Yarn Manufacture I : Principal of Carding & Drawing Prof. R. Chattopadhyay Department of Textile Technology Indian Institute of Technology, Delhi

Transcription

1 Yarn Manufacture I : Principal of Carding & Drawing Prof. R. Chattopadhyay Department of Textile Technology Indian Institute of Technology, Delhi Lecture 20 Blending on Drawframe (Refer Slide Time: 00:31) So, today s topic is Blending on Drawframe. The first question that comes to our mind is when to use a draw frame for blending. The blending means mixing up two different types of fibre. There is a difference between blending and mixing. In the case of mixing, we mix fibres up which are similar in nature like we mix cotton fibres, we can mix polyester fibres of different denier together; when we can mix, acrylic fibres between themselves of two different cross sections. So, when the fibres are of same nature and we mix them together, then the term which is used is called mixing of fibres. But, when we try to bring two fibres of different nature, then we use the term blending. Now, blending on draw frame, why should you blend on draw frame. There are two situations, when blending on draft frame is preferable. What are those situations? One is when each component of the blend required separate blow room processing lines and separate carding for opening, cleaning and sliver formation, then it is better that we do not take the fibres to blow room for blending. But, we will blend them on draw frame, because there is a possibility to bring several slivers together on draw frame.

2 And therefore, we can blend the slivers made from different fibres on draw frame. The reason is that fibres being totally different from each other, they need different processing line on blow room with different process parameters at the same. Similarly, they need different process parameters on carding machines. So, in these situations, we prefer to blend the two fibres in sliver form on draw frame. The other is when he this is required to maintain the blame proportion correctly, and mixing homogeneity is not really so important, but maintaining blend proportion is more important in that situation also, we prepare draw frame blending. Because, if you bring the slivers together, we can make slivers of a specific count the little variation in count. And then if we bring those slivers together, then the proportion of the two components or three components whichever we want, they can be maintained with within very narrow tolerance. So, proportion is more important than the real mixing homogeneity between the fibres. In these two situations, draw frame blending is practiced, and it is very much in use in the industry. Let us go to the next slide. (Refer Slide Time: 04:14) Draw frame is normally used for binary blend. The required blend proportion is obtained by adjusting two parameters. There number of slivers of each component that we can choose the number of slivers of component, suppose a and b suppose a and b are being mixed together or blend together. The other parameter, which we can adjust is the linear

3 density or count of each sliver. So, by manipulating count of sliver or their number, we adjust the blend ratio. Generally two passages of drawing is required for satisfactory mixing. This point is very important, because if I give only one draw frame passage, we get narrow strips of the two components within a sliver. So, if I choose eight slivers and suppose 4 of them are of component a, and another four are up component b, and then if we blend them together a slingers sliver that we produce, it will contain four strips four thin strips of component a, and another four thin strips of component b. And these strips will be very much visible. If we use two different colors for the two components, otherwise if the color is same, then we will not be able to really make the difference. But, if I choose one of them to be black the other one is white, then we can easily identify the black strips coming from one component, and white strips coming from another component. So, the after the first passage, we will have eight strips; four of them from one component, another four of them another component. So, this is not really giving me very nice mixing of two fibres, what we do? We go for one more stage that is we take these blended sliver and again process them on another draw frames. So that each of those trees again, there thin down and other 8 times or seve7 times depending upon the draft and the number of doubling that we use. So, now if we again use 8 doubling and 8 drafts, then with the final sliver we will get 64 total strips coming from two different components. And therefore, mixing will be better. And hence minimum two passages are required. If the density of the components also differs too much, then the linear density of the sliver consisting of low density fibre needs to be made little finer. This is also is important. See the bulk of the material depends upon the linear density, and the dense actual density of the fibre. So, the fibre is made from low density fibre, then the sliver bulk is going to be more. If the count of two components are same, suppose one is cotton the density is 1.52, then other fibre is made from polyester density is 1.34 or 38. So, if I blend them together and both the slivers are of same count, then the sliver made from polyester we will look very bulky, because density for the fibre is low. Similarly if we choose the other component to be acrylic, it will be still more bulkier. So, there could be difference in the bulk depending upon the density of the components that we choose

4 say in such situation, what we do? Ee adjust the linear density of the sliver made from low density fibre, so that when they are processed on the machines, there is not much difference in their actual bulk or volume of the two components. This is done to ensure that the bulky and non-bulky slivers are grip properly by the drafting roller pairs. Try to imagine there suppose there is a fibre, there is a sliver made from very bulky material. And the neighboring sliver is made from not so bulk material. When the both the slivers are grip between the bottom and top rollers the part, where the bulky material is there and the part where the not so bulky material is there. The bulky material will be gripped formally, because his volume is more, so thickness is more. And the neighboring material made from the other high density fibre, we will not be grip properly, because it thickness is going to be less. So, thickness differences will make the differences in terms of gripping power of the two come of two rollers on the sliver. And therefore, we have to adjust the hank of the slivers. The bulky material should be made little less, in terms of linear density or they should be made little finer. (Refer Slide Time: 10:38) Now, we come to this part that is sliver disposition in the creel, how do I place this sliver on the creel. Now, here let us say as an example polyester and cotton are blended together. So, the polyester is presented by the blue circles, and cotton represented by the white circles. And we are taking six slivers. And we have to blend them into proportion

5 of that means, we will have 4 polyester sliver and 2 cotton slivers. And both of them will be of same hank or same linear density. Now, we have four of one component, and two of another component. How do we arrange the slivers on the creel? So that during drafting we get a proper mixing or this person of the fibres coming from two different components in the final sliver. Our objective is well dispersed fibres within the cross section of the final sliver. Now, here is a an arrangement shown that is we start with a polyester followed by cotton, then we put 2 polyester and another cotton and the 6 position is also occupying by polyester. So, therefore this is how we can place 4 polyester slivers and 2 cotton slivers. So, there is a balancing act that is cotton placed between two polyester slivers. And if we now draft this material, we will have the strips made from each of those components. And these strips will be well placed, well dispersed within the cross section of the final sliver. But, in this type of arrangement sometimes it has been seen that there is a possibility of what is known as cockling of cotton sliver that is if sometimes the wave tension draft is reduced to avoid wave stretching, the arrangement shown in A can lead to cockling of the cotton sliver. So, what does it mean cockling, cockling basically means that we will find the cotton come part as the in the wave we will see them. They are forming wavy pattern that if we look at the wave that comes out from the draw frame, and you will see that the wave made from the polyester slivers are looks very nice, very uniform was the cotton part is giving you a wave we look, this is what is known as cockling. This is not good from the point of view of dispersion of fibres within the cross section. So, this can be rectified by rearrangement of the cotton sliver by shifting cotton sliver from position 2 to position 1, and position 5 to position 6. Now, we will show them that this is going to be the so we will shift cotton bring it towards the edge. And another cotton also we bringing towards the edge that means, we place the cotton in the first and the last location, and all the polyesters are placed in the middle. So, this is to avoid the cockling phenomena. And avail there has to be some compromise in this case compromise on the dispersion of the strips within the cross section of the final sliver, but we have to give priority to avoid the cockling of cotton sliver. So, this is what is done. So, cockling is eliminated as cotton sliver takes longer path to reach the trumpet. What happens that polyester wave, as soon as it comes out from the nip of the draw frame or

6 the top nip of the front pair of rollers? They try to retract the polyester fibres by nature is much more retractable than cotton. And therefore, when they try to retract, because the neighboring material is cotton, they will try to also pull the cotton along with them. And therefore what happens, cotton being placed in the previous case in between polyester, the retraction phenomena of polyester and cottons are different. And therefore, the cotton actually shows little waviness and we call it cockling. So, this can be avoided by this rearrangement of the slivers in the creel. (Refer Slide Time: 16:25) Disposition for a and blend; in the blend the disposition is very simple, you see that we have kept the polyester and cotton slivers one after the other. So, first is polyester followed by cotton, then again polyester, then again cotton polyester, and then cotton. So, this is wave if we press the material on the sliver, then there is a balance. And the final sliver is going to be quite well blended by the two components. So, this is how it can be done for 50 50, because fortunately we have same number of sliver of polyester or cotton. If I go for a blend like where we have 33 percent polyester that means, 2 polyester sliver and we have 4 cotton slivers; in that case, this could be the arrangement, we press both the polyester at the middle and in both sides we can place cotton. In this case, this is one way of balancing the disposition of the slivers, otherwise what one can think that if I place the polyester in between in between cotton, then in one side between 2 cotton I can place 1 polyester.

7 And between the other side 2 cotton also we can place polyester, so that is another way also we can do, so that there are 4 cotton slivers between 2 cotton slivers I can place them like this, I can putting it here, I can putting this in between this 2, this could be another arrangement. So, as to makes ensure that the dispersion of the strips within the final, within the cross section of the final sliver is there. (Refer Slide Time: 18:59) Now, this particular slide mean what is written, change in blend proportion with addition of sliver of any one component, in the case of 6 sliver blending. Now, when I am blending 6 slivers, and assume that all the slivers are of same linear density, then means each sliver is representing 16.6 percent mass right now ok, because there are 6 slivers. So, all six slivers is 100 percent. So, one sliver means 100 by 6, which will be So, if I take 6 slivers and one of them is a different component, then I have a mixture which is shown at the bottom of this diagram 16.6 is to 83.4 which is close to 17 is to 83. So, I will get a ratio 17 is to 83, if I choose only 1 sliver of a particular component. And rest five slivers coming from another component. If I go for 2, high get a ratio 33 is to 70 as shown. If I choose 3 of 1 component rest form coming from other component, then 33 each so I get a 50 is to 50, ratio. If I go for 4, I get 66.6 is to 33.3 that is what is very well known blend ratio. And if I choose 5 of 1 component and one of another component, I get that is 83 is to 17. So, by adding one increasing the number of slivers coming from one component, this

8 is how, these are the various blends that we can produce. So, and blends are very common and very popular, it is because we are trying to double 6 slivers and out of them 6 slivers. If one of them is coming from, one of them is representing 16.6 percent of the total mass. So, this is the steps in which the ratio is going to change, as I increase the number of slivers from 1 to 2, 2 to 3, 3 to 4, 4 to 5, and up to 6, so steps are 16.6 actually. So, all these steps are going up by 16.6 percent. (Refer Slide Time: 22:06) And when we go for eight sliver blending, and we have made a graph in a similar way, then each sliver in this case is representing 12.5 percent mass. So, now the steps earlier was 16.6 or eight sliver blending, it will be And the different ratios that we can generate is shown 12.5 is to , 37.5 is to 62.5 that is such ratio, also we can get it here as we were getting previously also. We can again get 63 37, 75 25, These are the various ratio combination that will get, when you use eight slivers blending provided the linear density of the component is same, then only these are the various blend ratio that we can generate. If we want to have any other ratio, then either we have to see suppose if I go for seven sliver blending total, then each sliver will be representing a mass of 100 by 7, which will be fourteen point something. So, this is for eight sliver blending, this For seven sliver blending, it will be And for previous one for 6 sliver blending is sliver

9 representing 16.6 percent of the mass. So, finite changes are possible, if I increase the number of slivers in the blend. So, within this we can vary our blend easily, and make different combinations of the 2 components, what one can also think of you know there are there are techniques by which I can generate some other blend ratio by manipulating slide this slivers, not only in the first passage of the draw frame. But on the second passage also we have we have some scope to change the blend ratio. There also we can if we go for 6 sliver blending six sliver doubling or 8 sliver doubling in the next passage, and I can choose some slivers, which already have been blended at the breaker stage. And I can choose some slivers, which have not been blended at all. And then again I can bring them together and blend them on the second passage of draw frame, and by that way also will be able to generate some more blend ratios. So, these are the different you know techniques by which we can adjust the blend ratio. The other one, which I have not stated is that you can also manipulate the linear density of the sliver, and that also gives you scope to adjust or to change the blend ratio. (Refer Slide Time: 25:54) Determination of blend proportion; both slivers have same linear density; this is the assumption to start with, because that will make the case simple. Number of slivers of component A that was let us say this is N A. Number of slivers of component B is N B. And there to be blended together, so it is a binary blend. So, blend proportion assuming

10 all slivers have same linear density, proportion of P A is going to be N A by N in to 100, where N is N A plus N B. So, N is the sum of total number of slivers of component A and component B sum together of these two components. Generally N is 6 or it could be 7 or it could be 8, we do not generally go beyond 8, because the machine may not be able to draft. So, many slivers, because the drafting force requirement is going to be very high. And therefore, we do not go the machine is capable to handle at the most eight slivers. So, this is how we will be able to find out the blend ratio of one component, if I know the ratio of one component, the other ratio can be easily found out. If I know P A in terms of percentage, P B will be 100 minus P A always, so that way we will be able to find out. What is you know percentage of the components in the blend by from the numbers of the slivers we take. (Refer Slide Time: 27:45) Now, if we take slivers of different linear densities, sometimes I many a time not really sometimes we take slivers of two different linear densities especially, when one component is made from fibre, which is too bulky and nature. And the other component is made from a fibre, which is not bulky at all like cotton is not bulky at all, whereas acrylic is very very bulky material, polyester also could be very bulky. Now, in those cases the linear density of the components may not be same. So, let us say component A linear density is H A, and number of sliver chosen is N A. Component B linear density is H B and number of sliver is chosen is N B. Therefore,

11 total number of slivers is N A plus N B, which is equal to N. So, blend proportion of A, we can now easily find out P A is going to be N A H A divided by N A H A plus N B H B into 100. This will give you the proportion of the component A in the final blend. Similarly, P B is going to be N B H B by N A H A plus N B H B into we are doing because we want to express it in percentage. So, this way we can find out P A and P B separately or we can find out one of them first the rest, the other one can be found out subtracting the percentage of component A or B from 100. So, if I want to find out P A, then P B known, so P is going to be 100 minus P B or if the P A is known to us, we will going to find it out P B will be 100 minus P A. So, this is how the calculation can be done to find out the blend proportion. So, this is how we blend the fibres on draw frame. (Refer Slide Time: 30:07) Now, we will discuss processing problems. So, you know about the machine, we have understood the process; we have discussed all these in the previous lectures. Now, you have fair understanding about the draw frame and process also. Now, we have to understand, how to tackle certain problem that we may face, and these are known as processing problems.

12 (Refer Slide Time: 31:01) So, there are many problems that we face in an industrial practice. And we need to know, what are the possible reasons if we know the reason, then probably we will be able to find out, what action is required to overcome those problems. So, let us say the first problem is poor running characteristics of the material. What does it mean poor running characteristics that mean, the machine is topping too frequently due to multiple resist could be there. And therefore, frequent stoppages mean loss of production, and lot of irritation for the operator also. He is working on the machine, he will be overwhelmed with the extra work that he has to do to set the machine right, which is very frustrating experience for the operator as well. So, poor running characteristics means loss of productivity as well as west generation as well as operation difficulty for the operators ok. So, what could be the reasons, reasons can be classified into three groups: fibre, process, and machine related problems could be there. There is a list of problems or reasons, which are stated here running (Refer Time: 32: 38) is poor, it could be because of honey due in cotton. Inadequate spin finish on synthetic fibres or poor quality or spin finish, too fine a fibre, too low or too high crimp, high bulk, low moisture content; these are all fibre related issues about problems. If we go to process, it could be in appropriate settings. Settings between the rollers are not confirming the length of the fibres or the bulk of the material that I am going to

13 process. High speed, the speed could be too high not suitable for the fibres that I am processing. Too much or too less humidity both are bad. For every process, there is a optimum humidity on the draw frame also. If I processing cotton or viscose, there is certain humidity that we need some temperature that we need if I processing synthetic fibres like polyesters 100 percent or acrylic or nylon or they are blend, then there is a different humidity and temperature that we need. So, we have to be very careful about the humidity part also. So, humidity too good, too low, too high both are bad. Too low means, there could be static generation and which may lead to lapping, and therefore stoppage. Too high humidity means fibres keeps on absorbing a lot of moisture, and they try to stick on the machine parts. Too low humidity means, there will no question between fibres a lot of flop we will generated, because question between the fibres is low. Especially, with fibres which are hygroscopic in nature like cotton or viscose, so both are bad. And the other thing is poor condition of the roller, what does mean surface cracks, groove filled with deposits, dust spin finish. So, grooves are no more active, because they are all filled up. And we have not clean the machine or there could be surface cracks on the top rollers. All these may lead to poor running a statistics. And therefore, we have to first find out, which one out of these is really responsible for poor running characteristics of the machine. And once we have identified that it is because of fibre or because of the process or because of the humidity or because of some problem with the machines, then once that is identified then solutions can be immediately given. The next one is lapping ok. So, lapping I have already discussed about lapping, lapping is wrapping of the drafted fleece around the rollers. Especially, bottom rollers or top rollers and that this is this wrapping continuously is known as lapping. See this machine speed is very very high and therefore, even if there is a lapping for few seconds there would be a wrap of fibres around the mesh, around the rollers and this is going to make the roller diameter so big that sometimes the rollers be simply bend also. So, therefore there are lapping detectors which will detect the lapping and immediately stop the machine. Anyway the lapping could be because of static generation in the case of synthetic fibres due to inadequate spin finish, low humidity, smear or spin finish. The spin finish is

14 getting removed from the surface of the fibre; that means, it is not adhering well with the surface of the fibres, and then they can smear it out and they will be deposited on the parts of the machine. And it will be a sticky material, because there will be temperature, the rollers will be heated as we run the machine and this tech sticky material will now catch the fibres and therefore, the fibres will start wrapping. Long and fine fibres because of their low bending rigidity, low crimp in synthetic fibres reduce readability and that can also lead to lapping. Splitting tendency of the wave between low cohesion and when the cohesion become less for hygroscopic fibres it is because of low relative humidity. And for hydrophobic fibres the cohesion is low if the spin finish is not correct, then the cohesion could be low or the fibres may repel each other if there is a generation of static electricity. Electricity static electricity will be same similar nature; so fibres will repel, the slivers also may ripple from each other, this possibilities are there with synthetic fibres. Poorly maintained rollers as already discussed in the previous case, cards or cracks on the roller surface, sticky material deposit on the rollers anything related to the roller also may lead to lapping. The other processing problem that we face is trumpet blockage and thereby the machine stops. The trumpet is blocking the material, trumpet is getting choked with the fibres; reasons fibres related spin finished position due to smear excessive moisture, static charge generation, too much variation in sliver mass. So, too much variability in sliver mean mass means, the thick part of the strivers will not be able to pass through the bore of the trumpet. So, trumpet bore should be able to accommodate a thick region, a thin region can easily pass through, but from the average if the mass goes up beyond 25 percent or 30 percent,then there is going to be a problem, because the material may not be able to pass through the trumpet, trumpet will get choked. And therefore, there will be breakage there will be discontinuity of the operations. Splitting from sliver accumulation of fibrous dust, if the dust is deposited within the trumpet, then a time may come when it will get completely choked with dust and fibres. The other one is too narrow trumpet bore, the trumpet bore selection has gone wrong; suppose by mistake we have not change the trumpet board, we have change the sliver linear density. Earlier we are processing some other from fibre viscose rayon only,

15 suddenly meet to some region have decided to process suppose a blend; viscose and let us say polyester. And polyester percentage is more and therefore, now the sliver has become very bulky and there may be some change in sliver linear density. Now, any such situations may lead to trumpet being choked with fibres, because bulky material may not be able to pass through the trumpet bore; unless we choose a trumpet bore of appropriate size. So, there are guidelines given by the machine manufacturers that if this is the count of sliver, then this are the bore that you have to choose all right. The other problem is drafting problem, this is very very great problem drafting problem. (Refer Slide Time: 41:56) Drafting problem basically mean that we may find, the sliver to be highly non uniform in nature there are lot of thick and thin regions coming out in the sliver. Earlier a sliver wave was visible in the old generation draw frames you will could go and see, in today s generation draw frames are running at such a high speed that is very difficult to see the structure of the wave. Anyway the drafting problem could be again due to inadequate spin finish leading to high inter-fibre friction, purpose of the spin finish is to reduce friction because, there is a lubricating agent in this spin finish especially we synthetic fibres. There could be high crimp, very high crimp and may lead to what springs means that the fibre is going to behave like a spring within the drafting zone. And the spring is stretched energy is stored and if the spring one end of the spring is released, the spring will retract

16 first this has been discussed earlier that crimpy fibre behave just like a spring within the drafting zone. So, if I take a spring and stretch it, and then I release one end, the other end will other end being gripped the spring will retract very fast this is going to happen with the fibres if they are too crimp in nature. We expect that the synthetic fibre we will lose their crimp by the time, they come to the draw frame stage, because the crimp that we give to the fibre is semi permanent in nature we need crimp for carding operations. To separate the fibres from each other crimp helps, to creative wave which will be little strong also we need crimp, because crimp of the fibres help to interlock the fibres and thereby it gives some amount of strength to the wave that is carded wave and therefore, the requirement of crimp is there especially for carding machine. Once the carding is over, we have produced the sliver there is no need of any crimp now. Now, crimp is a nuisance; so crimp till carding stage is important for us, crimp beyond carding is a nuisance for us is better to not have any crimp therefore, synthetic fibre manufacturers produces crimp which is known as semi permanent in nature; that means, by the time it has gone through the carding machines and fibres have been opened by the blow room machines, most of the crimps should be removed. So, there fibres can slide pass each other easily without giving drafting problem. For cotton, there is a problem because we all know that every cotton fibre or any variety of cotton fibres we will have lot of short fibres with them. Cotton is not like synthetic fibres where all the fibres all of same length, it contains lot of short fibres and by the definition of short fibre is generally any fibre less than 12 millimeter in length is considered to be short fibres in our case; from the spinning point of view and from the yarn point of view all. So, why do you say them short fibres, because these fibres actually do not contribute towards the strength of the fibre, strength of the yarn. So, from the point of view of strength of the yarn fibres length less than 12 millimeter, are not going to have any effect they only contribute towards mass. And these fibres in the drafting zone creates problem in terms of problem means that they create what is known as drafting wave, since these fibres becomes floating fibres that drafting zone and there movement becomes highly unpredictable in nature.

17 And hence they create what is known as drafting wave or mass variation in the fine and slivers. So, cotton the short fibres presents mainly to drafting problem, process narrow or wide setting in the break draft zone. See in the break draft zone the drafting force is very high, because the mass of material is very high; by a time it comes to the front zone the mass has reduced, but in the back zone the mass is equivalent to almost 6 slivers or 8 slivers. And here if the settings are narrow, force is going to be very high; if the setting is too wide, then there is a chance of generation of drafting wave even in the back zone itself though the wave that generates it also depends upon the extent of draft, draft is less in the back zone, but setting between the rollers is wider in the back zone. And therefore, there is a possibility that if I keep rewired setting, there is a risk of generation of drafting wave; if I keep a very narrow setting, there is a risk of pulling the fibres long fibres which may be simultaneously nipped my in between the nips of the back and the middle roller. So, wide setting is bad, narrow setting is also bad or the force may raise very high in the case of narrow setting, fibres like will be plucked from the nip of the back pair of rollers. All sort of things may happen, high bulk is also detrimental here and too much of humidity, we will also increase the drafting force in the back zone and also may cause your material to stick. So, all these process related problems could be there, the other one is damage to the roller surface or eccentric roller. We have discussed about the eccentric roller and it is influence. Roller surface being damaged also can lead to drafting related problems and not only that it fibres will stick to it, it can also may not be able to pull the fibres, if there is part of the sub part of the surface is damaged due to some reasons. And you know the damaged part is coming in contact with the bottom roller, the pressure is not getting properly transmitted to the fibres and therefore, fibres may not be able to be pulled properly by the damaged roller surface. The other one is it will thermal damage. Thermal damage is possible only with synthetic fibres. See cotton has no melting point, viscose rayon has no melting point. Therefore, cotton and viscose rayon this is these fibres are not going to be affected by heat. We have already discussed that the draw frames when they run lot of heat is generated, because there is a continuous abrasion between the fibres and the roller due to these abrasion this friction is there and frictional heat gets generated.

18 So, continuous abrasion means lot of generation of heat and this heat is going to increase the temperature of the drafting rollers. So, anything that will increase friction between the fibres, and that is possible if the spin finish, is not correct; then the friction between the fibres going to be very high synthetic fibres. And there could be very high friction between the fibre and the machine part. So, we use titanium dioxide on polyester fibres to control their brightness, this titanium dioxide this is not good for the rollers. Rollers get damaged as abrasion damage because of presence of too much of tiot on the fibres. So, for one purpose we need titanium dioxide, but at the same time we also should know that too much of this titanium dioxide may lead to abrasive damage of the top rollers, where we have synthetic rubber cover. And if it is show thermal heat will be generated, when the friction is very very intense because of very high coefficient of friction between fibres or when the speeds our predation is very high. then also the generation of heat is going to be very high. The other thing is narrow trumpet bore or quail a tube or dirty trumpet. So, there is a tremendous abrasion between the fibres and the inner wall of the trumpet, because as a big narrow passage and we are made a delivered narrow, because we want to compress the sliver; so that we can increase the strength of the sliver. We want to transform the sliver from a sheet to a round shape. And therefore, we need a trumpet which is conical geometrically and there is a narrow bore so that lot of compressive pressure develops. So, there is a lot of abrasion they are also. And hence if the bore is not of right diameter, then intensity of the abrasions going to be very high; and therefore, lot of heat we generated there also. So, generation of continuous heat because of friction, you will raise the temperature of these parts and they can damage the fibres especially, fibres which are susceptible to heat. So, heating up top rollers may reach 80 degree centigrade affecting the viscosity of the spin finish, where learning it may not affect the fibre as contact time is too short, but when the machine stops it may cause damage to the fibres. Even if the damage is restricted to 1 or 2 centimeter, it will affect 5 to 50 meter of yarn and the difference become visible only after dying. So, these statements are very important that is one is the temperature could be as high as 80 degree centigrade. And these components which are used in spin finish; it may not be

19 able to be such a temperature. So, viscosity of the spin finish is going to change and it means the frictional behavior of the fibre is going to change. The other thing is there the fibres are coming into contact with the machine parts is suppose 80 degree centigrade. So, a normal circumstance it may not matter, because the material is running at a very high speed, typically the speed of a draw frame while running on synthetic fibres could be let us say meters per minute ; that means, per minute it is going almost half a kilometer. See if the machine stopped you to any reason, you to lapping, you to sliver break whatever could be then it will be in contact with the heated part for a certain period of time. And the region of the sliver which is in contact with the machine part which is already at 80 degree centigrade that part of the sliver is going to get damaged, there is going to be some kind of internal damage to the fibres, because I am heating it, it is receiving heat from the part of the machines. So, even though it is restricted to 1 to 2 centimeter, the length of the yarn is going to be how much; you have to calculate the draft that we give to the sliver from sliver to yarn. So, typical draft that we give from sliver to yarn could be to the order of anything. So, if I multiplied these two, 2 centimeter by 300 we get 600 centimeters, and we converted into meter 600 centimeter divided by 100 that gives me 6; it could be 6 meter or it could be more, if the draft is more you do not know. So, thermal damage is possible with synthetic fibre. These have two you have to keep in mind. And therefore, what we do to avoid this thermal damage, to avoid the generation of static electricity we reduce the speed, when we process thermoplastic fibres on draw frame; you will see that the machine speed is brought down we can run cotton or viscose at high speed or not synthetic fibres all right. This is the process configuration.

20 (Refer Slide Time: 57:33) So, what we see here that for coarse rotor spun yarn, course rotor spun yarn what we give only one draft frame passage. So, you feed card sliver and if this is drainage on sliver, we do not go beyond one what is the reason; the rotor spun yarn is course that is we are producing six count eights count less than ten then these on these yarn there is not too much of demand up quality. So, whatever quality requirement is there, we can get that quality by giving one passage by giving one passage, whatever parallelization we achieve that parallelization we give me a yarn by the time this fibres go into the rotor room; there lot of change in the configuration of the fibre. You must know when if you are when you learn about the rotor spinning system, you will find even though fibres in the feed sliver is very very is highly parallel or oriented free from hooks that by the time I open them out; on rotor spinning machine and feed the material and it goes and get deposited within they rotated room, there are lot of change in the configuration of the fibres. We again create foot fibres and therefore, there is not much need to improve the parallelization or orientation of the fibres, in the feed slivers that we feed to the rotor spinning machines. And hence we give one draw frame passage, but it has been also seen that if we want to produce little finer counts not , but if you want to produce 16 18, then it is better to give two draft frame passages, because that whatever you know improvement we get in the fibres in the drawn sliver that helps to bring down the n breakage rate that is why for

21 coarse rotate spun yarn, one passage is sufficient; if I go for little finite rotor spun yarns, then you should go for two passages all right. Otherwise if I want to go for carded yarn the next, we give two passages first passage and second passage; two passages will reduce both type of hooks as we have discussed earlier leading hooks, trailing hooks and it will give you sufficient parallelization of fibres and orientation of fibres. However, suppose you go for a for vortex yarn production then we give three draw frame passages. We are not satisfied with two. We go for one more. Why, we have to improve the uniformity of the sliver, which also we can improve by having let us auto leveler; but we also improves the parallelization of the sliver, the orientation of fibres in the sliver, because here the sliver is directly fed to the vortex ceiling machine, there is no roving frame to further improve the orientation of the fibres. So, we for feeding sliver to a drafting unit like vortex yarn spinning, we need fibres to be highly oriented free from hooks in the feed sliver itself and this is only possible if we go for one more passage of draw frame. And therefore, in this situation we can go for three passages. So, depending upon the type of yarn we are to produce and type of technology we are going to use, we have to choose the number of passages that is all. And thank you.