamination. A combination of optical and capacitance measurement can differentiate between these two contaminations.

Sensor for detecting polypropylene kind of contaminationLoepfe employs triboelectric principle for detecting polypropylene kind of contamination. Fibers other than cotton acquire static charge due to friction.


Fibers such as polypropylene, polyester, polyacrylic etc. tend to develop negative static charge whereas nylon, wool, silk, etc. develop positive static charge. Cotton yarn carries static charge where such contaminant fiber is present. Cotton yarn is made to pass over a sensor with conductive ceramic where exchange of electron takes place between charged fiber present in cotton yarn and conductive ceramic. Measure of this triboelectric voltage determines contamination. Uster quantum clearers detect polypropylene from suitable interpretation of output from optical and capacitance principle.

6.4 Instrumental measurement of yarn faultsThe output from electronic measurement of yarn faults can also be used as a means to quantify and classify faults present in the yarn.

6.4.1 Dimensions of faultFollowing are the dimensions of yarn faults: • Fault thickness • Fault length • Extent of fault contrast (for contamination/ foreign fiber)

6.4.1.1 Thickness/cross-section deviation as a fault dimension

The thickness or diameter of fault may be expressed as a number indicating how many times greater the thickness of the fault is comparing with mean thickness. So number ‘2’ indicate that thickness of the fault is 2 times that of mean. Change in cross-sectional area is indicated in percentage. So 0% indicates no change in mean cross-sectional area. A cross-sectional area change of 100% means a thick place with 100% increase in cross-sectional area, i.e. double cross-sectional area than normal one. A thin place is indicated by minus % decrease in cross-sectional area, e.g. -30% indicates decrease in cross-sectional area by 30%. A thinner place can be indicated in terms of diameter as follows. When a fault is indicated in terms of multiple of yarn mean diameter (or thickness), number ‘1’ indicates normal diameter so a thinner place can be indicated by a fraction. So fault thinness indicated by 0.63 indicates that thinness is 0.63 times normal yarn diameter.


6.4.1.2 Length as a fault dimensionWhether a given diameter/ mass deviation is objectionable or not depends upon length over which it continues. A marginal increase in yarn diameter/ cross-sectional area continuing over a long length is objectionable. A fault with smaller dimensional increase in diameter/ cross-section over a smaller yarn length is not objectionable individually but its frequent occurrence over periodic/ non-periodic interval may be objectionable.

6.4.1.3 Extentofcontrastofcontamination/foreignfiberwith yarn

Whether a contamination/ foreign fiber is objectionable or not is determined by extent of its contrast with yarn as well as length over which it occurs. Greater contrast is more objectionable than a lesser one. Length of contamination/ foreign fiber is also to be considered.

6.4.2 Yarn fault classification

6.4.2.1 Graphical representation of a faultIn a graph of fault diameter (or cross-section) v/s fault length, any fault can be represented as a point (Fig. 6.9). Point ‘A’ in Fig. 6.9 indicates a fault with 200% increase in diameter and length of 4 cm. Electronic yarn clearer can record fault cross-section change as well as its length. If a testing system is developed that records each fault on graph of fault diameter (or cross-section) v/s fault length, each fault will be recorded as a point and output on graph will be in form of several points as shown in Fig. 6.9.

Figure 6.9 Graphial representation of a yarn fault

Figure 6.10 Uster Classimat II


6.4.2.2 Uster Classimat II, Classimat III and Classimat V yarnfaultclassificationsystems

For simplicity of presentation and interpretation of yarn faults present in the yarn, yarn fault classification systems are developed. Yarn fault classification is a system that records yarn faults and classifies them in various classes. Uster yarn fault classification is widely accepted worldwide. Figure 6.10 shows Uster Classimat II yarn fault classification of Uster. Uster Classimat II classifies yarn faults in 23 classes. Change in cross-sectional area is shown on ‘y’ axis and fault length in centimeters is shown on ‘x’ axis. Class ‘A1’ includes faults whose cross-section increase is greater than or equal to +100% and length from 0.1 to 1 cm. Class ‘B3’ includes faults whose cross-section increase is greater than or equal to +250% and length ranging between 1 cm and 2 cm. Class ‘I2’ include faults whose decrease in cross-section is below −45% and length exceeding 32 cm. Conversely, a fault say a cross-section increase of +175% and length of 3 cm fault is counted in class ‘C2’, ‘C3’ as well as in ‘C4’ or a fault with cross-section increase of 700% and length of 0.2 cm will be counted in class ‘A4’.Output of Uster classimat II is in form of number of faults present in yarn tested. An output for a test done with PES/cotton 65%/35% (blended yarn) of 20 tex yarn on Uster classimat II is shown in Fig. 6.11.

The output sheet is for 158 kilometers of yarn of 20 tex tested. The number of faults counted in classes ‘A1’, ‘A2’, ‘A3’ and ‘A4’ are 85, 12, 2 and 1, respectively. Similarly for classes (B1-B4), (C1-C4), (D1-D4) are (17,6,1,0), (8,2,1,0) and (3,2,1,1), respectively. Standard test length is 100 kilometers. Minimum 100 kilometers of yarn length has to be tested. The system also converts the faults counted for the tested length into faults corresponding to a standard yarn length of 100 kilometers. Subsequently introduced Uster Classimat III yarn fault classification system has four additional classes ‘A0’, ‘B0’, ‘C0’ and ‘D0’ over Clasimat II shown in Fig. 6.12(a). Current version Classimat V is introduced having

Figure 6.11 Uster Classimat II output


added features. Classimat II and III classify only thick and thin places and needed only capacitive sensors. Classimat V classifies contaminants and polypropylene also. Therefore, a separate optical contaminant sensor is provided. It also differentiates between vegetable and non-vegetable maters. Through interpretation of signals from capacitive and optical sensor, polypropylene contamination is also detected and classified. In classification of thick and thin places, 7 thick place and 11 thin place classes are added in Classimat V over Classimat III (Fig. 6.12b). Moreover, classifications of added parameters like foreign fibers, vegetable content and periodic faults is also given. When neps, thick and thin places, foreign matter, polypropylene, yarn evenness, imperfections and hairiness is found beyond acceptable limit, it is reported. Apart from this it has other features which become useful to analyze and optimize clearing limits, long-term analysis of all parameters and compare them to internal or international benchmarks, compare the test results with the best achieved during the last one year etc.

Output of yarn fault classification is useful in different ways as- 1. Quality of yarn spun on a spinning machine can be judged by testing

yarn using Uster classimat II/ III/ V. 2. Classification of yarn after clearing on winding machine indicates

efficiency of a yarn clearer. 3. From yarn fault classification output, corrective measures can be

taken in spinning. 4. Yarn fault classification helps in optimizing settings of electronic

yarn clearer. 5. It allows internal or international benchmarking.

Figure 6.12 Uster Classimat III and Classimat V


6.5 Basic yarn clearing with electronic yarn clearers6.5.1 Clearing levelYarn fault classification indicates fault level content in yarn. A fault is eliminated at the cost of interruption in winding and therefore increases winding cost. It would not be, therefore, worthwhile to eliminate all faults. The distinction has to be made between the defects to be removed, i.e. objectionable faults and the defects to be allowed to remain in the yarn (i.e. allowable faults) in order to maintain satisfactory level of efficiency of winding machine. Accordingly, there would be different levels of yarn clearing; a stricter level would aim at eliminating more faults whereas a liberal one would eliminate less faults.

6.5.2 Clearing curveOn fault length v/s fault diameter/cross-section diagram, a curve drawn that separates objectionable faults from allowable faults is called a clearing curve.

6.5.2.1 Desired clearing curveDesired clearing curve is a clearing curve that the user of the electronic yarn clearer desires to achieve (Fig. 6.13a). This curve reflects the judgment of the user and his demands in regard to the performance of the yarn clearer and is concave in shape owing to practical requirement. A fault corresponding to point ‘A’ (Fig. 6.13b) is very short in length but would be objectionable because it is several times thicker than yarn mean yarn diameter. A fault corresponding to point ‘B’ occurs over a shorter length and would not be objectionable because of its lesser diameter. However with same diameter, a fault corresponding to point ‘D’ would be objectionable owing to its greater length. A fault corresponding to point ‘C’ is not objectionable because of its shorter length as well as marginal increase in yarn diameter. However a fault corresponding to point ‘E’ is objectionable because marginal increase in yarn diameter continues over a long length. Thus, generally the more the standard yarn diameter exceeds, the less length can be tolerated in the defect. A thin fault does not cause an obstruction. Thin places become objectionable if they continue over longer lengths [point ‘F’]. For a thin place to be objectionable, cross-section decrease has to be at least by 30%.


6.5.2.2 Actual clearing curveActual clearing curve is a curve that can be practically achieved using an electronic yarn clearer. The user has not to input the desired clearing curve to achieve the desired clearing level but has to input values of sets of yarn diameter/ cross-section and fault length values in the setting panel of an electronic yarn clearer. Each set of value of fault diameter/ cross-section and length determines shape of clearing curve in a particular region. Therefore, clearer characteristics and its setting possibilities determine actual clearing curve. Modern clearers display clearing curve that would be obtained with given input of values.

6.5.3 Clearer characteristics

6.5.3.1 Broad categorization of yarn faultsYarn fault classification system classifies yarn faults in several classes. Practically, based on certain range of yarn fault diameter and length, yarn faults are broadly categorized into different groups as neps, short places, long places/ double ends / spinner’s doubles and thin places (Fig. 6.14).

Figure 6.13 Desired clearing curve

Figure 6.14 Broad categorization of yarn faults


• Neps – Neps are defects that are extremely short (no larger than few mm) and extremely thick in multiples of normal yarn diameter.

• Short places – Short places are defects of limited length and of substantial thickness/ cross-sectional increase.

• Long places, double ends and spinner’s doubles – Long places are defects of substantially longer lengths with marginal increase in yarn diameter/ cross-sectional area. Double ends are caused by two ends being pulled off simultaneously while spinner’s doubles are caused by two rovings spun together. These defects are extremely long.

• Thin places – Thin places are defects of substantially longer lengths with decrease in yarn diameter/ cross-sectional area.

In setting panel of an electronic yarn clearer, the user has to input values of sets of diameter and length that shapes clearing curve in particular region to selectively eliminate particular category of yarn faults.

6.5.3.2 Shaping a clearing curve through input of sets of values of fault diameter and length

As per requirement, the user has some desired clearing curve which he aims to achieve from a given yarn clearer. But the actual clearing curve that one can get with a given yarn clearer depends upon the technical concept of a particular clearer. In the controlling panel there is no provision to feed the clearing curve that one desires, but a set of instructions (settings) of length and diameter of fault that determines actual clearing curve that is achieved. Suppose the length and diameter of fault to be removed is set as – • Fault length 3 cm and fault diameter 2.5 With this setting, say, clearer is asked to remove faults with dimension greater than or equal to 2.5 times in yarn diameter and 3 cm in length. With this logic, theoretically, the clearing curve that one obtains with this instruction, would be as shown in Fig. 6.15(a).

Figure 6.15 Shaping a clearing curve through channels


It is quite obvious that the curve is not concave. With the same input values, form of curve shape obtained can be modified through suitable mathematical treatment. However, the curve obtained would not be able to eliminate neps, long thick places, spinner’s doubles and thin places selectively. For greater scope of selection of removal fault, more number of instructions of length and diameter of fault should be given.So if one more set of instructions is added as: 1. L = 3 cm, D = 2.5 times 2. L = 30 cm, D = 1.5 times The resultant clearing curve would be as shown in Fig. 6.15(b). With this added set of instruction, the long thick places are selectively removed which but neps and thin places would not be eliminated. If one more instruction only of diameter is added as: 1. L = 3 cm, D = 2.5 times 2. L = 30 cm, D = 1.5 times 3. D = 7 Then resulting clearing curve would be as shown in Fig. 6.15(c). This additional instruction will take care to remove the neps. User has to feed values of yarn fault length and diameter values in control panel. Each set of instruction of fault length and diameter is called a channel. Changing the values of yarn fault length and diameter changes the resultant curve generated. A channel is designated with a name depending upon the region of clearing curve it mainly shapes. With reference to Loepfe Zenit clearer the channels and setting range is given in Table 6.2.

Table 6.2

S r . No.

Channel Symbolic representation for diameter

Diameter Symbolic representation for length

Fault length in centimeters

1. Neps channel N 3 to 11 times – –

2. Short places DS 1.10 to 4.00 LS 1 to 10 cm

3. Long places DL 1.04 to 2.00 LL 6 to 200 cm

4. Thin places −D −6% to −60% −L 2 to 200 cm

With modern yarn clearing systems, clearing curve obtained with given channel setting values is projected into the classification window on screen for each group which helps in optimizing settings. In yarn path of modern winding machines, electronic yarn clearer sensing head is located after yarn splicer. After splicing, each splice is checked by


electronic yarn clearer. Separate clearing limits are to be input for splice. These setting values are active during the initial 35 cm of wound yarn on Loepfe Zenit yarn clearer.

6.6 Additional yarn clearingChannel clearing allows only basic yarn clearing which does not take care of elimination of many other disturbing faults like periodic defects, count variation, excessive CV variation, excessive hairiness, foreign fiber detection etc. To eliminate these places, additional set of instructions are to be input.

6.6.1 Detecting periodic defectsPeriodic yarn faults are thick and thin places, which always occur with the same distance. Such faults are caused in the spinning process when the yarn guiding elements are defective. An eccentric front roller of the ring spinning machine leads to a periodic faults of a wave length of 8 cm. The size of each individual fault is mostly not disturbing. But as a series of yarn faults, they can well be disturbing. Periodic yarn faults are known as ring spinning moiré. The user has to input four parameters for periodic defects (Fig. 6.16): • Minimum faults size • Minimum fault length • Distance from yarn fault to yarn fault • Number of faults until a cut takes place

Figure 6.16 Periodic defects

6.6.2 Eliminating bobbins with count variationsA bobbin with wrong count in a lot would adversely affect the quality of end product. Suppose a coarser count bobbin gets mixed in a lot, it would produce a thick line along very long length of woven fabric if woven as warp which is not acceptable. A bobbin belonging to the same lot may have count variations along its length. There are various reasons for count variations such as:


• deviations by mixing wrong bobbins • peeled-off or uneven roving can lead to varying counts within a

bobbin • missing of a fiber componentThere are two channels for detecting count variations: • To detect a wrong count bobbin getting mixed in a lot, at the start-up

of each bobbin, the channel monitors yarn count. On checking certain preset length, the clearer identifies whether count is correct or not. No action is taken if count is correct. For wrong count bobbin, the winding unit is stopped and a corresponding alarm is triggered. On automatic winding machines with suck back facility, the yarn length wound from wrong count bobbin is sucked away and the bobbin is ejected. This channel remains active during start-up phase only. The C-channel in Uster Quantum clearers monitor’s wrong count bobbin. The user has to set reference yarn length at start-up and extent of increase and decrease of mass/diameter to conclude about wrong count.

• The other channel monitors the yarn count over the whole winding process. The CC-channel in Uster Quantum clearers monitors wrong count bobbin. In this channel the user has to set extent of increase and decrease of mass/diameter as well as length of yarn within the bobbin to conclude about count variation.

6.6.3 Foreign fiber/ contaminant clearingWhether a given foreign fiber/ contaminant is objectionable or not depends upon degree of its contrast with the yarn as well as length. Optical principle is used for detection of foreign fiber in which comparison between reflections from normal yarn color and foreign fiber is carried out. A very dark fiber in a light yarn would produce a higher contrast than the same fiber in a yarn made of grey fibers. Similarly, a very light fiber in a dark yarn would produce a higher contrast than the same fiber in a yarn made of light colored fibers. The user has to input degree of contrast between foreign fiber/ contaminant and normal yarn as well as length. An individual contamination with lesser contrast with normal yarn and occurring over a short length would not be objectionable. However repeated occurrence of the same within a short distance is objectionable. In Loepfe Zenit clearer, the user has to input number of repetitions (range 0–9), monitoring length from 0.1 to 80 m and number of faults from 1 to 9999 can be selected separately for the detection of dark and light foreign matter.


Table 6.3 gives setting range for elimination of disturbing yarn faults for Uster Quantum 2 clearer.

Table 6.3

Subject Quality characteristics

Abbreviation Sensitivity Reference length

Options needed

Comment

Elimination of disturbing thick and thin places

Neps N 100…500% <1 cm The clearing curve can be optimized by means of 6 auxiliary setting points of S, L and T faults

Short thick places S 50…300% 1…8 cm

Long thick places L 20…200% 8…200 cm

Thin places T −12…−90% 2…200 cm

Elimination of wrong counts

Wrong bobbin (count variations during start up

CpCm

+1…80%

−1…−80%

20…1000 cm

Long thick and thin places (count variations during winding process)

CCpCCm

+1…+150% −1…−80%

60…1000 cm

Monitoring of long thick and thin places

Elimination of pearl chains (periodic thick places)

Pearl chain like yarn faults

PC 18…100% 1.6…800 cm

Q Furthermore, setting of the fault length: 1 – 50 cm and number of faults: 5-50

Elimination of foreign fibers

Dark foreign fibers in light yarns

FD 5…100% 0.2…100 % Q, F There are 6 auxiliary setting points for the FD-channel

Polypropylene fibers

PP 38…50% 1.0…10 cm Q, F PP Only available with C15 clearer

6.6.4 Online yarn fault classification displayModern clearing systems display online classification of faults.

6.6.4.1 OnlineclassificationofbasicyarnfaultsModern yarn clearing systems give online yarn fault classification. It displays Number of faults of given class eliminated as well as retained are displayed. Thus, number of yarn faults of each group remaining in a winding package after yarn clearing is also displayed. An option of alarm system is offered that alarms if number of yarn faults remaining in a winding package exceeds


predefined limit. Uster Quantum series of clearers display yarn faults as a scatter plot (representation of each fault as point) into the classification window.

6.6.4.2 Onlineclassificationofforeignfiber/contaminationAs discussed in 6.4.1.3, a foreign fiber/ contamination is characterized by its degree of contrast over yarn background and length over which it is present. Modern clearer systems give online classification of foreign fiber/ contamination where on ‘x’ and ‘y’ axis fault length and degree of contrast are indicated.

6.6.4.3OnlineclassificationofyarnsplicesAs discussed in 6.5.3.2, each splice is cleared according to clearing limits of splice channel. The clearing system displays online classification of splices.

6.7 Assessment of clearer performanceThe performance of the yarn clearer is assessed by two parameters – (i) Clearing efficiency and (ii) Knot factor.

6.7.1 Clearing efficiencyClearing efficiency is defined as the number of objectionable faults removed by a yarn clearer expressed as percentage of total of faults present in the yarn before clearing.

Clearing efficiency = Number of faults removed by yarn clearer

Number of faultspresent in yaarn before clearing×

100

Clearing efficiency of 35% indicates that out of 100 objectionable faults present in the yarn before winding, 35 are detected by the yarn clearer while 65 escape. Thus, higher the value of clearing efficiency better is the performance of yarn clearer.

6.7.2 Knot factorYarn clearer is expected to cause a yarn break only at objectionable faults. However, a yarn clearer may break yarn even in absence of yarn fault which is not desirable. Knot factor expresses performance of yarn clearer in this


regard. Knot factor is the ratio of total number of breaks caused by yarn clearer to total breaks caused to eliminate objectionable faults.

Knot factor =

Total number of knots (or splices) caused to piece all breakscaused byy yarn clearer

Number of knots (or splices) caused to replace onlyobjjectionable faults

For example, if numerator is 100 (100 is the number of knots put to join all breaks caused by yarn clearer) and denominator is 25 (out of 100 breaks only 25 breaks are caused to replace objectionable faults, i.e. 75 breaks are caused by a yarn clearer unnecessarily).

Then knot factor = 10025

4=

It indicates that the total number of knots put to join all breaks in yarn caused by the yarn clearer is 4 times greater than that caused to remove objectionable faults. Ideal value of knot factor is 1, i.e. a clearer breaks yarn only at yarn faults. Thus, higher knot factor indicates poor performance of a yarn clearer. Narrowing clearer setting may increase clearing efficiency but may result in an undesirable increase in knot factor. Upon a yarn break during winding, the yarn ends coming from supply package and winding package are required to be joined to resume winding.

6.8 Methods of yarn joiningThe ends of yarns may be joined by knotting or by a joint without knot. Spliced yarn joint is mostly a preferred method of knotless yarn joining.

6.8.1 Yarn joining by a knotThere are mainly three types of knots used to join ends on winding machines: dog knot, weaver’s knot and fisherman’s knot as shown in Fig. 6.17.

Figure 6.17 Various knots for yarn joining


Knot can be tied by hand or by a mechanical knotter [hand operated (on non-automatic winding machine) or automatic (on automatic winding machine)]. The knot should be resistant to slippage. A bulky knot should be avoided as it may cause serious obstruction at places like heald eye or reed to cause an end breakage or can hamper appearance to fabric. The tail ends should be shorter otherwise they can cause entanglement with neighboring ends in warp sheet. Fisherman’s, weaver’s and dog knot rank in decreasing order of resistance to slippage. In case of fisherman’s knot for ‘Z’ twist yarns, the overhead knots be ‘S’ knots and vice-versa. For doubled balanced yarns, the direction of overheads is not important. In practice it is not convenient to tie fisherman’s knot by hand. Weaver’s knot is easy to tie manually by hand with sized yarn compared to unsized yarn. With limpy yarn it becomes difficult to tie weaver’s knot. Portable hand knotters (weaver’s knotter or fisherman’s knotter) are used on non-automatic winding machines.

Figure 6.18 Portable pneumatic wet splicer on TFO twisting (Courtesy: Mesdan)

6.8.2 Yarn joining by a spliceKnot is a joint which is likely to cause a break on loom due to obstruction in a heald eye or reed during weaving, or can give bad appearance in fabric. To get rid of disadvantage of a knot, a knot-free yarn joint, called spliced joint


is developed. This joint is only slightly thicker than average yarn diameter, visually unobjectionable and does not cause obstruction to the mechanical operations and possess sufficient strength for further processing. A spliced joint can not be created by hand but requires a device called ‘yarn splicer’. A yarn splicer very commonly is a standard element on an automatic winding machine. Hand-operated splicers are also available to create a knotless joint at various stages (Fig. 6.18). There are three basic methods of yarn splicing: pneumatic splicing, mechanical splicing and electrostatic splicing. Pneumatic splicers are widely used whereas mechanical splicers find limited use. Electrostatic splicers have not reached the stage of commercialization. Twin-splicer is a mechanical splicer offered on Savio automatic winding machines as an option over pneumatic splicing.

6.8.2.1 Stages of splicing a spun yarnSpun yarn splicing involves three stages (Fig. 6.19). 1. First stage consists of removal of twist from some length of yarn ends

to be spliced. This operation is called untwisting or opening. 2. After removing twist, the opened yarn portions are overlapped on

each other. 3. Subsequently, the untwisted overlapped ends are twisted to rejoin the

yarn ends.

Figure 6.19 Stages of yarn splicing


6.8.2.2 Pneumatic splicingIn pneumatic splicing, operations of opening of yarn ends and their subsequent twisting is carried out pneumatically. Principle of pneumatic splicers of different makes is the same. However, construction of various elements, setting procedure, etc., varies from one make to the other. The following description of pneumatic splicing refers to Schlafhorst range of pneumatic splicers.

Splicing cycle on an automatic winding machineTypical splicing cycle on Schlafhorst automatic winding machine diagrammatically is illustrated in Fig. 6.20. As shown in Fig. 6.20(A), the yarn ends coming from winding package and supply package are led over a vortexing chamber. The bottom end coming from supply package is led over the vortexing chamber and then over the mouth of the untwisting tube located above vortexing chamber. It is held at the end by suction. A gripper holds the end coming from the supply package below vortexing chamber. The top end coming from winding package is led over the vortexing chamber and then over the mouth of the untwisting tube located below vortexing chamber. It is held at the end by suction. A gripper holds the end coming from the supply package above vortexing chamber. A lid closes the vortexing chamber. As shown in Fig. 6.20(B), compressed air supply is given to both the opening tubes and immediately the ends are cut by a cutter. Both ends get in to their respective opening tubes and are opened (Fig. 6.20C). Subsequently, the opened ends are brought into the vortexing chamber by action of feeder levers. Feeder lever of each end moves between two fixed guides that brings the ends into the vortexing chamber. A blast of compressed air in the vortexing chamber joins the overlapped ends (Fig. 6.20D) and thus a spliced joint is created (Fig. 6.20E). Figure 6.21 shows splicing cycle on Oerlikon Schlafhorst Autoconer winding machines. Yarn ends from supply and winding packages are placed in the splicer (Fig. 6.21A). Lid has closed the splicing chamber and yarn ends gripped at feed end and on cutting at the other end are sucked in their respective opening tubes (Fig. 6.21B). Figure 6.21(C) shows action of an opening tube. Untwisted ends are being withdrawn from opening tubes and brought in spicing chamber (Fig. 6.21D). Ends brought in splicing chamber are twisted (Fig. 6.21E).


Figure 6.20 Splicing cycle on an automatic winding machine

Figure 6.21 Spicing cycle on Schlafhorst Autoconer winding machines (Courtesy: Oerlikon Schlafhorst)


Opening of yarn endsTypes of opening tubes – Opening tubes: also called as untwisting tubes, retainer tubes or holding pipes open (i.e. untwist) yarn ends. Twist of some length of yarn is opened by air vortex. There are different types of opening tubes. Very common among them is a hollow tube cut with an oblique hole extending from outer surface to inner hollow portion. When compressed air flows through this hole from out side to inner hollow portion, a vortex of air is generated inside the tube. Direction of vortex depends upon obliquity of the hole. Therefore, opening tubes for opening ‘S’ and ‘Z’ yarns are different. For opening of ply yarns, having ‘S’ over ‘Z’ or ‘Z’ over ‘S’ twist, a vortex or air would not be able to open ends. For opening such yarns, a tube with axial bore may be employed (Fig. 6.22). The air molecules would move at high speed around yarn and set up pulsating yarn movement to open the twist. The axial bore tube can open up ‘S’ as well as ‘Z’ twisted yarns. Yarns such as compact yarns are difficult to open with usual opening tubes due to their consolidated dense structure. For opening such yarns, opening tubes with saw teeth inside are developed as shown in Fig. 6.22. The saw teeth offers aggressive surface to the cut yarn end for opening. Opening tubes with saw teeth are also used for opening high twist yarns. A ceramic guide plate is to be used with saw tooth opening tubes. High twist yarns would have tendency to shrink suddenly upon cutting the yarn. Due to this, yarn may move away instead of getting sucked into the opening tube. Therefore, ceramic guide on plate acts as an extension of opening tube beyond that plate which helps in sucking the yarn in the opening tube immediately upon cutting it. For opening stiff and very coarse yarns, blower opening tubes are used. Stiff and very coarse yarns become “stubborn” and offer greater resistance to sucking action of yarn in the opening tube. For such yarns blower nozzles are developed. Blower nozzles have inner bigger diameter that gives grater space for opening of coarse and stubborn yarns. Moreover, they extend more beyond cover plate so that the ends lie closer to opening tube and are sucked effectively in the opening tubes. Thus, different types of opening tubes are • Z-tube for opening of Z-twisted yarns • S-tube for opening of S-twisted yarns • Axial tube for S- and Z-twisted yarns • Saw tooth-tube for opening of high-twisted yarns (as Z- and S-type)

and compact yarns • Blower nozzles (for stiff and coarse yarns.)


Action of an opening tube – The flow of air generates partial vacuum inside the tube (increase in air velocity decreases the pressure). So, air out side the tube with relatively higher pressure, rushes into the tube. Therefore, if a yarn end is held outside the tube and cut, it would go inside the tube on passing compressed air. Inside, the tube yarn comes under influence of air flow and is untwisted to get parallel arrangement of fibers (Fig. 6.23). On opening of the yarn ends, some short fibers get removed from it.

Figure 6.22 Various opening tubes (Courtesy: Oerlikon Schlafhorst)

Figure 6.23 Action of an opening tube

Optimization of opening air pressure and duration – For creating a good splice, optimum opening is required. Opening action with a given opening tube is influenced by opening air pressure and its duration. It is necessary to optimize opening air pressure as well as its duration. Referring to Fig. 6.24, an excessive pressure and/or duration may twist yarn in opposite direction after opening it. An excessive pressure may detach a lump of fibers from opened ends which would result into a poor splice. Inadequate air pressure and/ or opening will not adequately open yarn ends. Only an optimally opened yarn ends result into good splice. On Oerlikon Schlafhorst splicers, opening pressure is adjustable between 0 and 10 bars. Practical range of pressure for most yarns is between 3 and 6 bars. Opening duration is adjustable between


0 and 700 milliseconds. Practical range of opening duration lies between 300 and 700 milliseconds.

Opening tube radial position – Opening tube radial position is also an important factor on Oerlikon Schlafhorst splicers that can be altered by a setting tool. Setting tool-angled arm position is compared with hour hand of clock (Fig. 6.25A). As shown in Fig. 6.25(B), standard position for ‘S’ twist yarn is • for upper opening tube 9 o’clock and lower one 3 o’clock. For ‘Z’ twist yarn, standard position is (Fig. 6.25C): • For upper opening tube 3 o’clock and lower one 9 o’clock. For exceptional cases, for both ‘S’ as well ‘Z’ twists, the recommended positions for upper and lower opening tube is 7 o’clock and 1 o’clock, respectively (Fig. 6.25D). This position gives more direct aggressive air pressure on yarn.

Figure 6.24 Optimun opening

Figure 6.25 Radial position of an opening tube


Why radial position of tube influences intensity of air action is illustrated in Fig. 6.26. Position of air supply for both the opening tubes is fixed which is shown in Fig. 6.26(A). Figure 6.26(B) shows it for lower opening tube for 9’oclock setting. It can be appreciated that the inlet air supply opening and air aperture on opening tube do not coincide with each other which lowers intensity of air action on yarn. For the same tube, in 1 o’clock position the inlet air supply coincides with aperture of opening tube which gives maximum intense air action for opening. Thus radial tube position influences the extent of offset of air aperture of opening tube with respect to inlet air supply opening and thereby affects intensity of opening. 7 o’clock to 1 o’clock position gives the most intense action where as deviation from this decreases opening air intensity.

Figure 6.26 Significance of radial position of opening tube

Splicing of overlapped opened endsAction of splicing chamber – Opened ends are overlapped into a chamber called vortexing/ splicing chamber where vortex of air twists the overlapped fibers and a spliced joint is created. Initially, two different principles of air movement were developed for hand-operated pneumatic splicer for filament yarns viz. the tangential system and the direct system. In tangential system, the inlet blowing orifices for compressed air generate air vortex in the spicing chamber which tends to twist the overlapped fibers. In direct system, the blowing orifice generates air turbulence in the splicing chamber which tends to thoroughly mingle the overlapped fibers and entangle them with one another to create a spliced joint. Applying these principles for spun yarns, the tangential system was found suitable for short staple yarns but not for long staple, plied or high twist yarns. The direct system was found ideal for long staple yarns, good for plied and woolen/ worsted spun yarns. For plied yarns


also this system gave good success rate. A suitable combination of these two can lead to desired result. Splicing chamber is also called as a prism in Oerlikon Schlafhorst splicers. Splicing chamber with the tangential system consists of two blowing orifices whereas that for the direct system is with one blowing orifice. A combination system has usually three blowing orifices: two for the tangential and the third one for direct. Some prisms have four, instead of two, blowing orifices for tangential and one for direct, i.e. five blowing orifices in total. Splicing chamber may be provided with an exhaust channel which is an additional cross-wise slit. Thus, major variables associated with prism construction are (1) height of prism, (2) width of splicing chamber, (3) number of blowing orifices (one, two, three or five), (4) in case of single orifice prism, shape (may be circular or rectangular) and dimension of orifice, (5) dimensions of blowing orifices in case of two/ four blowing orifices (tangential system and their distance from prism center), (6) option of exhaust channel and (7) prism material (aluminum alloy, steel, brass (for water splicer)). Figure 6.27 shows some splicing chambers. It is necessary to select an appropriate prism according to yarn to be spliced. A code is assigned to each variety of prisms. For example, in prism with prism code DZ 3/16.1E, each alphabet/ number indicates as follows: D = direct air pressure, Z = twist, 3 = size of the splice area (no scale), 16 = height of the prism (in mm), 1 = distance between splice holes and the middle of the prism (no scale), E = with venting channel Figure 6.28 diagrammatically shows what each digit/ alphabet of the code of prism signifies.

Figure 6.27 Splicing chambers


Optimization of splicing air pressure and duration – For creating a satisfactory splice it is necessary to optimize 1. splicing blast air pressure 2. blast duration Range of splicing blast pressure is 0–10 bar. Practical range is 3–7 bars. With regards to blast duration, two options are offered. In first option only single blast of desired duration is given. In second option, an initial blast of desired duration is given which is followed by pause of desired duration, and ultimately a final blast of desired duration is given. This blast–pause–blast pattern results into somewhat irregular air flow pattern which is found to give better result for some yarns. Practical experience says that single blast gives good appearance where as blast–pause–blast pattern gives good strength. Duration of blast is input in form of values in ‘Informator’. Value input multiplied by 20 gives blast duration in milliseconds. For example, if value of 8 is input for single blast, blast duration becomes 8 × 20 = 160 ms. For initial blast-pause-final blast pattern, three values are to be input, e.g. input of 5-3-6 gives initial blast of 100 ms, pause of 60 ms and final blast of 120 ms. Total blast duration should not exceed approx 440 ms (sum of values should not exceed 22). Feeder arm movement – Feeder arm draws opened yarn ends from the opening tube and places them in prism slot. Extent of motion of feeder arm determines amount of overlap. Greater movement would reduce the overlap and vice versa. Wet splicer/ water splicer/ injection splicer – For vegetable fiber spun yarns such as cotton, linen, etc., it has been proved that the application of water in combination with compressed air in splicing results into better splice. In a wet splicer (also called water splicer or injection splicer), distilled water is introduced along with compressed air. Wet splicer gives better splicing result for high twist cotton yarns, core spun elastane yarns, open end spun

Figure 6.28 Splicing chamber code


yarns, ramie yarns, etc. For wet splicer, it is necessary to supply distilled water. Recent Oerlikon Schlafhorst injection splicers are provided with electromagnetic dosing valves to give metered water during splicing. Due to introduction of water particles in splicing chamber, it becomes necessary to manufacture components, coming under influence of introduced water, from rust-free material. As splice portion becomes wet, capacitive principle of detection of yarn fault in an electronic yarn clearer is likely to give an error in measurement. Water introduction also increases soiling of splicer. Special multi-jet air nozzles are provided which blows compressed air periodically to keep splicer clean. Thermo-splicer – For synthetic yarns and their blends with animal fibers, it has been found that introducing compressed air for splicing at elevated temperature gives better splice. A thermosplicer is provided with an arrangement of elevating compressed air temperature before it is introduced in the splicing chamber. The temperature of the compressed air is to be set by inputting codes in form of values ranging between 0 and 12. With synthetic fibers as yarn constituent, elevating air temperature may affect fiber molecular arrangement which can alter dye pick up of yarn as well as strength in splice region. Therefore, overheating of air should be avoided.

Thermosplicer code

Air temperature

°C

Recommended material

Thermosplicer code

Air temperature

°C

Recommended material

0 0 No heating 7 108 Animal fibers

1 58 100% synthetic 8 117

2 66 9 125

3 75 Animal fibers with synthetic

10 133

4 83 11 142

5 92 12 150

6 100

Splicer for spun yarns with elastane core – A splicer for splicing core spun yarn with an elastic core is called ‘Elastosplicer’. Such yarn contains an elastane yarn (e.g. lycra) in core surrounded by twisted staple sheath fibers (e.g. cotton). In short, it is a staple spun yarn with presence of elastic core which imparts stretch to yarn. Presence of elastic core requires some modifications in usual splicer which are shown in Fig. 6.29. During first step of opening, when core yarn is cut by the scissors, the elastic core tends to contract instantaneously due to which yarn may jump back without getting


sucked in the opening tube. Therefore, at each opening tube, special brake pad is given. The brake pad prevents the yarn end from jumping away and ensures safe and reliable sucking-in of the yarn end by the opening tube. The brake pad holds back the opened yarn ends to guarantee a controlled withdrawal of yarn from opening tube. The bracket carrying scissor which cuts the end that goes into its opening tube is shifted away from prism so as to give increased length of yarn for opening which gives a better opening result. Prism for spun yarns with an elastane core may be with an additional slot for an improved control over central elastane core as shown in Fig. 6.30. Figure 6.31 shows a pneumatic splicer.

Figure 6.29 Splicing for a spun yarn with an elastane core (Courtesy: Oerlikon Schlafhorst)

Figure 6.30 Prism with five blowing orifices and with an additional slot for elastane core yarn


6.8.2.3 Mechanical splicingIn mechanical splicing, the operations of opening and twisting are carried out through mechanical means. Savio’s “Twin Splicer” is a commercially successful mechanical splicer. The yarn ends are opened up by passing them between two discs whose surfaces against yarn are made to move in mutually opposite directions. The extent of disc movement depends upon twist level in the yarn so as to adequately open up yarn ends. Re-twisting of overlapped opened ends is also carried out by the action of the discs. Very good yarn like splice appearance is achieved with Savio’s ‘Twin Splicer”. Precise settings are necessary with this splicer. Roller surface characteristics play a very important role in splicing. Mechanical operations lead to greater wear and therefore maintenance costs are higher which restricts its application.

6.8.2.4 Performance of splicerPerformance of a splicer is judged from splice quality. There are mainly two aspects to assess splice quality: consistent adequate splice strength and appearance. The splices should be strong enough to withstand stresses and strains of subsequent processes. Moreover, it is desired that other properties like elongation property, bending property, etc., should also be closer to yarn. Splices should not be visually objectionable and should offer higher resistance against fiber shifting through surface friction (with healds/ reed in weaving or knitting needles in knitting).

Figure 6.31 Pneumatic splicer (Courtesy: Oerlikon Schlafhorst)


Assessment of splice appearanceSplice appearance can be judged either by simple visual appearance or by comparing with photographs of standard splice. ATIRA has developed the standard for the appearance called SAG (Splice Appearance Grades). Similar to yarn appearance grade boards, appearance of a splice is rated on a numerical scale by developing fiducial standards. These sets of boards contain splices of grades 1 to 7 according to its appearance. This rating of a splice is referred as Splice Appearance Grade (SAG) and it is for the count range Ne 30 to Ne 70. SAG is also applicable for finer counts. Splice Appearance Grade of 1 is for best appearing splices and SAG of 7 for worst appearing splices.

Assessment of splice strengthSplice strength can be assessed in terms of Retained Splice Strength (RSS) or Splice Breaking Ratio (SBR). Retained Splice Strength is the strength of splice expressed relative to parent yarn strength and gives idea of proportion of parent yarn strength retained by yarn after splicing. Higher RSS indicates better splice strength. The SBR is introduced to characterize a splice for its RSS. To compute SBR, yarn breaking test is to be carried out keeping splice in the middle. It is to be noted whether yarn breakage takes place at splice (Splice ± 10 mm). If yarn breaks every time at splice, it does not indicate good splice performance from strength point of view. The SBR is computed by expressing the number of breaks in the splice zone as a percentage of the total tests. Higher SBR indicates poor splice strength. A splice with 40 SBR can be considered as a good quality splice.

To build a package on a winding machine, two motions are basically involved: package rotation and yarn traverse. This chapter discusses various methods of package driving and yarn traversing very commonly employed on winding machines.

7.1 Direct and frictional package drive For yarn winding usually package is required to be rotated. Principally, there are two methods of package driving: 1. Frictional or surface drive in which package is driven by frictional

contact with a drum driven by a motor (Fig. 7.1a). 2. Direct or spindle drive in which package is driven by mounting it on

a spindle which is positively driven from the motor (Fig. 7.1b and c). Figure 7.1(a) shows principle of drum drive. Motor drives drum. Package is mounted on a cradle and remains pressed against drum. As package diameter increases, cradle moves about its fulcrum. Pressure between drum and package influences package density. Figures 7.1(b) and (c) show principle of spindle drive. As shown in Fig. 7.1(b), motor shaft carries a toothed pulley which drives other pulley though toothed belt. The other pulley is fastened on spindle which is mounted on an arm. The arm is loosely mounted on motor shaft. Alternatively, motor may be mounted directly on spindle shaft eliminating toothed pulleys and belt as shown in Fig. 7.1(b). Package is mounted on spindle and rests on a freely rotating support roll. As package diameter increases, arm moves with motor shaft as fulcrum. Package density is influenced by pressure between package and support roll. Figure 7.1(c) shows principle of other possibility with spindle drive in which package is mounted on motor shaft. A press roll mounted on an arm remains pressed against package. As package diameter increases, press roll moves away from package axis.

7Package driving and yarn traversing


7.2 Frictional or surface drive with drumThe drums for package driving are made of various materials like steel, aluminum, bakelite, cast iron, etc. The surface of the drum may be engineered by coating or through surface treatments. Each drum material finds its suitability for specific applications. Factors like cost, capability of withstanding abrasive action of yarn during winding, drum material density (which determines its weight and thereby power consumption) influence selection of drum material. The drums are usually hollow to reduce weight. Aluminium drums are light in weight but possess poor abrasion resistance. Hard anodizing surface treatment is applied on aluminium drums to create a coating of thickness 60–80 microns to increase their abrasion resistance. This treatment makes drum surface porous that reduces contact between yarn and drum surface which lowers co-efficient of friction. Cast iron and steel drums are prone to rusting. Hard chromium plating prevents rusting and increases wear resistance. Bakelite drums are also lighter in weight and free from problem of rusting but have lower wear resistance. Steel drums have excellent

Figure 7.1 Surface and direct package drive (Courtesy: SSM AG and Peass Industrial Engineers)

Package driving and yarn traversing 161

resistance to abrasive as well as adhesive wear and have self-lubricating suface. Diffusion (nitriding) surface treatment on these drums eliminates chipping, flaking or peeling off (which may happen with chrome or nickel plating). Steel drums have longer life. Table 7.1 gives hardness of various drums. Bakelite drums are recommended for cotton yarns, hard anodized drums for acrylic fiber and man-made fiber blended yarns and steel drums for abrasive yarns like wool, jute and their blends.

Table 7.1 Surface hardness of various drums

Drum type Surface hardness (BHN)

Bakelite drum 33–56

Aluminium drum without coating 90–100

Cast iron drum 115–200

Hard anodized aluminium drum 495–534

Hard chrome 601–745

Winding drums are usually cylindrical in shape. When a cone is driven by a cylindrical drum, the surface speed of drum and cone are equal only at one point. This point is nearer to base of the cone, approximately at distance one-third the cone length from its base, and may not remain at same location throughout package build. As shown in Fig. 7.2(a), the surface speeds are equal at point ‘P’ ( )PB AB≅

13

. Towards cone nose from point ‘P’, drum

surface moves faster than cone surface and towards base, cone surface moves faster than drum surface. In region ‘AP’, faster moving drum surface applies torque on cone which tends to drive it. This becomes ‘driving torque’. In region ‘PB’, faster moving cone surface faces resistance from drum surface to cone drive. This becomes ‘resisting torque’. At ‘P’, driving and resisting torques are equal and opposite. Difference in surface speeds between drum surface and cone surface causes abrasion between yarn wound on cone and drum surface which may damage the yarn.

Figure 7.2 Abrasion between cone and cylindrical drum and possible solutions to minimize it


Figure 7.3(a) shows a cylindrical drum driving a cone. Suppose drum diameter is 90 mm and diameter of cone at the nose and base at the beginning of winding is 15 mm and 60 mm, respectively (Fig. 7.3a). Suppose ‘P’ is a point where drum and cone surface speeds are equal when cone diameter is 45 mm. Assume that position of this point remains the same throughout package build. Upon winding of 15 mm layer of yarn diameter of cone at the nose and base becomes 45 mm and 90 mm, respectively (Fig. 7.3b) and diameter at point P becomes 75 mm. 90p becomes drum surface movement in one rotation. Table 7.2 gives surface movement at nose and base in one drum rotation as well as ratios of surface speeds between drum and cone.

Figure 7.3 Reduction of abrasion between cone and cylindrical drum with package build

Table 7.2

Per drum revolution (a) (b)

Cone rotation per drum revolution 9045

2=9075

1 2= .

Surface movement at nose 2 × 15 × p = 30 p 1.2 × 45 × p = 54 p

Ratio of surface movements of drum and nose

9030

3ππ=

9054

1 66ππ= .

Surface movement at base 2 × 60 × p = 120 p 1.2 × 90 × p =108 p

Ratio of surface movements of base and drum

120 90

ππ= 1 33.

10890

1 2ππ= .

Following conclusions can be drawn: • Difference in surface speeds between drum and cone is higher at nose

than base. Therefore damage caused to yarn due to abrasion would be most severe at nose. Higher the cone taper, higher the difference between surface speeds of drum and cone.


• As the cone builds up, difference in surface speeds keep on reducing at nose as well as at base.

• Difference in surface speeds can be reduced by taking bigger bare cone dimensions with given cone taper.

The abrasion caused between the drum and the cone is most undesirable; especially for finer and delicate yarns. The abrasion generates heat which can lead to fusing of the thermoplastic component of the yarns. Therefore, the drum material should be such that heat generated is readily dissipated. Coating of chromium conducts away heat generated and minimizes rise in temperature due to heat accumulation. Other method suitable for plain face drum employs a loose shell on which portion of cone towards nose rests (Fig. 7.2b). Driving portion of cone is towards cone base. Other method is to replace the cylindrical driving drum by one that is slightly tapered (Fig. 7.2c). This method is suitable for plain face drums as well as grooved drums. On ‘Savio’ automatic winding machines, slightly tapered drums are used to drive cylindrical packages for the purpose of ribbon breaking which is discussed in Chapter 8.

7.3 Methods of yarn traversing To wind the yarn across full length of the package, it is necessary to traverse the yarn to and fro along the length of the package. Different methods of yarn traversing are: 1. Yarn traversing with a spirally slotted drum, i.e. rotary traverse 2. Yarn traversing with a reciprocating guide using a grooved cam 3. Yarn traversing with counter rotating blades 4. Yarn traversing with slit drum 5. Yarn traversing with yarn guide mounted on a toothed belt/ light wire

moved to and fro by a programmable servo motor 6. Yarn traversing with a traverse lever operated by a programmable

servomotor

7.3.1 Yarn traversing with a spirally slotted drum (rotary traverse)

This is the simplest method of yarn traversing consisting of a drum which is provided with spiral slots. Yarn traverses to and fro following these slots. The depth and width of the grooves is so designed that the yarn traverses from one end to the other without any reversal in between (Fig. 7.4). The drum also drives the package through surface contact.


Number of drum rotations in a single traverse is called number of turns on the drum. It is also called as number of crossings on the drum because number of turns on the drum equals number of times the helices on the drum cross

Figure 7.4 Grooved drum traverse (Courtesy: J. S. Metal Traverse Co.)

Figure 7.5 Number of turns/crossings of drum

Figure 7.6 Wide range of bakelite and steel grooved drums (Courtesy: J. S. Metal Traverse Co.)


each other along generator (Fig. 7.5). Figure 7.6 shows photographs of various grooved drums. The helix angle of the drums for linear traverse, i.e. for cheese winding, is the same from one end to the other. But drums designed for cones have the helix angle (angle between instantaneous direction of helix on drum and any plane perpendicular to drum axis) lesser on base side of cone and larger towards the nose. So, the spacing between successive crossing points is greater on nose side than on base side in order to get accelerated traverse. Abrasive action of yarn on drum surface tends to develop cuts, especially at crossing points of the grooves. Therefore, special ceramic inserts may be placed at crossing points on the drum which are wear resistant. Split drums were very common earlier having larger diameter of about 25 cm with ½ turn (i.e. half revolution of the drum completes single traverse). Split drum, which is hollow, is made into two halves (splits) which when put together on shaft forms a continuous groove which the yarn follows and traverses (Fig. 7.7). The distance between the last guiding point (point O) and the point of winding continuously varies; which is highest at extremes and lowest in the middle (highest at points ‘P’ and ‘R’ and least at point ‘Q’). This difference in length causes tension variations in yarn. At extremes, tension would be highest and at centre it would be lowest. To minimize these tension variations, an elliptical ring is provided in the hollow portion of the drum which equalizes the length of the yarn between last yarn guiding point and

Figure 7.7 Split drum

point of winding on package. Thus, rotary traverse is the simplest method of yarn traversing suitable for high winding speeds up to 1500–2000 m/min. Grooved drum traverse allows only random winding. It is not possible to vary traverse length. Therefore, bi-conical packages cannot be built with grooved drum traverse. Hard edge formation can be prevented either by giving lateral displacement to the drum


or package cradle which scatters reversal points at the extremes. If yarn breaks at the nip between the package and the drum during winding, it may be trapped in the groove of the drum and starts getting wound in the grooves of the drum to form a thick ribbon of yarn in the drum grooves. This phenomenon is called drum lapping. Drum lapping causes loss of production as well as yarn wastage. Automatic winding machines are provided with stop motions to detect drum lapping and stop the spindle. Drum lapping must be removed without damaging drum surface. To facilitate removal of drum lapping, special cut may be provided in the drum as shown in Fig. 7.8. A special scissor is inserted at this cut to remove lapping (Fig. 7.9). In order to minimize chances of wrapping, anti-wrap brushes may be fitted at the back of the drum.

Figure 7.8 Drum lapping Figure 7.9 Scissor for cutting drum lapping

7.3.2 Yarn traversing with a reciprocating guide using a grooved cam

The yarn is traversed by passing it through a guide, which reciprocates to and fro across the length of the package. On old drum winding machines for winding double flanged bobbins, all yarn guides used to be mounted on a sliding bar reciprocated to and fro by means of a cam. On a cross-winding machine, as the yarn is to be laid at an angle, the traverse speed is greater than parallel winding. Theoretically, the yarn guide must be reversed instantaneously (in zero time) at the point of reversal. The traversing guide moving with say speed ‘V’ must be brought instantaneously to speed ‘V’ in reverse direction. It is difficult to achieve this practically, especially if mass involved is higher. Therefore, the reciprocating masses should be made from materials as light as possible especially where higher traverse speeds are required. For slow speed winding systems like on open end spinning and TFO twisting, yarn traversing guides of a row of spindles are mounted on a common bar which is moved to and fro by a grooved cam as shown in Fig. 7.10. During cross winding, yarn traversing guide must reverse quickly at extremes in order to avoid greater deposition of yarn at the edges. In this mechanism, as all yarn


traversing guides are mounted on a common bar, inertia of the system is high and therefore it is suitable for low winding speeds. For higher winding speed applications, each spindle is provided with its own cam and a follower (Fig. 7.11a). A follower mounted on a sliding block follows a grooved cam due to which sliding block moves to and fro. Sliding block carries a yarn guide which traverses yarn to and fro. Yarn guide assembly is made from lighter material to reduce inertia. Cam, follower and sliding block are usually oil immersed to reduce friction. If traverse guide is fixed on sliding block, traverse stroke variation does not become possible with given cam and therefore bi-conical packages cannot be built. With suitable modification, traverse variation can be achieved with grooved cam traverse system. Principle of traverse stroke modification is shown in Fig. 7.11(b) and (c). As shown in Fig. 7.11(b), yarn guide is mounted on one arm of a lever having fulcrum on sliding block. The other arm of lever carries an anti-friction bowl which passes though slot of a bracket which can be tilted around a fulcrum. If slot of the bracket is not parallel to motion of sliding block but at an angle, lever would move around its fulcrum as sliding block moves from one end to the other. With position of slotted lever shown in Fig. 7.11(b), lever would tilt outwards on either side, due to which stroke of yarn guide would be longer than stroke of sliding block. With position of slotted lever shown in Fig. 7.11(c), lever would tilt inwards on either side, due to which stroke of yarn guide would be shorter than stroke of sliding block. If slotted lever is made to shift gradually from position shown in Fig. 7.11(b) to position shown in Fig. 7.11(c) as package builds up, traverse length can be shortened as required for a bi-conical package. Figure 7.12 shows principle of traverse stroke variation. Angular position of slotted bracket changes with an increase in package diameter. Growing package diameter changes cradle position which through suitable linkage alters angular position of slotted lever to shorten traverse length. To stagger reversal points at traverse extreme, input from other source in form of a small to and fro motion is given which causes periodic shortening and lengthening of traverse stroke. Thus, slotted bracket, on one hand, changes its angular

Figure 7.10 Grooved cam traverse for slow speed winding systems


position for traverse length reduction and on the other hand gets rocking motion which lengthens and shortens traverse stroke continuously. Photograph of such motion on a yarn texturising machine is shown in Fig. 7.13.

Figure 7.11 Grooved cam traverse for higher winding speeds

Figure 7.12 Traverse for a bi-conical package with staggering of reversal points

Figure 7.13 A cam traverse for a bi-conical package with staggering of

reversal points

Figure 7.14 “Tuan Evolution” range of winding machine with grooved cam traverse

(Courtesy: Fadis)


Figure 7.14 shows a winding unit of Fadis “Tuan Evolution” range of a winding machine with grooved cam traverse provided with traverse length variation. Groove angle for a grooved cam for winding a cylindrical package remains same from one end to the other. For cone winding, especially for steeper a cone taper (like 5°57’), groove angle should vary from one end to the other to permit accelerated traverse.

7.3.3 Yarn traversing with counter rotating bladesTraversing systems with reciprocating masses impose an upper limit on traverse speed and thereby on winding speed because of problem related to instantaneous reversal required at traverse extremes. To achieve very high traverse speeds, traversing systems without reciprocating masses are attempted which are described in patent literature. Traversing system with counter rotating blades is widely used on commercial machines. Figure 7.15 shows principle of yarn traversing with counter rotating blades and Fig. 7.16 shows photograph of its close-up view. It consists of two rotors carrying blades of same length, rotating about different centers in opposite direction having offset is of about 5 mm (Fig. 7.15). Centre of rotation of rotor carrying blade ‘1’ is towards left of midpoint of traverse, whereas that of rotor carrying blade ‘2’ is towards right. Each rotor has two blades. Yarn coming from supply package passes around a curved guide plate and then wound on package. One of the blades of rotors projects beyond guide plate and traverses yarn from one end to the other. Referring to Fig. 7.15(a) and (c), blade 1 is traversing yarn from left to right. As centre of rotation of rotor carrying blade 1 is towards left from centre of traverse, its protrusion from guide plate keeps on decreasing as it moves towards right as shown in Fig. 7.15(d). At right extreme of traverse, blade 1 does not protrude beyond guide plate and therefore yarn is relieved from wing of blade 1. At the same point, blade 2 meets wing of blade 1. As centre of rotation of rotor of blade 2 is towards right side of centre of traverse, blade 2 protrudes beyond guide plate. Therefore, at right extreme, blade 1 relieves the yarn which is picked up by blade 2 and yarn starts traversing from right to left as shown in Fig. 7.15 (e). Blade 2 would traverse yarn from right to left. At left extreme wing of blade 2 would relieve yarn where it would be picked up by blade 1. In this way, yarn keeps on traversing. In this method of traversing, blades continue to rotate in one direction. Thus, as reciprocating masses are eliminated, very high traverse speeds can be achieved. This principle of traversing is also used in take up winders where very high winding speeds are required.


With two blades in each rotor, in one rotation, each blade traverses yarn during its 90° movement. One rotation of rotor of completes two double traverses. With three blades in each rotor, in one rotation, each blade traverses yarn during its 60° movement. One rotation of rotor of completes three double traverses. This method of yarn traversing is suitable mainly for cylindrical packages as accelerated traverse cannot be achieved. As point on blade, traversing yarn is away from nip between package and press roll, very precise lay of yarn on package cannot be achieved. Traverse variation also cannot be achieved with this method of yarn traversing and therefore, bi-conical packages cannot be produced.

Figure 7.15 Yarn traversing with counter rotating blades

Figure 7.16 Winding machine with counter rotating blades’ traverse (Courtesy: SSM AG)


7.3.4 Yarn traversing with slit drum As shown in Fig. 7.17(a), a hollow drum carries a slit. Yarn enters the slit at lower end of slit drum, passes though hollow portion and then emerge out from slit at upper end. Subsequently, it is wound on the package. Yarn follows the slit of the drum which traverses it to and fro. This method of yarn traversing is used on sewing thread winding machines. Figure 7.18 shows yarn traversing with a slit drum.

Figue 7.17 Slit drum and servomotor based yarn traversing systems

Figure 7.18 Slit drum traverse (Courtesy: SSM AG)

Figure 7.19 Yarn guide on an endless wire (Courtesy: SSM AG)


7.3.5 Yarn traversing with yarn guide mounted on a wire/ toothed belt moved to and fro by a programmable servo motor

An endless loop of a wire/ light toothed belt is carried around a pulley (toothed for toothed belt) mounted on shaft of a servomotor (Fig. 7.17b). This belt passes around other two pulleys. Wire/ toothed belt between these two pulleys carries yarn guide. Servomotor, through its pulley, gives to and fro motion to toothed belt and thereby to yarn guide. Stroke of yarn guide as well as its motion can be controlled through a programmable drive to servomotor. Programmable drive allows variation in velocity of yarn guide at every point during each traverse of package build. Therefore, this method offers greater flexibility in packge build. Cylindrical as well as conical cross wound packages can be built. Programmable drive can control stroke length variation which offers great advantage in effective hard edge prevention, building bi-conical packages, etc. With programmable package drive, any mode of winding and laying parameters can be achieved. This principle of yarn traversing is used on SSM (Preciflex technology) and Fadis winders as well as Barmag ATT take up unit on texturising machines. Figure 7.19 shows yarn traversing with yarn guide mounted on a toothed belt moved to and fro by a programmable servo motor.

7.3.6 Yarn traversing with yarn guide mounted on a traverse lever moved to and fro by a programmable servo motor

In this method of yarn traversing, a traverse lever carries two arms of unequal length between which yarn is passed (Fig. 7.17c). These arms act as yarn traversing guide. Traversing lever mounted on a programmable servomotor shaft receives rocking movement. Therefore, yarn guide moves to and for to traverse yarn. Programmable drive allows variation in velocity of yarn guide at every point during each traverse of package build. Therefore, this method offers greater flexibility in package build. Cylindrical as well as conical cross wound packages can be built. Programmable drive can control stroke length as well as its position with respect to bare package which offers great advantage in effective hard edge prevention, building bi-conical packages, building dye packages with rounded edges, building packages with desired length, shifting position of winding with respect to bare package, etc. While building a conical package, desired traverse acceleration can be programmably selected. Relative position of traverse stroke with respect to


package can also be programmed. With programmable package drive, any mode of winding and laying parameters can be achieved. This principle of traverse is used on Schlafhorst Autoconer X5 PreciFX winding system as seen in Fig. 7.20.

Figure 7.20 Traversing system on Autoconer X5 PreciFX winder (Courtesy: Oerlikon Schlafhorst)

It is always desired to build fault-free winding packages fulfilling the requirements of the next process (warping, pirn winding, as filling on shuttle less loom, knitting, dyeing, etc.). Faulty winding packages are produced due to several reasons such as faulty settings, poor mechanical condition of machine, worn out elements, selection of wrong parameters, incorrect work practices, poor handling of materials and house keeping etc. Some common winding package faults and their remedies are discussed in this chapter.

8.1 Stitches or ‘jali’ on cones/cheeses (winding packages)

Fault of stitches or ‘jali’ is formed when the yarn falls outside the edge of the winding package (Fig. 8.1).

8Winding package faults and remedies

Figur 8.1 Stitches on a package

The main reasons for generation of this fault are the following: 1. Large tension variations during winding causes change in effective

traverse. High tension levels reduce the traverse, while low tension levels increase. Various possible causes of variation in yarn tension are as follows –

Winding package faults and remedies 175

• Changing parameters during unwinding like winding off radius and balloon height cause tension variations. Balloon collapse during unwinding leads to sudden tension fluctuation.

• Accumulation of fluff between the discs of disc tensioner does not allow the discs to be pressed against each other that cause reduction in tension. Sudden removal of fluff would cause sudden rise in yarn tension.

• If there are cuts in any element along yarn passage like yarn guides or rough surface of ring bobbin, yarn may get caught in cut portion leading to rise in tension. When yarn is released there would be sudden drop in yarn tension.

• Arrival of a thick place in disc tensioner can cause sudden rise in tension followed by tension drop.

2. Excessive play between the winding package and drum. 3. Jumping of yarn at the end of the traverse either due to the non-

alignment of the bracket with the drum or a nick (cut) in the groove (Fig. 8.2A).

4. The stitches may occur if the ‘traverse restrictors’ (where ever they are used) are not set properly.

5. A package starts wobbling when it is bare or holder has worn out. This can lead to formation of stitches.

6. On non-automatic winding machines, after yarn joining, the yarn must be kept at the package centre upon restarting. If it is carelessly released keeping it at side, a stitch would be formed on the package (Fig. 8.2B).

Figure 8.2 Stitch formation


8.2 Soft nose or base (wrinkles)Soft nose or base is a package fault in which a cone does not have a uniform density along its length; its base may be softer than the nose or vice versa (Fig. 8.3A). This defect generally occurs when the pressure at the nose or base is inadequate due to non-alignment of the cone surface and drum/ support roll surface (Fig. 8.3B).

Figure 8.3 Wrinkles

Figure 8.4 Tension bracket position Figure 8.5 Yarn sloughs

The other common cause is incorrect alignment of the tension bracket with respect to winding drum. The tension bracket should be so adjusted that the triangle formed with drum axis with the base and the point where starts to traverse as the vertex is an isosceles triangle [Fig. 8.4(a), where AB = AC]. This ensures equal tension in yarn at both extremes. If this is not set, then the yarn tension will be more on one side than other. The side with larger distance would be with higher yarn tension and therefore would be harder than the other nearer side [Fig. 8.4(b) where A B A C′ ′ ′ ′ ]. With inappropriate traverse acceleration also soft nose or base can occur. Sometimes the whole package is soft due to insufficient pressure between the drum and package or due to insufficient tension.


8.3 Yarn sloughsDuring unwinding from ring bobbins, occasionally several coils/layers of yarn slough off and are pulled off simultaneously from the bobbin (Fig. 8.5). If the coils slough off as a large bunch and do not get straightened, they are trapped at the clearer and do not pass on to the winding package. If however, these coils do not form a bunch then they may get straightened in to a loop of 3 strands as winding proceeds. If these loops escape through yarn clearer (not likely with an electronic yarn clearer), they would be wound onto the package to become problematic in subsequent processing. Ring frame bobbins should be properly built during ring spinning.

8.4 Wild yarnAny bunch of loose yarn getting attached to the yarn being wound onto the package is termed as wild yarn. The wild yarn may pass onto the winding package from the worker’s hand or from the surrounding due to poor housekeeping in the department.

8.5 Yarn entanglement on packageSometimes yarn gets entangled on the package that causes breakage during unwinding (Fig. 8.6) at subsequent process. On non-automatic winding machines, carelessness on the part of operator while knotting and releasing may cause entanglement. Yarn entanglement occurs if package gets lifted off the drum without an end break. Repeated knotting/splicing failure on automatic winding machines also results into yarn entanglement on the package.

Figure 8.6 Yarn entanglement on package

Figure 8.7 Snarls

8.6 SnarlsHigh twist yarns are twist lively, i.e. when slack they form snarls. Steaming of ring frame bobbins condition the yarns and reduce the snarling. On non-automatic winding machines, if yarn becomes slack while restarting after a stop, snarls may be formed and pass onto the package (Fig. 8.7).


8.7 Chaffed yarnA portion of yarn that has been rendered weak because of abrasion against any surface is called chaffed yarn. On a winding machine if broken thread stop motion does not function, same layer of yarn on the package keep on abrading with the drum/ support roll leading to chaffed yarn. On automatic winding machines, if suction arm that finds yarn from the package touches the package, chaffed yarn would result.

8.8 Patterning or ribboning Patterning or ribboning phenomenon associated with random winding is already discussed in Chapter 2 and Chapter 3. Figure 8.8 shows patterning on a random wound cone. In precision winding patterning or ribboning is prevented through suitable selection of traverse ratio. On a random winder, suitable measures are necessary to avoid pattern formation.

Figure 8.8 Patterning on a package

Figure 8.9 Disadvantages of pattern formation

When patterning takes place, only portion of yarn forming ribbon rubs against the drum surface (Fig. 8.9). This creates high pressure at contact points and leads to weakening of yarn in that portion. Moreover, density of package becomes uneven that does not allow uniform package dyeing. During unwinding, yarn may be caught at knuckle (Fig. 8.9); causing tension peak that may lead to yarn break, or simultaneous withdrawal of several coils.

8.8.1 Various measures for ribbon breakingVarious anti-patterning systems are developed to avoid ribbon formation. They may be simpler or complex with the use of highly sophisticated technology.

8.8.1.1 Lateral movement to package cradleOn very old machines, anti-patterning system consisted of an arrangement of giving to and fro motion to package cradle. However, this method is not


very effective in pattern breaking. It can split ribbon to certain extent. This movement is actually intended for hard edge prevention.

8.8.1.2 Skid principleWith grooved drum winders ‘skid principle’ is very commonly employed for ribbon breaking. In this principle, some slippage is brought about between drum and the package continuously. This slippage keeps on disturbing ratio of rotational speeds of drum and package, thereby the traverse ratio and breaks ribbons.

Switching drum drive motor ‘on’ and ‘off’Figure 8.10(A) shows method of ribbon breaking for a grooved drum winder. A pilot motor drives a cam which switches drum drive motor ‘on’ and ‘off’ 30–35 times/ minute due to which drum rotational speed does not remain constant but keep on rising and falling which introduces slippage between drum and package to break patterns.

Periodic lifting of package out of contact with the drumSlippage can also be introduced by periodically lifting package out of contact with the drum (Fig. 8.10B). This motion also introduces slippage necessary for ribbon breaking.

Drum speed modulation by mechanically interrupting drum drive On old models of machines like Autoconer 107/108, a friction roller receives drive from continuously rotating drive pulley. Friction roller drives drum pulley through surface contact. For anti-patterning, friction roller contact with drum pulley is periodically interrupted to cause drop in drum rotational speed (Fig. 8.10C).

8.8.1.3 Anti-patterning on winding machines with a separate thread guide traverse

On winding systems with a separate thread guide traverse, pattern formation can be avoided by modulating cam speed. Figure 8.10(D) shows principle of such system. Cam speed can be modulated by moving belt to and fro on conical pulleys. The variables associated with this principle are frequency (number of times belt is moved to and fro per minute) and amplitude (belt displacement). With such traverse, when traverse staggering is also simultaneously done to prevent hard edge formation, maintaining suitable synchronization between traverse staggering and traverse speed modulation becomes very important.


Traverse staggering as well as traverse speed modulation simultaneously influence traverse ratio. Upon reaching a pattern zone, if magnitude of disturbance of traverse ratio by both is equal and opposite, patterning would continue. Adequate care must be taken to avoid such situation.

Figure 8.10 Anti-patterning systems

8.8.1.4 Anti-patterning by periodic variation of package rotational speed with constant drum speed

Savio employs anti-patterning system without any change in drum speed. As shown in Fig. 8.11, conical package driven by a cylindrical drum is given an oscillating movement about vertical plane. As discussed in Chapter 7 (section 7.2), cone and drum surface speeds are same only at one point which is approximately 1/3rd the distance from base. Due to oscillating movement, this point keeps on shifting due to which package rotational speed keeps on changing although drum speed remains constant. Therefore, traverse ratio is continually disturbed to give ribbon breaking. To prevent hard edges for dyeing, the package is simultaneously given oscillating movement about horizontal plane. This method is not suitable for a cylindrical package over a cylindrical drum. For a cylindrical package a slightly tapered drum is used.

Figure 8.11 Anti-patterning principle on Savio machines


8.8.1.5 Electronic anti-patterningOn machines like Autoconer 238, each grooved drum is driven by an individual motor. Drum speed is electronically modulated to introduce slippage. The anti-patterning intensity, i.e. magnitude of percentage drop in drum speed is pre-selectable on a central control panel. The periodic time of anti-patterning cycle is required to be increased (i.e. decrease of frequency of anti-patterning cycle) with the increase in the actual package diameter which is also electronically managed. As shown in Fig. 8.12, at smaller package diameter, periodic cycle time is ‘t1’ which is smaller than that at larger package diameter which is ‘t2’. Drum surface speed is greater than package surface speed due to slippage.

8.8.1.6 Anti-patterningsystemstakingspecificactionatpattern zones on grooved drum winding systems

Some anti-patterning systems take specific action especially at pattern zone arrival. These systems incorporate sensors for monitoring drum and package rotational speeds.

Propack FX anti-patterning system on Autoconer winding machinesPropack FX anti-patterning system is provided on Autoconer automatic winding machines (Autoconer 338, Autoconer 5). With this patterning system also, programmed modulation of drum takes place to break patterns as discussed in 8.9.1.5. The system takes additional care during pattern zones. A separate motor is provided to regulate preset pressure between package and drum. Rotational speeds of package and drum sensed continuously by sensors are input to a winding head computer. Winding head computer computes the diminishing traverse ratio. Before package reaches a pattern zone, cradle

Figue 8.12 Electronic anti-patterning


motor reduces pressure between drum and the package so as to introduce extra slippage between the drum and package. After the pattern zone is over, the system restores the pressure between the drum and package to pre-selected value. Thus, this system increases effectiveness of pattern breaking during a pattern zone by cradle pressure reduction.

Figure 8.13 Principle of PropackFX anti-patterning system

Anti-patterning using multi-grooved drum on Murata winding machines

Figure 8.14 Anti-patterning with multi-grooved drum

A unique anti-patterning system is offered by Murata to increase effectiveness of pattern breaking on arrival of a pattern zone. It consists of a single drum having two sets of grooves. As shown in Fig. 8.14, drum ‘C’ has two sets of grooves, 2 turn as in drum ‘A’ as well as 2.5 turn as in drum ‘B’. Yarn can be made to follow any one of these grooves by a drum wind controller. Sensing rpm of drum and package, arrival of pattern zone is known through computer. If winding is carried out, say with 2 turn and


pattern zone arrives, drum wind controller shifts yarn to 2.5 turn groove track till pattern zone is over. Thus, switch over to other turn within the same drum is expected to shift winding to newer band of traverse ratios to wind without ribbon formation. The other multi-grooved drum combination offered is of combination of 1.5 turn and 2 turn drum.

Sensor based anti-patterning system with flexible winding systemsPrinciple of winding systems with individual programmable drive to package and traversing mechanism offering great flexibility in package building is discussed in Chapter 3. With such systems a pattern zone can be dealt with more effectiveness through ribbon free random wind while winding in a random mode.

185

Index

3 o’clock - 9 o’clock, 1517 o’clock - 1 o’clock, 1519 o’clock - 3 o’clock, 151

AAccelerated traverse, 17, 18, 69, 88,

165, 169, 170Action of an opening tube, 147, 150Actual clearing curve, 137, 138Actual traverse ratio, 23–5, 29, 30,

53, 60, 61After wind, 25, 26, 29, 30, 76, 82, 92Allowable faults, 123, 136Aluminium drums, 160Angle of envelope, 105Angle of wind, 15Anti-patterning using multi-grooved

drum, 182Anti-wrap brushes, 166Assembly winder, 66, 67, 101Assessment of clearer performance,

143Asymmetric drum, 88Autospeed, 115Autotense FX, 116Axial bore tube, 149

BBad piecing, 123, 127Balcon, 113, 114Balloon breaker, 112, 113Balloon collapse, 90, 175Balloon height, 103, 110, 111, 113,

114, 175Balloon rpm, 104, 115Barre, 127Basic yarn clearing, 136, 140Beam dyeing, 6, 7Beaming, 8Bi-conical packages, 48, 69, 83–5,

165, 167, 170, 172Blast duration, 154Blast-pause-blast, 154Blower nozzles, 149Blowing orifice, 152, 153, 156Brake pad, 156Bulge, 85, 86, 93, 103

CCapacitance clearer, 128, 130Cast iron and steel drums, 160CBC (Core Bicone), 81Ceramic guide plate, 149Ceramic inserts, 165Chaffed yarn, 178Cheese, 3–6, 11, 14–7, 88, 101, 103,

110, 114, 165, 174Clearer characteristics, 137Clearing curve, 136–39, 142Clearing efficiency, 143, 144Clearing level, 136, 137Clip cone packages, 88Close wind, 25–7, 95Coil angle, 15–8, 25, 27–39, 41–61,

69, 74–89, 92, 94, 95, 102, 103 Combination built, 100

186

Complimentary angle, 15Conductive ceramic, 132Cone, 3–6, 11Cone taper, 14, 17, 18, 69, 71–3,

162, 163, 169Coning oil, 76Contaminant fiber, 127, 130–32Count variations, 127, 140–42Crackers, 122Cradle, 83, 92, 93, 96, 159, 166, 167 Cross wound packages, 12–4, 18,

34, 83, 110, 172Crossing angle, 15, 16Crossing ratio, 15

DDead zones, 85Denting, 9Desired clearing curve, 136–38Dielectric constant, 129, 130Diffusion (nitriding) surface

treatment, 161Digitens, 116, 118Direct or spindle drive, 159Direct system, 152, 153Direct warping, 7, 95Disc tensioners, 105, 106, 109Dog knot, 144, 145Double ends, 137, 138Double gaiting, 123Drawing-in, 8, 9Drum lapping, 166Drum wind controller, 182, 183Dynamic symmetry ratio, 89Dynamic traverse acceleration, 69

EElastane fibers, 93Electromagnetic dosing valves, 155Electronic anti-patterning, 181

Electronic yarn clearers, 124, 126, 136

Electrostatic splicing, 146Embroidery packages, 76

FFault length, 72, 132–34, 136–40,

142, 143Fault thickness, 132Feed roll, 117, 118Feeder arm, 154Filter cartridge, 71, 82Filter winder, 66, 67, 101Fish bone pattern, 26, 27Fisherman’s knot, 144, 145Fixed or parallel blade type yarn

clearer, 124Flexible dye tubes, 76Fluff accumulation, 106, 109Flyer frames, 122Foreign fiber, 126, 127, 130–33,

135, 140–43Foreign fiber/ contaminant clearing,

141Foster cone, 17, 18Fragmented plastic bag, 127Friction spinning, 101Frictional or surface drive, 159, 160

GGain, 24, 26, 30, 82Gate tensioner, 105, 110, 116Gradual coil angle variation, 69Grooved cam, 35, 48, 49, 51, 52, 62,

68, 163, 166–69Grooved drum traverse, 35, 36, 83,

84, 88, 164, 165Guide distance optimization, 114Guide plate, 149, 169

187

HHairiness variation, 127Hand knitters, 145Hank, 5–7, 68, 100, 101, 119Hard anodizing surface treatment,

160Hard Chromium plating, 160Hard edges, 69, 76, 83, 84, 180Head wind, 25, 29, 30, 82, 92Heald, 1, 3, 9, 10, 157Helicont, 81Holding pipes, 149Human hair, 126, 130Hybrid winding, 34, 45

IImperfections, 127, 135

KKing spools, 69, 76, 88Knitting, 18, 70, 72, 75, 79, 82, 88,

95, 97, 98, 101, 123, 157, 174Knot factor, 143, 144Knotless joint, 146

LLinear gain, 24, 25 Loepfe Zenit clearer, 139, 141Long places, 137–39

MMechanical knotter, 144Mechanical splicing, 146Mechanical yarn clearers, 124–26Methods of yarn traversing, 34, 163Moiré/ periodic variations, 127Muff, 5, 6, 95, 101, 119 Mule Cop, 100Multiple loop balloon, 103Multiplicative type of yarn

tensioners, 104

NNecks, 103Neps, 110, 127, 135, 137–39, 142Nominal traverse ratio, 23–5, 27,

29, 30Non-vegetable matter, 130Nose unwinding, 14Number of crossings on the drum,

164Number of turns on the drum, 37,

79, 164

OObjectionable faults, 11, 123, 136,

143, 144Online classification of basic yarn

faults, 142Online classification of yarn splices,

143Online yarn fault classification, 142Open end spinning, 67, 101, 166Open wind, 25, 26, 82, 95Opening duration, 150, 151Opening pressure, 150Optical electronic yarn clearer, 128Optimum coil angle, 78, 80Optimum guide distance, 111, 112Over end withdrawal, 14, 102, 103,

118Over-squared cones, 43

PP wind, 69, 89, 90, 91Package density, 26, 29, 42, 43, 70,

77, 79, 83, 85, 92, 94, 95, 96, 120, 159

Package dyeing, 6, 47, 48, 70, 71, 73, 82, 85, 178

Packages with rounded edges, 48, 69, 85, 86, 172

188

Parallel side flanks, 44Parallel wound packages, 12, 13 Pattern repeat, 23–6, 82Pattern zones, 42, 47, 48, 51, 58, 77,

181Patterning, 19, 22, 23, 39, 42, 43, 45,

55, 74, 77, 96, 178–83Patterning or ribboning, 19, 178Periodic defects, 140Pilling, 127Pineapple cones, 69, 83Plastic packages, 75Pneumatic splicing, 146, 147Polypropylene, 76, 101, 127, 128,

131, 132, 142 Positive over feed, 118Precision winding, 23, 25, 26,

28–30, 33, 34, 39, 41–8, 51, 52, 54, 58, 60, 68, 69, 74, 76–8, 81, 82, 91, 94, 95, 97, 178

Precitens, 118Press roll, 48, 49, 54, 69, 83, 92–4,

159, 170Prism, 153, 154, 156Programmable servo motor, 163,

172 Propack FX, 181

QQ wind, 69, 89–91

RRandom winding, 32–9, 42Reciprocating guide, 56, 163, 166Reed, 1, 3, 7, 9, 10, 145, 157Remnants, 101Repeated knotting/splicing failure,

177Retainer tubes, 149Revolution gain, 24, 25, 30, 37

Rewinding, 11, 70, 95Ribbon free random wind (RFR), 55,

55, 58, 81, 183Ribboning, 19, 32, 178Ring frame, 102, 123Ring frame bobbin, 4–6, 66, 67, 100,

102, 110, 111–16, 123, 124, 127, 177

Rounded edges, 48, 69, 85, 86, 172Rounded side flanks, 85Rounding radius, 85Roving built, 100 Roving wound filter package, 73Rust stain, 126, 130

SSaddle formation, 79Saw tooth opening tubes, 149Scatter plot, 143Sectional warping, 7, 9, 95Semi-vertical angle, 14Sewing thread finish winding, 67Sewing threads, 70, 78, 82, 90Short places, 137–39Shoulder, 102Single loop, 103, 104, 111Sizing, 9, 123Skid principle, 179Slit drum, 163, 171Slubs, 122, 127Snarls, 177Soft nose or base (Wrinkles), 176Soiled fiber, 126Speedster fx, 113Spindle driven winders, 39, 48Spinners doubles, 122Spirally slotted drum, 163Splice, 121, 130, 139, 143–47,

150–58Splice appearance grade (sag), 158

189

Splice breaking ratio (sbr), 158Spliced joint, 121, 145–47, 152Splicing blast air pressure, 154Splicing chamber, 147, 152–58Splicing cycle, 147, 148Steel drums, 160, 161Step precision winding, 34, 45–8,

52, 54, 60, 69, 76, 77, 78, 81, 82, 94

Stitches or ‘Jali’, 174Suck back facility, 124, 141Sun cheeses, 88Support roll, 69, 83, 92, 93, 94, 97Surface drive, 34, 48, 49, 56, 62, 63,

93, 159, 160Swinging blade type or trap clearer,

124Symmetric drum, 88Symmetry ratio, 88, 89Synthetic foreign matter, 127

TTake up winders, 48, 50, 75, 81, 169Take up winding, 48, 67,Tangential system, 152, 153Tapered drums, 163Tension fluctuations, 70, 78, 79, 103,

104, 107, 110–15, 117, 118Tension peaks, 72–4, 79Texturising machine, 66, 67, 85,

168, 172Thermo-splicer, 155Thin places, 126, 127, 135–40, 142Thread guide, 35, 38, 179Transfer tail wind, 91Traverse acceleration, 16, 69, 88, 89,

172, 176 Traverse frequency, 56–9, 61Traverse length variation, 69, 82–7,

169

Traverse lever, 85, 163, 172Traverse position variation, 69, 87,

88Traverse ratio, 15, 18–27 Traverse speed, 17, 36–9, 49, 51, 55,

57, 65, 166, 169, 179, 180Traverse stroke modification, 167Traverse variation curve, 86, 87Traversing cam, 39, 48Traversing with counter rotating

blades, 163, 169, 170Tribo-electric principle, 128Twin-splicer, 146Twist distribution, 109Twist interference, 109

UUnconventional spinning, 11, 66, 67,

101Unevenness variation, 127UNIFIL loom winder, 3, 11 Untwisting tube, 147, 149Unwinding accelerator, 112, 113Uster Classimat II, 133–35Uster Classimat III, 134, 135Uster quantum clearers, 132, 141

VVariation of traverse stroke, 48Variopack, 93Vegetable material, 130Vortexing chamber, 147

WWarp tying machine, 10Warper’s beam, 5, 7, 9Warper’s bobbins, 12Wax pick, 98Weaver’s beam, 1, 3, 7–10, 183Weaver’s knot, 144, 145Wet splicer, 130, 145, 154, 155

190

Wild yarn, 177Winding ratio, 15Winding speed, 12, 18, 36, 37, 40,

41, 42, 49, 51–60, 61–5, 70Winding with varying coil angle,

54, 55Wrinkles, 93, 176Wrong count bobbin, 126, 141

YY cones or vi-cones, 76Yarn clearing, 72, 121, 123, 136, 140

Yarn entanglement on package, 177Yarn fault, 5, 6, 101, 121–143Yarn fault classification, 133–37,

142Yarn singeing, 66, 67Yarn sloughs, 176, 177Yarn tension meter, 120Yarn tensioner, 104, 109, 111,

116–18Yarn tensioning device, 104Yarn traversing with slit drum, 163,

171

Fundamentals of Yarn Winding (2013)

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