Indian Journal of Fibre & Textile ResearchVol. 19, March 1994, pp. 1-6

Studies on autolevellers in draw frame

K B Krishnan & T Balamuralikrishna

The Lakshmi Machine Works Ltd, Perianaickan Palayarn. Coirnbatore 641020, India

and

P Chellarnsni & S Karthikeyan

The South India Textile Research Association. Coimbatore 641 014. India

Received 19 May 1993; revised received 6 August 1993; accepted I October 1993

The results of the research work carried out on yarn count variation that could be achieved whileusing 3/3 drafting system fitted with a short-term, closed loop autoleveller are reported. It has beenfound possible to spin cotton yarns with a count CV of 1.2-1.4% while using autoleveller. Forcombed counts, single-passage post-comber leveller drawing appears to be sufficient. Due to the im-provement in count CV as a result of the use of autoleveller draw frame, lea count CV improves by1.2-1.6% and single yarn strength CV by 4%. End breaks in spinning also reduce substantially whileusing autoleveller draw frame. Of the total yarn count variation, between bobbin variation accountsfor 60% and the within bobbin variation for the rest.

Keywords: Autoleveller, Cotton yarn, Count variation, Draw frame

1 IntroductionStudies I conducted at the South India Textile

Research Association, Coimbatore, have shownthat it is possible, under good working conditions,to produce cotton yams with a count CV of 2%using draw frame without autoleveller and thatthe draw frame contributes for more than 65% ofthe total yam count variation. This study also re-vealed that incorporation of autoleveller at drawframe may be worthwhile for reducing count CVfurther. In addition, a number of studies havebeen reported on measures to control lea countvariation+".

Eddie king" has shown that while using autole-veller incorporated draw frames, it is possible toproduce 100% cotton and cotton/comber nail(60 : 40) rotor-spun yams with a count CV of 1.4-1.6% using chute feed carding system. In the caseof ring-spun yams with chute feed to cards, a stilllower value of count CV (1.1-1.5%) is achievable,according to him, when the draw frame is fittedwith long-/medium-/short-term autolevelling.Wulfhorst" has shown that only one drafting pas-sage with autoleveller after combing is adequate.The piecing waves are completely evened out,and on the upstream machines, there is no prob-lem with an over-parallelized sliver. He has alsoshown that while using single-passage post-com-ber leveller draw frame, even the average value of

count CV calculated for the yarns collected overa period of 38 weeks is less than 1.2% for 30scombed cotton yarn.

In this work, the influence of delivery speed indraw frame fitted with autoleveller on the obtain-able yarn count CV has been assessed for cardedcounts. The effect of single passage of post-com-ber leveller drawing vis-a-vis double passagedrawing on the obtainable yarn count CV hasbeen studied for combed count. In addition, ana-lyses are made to see whether the draw frame au-tolevellers reduce yarn count CV at the cost ofincreasing variation of some other wavelength.The influence of, autoleveller at draw frame onshort-term variation of sliver, roving and yarn, .and the extent of improvement in yarn strengthvariation for the yarns spun from levelled sliverhave also been studied.

2 Materials and MethodsCotton yarns of three different counts, viz. 40s

K (carded count), 40s CH (combed hosierycount), and 80s C (combed count) were used. Theimportant quality characteristics of the cottonsused for the above counts are given in Table 1.Using the autoleveller draw frame as finisher, de-livery speeds in the range of 250-500 m/minwere used for carded counts. For double passagedrawing, the finisher was leveller drawing. All

2 INDIAN J. FIBRE TEXT. RES., MARCH 1994

Table I-Quality characteristics of cotton used

Parameter Cotton

Sankar-o DCH-32Count 40sK&40sCH 80sC

2.5% Span length. mm 26.8 32.9

Uniformity ratio. % 48.9 43.5

Fibre bundle strength. g!tex(3 mm gauge) 21.7 25.8

Micronaire value 3.5 2.9

Maturity coefficient 0.842 0.784

Trash. % 4.3 4.5

Nail extraction at comber. % 18 18(for 40s CH)

K-Carded count; CH-Combed hosiery count; andC -Combed coom

Table 2-Count CV for 40s carded yams

Parameter Without auto- With autoleveller atleveller at finisher draw frame

draw frame

Finisher deliveryspeed. m/min

Count CV", 0;',

400

2.44300

1.19

400

1.17

500

1.40

a For assessing count variation, 100 cops were collected fromthe ring frame (running on the count under consideration)over a period of one week. Then from each cop, 2 non-con-secutive leas were prepared. A total of 200 leas were collect-ed in this fashion and used to determine the count Cv,

-

A. Grooved rollerB. Feeler rollerC. Middle rollerD. Delivery rollerE. Controlled drafting slivera. Main motorb. Lead techometerc. Planetary gearsd. Actual value tachoe. Variable speed motorf. Control unitm. Mechanical transmission

I. Signal converter2. Pulse generator3. Electronic memory4. Nominal value stage5. Measuring voltage6. Delayed measuring voltage7. Actual voltage8. Nominal voltage9. Lead voltage

10. Control voltage

Fig. I-Schematic diagram of the regulating and controlsystem for the levelling drafting system RSB 51

these studies were carried out using chute feedcarding system.

2.1 Salient Features of the AutolevellerThe draw frame used in this study has a 3 over

3 drafting system adjustable to the fibre lengths ofup to 80 mm. In the main drafting zone, the fibresare guided and controlled by a pressure bar. Atthe machine entry, the thickness of slivers beingfed are consistently monitored by a pair of tongueand grooved rollers (Fig. 1). The measured valuesare converted into electrical signals which areused to control the draft in the main drafting zonethrough servo drive change, thus evening out sliv-er variations. The auto leveller under considera-tion is an open loop autoleveller.

Closed loop systems can only compensate formedium- and long-term variations because of thelong time delay between detection and correction.However, open loop systems can compensatevariations of short-to-medium wavelength becauseof its much shorter time delay between detectionand correction.

3 Results and Discussion

3.1 Perfonnanee of Leveller Draw Frame rorCarded Counts

The count CV values obtained for 40s K yamswith and without using autoleveller at finisherdraw frames are given in Table 2 for different de-livery speeds. It is observed that the count CVimproves substantially when auto leveller is usedat the finisher draw frames. At the same deliveryspeed (400 m/min), the use of autoleveller at fin-isher draw frame improves count CV by 1.27%(absolute value). The improvement in yam countCV could be due to the improvement in drawframe slivers, since autoleveller is incorporatedonly at the draw frame. Therefore, CV valueswere also calculated for finisher slivers and rov-ings using equivalent cut lengths. The results(Table 3) suggest that the improvement in countCV (while using autoleveller incorporated drawframe) is due to the improvement in sliver CVand roving CV. While feeding the autolevelledsliver (which is more uniform in terms of weightvariations) to speed frame, the added variance(relative variance) due to the speed frame processgot reduced by about 26% (the added variancedue to speed frame process was about 68% in thecase of sliver without levelling, whereas it was on-ly 42% in case of autolevelled sliver). This agreeswell with the findings of Balasubramanian in that

KRISHNAN et al: STUDIES ON AUTO LEVEllERS IN DRAW FRAME 3

Table 3-CV of finisher draw frame sliver and roving forequivalent cut lengths (count, 40s carded)

[Finisher delivery speed, 400 m1min]

Without auto- With autoleveller atleveller at finisher draw frame

draw frame

CV of finisher sliver, %

CV of roving, %

1.65

2.14

0.92

1.10

Table 4-Within and between bobbin count variation for 40scarded yarn

[Finisher delivery speed, 400 m/min)

Without auto- With autolevellerleveller at at draw frame

draw frame

CountCV, %Between bobbin

Within bobbin

Total

1.89

1.54

2.44

0.93

0.711.17

in any drafting process, the extent of added irre-gularity is influenced by the input material irregu-larity.

Table 4 gives the within and between bobbincount variations for 40s carded yarns producedwith and without autoleveller at finisher drawframe. To estimate between and within bobbincount variations, the range method II was adopted.It is observed from Table 4 that the leveller drawframe improves both within and between bobbincount variations, the extent of improvement beingalmost same in both the cases with the overall im-provement in the relative variance (while using le-veller draw frames) at about 75%. The improve-ment in within bobbin count variation could bedue to the efficiency of the levelling system tohave short correction length. As per the manufac-turer's claim", the correction length in the levellerunder consideration could be maintained at 3.4-11.7 em and in such cases, autoleveller could defi-nitely be expected to improve within bobbincount variation in addition to between bobbincount variation.

To find out whether auto leveller, while improv-ing the sliver variations present at a particularr.ange of wavelength, increases the sliver variationat some other wavelength, variance-length curveswere taken for finisher slivers obtained with andwithout autoleveller at finisher draw frame. Thetrends are shown in Fig 2. However, further stud-ies are required to confirm these trends theoreti-cally.

2~'~~------------------------~4-0 o.live-ryspe-e-d,400mlrni

0-8

0·4~--::7:-_:-'::::---="::--::lL::---::L:--...L..-'-":~-=:::~o 0·02 0·05 0·, 0·2 0·5 ',0 3-0CUT LENGTH, m

Fig. 2- Variance-length curves for finisher draw frame sliver[Al-e-without autoleveller; and A2-with auto leveller]

To study the effect of delivery speed on yarncount variation, count CV was assessed for 40scarded yarn at 3 different delivery speeds and thecorresponding values are given in Table 2. Withinthe range of speeds covered for yarns producedusing leveller draw frame, yarn count CV doesnot vary significantly.

3.2 Performance or Leveller Draw Frame rorCombed Counts

To see the effect of number of post-comberdraw frame passages on count CV while using le-veller draw frame, 40s combed hosiery yarn (CH)was ·produced using single- as well as double-pas-sage post-comber draw frames. In both the cases,finisher draw frame was incorporated with the au-toleveller. Together with this, normal 40s CH wasalso produced with two passages of post-comberdrawing without autoleveller. The count CV va-lues are given in Table 5. No significant differencein count CV is discernible between yarns spun us-ing single passage drawn as well as double pas-sage drawn slivers. Figs 3a-c show the spectro-grams of comber sliver, double passage drawnsliver (without autoleveller) and. single passagedrawn sliver (with autoleveller). The piecingwaves that are introduced during combing (Fig.3a) are evened out after two passages of drawing(Fig. 3b) while using draw frame without autole-veller. However, these piecing waves are correct-ed out in the 1st passage itself (Fig. 3c) while us-ing leveller at draw frame and this could be thereason that no significant difference is observed in .count CV between yarns spun using single pas-sage as well as double passage drawn slivers if au-toleveller is fitted on the draw frame.

As in the case of carded yarns, the deliveryspeed of draw frame (for the two speeds coveredin the investigation) did not influence count CVmuch in 40s combed hosiery yarn. At a deliveryspeed of 250 m/min, the yarn count CV was

4 INDIAN J. FIBRE TEXT. RES., MARCH 1994

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Fig. 3-Spectrograms of (a) comber sliver, (b) second passage drawn sliver, and(c) autolevelled sliver (single passage)

Table S- Effect of post-comber drawing passages on count CV(count, 40s combed hosiery)

[Finisher delivery speed, 3S0 m/min IDouble passage Single passage

draw frame draw frame

Without With Withautoleveller' autoleveller autoleveller

CountCV,%

Yarn 1.75 l.J l.J9Roving' 1.53 0.99 1.00Draw framesliver 1.22 0.93 O.IlS

"In the case of roving and draw frame sliver, the CV values arefor equivalent cut lengths.

about 1.3% whereas at a delivery speed of 350m/min, it was 1.2%. Only two delivery speedswere tried due to the machinery limitation.

The variance-length curves were drawn for 40scombed hosiery yarns spun with and without au-to leveller at draw frame (Fig 4) instead of for fini-sher draw frame sliver, as in case of 40s cardedyarn, to ascertain the fact whether the levellerdraw frame while improving the count CV (CV at110 m length) increases the variation present in

'yarn at any other wavelength. Fig. 4 clearly showsthat leveller draw frame reduces the variationspresent in yarn at all the wavelengths (From 1 mto 110m for which the variance-length curveswere drawn).

O.liwry spHd,350 m/min

..:;.-u>-z::>0 3u

2

11 10 2S 50CUT LENGTH, m

75 100 110

Fig. 4- Variance-length curves for 40s combed hosiery yarns[Al=-withour autoleveller; and A2-with autoleveller]

In the case of 80s combed yarn, a count CV of1.32% could be obtained while using levellerdraw frame (single-passage post-comber drawing)as against 2.03% for draw frames without autole-veller. The corresponding CV values of rovingand draw frame sliver for equivalent cut lengthsare given in Table 6.

After incorporating autoleveller, for an averagecount CV of 1.3%, the between bobbin variationcontributes for about 60% of the total varianceand the within bobbin variation for the rest.

3.3 InRuence of Autolevelling at Draw Frame onShort-Term Variation

To find out the effect of auto levelling on short-term variation, U% values were assessed for drawframe sliver, roving and yarn (for all the 3 counts)

KRISHNAN et al.: STUDIES ON AUTO LEVELLERS IN DRAW FRAME 5

Table 6-Count CV values for yarn, roving and draw frameslivers (Count, 80s combed)

[Delivery speed, 350 m/min)

Without auto- Single passagedrawleveller at frame with auto-

draw frame leveller

Count CV, %

Yarn 2.03 1.32

Roving 1.93 1.20

Draw framesliver 1.63 0.99

Table 7- U% values for sliver, roving and yarn

40s Carded 40s Combed 80s Combedcount hosiery count count

A 8 A 8 A 8

Finishersliver

Roving

Yarn

3.345.40

16.51

2.78

5.6016.30

2.69

4.04

12.37

2.133.33

12.35

2.64

4.23

15.89

2.20

4.19

15.53

A- Without autoleveller at draw frame; delivery speed, 400m/min for carded counts and 35Q rnImin for combed counts.B-With autoleveller at draw frame; delivery speed, 500m/min for carded counts and 350 rnImin for combed counts.

obtained with and without autoleveller at drawframe and the results are given in Table 7. It isobserved that while using leveller draw frame, theshort-term variation in terms of U% decreasedsignificantly for draw frame sliver in all the 3cases. This is understandable from the variance-length curves of draw frame slivers obtained withand without autoleveller. Autoleveller reduced thevariations present even at 1 cm wavelength andthat is the reason for the improvement in sliverU%. However, there is no improvement in short-term irregularity of roving and yarn.

3.4 Influence of Draw Frame Autoleveller on YarnStrength Variation and End Breaks

Due to improvement in count CV (while usingleveller draw frame), the strength CV also im-proved, the improvement being 1.60% in 40scarded yarn and 1.23% in 80s combed yarn (ab-solute values). The respective improvements inrelative variance are 53% and 44% for 40scarded yarn and 80s combed yarn (Table 8).

In both the above yarns, the single yarnstrength CV improved by about 4% while usingleveller draw frame. This agrees well with thefindings of Ratnam'? that more than 50% varia-

Table 8-lmprovement in yarn strength variation while usingleveller draw frame

[Delivery speed: 350 rnIminJ

40s Carded 80s Combed

Without With Without Withauto- auto- auto- auto-

leveller leveller leveller levellerCountCV. % 2.44 1.17 2.03 1.32Lea strengthCV.% 5.08 3.48 4.90 3.67Single yarnstrength CV. % 12.13 8.36 13.96 9.28

tion in strength CV is explained by the variationin count. According to him, the theoretically ex-pected ratio of strength CV to count CV wouldbe around 1.7 under controlled conditions. Thismeans that whenever count CV would change, thestrength CV would also change.

In addition, due to the improvement in countCV, end breaks in spinning decreased from 12.5to 9.3 per 100 spindle hours in 40s combed ho-siery yarn. A more or less similar trend in endbreakage rate was observed for 40s carded and80s combed yarns.

4 Conclusions4.1 For the cottons studied, it is possible to spin

yarns with a count CV of 1.2-1.4% (in carded andlcombed counts) while using autoleveller incorpo-rated draw frames.

4.2 For the type of leveller draw frame consid-ered, a delivery speed of 500 m/min for cardedcounts and 350 m/rnin for combed counts ap-pears to be normal. Single-passage post-comberleveller drawing would be sufficient for combedcounts.

4.3 Of the total yarn count variation, betweenbobbin variation accounts f~r about 60% and thewithin bobbin variation for the rest.

4.4 While using short-term autoleveller at drawframe, sliver evenness improves. However, rovingand yarn evenness do not get affected by the useof leveller draw frame.

4.5 Due to improvement in count CV (while us-ing leveller draw frame), the lea strength CV im-proves by 1.60% in 40s carded counts and 1.23%in 80s combed counts (both are absolute values).The single yarn strength CV also improves byabout 4% for the above counts.

4.6 The use of leveller draw frames reduced theend breaks in spinning from 12.5 to 9.3 per 100spindle hours in 40s combed hosiery yarn.

6 INDIAN J. FIBRE TEXT. RES., MARCH 1994

AcknowledgementThe authors are thankful to Mr T.Y. Ratnam,

Director, SITRA, for valuable guidance duringthis work and to Mr M. Murthy for conductingexperimental trials. They are also thankful to MisLakshmi Machine Works Limited, Coimbatore,and to Mis Tamarai Mills Limited, Coimbatore,for the help in carrying out the experimental workat their units.

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