Indian Journal of Fibre & Textile Research.

Vol. 15, December 1990, pp. 164-168

I'

Influence of rotor speed in open-end spinning on yarn quality

K Gnanasekar, P Chellamani & S Karthikeyan

South India Textile Research Association, Coimbatore 641 014, India
Received 7 May 1990; accepted 25 July 1990

The change in yam quality with rotor speed has been investigated for 6 different mixings made out of
natural/man-made fibres. Above 40,000 rpm, polyester tends to become weaker whereas cotton, viscose and
polyester blends remain unaffected up to 55,000 rpm. Evenness and imperfections deteriorate for all the fibre
types as rotor speed increases. Explanations based on theoretical considerations have been offered for the
observed phenomena.

Keywords: Centrifugal force, Combing roller, Open-end spinning, Rotor speed, Wrapper fibres,
Yam characteristics

1 Introduction The waste mixing consisted of 30% cotton, 30%

In their study on rotor spinning, Grosberg and flat strips, 30% comber noils and 10% blowroom
Mansouri used a 46 mm rotor to spin cotton with a droppings. The properties of the fibres/rnixings are
length of 32 mm and found that the yarn strength given in Table I.
improved with the increasing rotor speed. From a In all the cases, second passage draw frame slivers
study on a 30.5 mm cotton, Barella and coworkers- of appropriate hanks were prepared and fed to
concluded that a rotor speed of 31,000 rpm is the Lakshmi-Rieter M 1/2 Rotor Spinning Machine,
optimum for a 56 mm diameter rotor. It was found equipped with 54 mm rotors and Elitex Rotor Box CE
that an increase in rotor diameter (from 46 to 56 mm) II,to spin I5s 0E yarn. While processing the cotton as
decreases the yarn tenacity and at speeds above well as man-made fibres, opening rollers clothed with
40,000 rpm it also decreases the yarn appropriate wires were used. The rotor speed was
elongation-at-break. Under the conditions varied from 36,000 to 60,000 rpm and the yarn
employed, an increase in either rotor speed or rotor samples collected at different rotor speeds were tested
diameter was considered detrimental to the yarn for: (i) Tenacity and CV % of strength, (ii) Breaking
properties studied. It is, therefore, felt that it will be of elongation, and (iii) Evenness and imperfections.
considerable use to Indian textile industry if The other process parameters used in this study are
comprehensive data are available regarding the given in Table 2.
nature and direction of change in yarn quality
attributes like strength, evenness, imperfections and 3 Results and Discussion
breaking elongation when rotor speed is changed for 3.1 Effect of Rotor Speed on Yarn Tenacity and Elongation
commonly used fibre types/rnixings in Indian mills The effects of increasing rotor speed from 36,000 to
using indigenous rotor spinning machines. This 60,000 rpm in steps of 4000/5000 rpm on yarn tenacity
study is an attempt towards this end. and breaking elongation of cotton, waste mixing,
polyester fibre and viscose fibre are given in Table 3.
2 Materials and Methods An increase in rotor speed increases the centrifugal
The following fibres/mixings were used: force acting on the yarn tail which is given by:
100% Cotton mixing Centrifugal force, cN/tex = un /20000
Waste mixing where W is the circumferential speed of the rotor in
100% Polyester m/s.
Because of this higher centrifugal force", better
100% Viscose consolidation of fibres deposited in the rotor groove
67/33 Polyeser/cotton could be expected which, in turn, will lead to higher
48/52 Polyester/viscose strength.

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 GNANASEKAR etal.: INFWENCE OF ROTOR SPEED ON YARN QUAUTY

Table I-Properties of fibres/mixings

Property 100% Wastemixing 100% 100%
Cotton (weighted Polyester Viscose
averagevalue)
2.5% Span length, mm 24.0 25.8 38.0" 38.0"
50% Span length, mm 11.1 11.0 --
Stelometerstrength 18.8 18.5 --
(3 mm gauge),g/tex
Micronairevalue,g/in 3.1 2.9 1.2b 1.5b
Maturity coefficient 0.78 0.78 --
Elongation, % --25 18
Moisture regain, % --0.4 12

aCut length, mm
bDenier

Table 2-Process parametersusedto spin 15sOE yam

Processparameter Fibre/mixing

100% Waste 100% 100% Polyester/ Polyester/

Cotton mixing Polyester Viscose cotton viscose
(67/33) (48/52)
Combing roller speed,
rpm (x 1000) 6 6 6 6 6 6
Draft 107.14 107.14 90.90 90.90 93.75 93.75
TPI 18.60 20.75 14.01 14.01 17.32 14.88
Rotor diam, mm 54 54 54 54 54 54
Separatorangie,deg 45 45 45 45 45 45
Type of doffing tube R 10 R 10 R 10 R 10 R 10 R)O

But the increasein rotor speedhas the following contribute towards yarn strengths.The proportion
three detrimental effects on yarn strength: of warpper fibres increaseswith increasein rotor
(i) When the rotor speedincreasesfor a given speed4and is expectedto causea reduction in yarn
twist, the yarn deliveryincreasesand to maintainthe strength.
linear density of yarn, feed rate also getsincreased The combined influence of the parameters
correspondingly.This affectsadverselythe efficiency discussed abovedeterminesthe directionof changein
of the combing roller in individualizing the fibres4. yarn strength at higher rotor speeds.
So,the fibres getdepositedin the rotor groovein the Higher rotor speedsgenerallybring down yarn
form of bunchesand not in singlefile. Accordingly, elongation owing to the higher cet:ltrifugal force
the yarn strengthwill be low. Experimentally,it has acting on the fibre ring at the rotor groove. This
been proved that the bunch coming out of the increasedcentrifugal force makes the yarn more
combingrollerto the rotor shouldnot havemorethan compactand this highercompactnessreducesfibre
4-6 fibres to have a reasonablestrength. slippage during tensile testing, resulting in loss in
(ii) The fibres coming out of the combing roller elongation.Further, becuaseof the higherfrequency
normally contain lot of hooks,loopsand otherfibre of wrapping at higher rotor speed,the wrappersact
deformations4. At higher rotor speeds,the time like constrictions on the yarn and whilst the flow of
allowed for thesefibresto getthemselves relaxedand strain along the length of the fibres composingthe
straightened is less which results in lower yarn yarn. As a result of thesetwo factors, elongation
strength. drops sharply with increasein rotor speed.
(iii) OE yarns are known for the presenceof From Table 3 it is observedthat for 100%cotton
wrapperfibres4.Thesewrapperfibres loosely wrap the yarn strengthdid not vary muchfor rotor speeds
around the surface of the OE yarn and do not 36,000-60,000 rpm. In the caseof wastemixing and

165
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INDIAN J,FlB~ TEXT. RES.,DECEMBER 1990

.-
..,0 .,
.Table 3-Effect of rotor speed.on yarn tenacityand elongation
[Yarn count',15s}
Fibre/mixing and yarn Rotor speed;rpm (x 1000)
property
36 40 45 50 ;55 60
100% Cotton
Tenacity, g/tex 11.73 12.00 11.48 11.73 -11.36
Elongation, % 8.29 7.73 7.24 6.53;~ 5.50
, ",Is
Waste Mixing
Tenacity, g/tex 10.37 10.53 10.58 10.27 9.94 9.52
Elongation, % 8.39 7.82 7.39 6.79 5.73 5.12
100% Polyester
Tenacity, g/tex 20.73 21.40 18.73 -18.38 17.79
Elongation, % 10.43 10.08 9.66 9.31 8.77 1.77
100% Viscose
Tenacity, g/tex 10.37 iO.22 9.72 9.91 9.79 9.66
Elongation, % 10.01 9.58 9.02 8.82 7.77 6.47

viscose, the strength remained more or less same up to Table 4-Effect of rotor speedon yarn evenness(V%)
50,000 rpm and thereafter it started falling, the fall in Rotor speed, Fibre/mixing
strength being about 7%. I:I°wever, for polyester rpm(xIOOO) 100% Waste 100% 100%
staple fibre yarns, the tenacIty decreased gradually Cotton mixing Polyester Viscose
with increase in rotor speed (from 40,000 rpm 36 102 125 130 124
onwards), the drop being about 16.8% at 60,000 40 12:5 13:5 13:0 12:2

rpm Th. 1 . 1 h. h d . th th. 45 12.4 13...1 13.2 12.3

.e re,anve y Ig er ro,p m yarn ~treng WI 50 .12.2 -13.5 12.5
Increase m rotor speed whIle processIng polyester 55 -132 137 132
fibres could be due to ~br,e softening whi~h arises 60 12.2 13:5 13:9 13:7
from the heat generated InsIde the rotor at hIgh rotor
speeds.. Fibres removed from polyester yarns -'
produced at 40,000 rpm and 60,000 rpm were
compared for strength and it was found that the 36,000 to 40,000 rpm and afterwards, the yarn
strength of fibres from yarns produced at 60,000 rpm evenness levelled off. At high rotor speeds, the degree
is lower by about 15% (Fibre strength is45 g/tex at a of combing of the fringe as also the draft between feed
rotor speed of 40,000 rpm as against 39 g/tex at 60,000 roller and combing roller are reduced. This leads to a
rpm). loss incombing roller efficiency in individualizing the
Table 3 shows that the yarn elongation reduced fibres, which is responsible for the deterioration in
with increase in rotor speed in all the cases, the evenness. However, the extent of deterioration due to
reduction being 2.79, 3.27, 2.66 and 3.54% (all increased rotor speed depends on the fibre type. It
absolute .values) for 100% cotton, waste mixing, appears that for some fibres, the deterioration in
polyester and viscose yarns respectively for an evenness with increase in rotor speed is very sharp at
increase in rotor speed from 36,000 to 60,000 rpm. the initial stages (when speed is increased from 36,000
to 40,000 rpm) and for some other fibres the
3,2 Effect of Rotor Speedon Yarn Evenness deterioration in evenness with speed is spread
The unevenness of .yarns spun from qifferent uniformly over the entire spectrum of rotor speeds.
fibres/~ixil)gs atdifferentro.tQrspe~ds ,is given in This aspect is to be confirmed by further trials.
Table:4. , For polyester and viscose yarns, the U% values at
The ~nevenness of yarns from cotton and waste rotor speed of 60,000 rpm were significantly higher
mixings showed a.tendency to iDGrease with increase than that at 36,000 rpm, Fibre softening 6and lack of
in r<:>tor speed. Ho':Never, the increas~ w!ls; sharp fibre individualization at higher rot()r speeds could be
(47"2:;3U%) when the. rotor speed ,w~s in~reased from the reason for the observed phenomenon.

,1(>(>
 GNANASEKAR etal: INFLtJENCE OF ROTOR SPEEDON YARN QUAUrY '

3.3 Effectof RotorSpeedon Yam Imperfections reduced and, therefore, thedefonnations (like loops
The number of imperfections/km in yams SpUD and hooks) in the fibre are increased w!1ich are
from 100% cotton, waste mixing, polyester fibre and responsible for higher imperfections.
viscose fibre at different Totor speeds are given in According to Manohar and coworkers 7, with
Table 5. Increase in rotor speed,in general, increased increasein rotor speed,the closelywound wrappers in
the number of imperfections in all types of yam. As in OE yarns increase. During testing of these yarns in
the case of yam evenness,the deterioration in yarn evennesstester, the closely wound warppers also get
quality in tenns of imperfections was sharp when the counted as neps. This could also be the reason for the
rotor speedwas increased from 36,000to 40,000 'rpm increase in neps in OE yams with increase in rotor
and afterwards it levelled off for 100% cotton mixing. speed.
For yams from waste mixing, polyester and viscose
fibres the increase in total imperfections was 74%, 3.4 Effectof RotorSpeedonPrope~ of BlendedYarm
139% and .143% respectively when rotor speed was The influence of increasing rotor speedfrom 36,000
increased from 36,000 t960,000 rpm. Howevt:r, for to 60,000 rpin on the physical properties of 15s
waste mixings and polyester the increase in yam polyester/cotton (67/33) and polyester/viscose
imperfections was rather steepwhen the rotor speed (48/52) yams is shown in Table 6. It is observed that
increasedabove 50,000rpm. In the caseof yams from both the yams did not exhibit any significant change
viscosefibres, the increasein imperfections with rotor inyam tenacity and yam evennesson increasing rotor
speed was unifonnly spread over different rotor speedfrom 36,000to 60,000rpm. In the caseof 100%
speeds. , polyester fibres, the high temperature developed
The higher number of imperfections in OE yam at inside the rotor at high rotor speeds causes
higher rotor speedscould be most probably due to the deterioration in fibre strength which is responsible
deterioration in fibre arrangement at' the rotor for the reduction in yam strength and increase in
gr90ve. At higher rotor speeds,the time allowed for unevenness.The addition of cotton or. viscose with
the fibres to align themselves on the rotor groove is polyester fibres appears to reduce the extent of

Table5-Effect of rotor speedon yamimperfections

Rotor Fibre/Mixing
speed,
rpm 100%Cotton Wastemixing 100%Polyester 100%Viscose
(x 1000)
Thin Thick Neps Thin Thick Neps Thin Thick Neps Thin Thick Neps
places places places places places places places places
36 I 21 72 14 211 722 37 74 20 13 64 29
40 20 152 303 16 204 791 24 117 37 12 74 24
45 15 14 69 18 212 907 19 107 14 8 87 37
50 12 109 304 16 135 721 16 83 20 11 105 53
55 14 35 270 16 225 938 23 99 8 17 113 45
60 11 127 241 71 296 1281 34 236 43 33 162 63
---
Table6-Effect of rotor speedon the propertiesof polyester/cotton
andpolyester/viscose
blends
[Yam count, 15s]
Rotor speed, Typeof yam
rpm (x 1000)
Polyester/cotton
(67/33) Polyester/viscose
(48/52)
,

Tenacity Elongation U% Imperfections/ Tenacity Elongation U% Imperfections/

g/tex % km g/tex % km
36 17.35 10.17 12.8 245 16.66 11.02 12.8 .263
40 17.05 9.76 13.4 465 16.38 10.66 13.3 309
45 17.04 9.39 13.3 462 16.46 9.95 13.2 362
50 17.05 8.91 13.4 421 16.65 9.84 13.3 406
55 17.22 8.51 13.5 404 l6.89 9.62 13.6 439
60 17.59 8.27 13.3 501 16.25 9.01 13.5 450

167
 INDIAN J,FIBRETEXT.RES"DECEMBER1990

deterioration of polyester fibres at high rotor tenacity more or less remains constant at different
speeds. rotor speeds.
The breaking elongation of polyester/cotton and 4.2 Higher rotor speeds generally decrease the
polyester/viscose open-end yarns decreased at yarn elongation for all the fibres/mixings due to the
higher rotor speedsas in the case of 100% polyester better consolidation of fibres in the rotor groove and
yarns, the fall in breaking elongation at 60,000 rpm thereby the avoidance offibre slippage during tensile
being 1.9 and 2.01% (absolute values) respectively testing.
for polyester/cotton and polyester/viscose yarns. 4.3 The various imperfections in yarns from all
The decreasein breaking elongation is most probably types of fibre/mixing show a steadyincrease at higher
due to the greater consolidation offibres in the rotor rotor speeds.
groove at higher rotor speeds. For polyester/cotton
h ' " fi ' ,h d Ac knowe I dgement
yarns, t e IncreaseIn Imper ecnons Wit ro,tor spee The authors are thankful to Mr T V Ratnam,
was too sharp when the rotor speed was.Increased Director SITRA for uidance and valuable
from ."sugges
36,000 to 40,000 rpm and thereafter It was only tIons
,' dunng gd y,
' ' th IS st u '

marginal. For polyester/VIscose yarns, the Increase

was uniformly spread over all the rotor speeds.The References
increase in yarn imperfections at higher rotor speeds 1 GrosbergP & MansourSA,J Text Inst,66 (1975)389.
could pe due to the formation of wrapper fibres on the 2 BarellaA, VigoJ P,TuraJ M & EsperonH 0, J TextInst.67
yarn surface at higher rotor speeds. (1976)253.
3 KrauseH W, Chemiefasern/Text-lnd, 26/78(1976)781,
.4 Balasubramanian N & ManoharJ S,Proceedings, seminaron
4 ConclusIons open-end spinning
(TheBombay TextileResearch
Association,
4.1 For cotton, viscose and waste mixings, the Bombay)1982,27.
yarn strength does not vary much between rotor 5 LunenschlossJ & KampenW, TextPraxlnt.31 (1976)1274,
speeds. For polyester yarns, the tenacity decreases 1394,
d 11 . h .. d h d b .6 Pillay K P R, Proceedings, joint seminar on open-end spinning
gra 0
ua y Wit Increase In ..system
rotor spee , t e rop eIng 0ifLMW& SIT L1.
'D A (Th e S ou th I n d .la T ex t .Ie
1 R esearc h

16.8 '/0 when rotor speed IS Increased from 40,000 to Association, Coimbatore) 1986, 53.

60,000 rpm. While spinning polyester/cotton and 7 ManoharJ S,RakshitAK& Balasubramanian

N, TextResJ.
polyester/viscose blends in OE system, the yarn 53 (1983)497.

~;!-

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168