Laboratory Practice in Knitting Technology

8/22/2019 Laboratory Practice in Knitting Technology

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mined for this, and the sample is cut so as to obtain a rectangle orsqua-re. Then, the sample area S is determined in m2 The sample with ameasured area is weighed on precision scales for determining its masE.ms in grams. The mass of 1 m

2, g, is determined using the formula

m = ms/S (28}

The loop module, yarn take-up, and the density ratio factor of the'knitted fabric are calculated by the aforementioned formulae.

Instructions on How to Compile the Check-Out Report

The check-out r eport must contain:(1) samples of analyzed knitted fabric, drawings of the face and reverse sides

of each sample, the graphical repr esentation of yarn laying with indicationof the interlocking repeat, and the description of main properties;

(2) for each sample, the experimental and adopted values of yarn linear density,

the values of Dh, Dv' L, C, a, In, U, the deviations in % of characteristicexperimental values from those adopted with indication of the causes ofthese deviations;

(3) the calculations used in designing the knit structure.

Re,'iew Questions

1. What knitted fabric produced from yarns of the same linear density and ofthe same yarn length in the loop can be more easily ravelled, i.e. of cottonyarn or of man-made yarns? Why?

2. What are the factors on which depends the degree of curling at the edgesof kni tted fabric?

3. Why is the fabric of jersey derivative structure narrower than plain jerseyfabric manufactured of yarns of the same linear density and with an equalnumber of wales?

4. Explain why knitted fabric which has been subjected to wet and heat treat-ment becomes thinner, larger in area, and does not curl at the edges.

5. Why are the jersey loops askew if the knitted fabric has been manufactured:from yarn with an unbalanced twist?

6. Why does a jersey derivative stitch ravel less than plain jersey?7. Why are the r everse wales in rib overlapped by the face wales, and ,yhat is-

the cause of this overlapping?8. Why is it the rib structures do not curl at the edges, ravel in the dir ection

reverse to knitting, and are twice as thick as the single structures? Is the'absence of curling a feature inherent in all ribs?

9. How does the rib width change with an increase in repeat?10. Why does rib stretch in width more than jersey?11. Why do interlock structures ravel less than rib structures?12. Why does reverse jersey (pur l stitch) tend to shorten in length and what an,-'

the causes determining the degree of this shortening?

9. ANALYSIS

OF THE STRUCTURE AND PROPERTIES

OF WARP KNITTED FABRICS

Objective: To get acquainted with the main kinds of knitted fab--rics in basic and derivative warp knitted stitches (single and double),.to acquire skill in their determination, graphical representations ofyarn laying, evaluation of properties, and designing of structural

characteristics.


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1. Make an analysis of samples with stitch structures: chain, tri-,cot, atlas, and their derivatives (single and double) from differentkinds of yarn. For each sample it is necessary:

(a) to study the particularities of stitch structure to determine theface and reverse sides, the direction and causes of curling, the loop

inclination in relation to the loop course, and to establish the direc-tion of knitting and ravelling of samples, as well as ravelling inten-:sity;

(b) to draw the graphical and analytical representation of yarn lay-ing, to determine the stitch repeats in width and height (Rb, Rh),yarn drawing-in and repeat of warping, types of loops in courses(open or closed);

(c) to establi h experimentally the kind of raw materials, the yarnlinear densit:: in tex (this being done only for some samples as indica-

ted by the teacher), the characteristics A and B, the stitch density,the length of the yarn in the loop l, and the mass of 1 m2 m;

(d) to calculate on the basis ofthe actual values l, D ,,, D" (establish-ed experimentally) the module of the loop (J, the density ratio fac-tor C, the mass of 1 m 2 m, the yar n tak e-up in the knitted fabricu.

2. Design the main characteristics of loop structure in knitted fab-rics of the stitches under examination, according t o a given yarn li-near density.

Basic ~warp knit stitches are stitches con isting of similar structuralelements (loop~) joined together in the simplest combination. Basicwarp stitches may be as follows: chain, tricot, and atlas (single and

dOllble).The deriyative warp knit stitches are formed of an undividablecombination of seYeral similar basic \yarp stitches \yhich are interla-ced in such a manner that bet\veen the wales of one structure there arethe wales of another structure or several such structures. Derivativesof warp stitches may be derivative single and double tricots (half-tricot, charme, T-shirts, etc.) and atlas derivatives (single and doub-le) .

\\'arp-kniLLeci fabric is formed from a yarn system called "the warp".

The warp yarns, after forming loops in one course, pass into the followingcourse, a~d, as a rule, the number of loops formed in the course is thesame as the nllm bel' of yarns in the warp. Due to this, loop formationin warp-knitted fabric features the presence of jllnctures J (Fig. 54a)connecting the carcasses of loops C in the ad jacent courses. Depend-ing on tbe method tho \varp yarn is layed on the needles, the loops


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R b

h '6r--;"i

~ 0 .( XJ l 1

X

ox

I. fY 0 u 0

'O Jx x x x

.~II U : g : '"0 j J 1 O c t' OU .[J x1 [

[. ,0 6 [J '4 2 0

J 2 ! 0 I 15t0

J 0 I 18t(0) (c)

I Numerical Numericaf

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two- stafe three - stafe'{cllrse record record

I 2 - 3 2-3-_2

!! 2'- 1 2 - 7- 1III 1 -0 1-0-01 J 7 !-2 '-2-21 2 - J 2-3-2

Num erlca'T

N tw o - stc:feC ours e recor

I4 - 54~Z

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are of the follmdng types: open loops (courses II and rV), closed lo-ops (courses, I, III), with one-side junctures (courses I, III), and

,,'ith two-side junctures (conrses II, IV).

''Varp-knitted fabrics haye a very intricate structnre. Usually

\\'arp-knit stitches are represented by a graph, and the symbols in

the graph designate the sequence in which the \\'arp yarn lays on the

needles. The graph of the warp knit giYes sufficient information onthe kind of yarn laying, possible properties, and knit design; it is

u"ed to establish the programme of bar operation on warp knitting

machines (setting the pattern chain).

For plotting a graph, use is made of a rectangular coordinate net

(Fig. 5 4 o b , c ). The points and cro"ses of the coordinate not are conside-red to be needles; the horizontal row of points designates the needles

of one bed, and the horizontal row of crosses-the needles of the other

bed (for two-bar n19cllines). The knitting courses produced by the

needle beds are numbered from the left side of the graph, the figures

running from bottom to top. As the full course of double knit is for-

med by the consecuti\'e operations of t\\'o needle beds, the numera-

tion of a loop course comprises rows Kith points and crosses (Fig.

5 4 o c ) . The inlerspaces between th(; yertical columns of points and cr os-ses are designated from right to left by figures in consecutive order

for warp knitting machines and by even numbers for Raschel machines

ero designates the beginning of the record from the right of the co lumn

of points (crosses) in which the extreme right loop of the repeat is dis-


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posed. ~arked on the graph is the sequence in which the yar ns ofeach bar ar e laid in each loop COllrse; the part of the line above the

point (cross) 0 means warp yarn laying on the needle, while the por-tion of the line under the point (cross) U -means yarn laying underthe needle.

\Vith graphical representation of warp knit, there is a warp thread-ing-up chart for the given bar (B1) where the dashes designate yarnsdrawn into the bar guides, and the circles-the yarns which have not

been drawn into the guides.As all the yarns of the given bar are laid on to the needles in the

same manner, it is sufficient to show on the graph how one yarn islaid. In the bar threading-up chart this yarn is designated b y a r e-ctangle.

The consecutiyc order of links in the pattern chain (program) i

established according to the line of yarn motion in the graph. Forthis, a nllmerical or analytical record of the structure is made (Fig.54d-j) , WIlen making a numerical record according to the graph, onlyyarn laying on the needles is shown, as laying of yarn under the need-les i n the 11llmerical record is regisLered automatically. The nllll1eri-cal record is always made from the bottom Ilpwards, starting from thebottom horizontal (fir st) row, i.e. in the order of course k nitting(the record is made and read from top to bottom). Fig. 54d, j illu-strates the numerical records of interlacing corresponding to the diag-

rams in Fig. 54b, c at the two-stage operation of the warp knittingmachine.

"Vhen the \york is carried ouL in two stages, for knitting one coursetwo racks of the bar are made: one for overlapping the yar n on theneedle, and the second for lappi ng the yarn under the needle. Thedirection of the rack in yarn overlapping in Figs. 54d, e is indicated

by the horizontal arrow, \\'hile the rack direction at yarn unclerlap-ping is sho\yn by the inclined arrow.

For reducing the impact load on bar racking in the case of three-

stage operation of the warp knitting machine, bar racking behind theneedles is effected in two stages.

The three-stage numerical record transformed from a two-stage re-cord (see Fig. 54d) is shown in Fig. 54e.

In looping diagrams, it is standard practice to indicate the struc-ture repeat by the width Rb and height RH.

Plain chain (Fig. 55a-d) is the simplest warp knit formed by lapp-ing the yarn on the same needle in all loop courses. It forms separate

wales (Fig. 54a, b) and may be with closed loops (RH =1)

or withopen loops (Fig. 54d, c) (Rr! =2).Plain chain cur ls into a spiral towards the face and ha s a slight

extensibility. It is usually used in combination with other stitches.Plain chain is the most important element in knitted nets, curtains,lace, fringe, cords, etc.

Single tricot (or English leather) (Fig. 56a, d) is a stitch formedby one warp; the tricot loops are disposed in an alternate ord er in


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two adjacent \\'ales (Rb = 2) (R H= 2). All loops in single tricothave single-face junctures. This tricot may be formed of closed, open,or alternate closed and open loops (Fig. 5Gb, c, d ); the junctures intricot are seen on the back. The loop skeletons in single tricot are

Fig. 55. Plain. chain and its graphi-

cal r epresentatlOn

inclined in relation to the line of the loop course in the direction reyerseto the disposition of junctures, this being caused by the tendencyof yarn kinked in loops to straighten.

The degree of loop inclination, which is determined by the anglea (see Fig. 5Ga ) , increases with the yarn elasticity and d ensity ofknitted fabric. Due to loop inclination, the loops of single tricot haye

a zigzag structure. Moreover, the loop skeletons in tricot tend to turnfrom the horizontal plane of the knitted fabric to the perpendicular

plane. As a r esult, at certain loop structure characteristics for a giYenkind of yarn, the face and reyerse sides of tricot are the same and

have the appearance of open texture fabric with small rhomboidalmeshes.

Owing to the disposition of loops in the tricot, curling of edges 011the samples of knitted fabric is barely visible. Single tricot ravels(separates along the line of wales) only in the direction reverse toknitting; this is the main drawback of knitted fabrics with a tricotstructure.

Single atlas is a stitch in which each yarn consecutively forms

loops in a multitude of adjacent wales. In single atlas (Fig. 57) there


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are loops with single-side and d ouble-"idejunctures. The smallest stitch repeat is Rb == 3 in width, and in height R H= 4. Thegraphical representation of yarn laying in

this atlas is shown in Fig. 54b. In high repeatmulticourse atlas the junctures connect theadjacent wales first in one direction, and thenin the r everse direction (to te initial wale). Inatlas, the loop carcasses are inclined in thedirection reverse to the direction of the ont-going juncture. Owing to this inclination ofthe loop skeletons, knitted tricot fabrics,when manufactured of single colour yarns,

F' 5- S' 1 II have cr oss stripes of different shades, andIg. I. mge a aswhen of rnulticoloured yarns, characteristiczigzag designs.

Single atlas may be of a plain or a complex structure. In plain at-las the yarns are laid in the simplest alternate order in opposite di-rections. A complex multi course atlas may be considered to be jerseyturned at an angle of a ~ 60.

Single atlas curls at the edges, similarly to jersey, and ravels inthe direction r everse to knitting; the fabric does not separate alongthe wales.

Single tricot derivatives are combinations of two, three, and moretricots mutually interlaced so that in the interspace between the ad-

jacent loop carcasses there are one, two, and more carcasses of loopspertaining to other tricots.

The tricot derivative obtained as a result of combining two tricotis called double-tricot or half-tricot (Fig. 5 8a ). The combination ofthree tricots is called T-tricot or "charnHl" (Fig. 5 8b), etc.

The half-tricot str ucture is formed of one warp, so that the loops ofeach yarn are disposed in turn in two wales, i.e. every other wale(Rb = 3, RH = 2).

The loops in the half-tricot stitch have only single-side junctures,and for this reason the wales (visible from the face) have a zigzag-shaped structure; from the reverse side of the structure, the loop ske-letons are intersected by junctures. The systems of junctures e, e'(Fig. 5 8 a ) form at the reverse side sharply visible false wales orienta-ted in the direction of the knit courses.

Samples cut out from grey knitted fabric of half-tricot structurecurl at the edges, i.e. along the line of courses towards the face, andalong the line of wales towards the reverse side. Half-tricot ravelswi th difficulty, and for its running at least three wales must be unra-

veled.Charme or locknit (Fig. 5 8b) differs f rom half-tricot in the length

of junctures. It is knitted from a one warp system and the loops areformed by one yarn in turn in ad jacent courses, every two wales

(Rb = 4; RH = 2). With an increase in derivation, the stitch repeat


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in width also increases, i.e. for four-tricot Rb = 5, for five-tricotRb=6andsoon.vVithanincreasein the value Rb, the length of jun-ctures also increases. Consequently the mass of 1 m 2 of fabric becomesgreater, and the angle of juncture inclination to the line of the loopcourse decreases, resulti.ng in the reduction of knitted fabric extensi-

bility in ~\Vidthand in higher lustre of the r everse siele of the fabric.

Fig. 58. Single tricot derivatives and their graphical representation

(a) half-tricot; (b) channe

Charme and other tricot d erivatives are even more difficult to ravelthan half-tricot, and this may occur only in the sense reverse to knit-ting; they curl at the edges the same as half-tricot.

Atlas derivatives have a structure similar to that of tricot deri-vatives; between the wales of one atlas are found one or several walesof a second or several similar atlases. In the atlas derivatives of thehalf-tricot type (Fig. 59), the yarns form loops over every other walein the direction over a length of several courses, and then in the sameorder in the other direction. The smallest repeat of such an atlas inwidth is Rbmm = 5, and of the charme type atlas Rbmin = 7.of the atlas of the type four-tricot, R bmin = 9 and so on; R Hminfor an atlas of any type is equal to 4. Atlas derivatives are heavierthan tr icot derivatives due to the increased length of their junctures.They are less extensible in width, can be unravelled with difficultyonly in the direction reverse to knitting, and, moreover, they cur l

from the edges in the same way as the standard single atlas.


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Double chain (Fig. 60a) is the simplest double warp knit withloops of one yarn forming two wales: a face and a reverse wale. Double


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ctures. Both sides of the knitted fabric have a zigzag shaped texture,the inclination of loops being greater on the fabric side formed by lo-ops with single-side junctures. Double rib tricot does not curl at ed-ges, and ravels (separates along the loop wale) only in the direction

CourseNumericalN

two-stoperecord

I2- 43-S

JIr2

3- 1

x(c)

N22 NtD 10,

(b)

reverse to knitting. The numerical record of the stitch is given inFig. 6ie.

Double rib atlas is also manufactured on machines with a stagge-red disposition of needles in the beds (as well as derivatives of rib

420

I 0 I b irb)

tricot and atlas). Such two-bar knitting machines do not find pra-ctical application in the knitting industry nowadays. Machines inwhich the needles in both beds are disposed "in file" are widely used.

Double tricot (Fig. 62a) is the simplest basic structure for mingthe fabric produced in these machines. In this warp structure eachyarn consecutively forms loops first in one course on the face and re-verse sides in the same wale, next, in the following course in the


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neighbouring wale on the face and reverse sides, and finally in theinitial wale. Both sides of double tricot have the same structure andall loops-single-side junctures; \\"ales are disposed in zigzag. Knit-

III

1I

xI

6 - 4 2 0I 0 I 181

ted fabric of this structure ravels only in the direction reverse to knit-ting. Fig. 62b shows yarn laying in double tricot.

Double atlas (Fig. 63) i s a warp knit structure in which the loopsare consecutively formed i n many adjacent wales first in one directionand then in the other. The minimum repeats of double atlas in

II

~J 0)

Fig. 64. Double half-tricot and its graphical representation

width and height are the same as in single atlas: Rb = 3, R H = 4.Knitted fabric of double atlas stitch does not curl and has the samestructure on both sides; it ravels only in the direction reverse to knit-

ting.Th d bl k it d i ti f d di t


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Double derivatives of tricot and atlas pertain to the first group.In the same way as in plain warp knits, by combining two doubletricots a half-tricot is obtained; by the combination of three tricots

Rb

!I I IY

II III

T J~

1 o I 181o I 1 18, [

(a) (b) I 0 I I 181(c)

Fig. 65. Graphical representa-tions of .

(a) double charme; (b) double four-tricot; double two-atlas

a double three-tricot (charme), etc. By the combination of two atla-ses a double two-atlas is formed.

The structure and looping diagram of a double two-tricot are shownin Fig. 64a, b. The graphs of double charme, double four-tricot and

Fig. 66. Warp stitches

(a) interlock tricot; (b) interlock atlas

double two-atlas are given in Fig. 65a, b, c. With increased deriva-tion, the length of junctures is increased, the extensibility is reduced,and the mass of knitted fabric is increased. The characteristic featu-re of double derivatives pertains to the fir st lroup in the same struc-ture of wales at the face and back sides.

Interlock warp knits constitute the second group. Interlock tri-

cot (R b = 3; R H = 2) and interlock atlas (R bmln = 4; R Hmln =


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~\to 8 (j 4 2 0

(0/

= 4) are formed just like weft interlock of two rib warp-knitted tri-cot and atlas (Fig. 66a, b). In these structures, the junctures connectthe adjacent wales in different loop layers. The face and back sideshave different structures: in tricot one side has loops with two-side

junctures, while the other has loops with one-side junctures and in

atlas-loops with one-side and two-side junctures. Interlock deri vati veof half-tricot with r epeats Rb=5, RH =2 (Fig. 67a, b) is formed

RF'7

Fig. 68. Graphical representation of interlockderivative of two-atlas

of two d erivative rib tricots, while the interlock derivative tripletricot (charme) with repeats R b = 7, R Ii = 2 from three interlockcharme, etc. The interlock derivative atlases have a similar structure.The graph of the interlock derivative two-atlas is given in Fig. 68.

The greater the derivation of interlock warp knit structures, themore their mass and thickness, while their extensibility in width de-creases. The wales have a zigzag structure; the inclination of waleswith two-side junctures is less than with one-side junctures. All the-se structures do not curl at the edges and ravel only in the sense re-verse to knitting.

Laboratory Practice in Knitting Technology

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