Yarn Manufacture I : Principle of Carding and Drawing Prof. R. … · 2018-10-05 · Yarn...

Yarn Manufacture I : Principle of Carding and DrawingProf. R. Chattopadhyay

Department of Textile EngineeringIndian Institute of Technology, Delhi

Lecture - 18Significance of Process Parameters

So, now we are going to discuss the Significance or the importance of different Process

Parameters.

(Refer Slide Time: 00:28)

Roller setting is one of the very important process parameters in draw frame. So, the

setting depends upon fibre length that is either 2.5 percent span length or 5 percent AFIS

length for cotton or staple length for manmade fibres it also depends upon the linear

density or the bulk of material between the rollers. And it also depends upon the level of

entanglement and parallelization of fibres in the sliver. So, these three are very important

factors that governs this sitting.


Here is a guideline for draft as well as roller setting on draw frame. So, draft if you look

at the table broad breaker and finish or draw frame the setting guidelines and the break

drafts are shown. Breaker draw frame is the first passage that we give to the card sliver

that is known as breaker draw frame or breaker drawing process. Then the drawn slivers

are again passed once more on second draw frame again. And this is known as the

second passage will be known as finisher drawing passage.

And, if we look at this setting part now, you can see that the back zone setting for carded

cotton as an example we have chosen 2.5 percent span length plus 10 mm the brake draft

could be 1.7 and the front zone the draft could be the rest of the draft, because most of

the draw frames we will have basically two drafting zones, and the setting in the front

zone it is 2.5 percent span length plus 6 mm.

Therefore, if we look at and compare the settings between the front and back zone what

we see is that, in the back zone span length plus 10 millimeter in the front zone it is span

length plus 6 mm. And same is true for the finisher passage also the setting in the back

zone is again 2.5 percent span length plus 12 mm and in the front zone it is 2.5 percent

span length plus 8 mm the setting can be done on the basis of f is 5 percent length as

well.


So, generally what we have seen from this table is this that the setting in back zone is

little wider than their setting in the front zone.

Now, why it is wider what are the reasons? So, we are discussing right now about the

breaker draft and passage all right. So, what happens that we feed card sliver and there

are lot of entanglements of fibres in the card sliver. So, because of these entanglements

which are present, and fibre also highly crimped and in a hook state the sliver can extend

more. So, a card sliver has the ability to extend more in comparison to the drawn sliver

or combed sliver made from the same fibre. So, because it can extend more before the

sliding action actually starts, hence we need a little wider setting in the back zone.

So, that we make sure that the sliding action commences and before that the sliver has to

extend. So, sufficient space has to be there to accommodate the extended sliver. Other

thing is that there is a high drafting force due to fibre entanglement, and bulk being more

in the back zone. In the back zone always the mass of material is more and because of

the presence of entanglement there will be very high drafting force; the high drafting

force mainly two plucking of fibres from the back roller nip.

So, we will not allow the drafting force to increase too much. And hence what we have to

do; we have to reduce the force and we can achieve it by widening the setting that is why

we have to keep the setting little wider also in the back zone.


If we compare the setting between breaker and finish a draw frame, you have to

understand what is the difference in the sliver which are fed to the breaker draw frame

and which are fed to the finisher draw frame. What we have seen is this that they are

setting a little wider in the breaker than in the finisher. In the finisher there is also a

chance for the setting to be kept at a higher level because of the reason which is stated

here that once the fibres or the slivers have undergone one draw frame passages there is

increase in the extent of fibre there is lot of straightening out action which has happened.

Because of the straightening out actions and removal of hooks removal of crimps the on

an average the fibres have extended now.

Now, when the fibres are little longer because of being certain out, we have to keep a

little increase setting in the back zone and also in the front zone. Therefore, in the

finisher draw frame we keep a little higher setting in comparison to the breaker because

fibre extent has changed fibres have straightened out. And hence we require little more

setting that is wider distance between the roller nips.

Now, what is the influence of roller setting?


If you look at the diagram which is on the right hand side top part what we see here that

as we increase setting, the irregularity of the drafted product is going to decline first and

then is going to increase. So, it passes through a minima and we have already now

discuss this points in some other previous lectures.

So, its almost its going to repeat it again. So, there is always an optimum setting between

the rollers at which the irregularity in the delivered sliver becomes minimum. If the

setting is increased beyond this optimum there is irregularity increases as there will be

inadequate control on the movement of short fibre, because if we increase the setting too

much most of the fibres will behave like short fibres. And therefore, they will move in a

erratic manner within the drafting zone and as a result there will be increase in

irregularity.

When the setting is low, the irregularity may also increase as many fibres will be

simultaneously gripped or nipped by both the nips of the drafting rollers and they will be

pulled out in the form of a bunch from the back roller nip and hence there is a there is an

increase in irregularity. So, that is why we get a minimum too wide setting is bad, too

narrow setting is also bad. Therefore, keeping in mind the length of the fibres and the

proportion of short fibres which are there, we have to find out what is the right setting

that we should keep so that we can minimize the generation of irregularity.

It is not that we will be able to avoid the generation of irregularity any drafting will

always lead to some now some increase in regularity, but we have to try to minimize the

generation by optimally adjusting the setting between the rollers.


Influence of sliver hank or sliver bulk; now this diagram which is shown here we are

showing here how the with the increase in setting how the irregularity is changing for a

single sliver for a double sliver and for six slivers combined together.

So, there are three different color lines indicating the number of slivers being fed to the

machine with the optimum setting if we feed more slivers to the drafting unit drafting

wave will be visible in the delivered sliver why? With the increase you know sliver bulk,

because as we feed more sliver bulk comity there is going to increase the drafting force

is going to increase which may cause fibres to be plucked from the back roller nip

causing rise in it is regularity.

So, the optimum setting that we get for single sliver, let us say if I keep the setting at that

level and feed two slivers. Then we will find that we are not getting an optimum there

you have to move towards the right hand side, and you will get a new setting where we

will find the optima for double sliver being fed together

similarly at that level of setting which you have obtained for two slivers if I increase the

number of slivers that is from 2 to if we go to 6, then we will find that one is there is a

increase in the irregularity and there the minima the optimum setting is actually shifting

towards the right hand side; is all because there is a increase in bulk there is a increase in

drafting force. So now, the situation is different when I feed more and more sliver, and

again you have to find out where the new optima is.

So, depending upon the number of sliver that you feed, bulb being different we have to

find out where is the new optima. So, as we change the number of sliver that you feed

you have to again find out where the new optimum lies as we move from 5 sliver to 6 6

to 7 7 to 8.


Other than sitting the next process parameter is delivery rate, at what speed you should

produce this sliver. The delivery rate has to be judicially decided based on type of fibre,

that is whether the fibre is manmade or cotton.

And if it is cotton whether it is carded cotton or combed cotton and it also depends upon

the condition of the machine how old the machine is. What is the recommended speed

suggested by the machine manufacturers. Whenever we buy a machines the machine

manufactures such suggests certain speed for different fibres. So, they already know that

at what speed the machines would run from the engineering point of view.

Going beyond the recommended speed whatever has been suggested by the machine

manufactures may lead to two things, one is roller vibration and noise. The vibration will

introduce irregularity into the draft get sliver, that is why the machine manufacturers

suggest certain speed and one should not try to go beyond their speed in order to enhance

the productivity, because the engineering design of the machine in terms of bearing in

terms of the load that is acting on different parts the dynamic forces which acts on the

machine parts all these are designed for a certain range of speeds only.

If I go beyond that, then there is a chance of vibration there is a chance of noise and

hence any vibration we will lead to generation of irregularity. But typically their speeds

which are used or so, shown on the right hand side one manmade fibre it can vary

between 300 to 500 meters per minute combed cotton 300 to 600 meters per minute

carded cotton, 400 to 800 meters per minute and viscose rayon 400 to 800 meters per

minute.

So, what we see that for carded cotton and viscose rayon the range of speed is little more

than combed cotton or more in comparison to manmade fibres. So, what is the reason for

this? Well possessing manmade fibres other than viscose rayon. Viscose rayon is the only

exceptions right we have seen that the speeds of processing is same or similar to what we

give for carded cotton

But for other fibre like polyesters that is see, which is very popular fibres and processed

the speed is less.


We will discuss why the speed is less the other factors which can affect the speeds are

fineness of the fibre. The fibres are very fine even for cotton fibre to the fibres are fine

then we have to reduce the speed because the incidence of frequent lapping that we have

to remember that the rollers get lapped. The drafted wave has a tendency to follow the

curvature of the roller and at times they follow it and get wrapped around it. And, that

leads to basically breakage of the sliver or it may lead to theme players getting generated

in this sliver. So, these lapping incidence has to be reduced and this is more with fine

fibres because fine fibres are they have less bending rigidity, they are flexible and

compression to coarse fibres. So, we find incidents of lapping more on fine fibres.

So, for the same type of fibre if it is cotton or if it is polyester if we go from coarse to

finer side then also you have to reduce the speed fibres with considerable crimp leads to

drafting problem, because the crimpy fibre behave like springs within the drafting zone.

So, they extend and when they are suddenly released they retract.

So, this extension and retraction is a source of irregularity generation in the drafting

zone. So, fibres which are too crimpy also lead to different types of drafting problem.

And therefore, we have to reduce the speed when we have too much of crimp in fibres.

Fibers with spore spin finish a synthetic fibres this spin finish is not correct then there is

a possibility of static electricity generation.

Static electricity generation is a big problem with fibres like polyester, acrylic nylon.

And hence, whenever we try to process these fibres, we have to reduce the speed the

production speed in comparison to what we can keep for cotton or for viscose rayon.

Because viscose rayon and cotton do not have this problem of generation of static

viscosity, because their hygroscopic fibre they can absorb moisture and hence the

possibilities of static equisetic generation is not there with viscose rayon and cotton.

Too long a fibres means, very high dynamic drafting force drafting force will increase

because the fibres being long there is a lot of contact between the this fibre and its

neighbors the surface area is more. And therefore, drafting force is going to increase

phenomenally with long fibres. And that could be chance of uncontrolled drafting and

also possibilities of roller lapping. So, when we processed long fibres we have to reduce

the speed or production.

So, its synthetic fibres chances of static generation is there and that is why reduce speed

and the other issue for between if we compared between card sliver and the combed

sliver with combed sliver we reduce speed, because combed sliver what is the difference

between combed sliver and carded sliver the difference is the combed sliver the short

fibres are not there, and because of the comb being actions all the fibres are very straight

and parallel. So, fibres are highly parallel they have been separated by the combing

needles which you learn later. And therefore, combed slivers are very very weak as well

because of removal of crimps from fibre and paralyzation between the fibre.

There is no interlocking between the fibres too much parallelization is there, and these

combed sliver or comb sliver yes the fibres in combed slivers are also prone to lapping

around the rollers. So, to avoid this lapping tendency, we have to also reduce speed while

processing cone material.


Now, from the speed we move to the next parameter which is roller pressure. Top rollers

as we all know are pressed against the bottom roller. So, that the fibres are held by the

rollers firmly and move it at its speed. So, all these rollers are pressed against each other

there is a pressure, the pressure is to the order of 60 to 80 kg force very high level of

pressures we generally apply and we make sure that the top one which is friction driven

gets its drive from the bottom ones though in between there is a layer of fibres which is

lying.

The back roller pressure is little more than the front roller pressure it is any simple the

bulk or material is more between the back rollers. Because as if the material comes to the

front roller side there is a draft which is acting the sliver is thinning. So, as the material is

thin down the mass of material is less, and hence we can have less force on the rollers.

So, the back roller more force or more pressure and the front rollers less force because

fibre bulk is less there. The other thing is manmade fibres are very very smooth and

slippery, and in the manmade fibre there is no short fibres as we have found them in the

case of cotton.

So, being very long most of the fibres are long, and the surface area of the contact is also

more hence what happens? Higher force is required to grip them effectively between the

rollers and transmit motion to them, this is the reason see cotton has convolutions the

surface of viscose rayon have solutions. So, the surface of cotton or viscose rayon is little

rough in comparison to the cylindrical fibres like let us say polyester or nylon, actually

even though it actually cross section is not really circular, but the surface of the fibre is

very very slippery.

So, these fibres are slippery in nature the surface, fibres purpose of these fibres and

hence. So, if you want to grip them we need more force on them. And that is why the

pressure on the roller will be more if we are processing synthetic fibres other than

viscose rayon. And not only that viscose rayon also we increase pressure to the extent of

20 to 30 percent because viscose rayon even though surface is selected still the surface is

smooth in comparison to cotton.

So, with viscose rayon also the pressure is increased by 20 to 30 percent whereas, for

polyester it can increase by 30 to 40 percents. So, remember this that whenever you

process manmade fibres pressure needs to be raised, because the surface is slippery

within synthetic fibres that could be different types of cross sections; but even then the

surface of these fibres are much slippery in nature in comparison to what we see in the

case of cotton.

We can find out how much pressure is acting.


.

If n slivers each of width w are pressed together by a force F on them, then the normal

force per unit width of the sliver is going to be F by N w, here there is a assumption.

Assumption is that if we have n number of slivers in between two rollers and the contact

is only established between the fibre and the roller. The rollers are quite long enough so,

that they can accommodate 6 or 8 sliver side by side.

So, we are assuming that beyond the width of the n number of sliver that you are feeding

the rollers are not in contact with each other. So, entire pressure that we keep on the top

roller is getting transmitted through the fibres to the bottom roller only. And therefore,

we can say the force on them is going to be F by N w inadequate roller pressure may lead

to roller slippage on the contrary too excessive pressure may bend the bottom rollers and

would require more energy to run them.

So, between these two contrary requirements, we have to find out what is the optimum

pressure that we need. So, a typical pressure suppose say of 70 kg force with the typical

sliver in a compressed state is going to be around 2.5 centimeter almost an inch. And if I

feed 8 slivers then the pressure per unit width is shown here is around 34.3 Newton per

centimeter or 3.5 kg per centimeter that much pressure we require to grip the material

effectively between the rollers.


Another parameter these tension draft, these tension draft generally does not get much

attention or much importance, but it is sometimes become very very significant its

influence. Tension draft is employed to ensure that is sliver or the fibrous wave remain in

a top state while being possessed with there are regions where tension draft is applied

what are those regions let us first try to look at. The locations are between the front

drafting roller and coiler calendar roller front drafting roller that is the delivery rollers of

the machine, and the calendar rollers with it they are in the coiler between these two

there is certain distance the material has to travel. And we do not allow the material to

accumulate.

So, there has to be little tension and the small tension is known as tension draft. So, that

draft is generally little more than 1 little more than 1, but we will see that it could be less

than 1 also why it is we will discuss this the other location is between sliver guiding

roller and back roller of the drafting system that is the creel draft. That in the creel as you

leave the sliver from this from the can and the sliver has directed or guided to us the

drafting unit. There is a little tension that we keep on the sliver and there is a tension

draft there is also known as creel draft.

So, the magnitude of draft is always close to one it is generally little more than 1. So, the

table shows here the kind of creel draft we keep 1.01 1.02 that is the typical; that means,

the speed of the guiding roller is little less than the surface speed of the back roller of the

drawing system. If we look at the tension draft in the breaker and finisher stage one

important difference is for the breaker machine the tension draft with the web tension

draft is little less than 1. The draft being less than 1 what does it mean it basically means

that there is a feeding is more than the delivery that is I am feeding more length and

taking out less. So, there is a chance of accumulation still we keep a draft which is less

than 1.

But the finisher we keep a draft more than 1 as usual about not too much you have

remember as a draft have 1.05 1.06 we should not keep to keep the material and that

taught state, because that will lead to irregularity into the drafted product. Because, such

a long distance they are traveling there is no guidance to them this stretch is too much,

then there is going to be sliding action between fibres, and it is any sliding means

drafting actions and drafting action basically means that the chance of development of

irregularity. And therefore, we have to ensure that the tension draft should not be high

enough which can lead to sliding between the fibres.

Now, why tension draft it less than 1 that we need to discuss?


.

The tension draft depends upon the elasticity of the sliver or the drafted wave which in

turn is affected by the nature of fibre, the crimp in the fibre, the degree of fibre

entanglement within the sliver, these are the important factors which decides the

elasticity of the sliver. The drafted wave that moves out from the delivery roller when

released from the front roller nip it detracts while the fibres are being processed they are

under tension from back zone to front zone as soon as they are released from the front

roller nip. Before they reach the coiler calendar roller there is a sudden go for relaxation

and the fibre drafted wave can retract retractions.

If there is retract tension will develop in the wave and which will lead to uncontrolled

sliding between fibres, and that may result in irregularity. Therefore, to counter this is the

web tension draft we have to keep less than 1. See the possibilities of retraction is there

because the fibres are retractable in nature then we must keep a draft which is less than 1

so, that even if there is try to contract we are taking out less feeding mode. So therefore,

the possibilities of sliding action will not be there. But by the time the sliver goes to the

finisher drawing stage there is not much crimp and entanglement left in the finisher

sliver and hence tension draft more than 1 is to be maintained.

This is the tension draft the web tension draft which we maintain less than 1 is in the

breaker stage while possessing cotton, whether by that time the material goes to the next

draw frame stage as a finisher drawing stage the crimps are no more they are in the fibre,

they have all lost most of it. And because, there is another passage of drawing the fibres

are passing through and entanglement also less the retraction possibilities it goes down.

And therefore, we keep a tension draft which is more than 1, when you go to the fresher

drawing stage.


Influence of drawing on fibre configurations. Now what is the purpose of drawing? If

you go back to the original objectives or drawing you will find that one of the purpose of

drawing is to realize the fibres, to unhook the fibres to improve their orientations and all.

So, this particular table gives you an idea it is trying to quantify what happens to the

hooked fibre that we see in the card sliver.

So, if we look at this table then what we find? In the last row percentage of reduction in

hook ok. So, what we see here that, if I go by the column number one trailing hooks

reduction in 68.4 percent, leading who reduction is 442.1 percent. So, these values if we

see there is a tremendous improvement in the hooked fibres and we have categorized the

fibre terms of trailing hook leading hook both and hook you hook in trailing direction

and you hook in leading directions all types of hooks are here and that is straight fibres s

and o means others different categories of fibres are there and.

What we see here is that there is a in each category there is a improvement hooks are

going down and down and straight fibres are also increasing what all there is

improvement that is what happens. That is as we process the material that is from on the

breaker draw frame and finisher draw frame stage there is a tremendous improvement in

the overall configuration of the fibre.

That is the fibres are becoming more and more straight more and more parallel and the

hooked part of the fibres hooks are basically vanishing. So, in the end there were little

hooks which will be left.


There is always a in this question comes to our mind that why do you need two draft in

passages or three passages. So, we will see that one of the reason why do you need two

draft in passages, is to ensure that most of the hooks which we see in card slivers are

remove to the maximum extent.

Now, if we study this particular diagram carefully, and we see that the two types of

hooked fibre that we find in the card wave or in the card sliver they are represented by

two different colors. So, trailing hooks they represented by the orange color and the

leading hooks by the blue color. So, in the card can you see from the wave as it enters,

and you have seen already that in a card wave or in a card sliver with reference to the

direction of delivery trailing hooks are more in number than leading hooks.

So, let us concentrate on these two types of hook trailing hook and leading hook. So, in

the card sliver trailing hooks are more and this trailing and leading hook definition is

with respect to the direction of delivery from the carding machine. Now when this sliver

is packed in a can and then withdrawn there is a reversal that what goes in first that

moves out last from the can. So, the part of the sliver that goes first there remains at the

bottom and the part that goes last this withdrawal first. So, there is a reversal because the

reversal there is a direction change of the hooked ends also. So, when he remove sliver

from the card can there is a change in direction.

So, what we see here? In the first draw frame passage the trailing hooks are being fed in

the leading directions and leading hooks are being fed in the trailing directions. If we

look at the diagram the trailing hooks this is in orange color it is being fed in the leading

direction because there is a reversal be because, the sliver has impact into a the can of the

can we are removing this sliver.

So, there is a reversal now in a draw frame the drafting operation helps in removing

trailing hooks more than leading hooks. Because of the sliding action between the two

group of fibres within drafting zone the any fibre with the hook at the trailing end will be

straightened out easily whereas, if a fibre same fibre is fed with a leading and hook it is

not going to be removed preferentially. So, in any drafting zone trailing hook removal

will be more in number in comparison to leading hooks.

And therefore when I pass the material to the first draw frame passage most of the

leading hooks, which are there in the card sliver they are being fed as trailing hooks now

and therefore, most of them will get removed. However, the trailing hooks in the card

sliver which are more in number they are being fed in leading direction. So, their

removal will be less in the first passage. And then the material moves in to the draw

frame can after the first passage and then again we lift it and fit to the second machine

that is the finish or draw frame.

So, there if we see now direction of presentation of the hooked fibre the orange fibres are

being presented in the trailing directions and the leading hook fibres is presented as blue

fibres in the leading directions. Now again, a drafting is going on the breaker draw frame

and now what will happen that most of the trailing hooks with reference to carding

machine or card sliver labor are now being presented in the trailing direction in the

drafting zone of the breaker draw frame. So, they will all get removed preferentially.

So, second draw frame passage will be more effective in removing the trailing hooks

than the leading hooks. Training hooks means these are trailing hooks with respect to the

carding machine delivery directions. And hence, what we need with the earliest two draw

frame passage to take care of removal of trailing and leading hooks.


So, whatever I have told the same thing is being stated here that in the first drawing

passage all trailing hooks in card sliver would expect to card delivery are presented in

trailing directions. And they do not get removed preferentially in compassion to leading

hook presented in the trailing directions.

Exactly this is what was stated and the second drawing passage majority trailing hooks

with respect to card are now presented in trailing directions and are preferentially

removed. Therefore, two passages are bare necessary to remove both type of hook fibres

and hence from the point of view of removal of hooked fibres two passages are required,

and we the practice in the industries also what going for two passages. Why the trailing

hooks are more removed or preferentially removed?

Now if we imagine that the fibre with a trailing which is trailing and hooked is moving

to the drafting zone the hooked end is short. So, the leading end as is as soon as it is

gripped by the front pair of rollers this end is being pulled at a faster speed. The hooked

end is now brushing against these slow moving fibres. And now there is a friction

between the hooked end and the slow moving fibres. And therefore, the hooked end will

be easily unhooked, if I now focus on the orange fibre with a hooked end and the leading

part of the fibre.

Now, when this fibre moves through the machine, the hooked end itself will get caught.

So, both limbs or the hooked will be caught by the front roller nip and now the fibre

suddenly gets accelerated, but there is nothing left in the trailing part of the fibre trailing

end of the fibre. So, the hooked end remains hooked end and their chances of removal is

very very low.

So, leading hook removal is actually less in any draw frame passage if the fibre and

trailing end of the fibre is has being hooked, that we will get unhooked very easily. But

one can still feel that does not mean the leading whose will never get removed still they

get removed while they are passing to the drafting zone we could, because before they

reach the front roller nib the faster moving fibres are brushing against the hooked part

this fibre. Let us say a fibre with a leading and hooked is gradually approaching the

drafting zone, and being delivered slowly and slowly into the drafting zone, but still

moving at the speed of back roller.

So, when the hooked part is has gone middle of the drafting zone, now what is

happening, but this hooked part is in contact with many other fibres moving at a faster

speed. Those fibres are going to now unhook this end therefore, some reading hooks also

we will get removed, whenever we you know go for a drawing passage. So, both type of

hook has a chance to be removed, but fibres with trailing and hook has a better chance of

removal than the other one.


In the drawing what happens therefore, there is a removal of hook 10 there is a

straightening of fibres there is improvement in homogeneity because there is a doubling

actions. And there is improvement in mass uniformity all are achieved the number of

passages; however, are restricted to two usually why? More drawing passages make this

sliver very weak progressively due to over privatization of fibres without any further

significant improvement in uniformity. So, you do not go for the third passage in general

because you do not gain much by giving one more passage on the contrary this sliver

becomes very weak because fibres becomes two parallel with each other.

Few hooked fibres which are still left after second drawing passage, get removed by the

drafting processes on speed frame and ring spinning. It is not that we will be able to

remove all hooked ends by giving two draw frame passages to the material. However,

that at some more passages which are left like combing passage is there if not combing

speed frame is there ring frame is there. So, they are still drafting left on speed frame and

not only in spinning machine and on these two machine again there is a chance or there

is scope for the removal of hooked fibre


Over parallelization on the contrary leads to frequent sliver breaks, if I go for three

passages. When the slivers are lifted from the can and fed to the speed frame this also

you have to remember there is no point in going for three draft and passage because

slivers becomes two weak and frequent bricks would not be expected, when spinning is

performed directly from slave sliver using high speed apron drafting system. Let us,

since vertex spinning more than two passages become necessary to make the fibres

thoroughly homogenized straightened and parallel.

In some specific instances where we are spinning a yarn directly from sliver as an

example vortex spinning; the drafting system is an apron drafting system there and we

feed sliver there. Now in this case the draft is there is very high and the speed of drafting

is also very high. So, in a situation like this the input material that is the sliver has to be

very very uniform homogenized and the fibre has to be very very parallel because the

draft in the machine is very very high.

So, in this kind of situation we have to go for three draw frame passages, but knowing

that there is a chance of over parallelization and sliver may be weak. So, to compensate

that what we do? The sliver strength is maintained by compacting it by passing it to a

very narrow trumpet. So, you have to pass the material or the sliver through a narrow

trumpet there we try to compact it and we want to enhance the strength of the sliver that

is what we generally do.


This particular table is giving you an idea about the influence of draw frame passage on

certain property that is uniformity tenacity and strength of the sliver.

So, card sliver first passage drawn sliver and second passage drawn slivers are shown

here it is a mixing of J 34 cotton and S 6 cotton the ratio of three fifty. So, what we seen

here is that, as you go from card to first draft and passage the uniformity improves,

second passage also uniformity improves. Tenacity part if we see card sliver is stronger

or strength if we compare card sliver is stronger in comparison to first draw frame

passage sliver. And that is little stronger than the second passage drawn sliver. So, this is

the actual data which also supports the fact that with parallelization this sliver is

becoming weak strength goes down uniformity improves.


Now, we discuss another important concept called blending delay. On the draw frame

there is a scope of blending or mixing 6 to 8 slivers.


So, we can quantify the mixing capability of the machine by a term known as blending

delay blending delay time is defined as the production time difference between the first

and the last sliver can being doubled together on a draw frame that is what is the

definition of blending delay is.

The here if we look at the diagram see that the can one can two goes up to can n and all

these cans are then brought. So, these cans are being produced by one carding machine

let us say and they are being fed to the draw frame. So, I am pressing the cans as shown

here 1 up to n. Generally n could be 6 or 7 or 8 and they are being pressed here one after

the other and then they are all drawn and we in produce one sliver. So, material from n

cans have an opportunity to get mixed together.

So, the time difference in the production of the first can to the last, can ease and you

know gives us an idea about the mixing of the material.


Now to find out the blending delay time we have the following in the set of equations we

can derive easily very very simple, let that be n number of sliver cans which are getting

doubled m is the sliver weight in each can there is a can capacity b there a what is speed

of the carding machine.

They are all coming from the same carding machine at time t equal to 0 we start putting

the sliver cans alright. Time required to produce a full to sliver can is m by v where m is

the weight that is there and v is the delivery speed in terms of not meters per minute, it

should be actually kg per minute. Therefore, time required to feed one can is m by v

minute. The first full can is produced at time t which is t one is m by v minute in a sliver

can be produced at time t equal to n n into m by v minute

Therefore, blending delay time will be t n minus t 1 and that is equal to n into m by v

minus m by v and that becomes gives you if I m by v takes common it become m by v

into n minus 1. So, that is the time difference of filling or producing the first can and the

last can which are getting doubled together on the draw frame.


Let us say this sliver from 8 cans are being doubled together and draw frame the can

capacity is 30 kg, the card production rate is 54 kg per hour what would be the blending

delay time? So, time taken to produce first can is 54 by 60 into 30 that is 27 minute time

taken to produce 8 can is going to be 27 into 8 is 2016 minute.

Therefore, blending time is going to be the difference between these two that is 189

minutes; that means, whatever the machine is producing over one at 189 minutes this

material. Now are getting a chance to get mixed again on the draw frame.

So, that is end of today’s discussion.

Thank you.

Yarn Manufacture I : Principle of Carding and Drawing Prof. R. … · 2018-10-05 · Yarn...

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Transcript of Yarn Manufacture I : Principle of Carding and Drawing Prof. R. … · 2018-10-05 · Yarn...