Indian Journal of Fibre & Textile ResearchVol. 20, March 1995, pp. 17-22

Drafting of jute: Part II-Towards making regular yarns

U Datta, S C Bhadra & S Palit

Indian Jute Industries' Research Association, 17 Taratola Road, Calcutta 700088, India

Received 17 December 1993; revised received 8 August 1994; accepted 19 October 1994

Contribution of different components to irregularity in sliver and yarn has been examined criti-cally. It has been observed that the contribution of drawing machine to the irregularity of finisherdrawing sliver and yarn is maximum. The effect of carding machines on irregularity may be reducedto minimum by repeating at least one drawing operation as a leveller at a suitable stage. The use ofleveller reduces the long-term variation of yam significantly; a minimum value of 3% could beachieved for a yam of 278 tex. However, the use of leveller has limited effect on short-term varia-tion, which is expected to be reduced around 13% through modification of finisher drawing machineor incorporation of other drafting system at this stage.

Keywords: Drafting, Faller bar waves, Jute yam, Leveller, Sliver irregularity, Yam irregularity

1 IntroductionAfter carding, jute slivers are subjected to three

stages of drawing operation involving a totaldoubling of 12 and draft ranging between 204and 278. The machine parameters of the threestages of drawing have been discussed elsewhere 1•

During carding and drawing operations, waves(thick places) of varying length and amplitude aregenerated due to the action of rollers of the cardand faller bars of drawing machines as well asdue to irregular feeding at breaker card. Thewaves may be categorized as long, medium andshort depending on the average length of the fi-bres", In carding, the waves are normally long andmedium by character coupled with high ampli-tude. During drawing operations the waves gener-ated due to faller bar action are short in naturewith low amplitude. Another irregularity is ob-served at drawing and spinning stages due to ran-dom fibre arrangemenr'. The faller waves are gen-erated due to faults of open gill system of draft-ing. However, the faller waves of first and seconddrawing stages are levelled, to some extent,through doubling at a constant phase differenceon a doubling plate". The scope of levelling thefaller bar waves is not there at finisher drawingstage, where doubling preceeds drafting. Hence,irregularity of a drawing sliver may be assigneddue to (i) long and medium waves (carding}, (ii)faller bar waves (machine faults), and (iii) randomfibre arrangement (fibre properties). In short, sliv-er irregularity comprises of irregularities due tocarding, drawing and fibre quality.

All these waves of different characters generat-ed from feeding, roller, faller bar actions and fibredistribution are lengthened by draft and ampli-tudes are reduced by doubling in the subsequentprocesses. Ultimately, in yarn, all these waves ex-ist superimposed one over the other along withthe irregularity imposed during spinning. In otherwords, yarn is formed with a continuous strand offibres having short waves superimposed on longand medium waves generated during carding,drawing, spinning as well as due to random dis-tribution of fibres.

In the present study, the contribution of diffe-rent components to irregularity has been estimat-ed using mathematical models for slivers of diffe-rent stages of drawing. An attempt has also beenmade to reduce the effect of the waves to pro-duce regular sliver and yam therefrom. For thepurpose, a number of experiments were carriedout in UIRA pilot plant as well as in membermills.

2 Mathematical ModelsThe use of drawing process with same draft

and doubling is observed in flax and cotton pro-cessing to level the slivers after carding". Thisprocess may be applicable in jute drawing alsowith some modification in the process of doublingof first and second drawing stages. It is due to thefact that the doubling operation of these twostages is carried out on a doubling plate afterdrafting operation and the number of doubling isfixed at 2 and 3 respectively for first and second

18 INDIAN 1. FIBRE TEXT. RES .. MARCH 1995

drawing stages. With a view to using same draftand doubling, first drawing may have draft anddoubling 4, second drawing 6 and finisher draw-ing 9, within the range of draft of the machines.To use a doubling of 4 at first drawing, it is ne-cessary to put 2 slivers together in each of thetwo feed slots of the machine and double the twodrafted slivers on the doubling plate. Similarly, insecond drawing, to obtain a doubling of 6, twoslivers are to be fed together to get three draftedslivers, which may be doubled as usual. However,finisher drawing requires no such change for adoubling of 9 instead of normal 2 since it has nodoubling plate for the purpose.

The Eqs (4), (5) and (6), developed earlier! toevaluate thickness (CV%) of first, second and fini-sher drawing slivers respectively for normal draftand doubling process, may be modified accor-dingly as above and are reduced to the followingequations for repeating the drawing operationswith same draft and doubling:

cvi ." cvi i-: /4 + 26.55 (for first drawing)... (1)

CV~,i = CV~,i-: /6 + 13.95 (for second drawing)... (2)

CV;, i= CV~,i-r /9 + 95.40 (for finisher drawing)... (3)

where i is the ith repeat operation of the drawingstage.

The equations reveal that if a sliver with certainirregularity (within the range of that stage) is pro-cessed with same draft and doubling at that stagerepeatedly, the output irregularity approaches aminimum value. For example, applying observedirregularity of first drawing sliver as input (CV10)

in Eq. (1), the irregularity of sliver after first re-peat (CV1,1) can be estimated theoretically. Sim-ilarly, for second and third repeat and so on. Forsecond and finisher drawing sliver irregularities,Eqs (2) and (3) may be applied similarly puttingthe observed irregularities as input (CV2 0 andCV3,o respectively) for first repeat. Again, puttingCV1•O' CV2,o and CV3,o equal to zero in Eqs (1),(2) and (3), the output irregularities of fir" sec-ond and finisher drawing slivers become 26.55= 5.15, )13.93 = 3.73 and )95.40 = 9.76 respect-ively, which may be considered as the minimumirregularities of the slivers theoretically when in-put slivers are totally even. From the above, it isclear that the use of leveller (drawing operationwith same draft and doubling) at a suitable draw-ing stage may improve sliver irregularity, whichmay produce regular yam. The minimum irregu-

larities so obtained after repeat operations at eachstage may be regarded ~ irregularity free fromlong and medium waves generated during cardingoperations.

The minimum irregularity so obtained com-prises of two components, viz. irregularity im-posed by processing machine and irregularity dueto random distribution of fibres in silver. Baner-jee6 observed that the contribution of random ar-rangement of fibres may be estimated by1301rn ... (4)where n is the number of fibres in the cross-section.

The irregularity due to machine could be esti-mated by subtracting the value of irregularity dueto fibre arrangement from the minimum irregular-ity after levelling the sliver. Mathematically, thetotal relative variance of sliver of any stage ofdrawing and yam may be expressed as a sum ofcomponent relative variances as follows:(CV T )2 =(CYW )2 + (CYM)2 + (CYF )2 ... (5)where CY T = Total irregularity

CYw= Irregularity due to long and mediumwaves

CYM = Irregularity due to machineCY F= Irregularity due to random arrange-

ment of fibres .

3 Materials and MethodsFor the experiments, good quality of jute (TD3

variety) was used and 4% jute batching oil wasapplied on it (by weight) in the form of oil-in-water emulsion. The softened material was thencarded through JF2 breaker card and JF3(L) fini-sher card. Finisher card sliver weight was main-tained around 80 ktex at 30% moisture regain.The carded sliver was processed through Lagan'sOpen Screw Gill first, second and finisher draw-ing machines with normal draft and doubling. 278tex yam was spun through Mackie's 4.25 in aprondraft spinning frame with 16.8 twistldm and a fly-er speed of 4500 rpm.

Forty metres of first drawing sliver was collect-ed and its irregularity was measured. After testing,it was divided into 4 equal segments of 10 m eachwithout any strain and deformation. The segmentswere processed through first drawing again withdraft and doubling of 4. Sliver (40m) so obtainedwas tested for irregularity and divided again into4 pieces of 10 m each and processed with samedraft and doubling. The process was repeated andirregularity was tested again and again till last twovalues of irregularity were almost same. Similarly,60 m of sliver was collected from second drawing

~DATI A et al.: DRAFl1NO OF JUTE

stage and divided into 6 pieces of 10 m each aftermeasuring' irregularity. The slivers were processedrepeatedly with 6 draft and doubling and testedfor irregularity till minimum value was attained.At finisher drawing stage, 405 m of sliver wascollected and its irregularity was tested. It was di-vided into 9 segments of 45 m each and pro-cessed through the stage with draft and doublingof 9 repeatedly and irregularity was measuredafter each repeat following the above method., Five experiments were carried out to simulatethe above experiments as per plan in Table 1. Inthe plan, experiment no. 1 is the normal sequ-ence, experiment nos 2, 3 and 4 involve one le-veller each at first, second and finisher drawingstages respectively. Experiment no. 5 involves oneleveller at each stage of drawing. Yams were spunand tested for linear density, irregularity, long-term variation and tenacity.

Semi-bulk trials were conducted in two membermills using second drawing as a leveller to con-firm the findings of the above iexpenments. In

Table 1-Plan of experiments

"Experiment No.Process

1 2 3 4 5(Normalsequence)

First drawing 4/2 4/2 4/2 4/2 4/2Draft/Doubling

First drawingleveller 4/4 4/4Draft/Doubling

Second drawing 6/3 6/3 6/3 6/3 6/3Draft/Doubling

Second drawing 6/6 6/6levellerDraft/Doubling

Finisher drawing 9/2 9/2 9/2 9/2 9/2Draft/Doubling

Finisher drawing 9/9 9/9levellerDraft/Doubling

No. of passages 3 4 4 4 6of drawing

216 864 1296 1944 4665Total draft! - - -- -- --

doubling 12 48 72 108 2592

Spinning draft 12 12 12 12 12

"Experiment nos 2, 3 and 4 involve one leveller each at first,second and finisher drawing stages respectively and experi-ment no. 5 involves one leveller at each stage of drawing.

19

these trials, yams of 278-600 tex were spun andthe properties mentioned above were tested.

The irregularity of first and second drawingslivers was determined on the basis of 300 thick-ness readings using ST1 and STI (Sliver Irregular-ity Testers) developed by UIRA and thicknessCV% was calculated. Irregularity of finisher draw-ing sliver and yam was measured through UsterEvenness Tester at a speed of 8 and 25 mJminrespectively for 5 min. U% was converted toCV/o by using the equation CV/o = 1.25 U%.

The linear density (tex) of the yams was mea-sured on the basis of weights of 25 hanks of67.5 m each. The hanks were collected from ran-domly selected 5 bobbins and 5 hanks from eachbobbin. CV/o of the hank weights was calculatedto determine the long-term variation of the yams.

Single yam strength was tested using Good-brands Yam Strength Tester at a gauge length of60 ern and traverse rate of 30 ern/min. The aver-age of 200 ·tests from the selected 5 bobbins wascalculated. The average strength (g) was dividedby the tex of the yam to calculate tenacity. Fibrefineness of finisher card sliver was determinedfollowing the air flow method.

4 Results and DiscussionThree different methods were used to deter-

mine the irregularity of slivers and yams. It wasdue to the fact that shorter test lengths were pre-ferred to conduct repeat operations at the draw-ing stages for easy handling of the samples andtesting after each repeat. However, compatibilityof the different test methods was varified by mea-suring the irregularity of slivers. Among thesemethods, it was observed that thick sliver of firstdrawing stage was difficult to run through Usterat a speed of 25 m/min and so it was tested at aspeed of 8 m/min for comparison with STl. How-ever, second drawing slivers were tested at boththe speeds of 8 m/min and 25 m/min in Uster tocompare the values with STI as well as amongthemselves. The results are given in Table 2,which reveal that the irregularity values of theslivers of different stages of drawing, evaluated bydifferent test methods, have practically no differ-ence.

Irregularity of the slivers of different stages ofdrawing after levelling (applying 1-4 repeat oper-ations) has been shown in Table 3 along with thetheoretical values following Eqs (1), (2) and (3)and using the observed values of irregularity asinput for first repeat. It- is observed from the tablethat the theoretical values are in good agreementwith the observed values and almost stable after

20 INDIAN J. FIBRE TEXT. RES., MARCH 1995

Table 2-Comparison of irregularity of slivers using differenttest methods

Thickness CV'/o Uster CV'/o

STl STI 8 mlmin 25 mlmin

First drawing sliverSample 1 11.5

2 14.3Second drawing sliver

Sample 123

Finisher drawing sliverSample 1

234

56

STI and STI-Sliver irregularity testers developed by IJIRA.

11.0

14.5

9.0 9.4 9.39.1 8.9 9.08.4 8.5 8.6

15.0 15.411.9 12.510.6 10.014.4 14.810.0 10.121.7 21.6

Table 3-Sliver irregularity (thickness CV"/o/Uster CV%) afterrepeated drawing operations

No. of First drawing Second drawing Finisher drawingrepeats

A B A B A B0 10.6 7.4 8.0 11.01 7.6 7.4 5.7 5.0 10.4 10.42 6.8 6.3 5.5 4.3 10.4 10.43 6.3 6.1 5.3 4.24 6.3 6.0 5.3 4.1

A-Observed; B- Theoretical.

Table 4- Irregularity due to random fibre arrangement(Fibre fineness, 1.9 tex)

First drawing sliverSecond drawing sliverFinisher drawing sliverYarn

No. of fibres incross-sections (n)

16,1288,0641,792

139

CVf= 130/Jn("!o)1.021.44

3.098.80

ExperimentNo.

Table 5- Yarn test results

Yarn properties

Linear Tenacity, g/tex Uster Weightdensity Av.±SE CV'/o CV%

tex

255 12.0±0.16 18.1 5.0259 12.5 ±0.15 17.7 3.5259 12.5 ±0.15 17.1 3.3269 12.5 ±0.14 17.0 3.0257 12.2±u.14 17.2 3.1

12345

second repeat at first drawing and after first re-peat at second and finisher drawing. However, therate of decrease in irregularity of finisher drawingsliver, applying repeat operation, is much lessthan that observed in first and second drawingslivers. It is due to the fact that finisher drawingsliver contains less variation due to long andmedium waves.

It is also observed from Table 3 that the achiev-able irregularity of slivers is 6.3%, 5.3% and10.4% respectively for first, second and finisherdrawing stages.

Irregularity due to random arrangement of fi-bres in the slivers of drawing stages and yam(Table 4) reveals that its effect is considerable infinisher drawing sliver and yam. It is due to lessnumber of fibres in their cross-sections.

The results of the experiments 1-5 (Table 5)show that experiment nos 3, 4 & 5 produced re-gular yams with around 17% irregularity and 3%long-term variation (weight CV'/o). This may beregarded as the optimum irregularity for this qual-ity of yam using the fibre and the processes men-tioned. Among the processes, use of a leveller atsecond drawing is most convenient for productionpurpose. Use of finisher drawing as a leveller haspractical problems which are discussed later. Theprocess of using leveller at each stage of drawingis expensive and cannot be considered useful inpractice since using one of the other two pro-cesses similar yam quality can be obtained. How-ever, it may be mentioned here that in the experi-ments 1-5 (Table 1), the total doubling at thedrawing stages ranges between 12 and 2592 ofwhich 72 appears to be optimum beyond whichfurther improvement in yam quality is notobserved.

During mill trials, leveller was used to produceregular yams using normal fibres used by the re-spective mills. The yam test results (Table 6) cor-roborate with the findings of the experiments. It isinteresting to note that both in the experimentsand bulk trials in the mills, decrease in irregularityof slivers has marginal effect on the irregularity ofyams but has considerable effect on long-termvariation (weight CV'/o). It is mainly due to thepresence of faller bar waves in finisher drawingsliver and irregularity imposed by spinningmachine.

The contribution of different components tosliver and yam irregularity was calculated separ-ately applying Eq. 5 and using observed minimumsliver and yam irregularity values. The results are

DATI A et al: DRAFTING OF JUTE 21

N 400r--------~---------..,Long I ••••dium

~ Waves•.•.•300sea'c~200••>-a '0••0:

OL-~~~~~~~~EmFirst 5Kond

Drawi ng DrawingYarn

Fig. 1-Contribution of different components to sliver and yarn irregularity

Table 6 - Yarn test results- Mill trials

Mill Process Linear Tenacity, g/tex Uster Weightdensity Av.±SE CV'/o CV'/o

tex

A Normal 278 12.6±O.16 19 4.84 Drawing 266 13.2±O.13 18 3.0

B Normal 348 13.2±O.17 18 6.14 Drawing 324 13.9 ±0.16 I7 3.5

B Normal 462 13.4±0.15 I7 5.34 Drawing 476 14.0±0.14 16 3.3

B Normal 607 13.5 ±0.14 16 4.34 Drawing 583 14.5 ±0.13 14 2.8

Table 7-Contribution (%) of different components to sliversof different stages and yarn

Component Drawing stage Spinningstage

First Second Finisher

Long and medium waves 68 65 16 6Machine 31 33 76 71Rtbre arrangement 1 2 8 23Total 100 100 100 100

shown graphically in Fig. 1 in terms of relativevariance. It is observed that the effect of irregular-ity due to long- and medium-term waves is maxi-mum in first drawing sliver and it gradually re-duces with minimum being in finisher drawingsliver and yarn. Contribution of machine is mini-mum in second drawing sliver and it increases ra-pidly in finisher drawing sliver and yam due toobvious reasons of drafting faults of finisherdrawing machine and high draft in spinning. Theeffect of fibre distribution is also maximum inyarn due to the same reason.

The relative contribution of the different com-

ponents as a percentage to total relative varianceis shown in Table 7 separately for different stagesof drawing and spinning. It is clear from Table 7that the contribution of machine in finisher draw-ing sliver and yarn is maximum and almost samewhile .draft of spinning is much longer than that offinisher drawing. It is obvious that apron draftsystem of spinning has better control on fibresthan gill drafting system of the drawing machine.Moreover, the faller bar waves in finisher drawingsliver has no chance of reduction by way ofdoubling at this stage. These are the reason formaximum machine contribution in finisher draw-ing sliver. It is perhaps worthwhile to mentionhere that if drafting system of finisher drawing ischanged or a proper doubling system is adoptedto reduce faller bar waves, machine contributionmay be reduced to half, similar to as observed inthe other stages of drawing. This indicates thatthrough modification, finisher drawing sliver irre-gularity may be as low as 8% and in yarn there-from, 13%.

5 ConclusionRegular jute yarns may be produced through

the use of leveller, which reduces sliver irregular-ity, resulting in reduction in long-term variation ofyarns. A leveller may be used at second or finish-er drawing stage with same draft and doubling.However, practical experience reveals that use ofleveller at second drawing stage is more conve-nient due to the fact that it does not require anychange of the machine. On the other hand, use ofleveller at finisher drawing has practical problemslike frequent breakage of thin sliver, leading tomissing ends and longer creel to accommodate 9doubling at the back of the machine, which re-quires modification. However, use of leveller hasmarginal effect on yarn irregularity, mainly due tothe presence of faller bar waves in finisher draw-

22 INDIAN J. FIBRE TEXT. RES .. MARCH 199'i

ing sliver which are lengthened by draft duringspinning operation. To reduce yam irregularityfurther, it is necessary to change the drafting anddoubling system of the finisher drawing machineso that formation of faller bar waves is reduced.

AcknowledgementThe authors are thankful to the management

of Champdany and Gondalpara mills for extend-ing cooperation in conducting the trials.

References1 Datta U, Bhadra S C & Palit S, Indian J Text Res, 13

(1988) 80-83.2 Booth J E, Principles of textile testing (National Trade

Press Ltd., London), 1961,402.3 MartindaleJ G,J Text Inst, 36 (1945)T35.4 Atkinson R R, Jute fibre to yarn (Chemical Publishing Co.

Inc., New York), 1965, 113.5 Foster GAR, Mannual for cotton spinning, Vol. IV, Part 1

(The Textile Institute, Manchester), 1958,34, 138.6 Banerjee B L, J Text Inst, 57 (11) (1966)T 530-538.