Indian 10urnal of Fibre & Textile Research Vol. 28 . March 2003 . pp. 9-15

Influence of wire point density in cards and combers on neps in sliver and yarn quality

K P Chellamani". D Chattopadhyay & V Thanabal

The South India Textile Research Association. Coimbatore 64 1014. Indi a

Received 18 December 2001; accepted 30 January 2002

Card slivers were produced from two Indian cottons of micronaire values 2 .7 and 3. 1 in a 4th generation card using flat tops of five different wire point densities and spun into 80s and 100s combed yarns. Card sliver neps as well as imperfections in the corresponding yarn samples produced using those slivers were estimated. Conducting trial s were also carried out using cylinder wires. flat tops and combing segments of variable density. Cylinder wires of variable density in card reduce sli ver and yarn nep content by about 35%. Combing segments with 4 partitions in comber produce slivers and yarn s with about 25% lower neps as compared to combing segments of 2 partiti ons.

Keywords: Carding. Combing segments. Cotton. Flattops. Neps. Yarn imperfec tions

1 Introduction In the spinning process, neps are removed

primarily during carding and combing. The extent of nep removal varies between 60% and 85% during carding and 50% and 70% during combing, depending on the cotton used and the process parameters employed. As per the earlier studies I by SITRA, in Indi an cottons the neps of 550jl size are higher whereas in foreign cottons 750jl s ize neps occur frequently. The neps below 650jl are generally considered as small er size neps and those above 650jl as larger size neps. In Indian cottons, the ratio of smaller size neps to larger size ones is about 55:45. The occurrence of higher level of smaller size neps in Indian cottons affects yarn imperfections in fine and superfine counts. Hence, to improve quality of these yarns, measures to eliminate smaller size neps during processing assume sign ifi cance.

Kluka et at. 2 studied the influence of raw materi al and process parameters on yarn neppiness. They reported that the yarn neppiness is influenced primarily by the number of neps in raw materials. Accord ing to Farber3

, the neps in yarn are influenced not only by the number of neps in intermediate products but also by their mean size and distribution . He concluded that for each yarn linear density, there is a cri tical nep size in the sli ver or roving above

"To whom all the correspondence should be addressed. Phone: 2574367; Fax: 0091-0422-257 1896: E-mail: sitra@v:;nl.com

which the nep will be identified and registered by unevenness tester as a yarn fault. Studies by Kanai et al. 4 revealed that the nep removal efficiency of card increases with sharpness of fl at and cylinder wires. New (sharper) wires were found to produce sli vers with fewer neps.

However, the influence of higher wire point density flat tops in card , variable density cylinder wire and flat tops in card . and different types of combing segments (half laps) in comber on smaller size neps in sliver is yet to be established. The present study was, therefore, undertaken with the following objecti ves:

• To assess the influence of flat tops of variable wire point density in carding on smaller size neps in card sliver and yarn qua lity. • To study the influence of variable density cyl inder wires and variable density flat tops on smaller si ze neps in card sli ver and yarn quality. • To evaluate the impact of different combing seg­ments (half laps) in comber on smaller size neps in comber sli ver and yarn quality.

2 Materials and Methods 2.1 Flat Tops of Variable Wire Point Density

Flat tops of five different wire poin t densities were used for the study in a 4th generation high production card, equipped with cy linder wires of 860 PPSI (Table I ). Cottons of 2.7 and 3. 1 micronaire va lues were processed through the card. The major quality characteri stics of the two cottons are given in Table 2. Card sli ver neps as well as the imperfections in yarns

10 IND IAN J. FIBRE TEXT. RES., MARCH 2003

Table I - Wire point density of fl at tops and cy linder wire in the card

Flat tops Flat tops PPSI

PPS I Cy li nder wire PPS I' %

348 40

435 50

532 60

560 65

635 75

PPSI - Poi nts per square inch a Cy linder wire PPSI, 860

Table 2 - Quality characteristics of cottons

Parameter Cotton

2.7"

2.5% Span length, mm 32.7

Un iformity rat io, % 44. 1

Bundle strength , g/tex 25 .3

Elongation, % 5.4

Neps/g

,.; 650p. 164

> 650p. 136

Total 300

a Micronaire value

3. 1"

35.7

44.8

25 .8

6.9

125

100

225

Table 3 - Process parameters maintained during carding

Parameter

Sl iver hank, Ne

Deli very speed, m/min

Cylinder to fl at setting, mm

Feed plate to li cker-in sett ing, mm

Flat speed, mm/m in

Cy linder speed, rpm

Licker-in speed, rpm

Va lue

0. 18

90

0.25 ,0.20,0.20 & 0.20

0.60

200

450

950

produced using those sli vers were estimated. The process parameters employed during carding are given in Table 3.

2.2 Variable Density Cylinder Wires and Flat Tops Cy linder wires and fl at tops of uniform density are

commonly used in mills. Of late, the cy linder wires and fl at tops of variab le density are being offered by card wire manufacturers with a view to improve sliver quality. Three trials were carried out using these wires and the details are g iven in Table 4 .

Cottons of 2.7 and 3. 1 micronaire values were processed in all the 4 tri als. Card sli ver neps and the corresponding yarn imperfec tions were es timated.

Table 4 - Trials using uniform and variable density cy linder' wires and fl at tops

Wire Type of cy linder wire Ty pe of fl at tops combina-

tion Uni fo rm density Unifo rm density (860 PPS I) (532 PPSI)

2 Uniform density Variable density (860 PPS I) (435 - 581 PPSI with

an average of 532 PPSI)

3 Vari able density Uniform density (700 - 1000 PPSI wi th (532 PPSI) an average of 850 PPSI)

4 Variable density Variable density (700 - 1000 PPSI with (435 - 58 1 PPS l with an average of an average of 850 PPS I) 532 PPSI)

Table 5 - Needling pattern in combing segments

Type of combing Points /cm2

segment

Conventional (with 2 partitions)

1 SI Partiti on 27 2nd Partition 48

Mod ified (with 4 partitions)

1 s, Partition 2nd Partition 3rd Partition 4'h Part it ion

35 54 58 64

Total no. of points in the combing segment

2080 11 776

Total 13856

28 16 4352 4608 5120

Total 16896

2.3 Conventional and Modified Combing Segments (Half Laps) Two types of combing segments (conventional and

modified) were used in the study. The needling patterns in the two types are shown in Table 5. The needling pattern in modified combing segments helps for easy opening of the fibre fl eece at the start of combing and for gradual increase in intensity of combing as the half lap advances . Card sli vers made out of 2.7 and 3.1 micronaire cottons were processed in combers equipped with conventional as well as modified combing segments and subsequently they were spun into 80s and 100s combed yarns. Neps in comber sli vers, and imperfec tions and class imat faul ts in the corresponding yarn samples were estimated.

3 Results and Discussion 3.1 Influence of Flat Tops of Variable Wire Point Density on

Sli ver Neps and Yarn Imperfections

Neps in blowroom lap as well as in card slivers produced using fl at tops of di fferent wire point

CHELLAMANI el al. : INFLUENCE OF WIRE POINT DENSITY IN CARDS AND COMBERS ON NEPS 11

densities in the card are shown in Fig.I. With the increase in wire point density of flat tops, the neps in card sliver show a tendency to reduce both for 2.7 and 3.1 micronaire cottons .

Nep level in card sliver is found to be minimum for a flat top with PPSI (points per square inch) in the region 532-560 for 2.7 micronaire cotton. As compared to 348 PPSI, the flat tops of 532 PPSI produce card sliver with 40% lower neps. Further increase in PPSl of flat tops does not reduce the nep content in card sliver. The cylinder-flat interaction in a card consists of following two phenomena: (i) Fibre-to-fibre individualization as the flats move over the cylinder surface. (ii) Lodging the unopened fibre clusters and seed coat fragments that are continuously thrown towards the

en ---Ul 0-Q)

Z

700 .-------------------------------~

600

500

400 '

300'

200

10

0

600

500

4()()

3()0

200

100

Cotton with Micronaire Value - 2.7 Blowroom lap:

<> ~ 650 Microns

o > 650 Microns

o TOlal

Card sliver:

• :> 650 Micro ns

* > 650 Microns

* Tal I

Cotton with Micronaire Value - 3.1

O +---------,,---,----r---.----.---~

348 435 532 560 635

Flat Tops,PPSI Fig.1 - Neps in blowroom lap and card sliver

flat tops by the cylinder due to the centrifugal force . The seed coat fragments and fibre clusters are subse­quently removed as flat strips.

The increase in PPSI of flat tops beyond a certain level could be logically expected to impair the lodg ing of heavier impurities by the flats due to relatively less space between the wire points and consequently these heavier impurities go along with the card sliver and get counted as neps . This could be the reason why the card sliver neps do not reduce when the PPSI of flat tops is increased beyond the region 532- 560. The flat waste while using fl at tops of different PPSI is shown in Fig.2. Flat strips continue to increase up to 532 PPSI of flat tops and afterwards these remain more or less constant. This substantiates the hypothesis that the efficacy of flats in removing fibre clusters and seed coats doesn ' t improve beyond a certain level of wire point density.

For a flat top of 532 PPSI, the ratio of PPSl of fl at tops to cylinder works out to 60%. At this PPSI ratio , the nep removal efficiency (NRE) of card is found to be around 65% for smaller size neps (~ 6'50 ~) and around 85% for larger size neps (> 650 ~) with the overall NRE of 75%. A more or less simjl ar trend was discernib le while processing 3. 1 micronaire cotton.

To evaluate the effect of high PPSI flat tops on yarn imperfections, the 80s and ] OOs combed yarns were produced using slivers made out of 2.7 and 3. 1 micronaire cottons processed through flat tops of different PPSI (Fig.3). Yarns produced from 532 PPSI flat tops show less imperfections by about 30 -35% in 80s and ] OOs combed yarns as compared to yarns produced from 348 PPSI fl at tops; the reduction being mainly due to the decrease in thick

~

~ V)

ro ~

'" u::

4~----------------------------~

3.5

3

2.5

0 348 435

• Ca llan wilh Micronaire value - 2.7

* Callan wilh Micronaire vaiue - 3.1

532 560 635 Flat Tops,PPSI

Fig.2 - Flat waste during carding

12 INDI AN 1. FIBRE TEXT. RES., MARC H 2003

places and neps. The observed improvement in yarn imperfections is fu lly explained by the corres­ponding reduction in card sliver neps. With PPSI hi gher than 532, the yarn quality does not get altered in both the counts.

1400 .---------------------------~

1200

1000

800-

o

• 80s Combed

* 100s Combed Cotton with Micronaire

val ue - 2.7

1400 .,..---------------------------~

1200

1000

800

Cotton with Micronaire value - 3. 1

o ~---r--~r_--,---~----~--~ 348 435 532 560 635

Fl ,H Tops, PPSI

Fig. 3 - Total imperfec tio ns in yarns

3.2 Influence of Variable Density Cylinder Wire and Flat Tops on Sliver Neps and Yarn Imperfections

Vari able density cylinder wire and fl at tops are recent introductions in the spinning industry for improving card sli ver quality . A study has been carried out to assess their usefulness. Constant and vari able density cylinder wires and flat tops were used in 41h generation card to produce sli ver samples from 2.7 and 3. 1 micronaire cottons. The details of wire point density of cy linder and flat tops and the quality of card slivers produced are given in Table 6.

Vari able density cy linder wires reduce sliver neps to about 35 % fo r both the cottons . The reducti on is 45-50% in the case of larger size neps (> 650jJ.) and about 30% for smaller size neps (S 650). However, the variable density fl at tops do not have any impact on sli ver neps. In case of constant dens ity cy linder wire, the ai r current that is generated due to cy linder rotation escapes through the gap between the rows of wires. But while using variable density wires, there is restriction on airflow due to the change in pitch density of wires at different places over the cylinder surface. So, air is pushed upwards towards the flat, which, in turn , helps for further opening of clusters present in the fibrous material over the cy linder wires .

The reduction in sliver neps obtained wh ile using variable density cy linder wires is reflected in the quality of respective yarns as shown in FigsA and 5. Yarns produced using variable density cy linder wires show 25 - 35% lower number of thick places and around 40% lower number of neps. The improvement in yarn imperfections is fou nd to be more or less the same fo r both the cottons and fo r both the counts.

Table 6 - Type of cyli nder wire and nat tops used and nep content in card s li ver

Wire Cylinder wire Flattops Ne~ content in card sliver (Ne~s/g) combination 2 .7 Micronaire collon 3.1 Micronaire cOllon

:0; 650 J1. > 650 J1. Total :0; 650 J1. > 650 J1. Total

Uniform density Uniform density 107 51 158 10 1 47 148

(860 PPSl ) (532 PPSI)

2 Un ifo rm density Variabl e dens ity (860 PPSl ) (435 - 58 1 PPSI 11 6 5 1 167 98 47 145

-Avg.532 PPSI )

3 Variable density Uniform density

(700 - 1000 78 27 105 67 24 9 1 PPS I - Avg.850 PPS I)

(532 PPSI )

4 Var iable density Variab le dens ity (700 - 1000 (435-58 1 PPSI 8 1 29 11 0 69 26 95 PPSI -Avg.850 PPS I) -Avg.532 PPS I)

CHELLAMANI el at.: INFLU ENCE OF WIR E POINT DENSITY IN CARDS AND COMBERS ON NEPS 13

V1 C o U <.8 ~

1050-r--------- --------, Caunl:80s Combed ~ Thin places Cattail with Micronaire

900 Value _ 2.7 lTII1 Thick places

750 o Neps

600

450

300

150

O~~~~~~ac~uu~~~~~~

1050.,..-- - --------------, Count : 1005 Combed

0.. 900 :::

750

600

450

300

ISO

2 3 4

Wire Combination

Fig.4 - Imperfections in yarns produced using constant and vari­able density cylinder wires and flattops

3.3 Effect of Different Combing Segments (Half Laps) in Comber on Sliver Neps and Yarn Quality

Card sliver samples of 2.7 and 3.1 micronaire cottons were processed in a 3rd generation comber using combing segments of 2 partitions as well as 4 partitions. The process parameters employed during combing are given in Table 7. Nep contents in the comber sliver samples are shown in Fig.6.

Combing segments of 4 partitions produce slivers with about 25% lower neps as compared to combing segments of 2 partitions in both the cottons. The reduction is practically same for both smaller and larger size neps. In the combing segment of 4 partitions, the wire points are coarser in the initia l row and become gradually finer in subsequent rows. The more open points in the initi al rows enable better straightening of fibres in the fringe, which, in turn, assists in efficient removal of neps by the closely spaced latter rows.

1050 ....._-------:----==-::;;;-:---;---, COUI1! :XOS Combed ~ Thin places ("0((011 with Microl1aire lTII1 Th · k I

900 Value _ 3. 1 IC p ace

,... ,... ..::.:

"f.

'-' v "-:... U 0.. E

IS

1050

900

750

600

o Neps

Count: 1005 Combed

1

Wire Combinat ion

Fig.5 - Imperfections in yarns produced using constant and vari ­able density cylinder wires and fl at tops

Table 7 - Process parameters maintained during combing

Parameter

Nips/min

Feed weight, g/m

Feed/nip, mm

Type of feed

Top comb depth

Nipper to combing segment setting, mm

Amount of noil extrac ted, %

Value

ISO

S5 4.S

Backward

+ 0.5

0.35

IS

80s and 100s combed yarns were spun separately using comber sli vers of 2.7 and 3.1 micronaire cottons. Yarn imperfections , particularly thick pl aces and neps, get reduced by 25-30% in both the counts while using 4-partition combing segments as illustrated in Figs. 7 and 8. The 4-partition combing segments in comber also bring down the short thick pl aces measured in Class imat system by about 60% and long thick places by 35-50% in 80s and 100s counts as shown in Figs.9 and 10.

14 INDI AN J. FIBRE TEXT. RES., MARCH 2003

00

Vl 0-OJ Z

E -'"

'n

.2 u ~ t; ~

40 .-----------~~~--~~ Combing Segment With

Colton with Micronairc value - 2.7

~650

1ZJ 2

[34

> 650

Nep Size, Microns

Fig.6 -- Nep content in comber sli ver

700 ~----------------------~

600

500

400

300

200

100

a 700

600

SOU

400

300

200

100

COllnt:XO, Combe<l lotion wit h Microll:lire va lue - 2.7

Count: laOs Combed

•

• Thin places

"*" Thick places

.. N(~ ps

• o L---~-----r----r----r--~

Partit ions Partitiuns

Type or Co mbing Segmenl

Fig.7 -- Yam imperfections for different types of combing segmenls

~ ..:2

'f> c 0

U .~ i:; 0-e

400 '-(-·-ll -lIl-lt-:X-'O-S-C~·-O-ln~b-e~d--------.--Th-i-n-PI-.-ce-s-'

350

300

250

200

150

100

50

0

500

400

300

200

100

Cotton wi lh Micronnlre

*-----_--1.. ""*

• • Count: laOs Combed

• • O+---~----'---~-----r--~

2 Part it ions

4 Pnrt itions

Type o f Combing Segment

Fig.8 -- Yarn imperfections for different types of combing segments

E --'" 0 0

,~

0

>< ~ ::l

"" u... --'" .~

1=

2 (/)

4

3

2

0

Count : 80s Combed

2.7

Combing Segment With

lZ] 2 Panitions

g:g 4 Panit ions

Count: 100s Comt ed

3.1

Micronaire Value of Colton

Fig.9 -- Yarn short thi ck faults for different types of combing segments

CHELLAMANI et al.: INFLUENCE OF WIRE POINT DENSITY IN CARDS AND COMBERS ON NEPS 15

50~--------------____ ~ Count: 80s Combed

40

30

20 E ~ o o 10

30

20

10

2.7

Combing Segment With IZ:l 2 Partitions

~ 4 Partitions

3.1

M icronairc Value of Cotton

Fig.l0 -Yarn long thick faults for different types of combing segments

3.4 Quality of Yarns with 532 PPSI Flat Tops, Variable Density Cylinder Wires and Combing Segment of 4 Partitions Combed yarns of 80s and 100s counts were

produced using 3.1 micronaire cotton with (i) 532 PPSI flat tops, (ii) variable density cylinder wire in card, and (iii) combing segments of 4 partitions in comber. Total imperfections in these two yarns are found to be 305/km and 450/km respectively , which are close to international 25 % statistics level for yarn imperfections.

4 Conclusions 4.1 Nep removal efficiency (NRE) of card is maxi­mum for a flats to cylinder PPSI ratio of 60% while using 860 PPSI cylinder. At this PPSI ratio, the NRE of card is around 65% for smaller size neps and

around 85% for larger size neps with an overall NRE of 75%. Fine and super fine yarns produced using 60% PPSI ratio in card have less imperfections (30-35%) in fine and superfine counts. 4.2 Variable density cylinder wires in card reduce card sliver neps by about 35%. The reduction is relatively more (45 - 50%) in the case of larger size neps and less (30-35%) for smaller size neps. The reduction in card sliver neps with variable density cylinder wires is fully reflected in the quality of the corresponding yarns. 4.3 Variable density flat tops do not affect card sliver quality. 4.4 The use of combing segments with 4 partitions in comber produces slivers with about 25% lower neps as compared to combing segment of 2 partitions. Yarn imperfections, particularly thick places and neps, get reduced by 25-30% in fine and superfine counts while using 4-partition combing segments. Infrequent yarn fau lts measured by Classimat system also get reduced by 60% in the case of short thick places and 35-50% in the case of long thick places. 4.5 Combed yarns of 80s and 100s counts produced using 532 PPSI flat tops in card, variable density cyl­inder wires and combing segment of 4 partitions are found to have imperfections matching with interna­tional 25% statistics level.

Acknowledgement The authors are thankful to Mr. V J Kumar and Mr.

M K Vittopa of Spinning Division, SITRA, for conducting the trials.

References 1 Chellamani K P, Chattopadhyay D & Thanabal Y, Asian Texf

J, 8 (1999) 120.

2 Kluka A, Matusiak M & Frydrych I, Yam neppiness - Influ· ence of raw mare rial qualify and process fechnology, paper presented at the International Cotton Conference, Bremen , Germany, 11 - 14 March 1998.

3 Farber C, The significance of AFIS nep and frash panicle count in defermining impeifection levels of callan yarns, paper presented at the International Cotton Conference, Bremen, Ger­many , 6-9 March 1996.

4 Kanai H, Yaggu K, Etsuya K, Shiomu T, Taoka S & Ho­sakawa J, J Text Mach Soc Japan , 47 (1994) 84.