Indian Journal of Fibre & Textile Research Vol. 29, March 2004, pp. 39-43

Optimization of speed frmne process paraIneters for better yarn quality and production

S M ishtiaquc", R S Rcngasamy & A Ghosh

Department o f Tex til e Techno logy, Indian Institute of Technology, New Delhi 110 016. India

Received 3 April 2003; accepted 16 Jlllle 2003

The innuence of nyer speed, top roller pressure and size of middle condenser in the drafting reg ion o n v:Jrious characteristics of rov ing and ya rn has been studied. The 130x and Behnken factorial design h:JS been used to opti mi ze these speed fram e m:Jchine variables. In each case, the optimum conditi ons within the industrially acceptable limits of the process are establi shed. It is observcd that the n yer spccd higher than 1040 rpm and the top roller pressure hi ghe r Ihan 2.2 kg/c m~ are not suitable wi thin the ex perime ntal zone ex plored. The optimum middle condenser wid th is fou nd to be 8 mm with the present experimental set-up.

Keywords: Conde nser width , Cotlon, Factorial design , Flycr spccd , Top ro ller pressure IPC Code: Int. C I7 D02G 3/00

1 Introduction It is a recognized fac t that more than 60% of world

yarn production is currently done by ring spinning method. An important machine involved in this method continues to be the speed frame. It is desirable to produce high quality roving at high production rate under flexible processing conditions. This can be achieved by means of process optimization in speed frame.

The literature hardly reports any study regarding the optimization of speed frame parameters. In the present work, an attempt has been made to optimize speed frame process parameters, viz. flyer speed, top roller pressure and size of middle condenser by using Box and Bhenken factorial design I. These factors have been exclusively selected as they influence the machine productivity to a greater extent than other factors, viz. draft distribution and roller setting.

2 Materials and Methods

2.1 Preparation of Samples

The Sankar-6 cotton was processed on a modern Rieter blow room line and Rieter C-4 card. The carded slivers were given two passages through sliver lap former and ribbon lap former and then processed on Rieter E7/5 comber. The combed slivers were

"To whom all the correspondence should be addressed. Phone: 26591410; Fax: +91-11-26581103; E-mai l: inshtiaque54@ hotmail.com

drawn on a Rieter RSI3-8S1 draw frame to produce finisher slivers of 0.12s Ne. As per as the factoria l design (Table 1), the 15 rovings with 0.9s Ne and 1.34 twi st multiplier were prepared on Lakshmi LF l400A speed frame. The actual levels of variables are given in Table 2. To study the different yarn properties, each roving sample was spun into a 30s Ne yarn with 3.79 twi st multipli er on Lakshmi LG/5 ring frame. The yarn samples were tested for various properties.

2.2 Testing of Samples

The Uster tester 3 was ll sed to measure the evenness of roving and yarn, yarn imperfections and

Table I-Box and l3ehnken design for three variables

Expt. Level of variables No X I .1'2 X,

I -I -I 0 2 - I I 0 3 -I 0 4 I 0 5 - I 0 -I 6 -I 0 7 0 - I 8 I 0 I 9 0 -I - [ 10 0 -I II 0 - I 12 0 I I 13 0 0 0 14 0 0 0 15 0 0 0

40 INDIAN J. FIBRE TEXT. RES ., MARCH 2004

hairiness index. The yarn samples were tested on the Uster Tensorapid 3 for yarn tenacity and elongation-at-break. Starting from the initia l doff to full doff the total breakage was observed for each run of the samples in speed frame. The breakage rate was calculated as number of roving breaksll 00 spindle / h.

3 Resul ts and Discussion Experimental results for all the 15 samples are

given in Table 3. The response surface equation for various roving and yarn characteristics as well as roving breakage rate are g iven in Table 4 along with the square of correlation coefficients between the ex perimental values and the calculated values obtained from the response-surface equations. The experimental results have been explained with respect

Table 2-Actual levels corresponding to coded levels

Variable

Flyer speed (XI)' rpm

Top roller pressure (xz). kg I cmz

Middl e condenser width (x, ), mill

Coded level - I 0 +1

900

1.9

8

1040

2 .2

II

11 80

2.5

14

to the experimental zone considered within the industrially acceptable limits of each process variable.

3.1 Roving Irregularity

Figure 1 shows the influence of flyer speed and condenser width on roving in-egu l

ISHTIAQUE et al.: OPTIMIZATION OF SPEED FRAME PROCESS PARAMETERS 41

the fibre ribbon becomes too large and as a consequence inter-fibre frictional contacts decrease. This drastically reduces the extent of friction field s of the back and front beard fibres in a drafting zone, leaving a long uncontrolled region of fibres. As a result, the drafting irregularity arises, leading to higher value of U%. Whereas, as the top roller pressure increases, the roving U% initially decreases

11. (b)

E E

w N

Vl

Ct:: W Vl

8 z w 900 10'0 1180 0 z 0 u

F LYE R S PEE D I rpm)

Fig. I-Effect of flyer speed and condenser size on ' rov ing irregularity [Top roller pressure: (a) 1.9 kg/cm1, (b) 2.2 kg/c l112, and (c) 2.5 kg/crn2]

and then increases. The initi al increase in top roller pressure narrows down the gap between the pressure fields of back and front beard of fibres and exerts better control over the fibres, resulting in good consolidation and hence controlled fibre movement in the drafting zone. This leads to reduction in roving U%. At high top roller pressure, there may be overlapping between the back and front pressure fields in the main drafting zone4 , which hinders the smooth and proper fibre motion, thereby resulting in higher roving U%.

3.2 Roving Breakage Rate Figure 2 shows the influence of flyer speed,

condenser width and top roller pressure on roving breakage rate. It is appreciated that as the flyer speed increases the roving breakage increases continuously but it reduces with lowering the condenser size. As the flyer speed increases, the roving force in conjunctions with the friction condition in the fl yer leg increases, which is responsible for more breakage of roving. The decrease in condenser size restricts the ribbon width at front roller nip, so that the edge fibres remain on the main body of the roving. Also, the compactness of the drafted ribbon ensures more strength of roving. Thus, the breakage rate with the use of nalTOW condenser reduces. The increase in top roller pressure first reduces and then increases the roving breakage rate .

3.3 Yarn Irregularity From the R2 value of yarn U%, it can be concluded

that the selected independent variables do not influence yarn U% significantly . Generally, the changes in roving U% result in yarn U%, however the present study shows an exception in this regard, which may be due to the experimental set up.

3.4 Yarn Imperfections Figure 3 shows the influence of flyer speed,

condenser width and top roller pressure on the yarn imperfections. The yarn imperfections decrease with the increase in flyer speed up to -1000 rpm and then increase with the further increase in flyer speed. This could probably be due to the fact that as the flyer speed increases, the drafting speed also increases to keep the roving twist constant. Floating fibres are more likely to take up intermediate speed at higher drafting velocities than at low drafting speed due to the increase in the ratio of dynamic frictional force to static frictional force. The probabi lity of floating fibre moving at intermediate velocities increases with the

42 INDIAN J. FIBRE TEXT. RES. , MARCH 2004

velocity of rollers5. On that bas is, Taylor6 suggested that the intermediate velocities of the fibres in a drafting zone help to shuffle or randomize fibres as the speed increases, which would produce better quality roving and the imperfec tions at yarn stage decrease. But with the further increase in fl yer speed, the shearing action of the roving with the fl yer eye

E E

11 w N

Vl

a: w Vl z w 8 0 900 z 0 11. u

FLYER SPEED (rpm)

Fig. 2-Effect of fl yer speed and condenser, size on rovinf breakage rate [Top ro ller pressure: (a) 1.9 kg/c m-, (b) 2.2 kg/cm-, and (c) 2.5 kg/cm2j

increases and air-drag on the roving in the fl yer leg also increases. This leads to fallout of some fibres from the roving. These factors are responsible fo r the ill1crease in yarn imperfections. Yarn imperfec ti ons diecrease with the decrease in condenser size. The top ro ller pressure has similar infl uence on the yarn imperfections like roving irregularity.

E E

w N

Vl

a:: w Vl z w 0 z 0

11.

u

FLYER SPEED (rpm)

Fio. 3-Effect of fl yer speed and condenser size on yam '" ,0 imperfec tions [Top ro ller pressure: (a) 1.9 kg/c m-, (b) 2.2 kg/em-, and (e) 2.5 kg/cm2] .

ISHTIAQUE et al.: OPTIMIZATION OF SPEED FRAME PROCESS PARAMETERS 43

11.

E E

w ~ Vl

a:: 11 w

Vl Z W £:)

Z 0 U

S 900 1180

FLYER (rpm)

Fig. 4--Contours for yarn tenacity

3.5 Yarn Hairiness Index Yarn hairiness does not change appreciably by

changing the speed frame process variables. This clearly shows that the yarn hairiness and its generation for a given fibre type are governed, to a large extent, by the ring frame process parameters and machine condition.

3.6 Yarn Tenacity The response-surface equation for yarn tenacity

(Table 4) indicates that the top roller pressure has no significant influence on yarn strength. The contours of yarn tenacity are shown in Fig. 4 and it can be concluded that yarn tenacity increases with the decrease in condenser size. Thi s arises due to the compactness of fibres by using narrow condenser. However, with the increase in flyer speed the yarn tenacity initially decreases and then increases. The improvement of yarn tenacity at higher flyer speed can be explained on the basis of the fact that at higher flyer speeds, the roving tension increases and this helps for straightening out of fibres as they emerge from the front roller nip , thereby improving the mean fibre extent. This may also help to increase the yarn strength at higher flyer speed.

3.7 Yarn Elongation-at-break Low R2 value shows poor degree of association

among the yarn breaking elongation, flyer speed, top roller pressure and condenser width.

The optimum experimental region was found by superimposing the contours of different independent variables at different levels for various properties of roving and yarn. After critically considering all these factors, the optimum values selected are: flyer speed, 1040 rpm (0 level); condenser width, 8 mm (-I level) ; and top roller pressure, 2.2 kg/cm2 (0 level).

4 Conclusions 4.1 With the increase in flyer speed, the roving U% & breakage rate increase but imperfections & yarn tenacity initially decrease and then increase. 4.2 As top roller pressure increases, the roving U%, roving breakage rate and yarn imperfections initially decrease and then increase. But top roller pressure has no significant influence on the other properties. 4.3 Lower condenser width improves most of the quality parameters but decreases roving breakage rate. 4.4 The optimum values of different variables are: flyer speed, 1040 rpm; top roller pressure, 2.2 kg/cm2; and condenser width, 8 mm.

The lower R2 values for different yarn properties with respect to speed frame process variables indicate that the yarn quality is not only governed by the roving quality but also, to the large extent, by the ring frame process parameters. Hence, the optimization of ring frame process parameters in this regard is highly essential.

References I Box G E P & Bhenken D W, Tecl1ll0llletrics, 2 (1960) 455. 2 Schulz G, Mellialld Textilber, 68 (8) (1987) E 238. 3 Bohmer I, Melliand Textilber, 73 (6) (1992) E 214. 4 Klein W, The Mallllal of Textile Technology: Vol. I - The

Techllology of Short Staple Spilllling (The Textile Institute, Manchester), 1987, 31.

5 Audivert R & Vidiella J E, Text Res J, 32 (1962) 652. 6 Taylor D S, J Textillst , 50 (1959) T-233.