CHAPTER 4 THE INFLUENCE OF CARDING VARIABLES …shodhganga.inflibnet.ac.in/bitstream/10603/29620/9/09_chapter 4.pdf · sliver hank and flat speed in order to produce card sliver with

116

CHAPTER 4

THE INFLUENCE OF CARDING VARIABLES ON

FIBRE DAMAGE AND CONFIGURATION OF SEMI-HIGH

PRODUCTION AND HIGH PRODUCTION CARDED

SLIVER PRODUCED FROM MICROFIBRES

4.1 INTRODUCTION

The purpose of this chapter is to investigate the interaction of

carding variables and to identify the optimum combinations of doffer speed,

sliver hank and flat speed in order to produce card sliver with minimum fibre

breakage. This chapter is also concerned with fibre configuration of card

sliver produced from microdenier fibres comprising modal, lyocell, polyester

and polyester-cotton blend produced on semi high production (modal) and

high production cards.

During the 60s and 70s, a great deal of work on fibre configuration

of card and draw frame slivers was carried out but most of the studies were

conducted on cotton. This chapter discusses some of the aspects such as mean

length, short fibre content and neps in the card sliver produced from

microdenier fibres as unlike cotton fibres, they are susceptible to fibre

breakage during carding. Fibre breakage assumes considerable importance as

it affects yarn strength and any investigation on the yarn structure is masked

by fibre breakage. Sliver cohesion has also been determined as it discloses

drafting force, inter fibre friction, fibre finish and hooks which are affected by

flat speed, delivery hank and doffer speed. Statistical analysis such as

117

goodness of fit, regression coefficients, ANOVA, interaction plots and

correlation coefficients were carried out for each of the response

characteristics and have been reported. Residual analysis was done for validating the models.

4.2 MATERIALS AND METHODS

The details have already been discussed in Chapter 3. The

evaluation of card sliver fibre properties produced from semi-high production

cards for mean length, short fibre content and neps per gram were done using

both Advanced Fibre Information System (AFIS) and manual Baer sorter

method as there was better correlation between the two methods. It may be

mentioned that Hwang et.al (2001), have used manual baer sorter method for

analysing the card sliver.

4.2.1 Design of Experiments

To conduct the experiments efficiently with respect to the above

mentioned variables, three levels Box-Behnken model is used for designing

the experiments optimally and to create respective response surfaces as shown

in Table 4.1. As each response is a linear function of independent variables,

so the approximating function is first order model.

Y = B0+B1X1+B2X2+B3X3+B12X1X2+B13X1X3+B23X2X3+B11X12+B22X2

2+B33X32

(4.1)

In order to obtain a more systematic understanding of these process

conditions and to establish a quantitative basis for the relationships between

the carding variables and sliver quality, response surface was employed in the

study. The objective is to develop an empirical model to guide the forth

coming research methodology on how to further improve the card sliver

118

quality and to determine the optimum values of these parameters to be used in the processing of microfibres.

The Box and Behnken (1960) has been used successfully for

material and process optimization in numerous studies including various

textile processing applications. This approach has the advantage of taking into

account the combined effects of several parameters and it uses statistical

methods to fit an empirical model to the experimental data. The use of a

model to describe the effects of the processing matters permits the

representation of the influencing parameters in a simple and systematic way

and prediction of the results of the experiments with different parameters.

Thus Box and Behnken model not only gives an overview of the processing

parameters but also their influence on each other. Further more, it helps to

obtain the surface contour of these parameters using experimental and

predicted value. These contour plots outline the processing window and point

out the direction to attain the optimum condition. A three variable factorial design was used.(Table 4.1)

Table 4.1 A three variable Box and Behnken design

Run X1 X2 X3 1 -1 -1 0 2 -1 1 0 3 1 -1 0 4 1 1 0 5 -1 0 -1 6 -1 0 1 7 1 0 -1 8 1 0 1 9 0 -1 -1 10 0 -1 1 11 0 1 -1 12 0 1 1 13 0 0 0 14 0 0 0 15 0 0 0

119

The card sliver neps, short fibre content and mean length

corresponding to different experimental runs are given in Table 4.1. Using

SYSTAT 10 package, the regression coefficient were determined. The

coefficients were tested for significance at the 95% confidence level. Only

significant terms were taken into consideration for a further investigation of

the results. The response surface equation of sliver mean fibre length as

observed through manual method is given by

29.543-0.793X1-0.383X2+0.857X3+0.522X12-0.170X1X2+0.270X1X3 (4.2)

The procedure used to optimize the carding variables for achieving optimal

performance is shown in flow chart below.

Choose Response Choose variables

Mean length Doffer speed (X1)

Short fibre content Sliver hank(X2)

Neps Flat speed(X3)

Experimental Design

Regression analysis

Development of the response surface

Contour plot of the response surface

Search for optimum operating conditions

120

The coefficient of determination (R2) between the experimental

values and the calculated values obtained from the equation was found to be

0.945. Therefore the response surface agrees fairly well with the experimental

data and the variables considered in the study have substantial influence on

the responses. Contour maps were constructed by using the regression

equation. The experimental results have been explained with respect to the

experimental zone of each process variables considered in the study.

4.3 RESULTS AND DISCUSSION

The mean test results obtained for the micro modal samples are

given in the Table 4.2.

Table 4.2 Mean test results of sliver quality for micromodal fibres

Run No X1 X2 X3

Neps Neps Mean

Length Mean

Length Short Fibre

Content Short Fibre

Content mm mm % %

AFIS Manual AFIS Manual AFIS Manual 1 -1 -1 0 7 3.4 29.4 31.05 5.31 4.47 2 1 -1 0 7.3 4.4 27.83 29.71 7.93 5.49 3 -1 1 0 8.8 5.2 28.95 30.78 6 4.67 4 1 1 0 9.3 6 27.6 28.76 8.3 6.2 5 1 0 -1 10.5 7.2 26.63 27.9 9.6 7.04 6 -1 0 -1 9.5 6.3 28.53 29.93 6.77 4.79 7 1 0 1 7.8 4 29.1 30.72 5.82 4.72 8 0 -1 -1 10.8 6.8 28.25 29.44 7.23 5.69 9 0 1 -1 10.5 6.6 27.35 28.38 8.73 6.49

10 0 -1 1 6.8 3.4 28.53 30.45 6.77 4.92 11 0 1 1 7.2 4.5 28.05 29.67 7.52 5.52 12 -1 0 1 6.5 2.6 29.73 31.67 4.77 4.03 13 0 0 0 8 5.2 28 29.47 7.5 5.69 14 0 0 0 8.3 5.6 28.2 29.72 7.3 5.66 15 0 0 0 8.3 4.8 28.13 29.67 7.6 5.6

Run Code Doffer Speed (rpm/mpm)

Delivery Hank (Ne/ktex)

Flat Speed (inch/min/mm/min)

X1 X2 X3 1 9/19.2 0.155/3.16 6/152.4 0 7.5/16 0.17/3.47 4/101.6 -1 6/12.8 0.185/3.19 2/50.8

121

Using software such as SYSTAT, subsequent to feeding of all the main results of fifteen runs for each response (quality parameters), the coefficients of response surface polynomial second order equation given below is derived along with the regression coefficient (R2)

Y= B0+B1X1+B2X2+B3X3+B12X1X2+B13X1X3+B23X2X3+B11X12+B22X2

2+B33X32

(4.3)

The polynomial equation and regression constant found are tabulated in Table 4.3 It is interesting to note that R2 shows an increase in manual testing in all the cases as compared with AFIS tester, for the responses considered. This shows the creditability of the manual method and justifies its use as pointed out by Hwang et al (2001).

Table 4.3 Quadratic Equations and Regression Constants for Micromodal

Responses (Y) Testing Quadratic Equation Cor.Coefficient-

R2 Neps Per

Gram AFIS 8.246+0.387X1+0.488X2-1.625X3-0.181X1

2+0.544X32+0.175X2X3

0.914

Neps Per Gram Manual 5.154+0.513X1+0.538X2-1.550X3-0.369X1

2

+0.206X32+0.125X3X1+0.325X2X3

0.946

Mean Length AFIS 28.073-0.681X1-0.257X2+0.581X3

+0.398X12+0.318X3X1+0.105X3X2

0.886

Mean Length Manual 29.543-0.793X1-0.383X2+0.857X3+0.522X1

2-0.170X1X2+0.270X1X3

0.945

Short Fibre Content AFIS 7.521+1.1X1+0.414X2-0.931X3-0.709X1

2-0.445X3X1-0.187X3X2

0.891

Short Fibre Content Manual 5.653+0.686X1+0.298X2-0.603X3-

0.477X12+0.128X2X1-0.390X1X3

0.968

4.4 EFFECT OF PROCESS PARAMETERS ON NEPS PER

GRAM OF MICROMODAL FIBRES

Figures 4.1a, 4.1b to 4.3a, 4.3b show the contour graphs obtained

for mean length at various conditions.

122

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

7

8

9

neps at doff 6

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

7

8

9

10

neps at 7.5

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

7 8

9

10

neps at doff 9

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

4

6

neps at doff 6

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

4

6

neps at doff 7.5

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

4

6

neps at doff 9

(a) AFIS Testing (b) Manual Testing

Figure 4.1 Contour plots for Neps per gram at different doffer speeds

6 rp

m

7.5

rpm

9 rp

m

123

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

7

8

9

10

neps at hank 0.185

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

7

8

9

10

neps at hank 0.17

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

8

9

10

neps at hank 0.155

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

4

6

neps at hank 0.185

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

4

6

neps at hank 0.17

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

4

6

neps at hank 0.155

(a) AFIS testing (b) Manual testing

Figure 4.2 Contour plots for neps per gram at different delivery hanks

0.18

5 N

e 0.

17 N

e 0.

155

Ne

124


Figure 4.3 Contour plots for neps per gram at different flat speeds

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

10

neps at flat 2

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

8

neps at flat 4

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

7

neps at flat 6

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

han

k

flat 2

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

han

k

4

flat 4

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

han

k

4

6

flat 6

2 in

/min

4

in/m

in

6 in

/min

125

The response surface contour graphs are drawn for the above

mentioned quadratic equations and the same is given in Figures 4.1a, 4.1b to

4.9a, 4.9b. The optimum process conditions towards minimizing neps per

gram and short fibre content and maximizing mean length are derived by

overlapping the contour plots to find the common area of the contour meeting

the above requirements. The common area gives the most optimum process

condition required

The effects of carding variables on neps per gram of card sliver

produced from micro modal fibres using semi high production cards are

shown in Figures 4.1a, 4.1b, 4.2a, 4.2b and 4.3a, 4.3b for both AFIS and

manual test methods.

It is apparent from Figures 4.1a and 4.1b that as the hank

becomes finer, the neps/gram shows a decrease keeping doffer

speed constant. This is a well known phenomenon as with

increasing hank, the number of fibres decreases in the cross

section of the card sliver.

Figures 4.2a and 4.2b show the relationship between doffer

speed on neps keeping hank constant. It is noticed that with

increase in doffer speed, the neps show an decrease. This is

due to the stretching of fibres at higher doffer speed which

results in reduction of neps.

Figures 4.3a and 4.3b show that doffer speed has a tendency to

increase the neps at a constant flat speed. This is due to the

fibre breakage which is likely to occur at higher doffer speed.

126

4.5 OPTIMUM PARAMETERS - NEPS PER GRAM–

MICROMODAL

The following are the optimum carding process parameter

combinations derived from the procedure explained above using contour

graphs for micromodal shown in Table 4.4.

Table 4.4 Optimum Process Conditions Derived for Neps per Gram

(Micromodal)

Doffer Speed (rpm/m/min)


Flat Speed (Inch/min/mm/min)

Neps Per

Gram (AFIS)

Neps Per Gram

(Manual)

1 Minimum 6rpm/12.8

m/min

Medium 0.170Ne/3.47ktex

Medium 4inch/min/101.6

mm/min 7.5 4

2. Minimum 6rpm/12.8

m/min


Maximum 6inch/min/152.4

mm/min 6.75 3.5

3. Maximum

19.2 (m/min) Finer

0.185Ne/3.19ktex


mm/min 7 3.5

4.6 EFFECT OF PROCESS PARAMETERS ON MEAN

LENGTH


for mean length at various conditions.

127

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

29

ml at doff 6

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

28

ml at doff 7.5

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

27

28

ml at doff 9

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

30

31

ml at doff 6

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

29

30

ml at doff 7.5

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

29

30

ml at doff 9


Figure 4.4 Contour plots for mean length at different doffer speeds

6 rp

m

7.5

rpm

9

rpm

128

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

28

29

ml at hanks 0.185

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

28

29

ml at hank 0.17

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

27

28

29

ml at hank 0.155

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

29

30

31

ml at hank 0.185

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

29

30

31

ml at hank 0.17

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

28

29

30

ml at hank 0.155


Figure 4.5 Contour plots for mean length at different delivery hanks

0.15

5 N

e 0.

170

Ne

0.18

5 N

e

129

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

27

2829

ml at flat 2

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

2829

ml at flat 4

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

29

ml at flat 6

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

28

29

30

ml at flat 2

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

29

30

ml at flat 4

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

30

31

ml at flat 6


Figure 4.6 Contour plots for mean length at different flat speeds

2 in

/min

4

in/m

in

6 in

/min

130

The effects of carding variables on mean length of card sliver

produced from micro modal fibres using semi high production cards are

shown in Figures 4.4a, 4.4b, 4.5a, 4.5b and 4.6a, 4.6b for both AFIS and

manual testing methods.

It is apparent from the Figures 4.4a, 4.4b that with increase in

delivery hank, mean length shows an increase keeping the

doffer speed constant. This is due to less number of fibres in

the sliver, the mean length tends to increase by stretching.

The effect of doffer speed on mean length shown in

Figures 4.5a, 4.5b that increasing the doffer speed has led to

an increase in the mean fibre length keeping the hank

constant. An increase in the doffer speed has the effect of

stretching the fibre and thus has led to an increase in an mean

length.

Figures 4.6a and 4.6b show that by increasing the doffer speed

has led to an decrease of mean length keeping the flat speed

constant.

4.7 OPTIMUM PARAMETERS - MEAN LENGTH –

MICROMODAL

The following are the optimum carding process parameter

combinations derived from the procedure explained earlier for mean length of

micromodal fibres shown in Table 4.5.

131

Table 4.5 Optimum process conditions derived for mean length

(Micromodal)

Doffer Speed

(rpm/m/min)

Delivery Hank

(Ne/ktex)

Flat Speed

(Inch/min/mm/min)

Mean Length (AFIS)

Mean Length

(Manual)

01. Minimum

6rpm/12.8 m/min

Medium

0.170Ne/3.47ktex

Medium

4inch/min/101.6 mm/min

29.25 mm

30.75 mm

2. Minimum

6rpm/12.8 m/min

Medium

0.170Ne/3.47ktex

Maximum


29.3 mm

31.5 mm

3. Maximum

19.2 (m/min)

Finer

0.185Ne/3.19ktex

Maximum


28.9 mm

30.7 mm

4.8 EFFECT OF PROCESS PARAMETERS ON SHORT FIBRE

CONTENT


for short fibre content at various conditions.

132

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

6

sfc at doff 6

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

8

sfc at doff 7.5

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

8

sfc at doff 9

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

Spe

ed

sfc at doff 6

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

Spe

ed

5

6

sfc at doff 7.5

-1.0 -0.5 0.0 0.5 1.0Delivery hank

-1.0

-0.5

0.0

0.5

1.0

Flat

Spe

ed

5

6

7

sfc at doff 9


Figure 4.7 Contour plots for short fibre content at different doffer speeds

6 rp

m

7.5

rpm

9 rp

m

133

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

6

8

sfc at hank 0.185

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

6

8

sfc at hank 0.17

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

spe

ed

66

8

sfc at hank 0.155

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

Spe

ed

5

6

sfc at hank 0.185

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

Spe

ed

5

6

sfc at hank 0.17

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Flat

Spe

ed

5

6

7

sfc at hank 0.155


Figure 4.8 Contour Plots for Short Fibre Content at different Delivery

Hanks

155

Ne

170

Ne

185

Ne

134

-1.0 -0.5 0.0 0.5 1.0Doffer speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

han

k

7

8

9

sfc at flat 2

-1.0 -0.5 0.0 0.5 1.0Doffer speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

han

k

6 7

8

sfc at flat 4

-1.0 -0.5 0.0 0.5 1.0Doffer speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

han

k

6

sfc at flat 6

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

5 6

7

sfc at flat 2

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

5

6

sfc at flat 4

-1.0 -0.5 0.0 0.5 1.0Doffer Speed

-1.0

-0.5

0.0

0.5

1.0

Del

iver

y ha

nk

5

sfc at flat 6


Figure 4.9 Contour plots for short fibre content at different flat speeds

2 in

/min

4

in/m

in

6 in

/min

135

Figures 4.7a and 4.7b show the relationship between delivery

hank and short fibre content keeping the doffer speed

constant. With increase in delivery hank, i.e. finer hank, the

short fibre content decreases. It was already reported that an

increase in delivery hank had led to a decrease in neps. Thus

short fibre contents and neps seem to follow the same trend.

It is apparent from the Figures 4.8a and 4.8b that as doffer

speed increases, the short fibre content decreases keeping the

hank of sliver constant. A decrease in short fibre content is

favourable for getting good quality yarn. This is due to

stretching of fibres which tends to increase in strength thereby

lowering the breakage. Also, when fibres are buckled,

stretching of fibres will increase the elongation and chances of

breakages are less. This is in agreement with findings of

Hearle, Thakur and El-Behrey (1961).

Figures 4.9a and 4.9b shows the effect of doffer speed on

short fibre content at a constant flat speed. It is clear that with

an increase in doffer speed, short fibre content tends to

increase in the card sliver. This is due to fibre breakage at

higher tensions. It is likely that when flat speed is kept

constant, the fibres are stretched by the higher doffer speed

which results in maximum fibre breakage.

4.9 OPTIMUM PARAMETERS - SHORT FIBRE CONTENT –

MICROMODAL

From the foregoing results and inferences, the following are the

optimum process condition for the micromodal processing shown in

Table 4.6.

136

Table 4.6 Optimum process conditions derived for short fibre content

(micromodal)

Doffer Speed

(rpm/m/min)


Flat Speed (Inch/min/mm/min)

Short Fibre

Content (AFIS)

Short Fibre

Content (Manual)


m/min


Medium 4inch/min/101.6

mm/min 5.75% 4.5%


m/min



mm/min 5.5% 4.25%

3. Maximum

19.2 (m/min) Finer

0.185Ne/3.19ktex


mm/min 6.5% 4.5%

4.10 HIGH PRODUCTION CARDS

The results of the high production cards are discussed below.

Table 4.7 Results of statistical analysis for mean length of

micromodal, microlyocell, micropolyester and polyester-cotton blend in high

production cards.

137

Table 4.7 The effect of carding variables on mean fibre length and short

fibre content in respect of microfibres

Character Correlation coefficient

(r) Distribution Fit

Measurement

Parameter

Process

Analysis

Method

R- sq %

Process Effect(P value)

Interaction

Optimum

Doffer Hank Flat Doffer( Hank Flat

Micromodal -0.23 Normal AD =0.351

P=0.451

General Linear model-26.79%

0.639 0.421 0.958 160 0.18 12

Microlyocell -0.790 Jhonson SB

=-0.22874

=0.90557 =2.0097

=30.913

Regression-6%

0.477 0.865 0.721 160 0.2 12

Micropolyester -0.470 Cauchy =0.21125 =35.481

Regresion-44%

0.022 0.326 0.497 160 0.18 10

Polyester-Cotton blend

(65:35) -0.52 Gen. Extreme Value

k=-0.52028

=0.54031 =32.502

Regression-39.5%

0.083 0.098 0.611 160 0.18 12

4.11 THE EFFECT OF CARDING VARIABLES ON MEAN

FIBRE LENGTH AND SHORT FIBRE CONTENT IN

RESPECT OF MICROFIBRES

4.11.1 Micromodal

The results for the mean length of micromodal, micro lyocell,

micro polyester and polyester-cotton blend are tabulated in Table no 4.7. It is

clear that the mean length of micro modal follows normal distribution while

micro lyocell follows Johnson SB distribution, Micro polyester follows

Cauchy, while polyester cotton blend follows Weibull distribution. The

characteristic parameters related to these distributions are also given in Table

no 4.7. An analysis of variance (ANOVA) was conducted to find the effect of

carding variables on the mean length of fibre in card sliver. It is noticed that

from table 4.7 none of these variables has any impact on mean length

138

(P>0.05). The correlation between short fibre content and mean length is poor

(r = -0.23). Figure 4.10 shows the frequency distribution for mean length of

micromodal fibres. Figures 4.11 and 4.12 show the residual plots and

interaction plots for mean length of micromodal fibres.

Mean Length (mm)

Freq

uenc

y

31.831.631.431.231.030.830.630.4

4

3

2

1

0

Micromodal Mean Length (Avg)

Figure 4.10 Histogram for mean length of micromodal

Residual

Per

cent

1.00.50.0-0.5-1.0

99

90

50

10

1

Fitted Value

Res

idua

l

31.631.431.231.0

0.50

0.25

0.00

-0.25

-0.50

Residual

Freq

uenc

y

0.60.40.20.0-0.2-0.4-0.6

6.0

4.5

3.0

1.5

0.0

Observation Order

Res

idua

l

151413121110987654321

0.50

0.25

0.00

-0.25

-0.50

Normal Probability Plot of the Residuals Residuals Versus the Fitted Values

Histogram of the Residuals Residuals Versus the Order of the Data

Residual Plots for Micromodal Avg-GLM

Figure 4.11 Residual plots for mean length of micromodal

139

Doffer Speed MP M_1

31.5

31.0

30.5

Hank Ne_1

Flat Speed Inc/mint_1

141210

0.220.200.18

31.5

31.0

30.5

160140120

31.5

31.0

30.5

Doffer

160

SpeedMPM_1

120140

Hank

0.22

Ne_10.180.20

Flat Speed

14

Inc/mint_11012

Micromodal-ML-Average

Figure 4.12 Interaction plot for mean length Vs carding variables of

micromodal

Examination of the residuals should be an automatic part of any analysis of variance (ANOVA). If the model is adequate, they should be structureless; that is, the residuals should contain no obvious pattern. Through a study of residuals, many types of model inadequacies and violations of the underlying assumptions can be discovered. Model adequacy checking usually consists of plotting the residuals. It is helpful to examine a normal probability plot, a plot of residuals versus fitted values and a plot of residuals versus each regression variables. If there are variables not included in the model that are of potential interest, then the residuals should be plotted against these omitted factors. Any structure in such a plot would indicate that the model could be improved by the addition of that factor. Krifa (2008) has discussed the fibre length distribution in cotton processing by a finite mixture models; this was used to derive a parametric expression of the fibre length probability density function. The model was applied to a multitude of empirical length distribution which proved to adequately parameterize the complex distribution patterns as well as express the intrinsic and process related factors determining their shape.

Mea

n le

ngth

(mm

)

140

4.11.2 Microlyocell

The results obtained in respect of microlyocell fibre in carding are

given in Table 4.6. It may be seen that the chosen levels of carding variables

do not have any effect on mean length. However, the correlation between

mean length and micro lyocell is good (r= -790) and significant. Based on the

trend obtained between the carding variables and mean length, the optimum

carding parameters for achieving maximum mean length are reported.

Figure 4.13 show the probability density function of microlyocell fibres.

Figure 4.14 shows the frequency distribution for mean length of microlyocell

fibres. Figures 4.15 and 4.16 show the residual plots and interaction plots for

mean length of microlyocell fibres. This information will be of useful to the

user industry.

Probability Density Function

Histogram Johnson SB

x3332.832.632.432.23231.831.631.431.231

f(x)

0.36

0.32

0.28

0.24

0.2

0.16

0.12

0.08

0.04

0

-0.04

Figure 4.13 Probability density function of microlyocell fibres for mean

length

Prob

abili

ty f(

x)

Mean length (mm)

141

Parameters

- shape parameter

- shape parameter ( )

- scale parameter ( )

- location parameter

Domain

Probability Density Function (PDF)

(4.4)

where

Mean Length (mm)

Freq

uenc

y

32.832.432.031.631.2

3.0

2.5

2.0

1.5

1.0

0.5

0.0

MicroLyocell Mean Length (Avg)

Figure 4.14 Histogram for mean length of microlyocell

142

Residual

Per

cent

1.00.50.0-0.5-1.0

99

90

50

10

1

Fitted Value

Res

idua

l

32.232.132.031.931.8

1.0

0.5

0.0

-0.5

Residual

Freq

uenc

y

0.80.40.0-0.4-0.8

3

2

1

0

Observation Order

Res

idua

l

151413121110987654321

1.0

0.5

0.0

-0.5



Residual Plots for Microlyocell Avg

Figure 4.15 Residual Plots for mean length of microlyocell

Doffer speed(mpm)

32.5

32.0

31.5

Sliver hank(Ne)

Flat speed(inch/min)

141210

0.220.200.18

32.5

32.0

31.5

160140120

32.5

32.0

31.5

Doffer

160

speed(mpm)120140

Sliver

0.22

hank(Ne)0.180.20

Flat speed(inch/min)

14

1012

Interaction Plot -Mean length-for Microlyocell Avg

Figure 4.16 Interaction Plots for mean length

Mea

n le

ngth

(mm

)

143

4.11.3 Micropolyester

In this case, the Cauchy gives the best distribution and the

characteristic values are given. The correlation between short fibre content

and mean length is very low (r = - 0.47) and the carding variables have no

effect on mean length. From the interaction plot shown in Figure 4.20 the

optimum values for the carding variables were selected and reported. The

results will be of immense use to the spinners. Figure 4.17 shows the

probability density function of micropolyester fibres for mean length. Figure

4.18 shows the frequency distribution for mean length of microlyocell fibres.

Figures 4.19 and 4.20 show the residual plots and interaction plots for mean

length of micropolyester fibres.


Histogram Cauchy

x504540353025

f(x)

2

1.6

1.2

0.8

0.4

0

-0.4

-0.8

-1.2

Figure 4.17 Probability density function of micropolyester for mean

length

Prob

abili

ty (f

(x)

Mean length (mm)

144

Cauchy distribution is

(4.5)

where t is the location parameter and s is the scale parameter. The case where

t = 0 and s = 1 is called the standard Cauchy distribution. The equation for

the standard Cauchy distribution reduces to

(4.6)

Since the general form of probability functions can be expressed in

terms of the standard distribution, all subsequent formulas in this section are

given for the standard form of the function.

Mean length (mm)

Freq

uenc

y

38373635343332

7

6

5

4

3

2

1

0

Micropolyester-Meanlength-Average

Figure 4.18 Histogram for mean length of micropolyester

145

Residual

Per

cent

210-1-2

99

90

50

10

1

Fitted Value

Res

idua

l

37363534

2

1

0

-1

-2

Residual

Freq

uenc

y

1.51.00.50.0-0.5-1.0-1.5-2.0

4.8

3.6

2.4

1.2

0.0

Observation Order

Res

idua

l

151413121110987654321

2

1

0

-1

-2



Residual Plots for Micropolyester Avg

Figure 4.19 Residual Plots for mean length of micropolyester

Doffer Speed MP M_1

37.0

34.5

32.0

Hank Ne_1


141210

0.220.200.18

37.0

34.5

32.0

160140120

37.0

34.5

32.0

Doffer

160

SpeedMPM_1

120140

Hank

0.22

Ne_10.180.20

Flat Speed

14

Inc/mint_11012

Micropolyester-Average-Interaction plot

Figure 4.20 Interaction Plots for mean length of micropolyester

4.11.4 Polyester Cotton Blend

The data on mean length follow Weibull distribution and the scale

parameters closely follow the mean length. The correlation between short

fibre content and mean length is not satisfactory (r = -0.52). The optimum

carding variables were taken from the interaction plot for getting the optimum

Mea

n le

ngth

(mm

)

146

mean length and are reported. Figure 4.21 show the probability density

function of polyester cotton blend for mean length. Figure 4.22 shows the

frequency distribution for mean length of micropolyester-cotton blend.

Figures 4.23 and 4.24 show the residual plots and interaction plots for mean

length of micropolyester-cotton blend.


Histogram Gen. Extreme Value

x33.433.23332.832.632.432.23231.831.6

f(x)

0.48

0.44

0.4

0.36

0.32

0.28

0.24

0.2

0.16

0.12

0.08

0.04

0

-0.04

Figure 4.21 Probability density function of micropolyester cotton blend

for mean length

The general formula for the probability density function of the

Gumbel (minimum) distribution is

(4.7)

Prob

abili

ty f(

x)

Mean length (mm)

147

where is the location parameter and is the scale parameter. The case where

= 0 and = 1 is called the standard Gumbel distribution. The equation for

the standard Gumbel distribution (minimum) reduces to

(4.8)

P/C Blend Avg

Freq

uenc

y

33.2533.0032.7532.5032.2532.0031.75

4

3

2

1

0

P/C blend-Average

Figure 4.22 Histogram for mean length of micropolyester-cotton blend

Residual

Per

cent

1.00.50.0-0.5-1.0

99

90

50

10

1

Fitted Value

Res

idua

l

33.0032.7532.5032.2532.00

1.0

0.5

0.0

-0.5

Residual

Freq

uenc

y

0.750.500.250.00-0.25-0.50

4.8

3.6

2.4

1.2

0.0

Observation Order

Res

idua

l

151413121110987654321

1.0

0.5

0.0

-0.5



Residual Plots for P/C Blend Avg

Figure 4.23 Plots for mean length of micropolyester-cotton blend

148

Doffer Speed MP M_1

33.0

32.5

32.0

Hank Ne_1


141210

0.220.200.18

33.0

32.5

32.0

160140120

33.0

32.5

32.0

Doffer

160

SpeedMPM_1

120140

Hank

0.22

Ne_10.180.20

Flat Speed

14

Inc/mint_11012

P/C blend-Average-Interaction plot

Figure 4.24 Plots for mean length of micropolyester-cotton blend

4.12 NEPS ANALYSIS

The results of effect of carding variables on neps are discussed

below.

4.12.1 Micromodal

The results of the statistical analysis of the card sliver neps obtained

with carding variables are given Table 4.8. It is interesting to note that for

micro modal D.Uniform distribution is found to follow, while the data fit

Poisson distribution in respect of microlyocell and micropolyester samples.

With regard to polyester-cotton blend, negative binomial distribution has been

found to follow. Generally neps in card sliver follow Poisson distribution. An

analysis of variance tests conducted shows that the chosen level of carding

variables have any significant effect on neps. The relationship between

carding variables and neps as seen from the interaction plots shows different

runs and from these, the optimum values are extracted and reported.Figure

4.25 show the probability density function of micromodal fibres for neps.

Mea

n le

ngth

(mm

)

149

Figure 4.26. illustrates the frequency distribution of neps for micro modal

fibres. Figures 4.27 and 4.28 shows the residual and interaction plots for neps

per gram of micromodal fibres.

Table 4.8 Results of statistical analysis for neps/gram of micromodal,

microlyocell, micropolyester and polyester-cotton blend in

high production cards

Character Distribution Fit

Measurement Parameter

Process Analysis Method

(Regression) R- sq %

Process Effect (P value)

Interaction Optimum

Doffer speed

Hank Flat speed

Doffer speed

Hank Flat speed

Micromodal D. Uniform a=0 b=7 R-Sq = 17.6%

0.386 0.769 0.254 160 0.2 10

Microlyocell Poisson =7.8 R-Sq = 4.1% 0.662 0.802 0.662 160 0.22 12

Micropolyester Poisson =6.0667 R-Sq = 11.0%

0.417 0.758 0.476 160 0.18 10

Polyester-Cotton blend

Neg. Binomial n=6

p=0.40607 R-Sq = 29.6%

0.329 0.095 0.620 160 0.18 12


Sample D. Uniform

x6543210

f(x)

0.28

0.26

0.24

0.22

0.2

0.18

0.16

0.14

0.12

0.1

0.08

0.06

0.04

0.02

0

Figure 4.25 Probability density function of micromodal for neps

Prob

abili

ty f

(x)

Neps

150

The general formula for the probability density function of the

uniform distribution is

(4.9)

where A is the location parameter and (B - A) is the scale parameter. The case

where A = 0 and B = 1 is called the standard uniform distribution. The

equation for the standard uniform distribution is

(4.10)

Neps/gram

Freq

uenc

y

6543210

4

3

2

1

0

Neps-Micromodal-Average

Figure 4.26 Histogram for neps per gram of micromodal

151

Residual

Per

cent

5.02.50.0-2.5-5.0

99

90

50

10

1

Fitted Value

Res

idua

l

54321

2

0

-2

-4

Residual

Freq

uenc

y

3210-1-2-3-4

6.0

4.5

3.0

1.5

0.0

Observation Order

Res

idua

l

151413121110987654321

2

0

-2

-4



Residual Plots for Micromodal(Average)

Figure 4.27 Residual Plots for neps per gram of micromodal

Doffer Speed MP M_1

5.0

2.5

0.0

Hank Ne_1


141210

0.220.200.18

5.0

2.5

0.0

160140120

5.0

2.5

0.0

Doffer

160

SpeedMPM_1

120140

Hank

0.22

Ne_10.180.20

Flat Speed

14

Inc/mint_11012

Micromodal-Neps-Interaction-Average

Figure 4.28 Plots for neps per gram of micromodal

Nep

s

152

4.12.2 Microlyocell

The results of micro lyocell fibres show that the chosen level of

carding variables have no influence on neps. The optimum carding parameters

for getting a lower value of neps are extracted from the interaction plot

diagrams and reported. It is found that the neps are high in microlyocell in

comparison to micromodal fibres which may be due to the susceptibility of

fibrillation of microlyocell fibres. Figure 4.29 gives the probability density

function of microlyocell fibres for neps. Figure 4.30 gives the frequency

distribution for neps for micro modal fibres. Figures 4.31 and 4.32 show the

residual and interaction plots for neps per gram of microlyocell fibres.


Sample Poisson

x1816141210864

f(x)

0.22

0.2

0.18

0.16

0.14

0.12

0.1

0.08

0.06

0.04

0.02

0

Figure 4.29 Probability density function of microlyocell for neps

The Poisson distribution is used to model the number of events

occurring within a given time interval.

The formula for the Poisson probability mass function is

(4.11)

Prob

abili

ty f

(x)

Neps

153

is the shape parameter which indicates the average number of

events in the given time interval.

Neps/gram

Freq

uenc

y

1816141210864

5

4

3

2

1

0

Neps-Microlyocell-Average

Figure 4.30 Histogram for neps per gram of microlyocell

Residual

Per

cent

1050-5-10

99

90

50

10

1

Fitted Value

Res

idua

l

109876

10

5

0

-5

Residual

Freq

uenc

y

10.07.55.02.50.0-2.5-5.0

4.8

3.6

2.4

1.2

0.0

Observation Order

Res

idua

l

151413121110987654321

10

5

0

-5



Residual Plots for Microlyocell(Average)

Figure 4.31 Residual Plots for neps per gram of micromodal

154

Doffer Speed MPM_1

15

10

5

Hank Ne_1


141210

0.220.200.18

15

10

5

160140120

15

10

5

Doffer

160

SpeedMPM_1

120140

Hank

0.22

Ne_10.180.20

Flat Speed

14

Inc/mint_11012

Microlyocell-Neps-Interaction-Average

Figure 4.32 Interaction plots for neps per gram of micromodal

4.12.3 Micro Polyester

Data of neps in this class follow Poisson distribution which is well

known. It is interesting to note that neps are low in comparison with

microlyocell fibres. The carding variables for optimum nep count as inferred

from the interaction plot diagrams are reported. Figure 4.33 shows the

probability density function of micropolyester for neps. Figure 4.34 gives the

frequency distribution for neps. for micro modal fibres. Figures 4.35 and 4.36

give the residual and interaction plots for neps per gram of micro polyester

fibres.

Nep

s

155


Sample Poisson

x1312111098765432

f(x)

0.22

0.2

0.18

0.16

0.14

0.12

0.1

0.08

0.06

0.04

0.02

0

Figure 4.33 Probability density function of micropolyester for neps

Neps/gram

Freq

uenc

y

1412108642

6

5

4

3

2

1

0

Neps-MicropolyesterAverage

Figure 4.34 Histogram for neps per gram of micropolyester

Prob

abili

ty f(

x)

Neps

156

Residual

Per

cent

840-4-8

99

90

50

10

1

Fitted Value

Res

idua

l

87654

5.0

2.5

0.0

-2.5

-5.0

Residual

Freq

uenc

y

6420-2-4

6.0

4.5

3.0

1.5

0.0

Observation Order

Res

idua

l

151413121110987654321

5.0

2.5

0.0

-2.5

-5.0



Residual Plots for Micropolyester(Average)

Figure 4.35 Residual Plots for neps per gram of micropolyester

Doffer Speed MPM_1

12

8

4

Hank Ne_1


141210

0.220.200.18

12

8

4

160140120

12

8

4

Doffer

160

SpeedMPM_1

120140

Hank

0.22

Ne_10.180.20

Flat Speed

14

Inc/mint_11012

Micropolyester-Neps-Average

Figure 4.36 Interaction plots for neps per gram of micropolyester

Nep

s

157

4.12.4 Polyester Cotton Blends

Data on this class seem to follow Weibull distribution . In this case

the neps are found to be high obviously due to cotton which is blended with

polyester. Here also the chosen level of carding variables do not affect the nep

level in the card sliver. Optimum carding parameters for obtaining lower nep

level for this class of microfibres are reported. Figure 4.37 gives the

probability density function of polyester cotton blends for neps. Figure 4.38

gives the frequency distribution for neps. for micro modal fibres. Figures 4.39

and 4.40 show the and interaction plots for neps per gram of micropolyester-

cotton blends.


Sample Neg. Binomial

x22201816141210864

f(x)

0.28

0.26

0.24

0.22

0.2

0.18

0.16

0.14

0.12

0.1

0.08

0.06

0.04

0.02

Figure 4.37 Probability density function of polyester cotton blends for

neps

Prob

abili

ty f

(x)

Neps

158

Neps/gram

Freq

uenc

y

22.520.017.515.012.510.07.55.0

4

3

2

1

0

Neps-PC blend-Average

Figure 4.38 Histogram for neps per gram of micropolyester-cotton blend

Residual

Per

cent

1050-5-10

99

90

50

10

1

Fitted Value

Res

idua

l

15.012.510.07.55.0

10

5

0

-5

Residual

Freq

uenc

y

10.07.55.02.50.0-2.5-5.0

4

3

2

1

0

Observation Order

Res

idua

l

151413121110987654321

10

5

0

-5



Residual Plots for P/C blend(Average)

Figure 4.39 Residual Plots for neps per gram of micropolyester-cotton

blend

159

Doffer Speed MPM_1

24

16

8

Hank Ne_1


141210

0.220.200.18

24

16

8

160140120

24

16

8

Doffer

160

SpeedMPM_1

120140

Hank

0.22

Ne_10.180.20

Flat Speed

14

Inc/mint_11012

PC blend-Neps-Average

Figure 4.40 Interaction plots for neps per gram of micropolyester-cotton

blend

4.13 STUDY OF FIBRE CONFIGURATION IN CARD SLIVER

PRODUCED FROM MICROFIBRES IN HIGH

PRODUCTION CARDS

The effect of carding delivery speed on cutting ratio, combing ratio,

and orientation index for micromodal, microlyocell, micropolyester and

micropolyester-cotton blends in forward and backward directions are shown

in Table 4.9 and discussed below.

4.14 EFFECT OF DOFFER SPEED ON FIBRE HOOKS

The effect of delivery speed on fibre hooks for various microfibres

is discussed below.

Nep

s

160

4.14.1 Micromodal Fibres

The results of combing ratio, cutting ratio and orientation index for

different doffer speeds in forward and backward directions processed in a

high production card are given in Table 4.10. It is apparent that combing ratio

values remain unchanged in forward and backward directions. While cutting

ratio show an increase with increase in doffer speed in the forward direction,

no change is noticed in the backward direction. Fibre orientation index is

found to be higher in backward direction than the forward direction but the doffer speed has no effect on it.

Table 4.9 Effect of carding delivery speed on cutting ratio,combing ratio, and orientation index for micromodal, microlyocell, micropolyester and micropolyester-cotton blends in forward and backward directions

Fibre Micromodal Microlyocell Micro polyester P/C blend

Fibre fineness

(dtex) 1 1 0.9 0.9

Sliver Hank (Ne)

0.20

Fibre length(mm)

34 34 38 38

Carding delivery

speed(mpm) 120 160 120 160 120 160 120 160 120 160 120 160 120 160 120 160

Direction F F R R F F R R F F R R F F R R

Combing ratio 0.74* 0.72 0.76* 0.71 0.74 0.73 0.75* 0.72 0.85* 0.74 0.71 0.75* 0.7 0.8* 0.74 0.76*

Cutting ratio 0.075 0.092 0.067 0.06 0.1 0.08 0.12 0.05 0.09 0.09 0.10 0.05 0.12 0.09 0.06 0.08

Orientation index

92.4 91 93.3 93.7 90 91.1 87.7 94.8 91 90.7 89.5 94.6 87.4 90 93.1 91.8

* Indicates statistical significance

161

Table 4.10 Effect of carding delivery speed on cutting ratio, combing

ratio and orientation index for micromodal fibres

Fibre Micromodal Fibre fineness(dtex) 1

Sliver hank (Ne) 0.200 Fibre length (mm) 34 Carding delivery

speed(mpm) 120 160 120 160

Direction CRF CRF CRB CRB Combing ratio

Mean 0.74* 0.72 0.76* 0.71 CRF- CRB -0.02 0.01

CV% 0.64 0.66 0.63 0.68 TAct(Table T95% =2.101) 9.26 23.14

Cutting ratio Direction CutF CutF CutB CutB

Mean 0.075 0.092* 0.067* 0.06 CutF-CutB 0.

008 0.032

CV% 0.64 0.52 2.43 2.71 TAct(Table T95% =2.101) 78.6 9.59

Orientation index Direction OIF OIF OIB OIB

Mean 92.4* 91 93.3 93.7* OIF-OIB -0.9 -2.7

CV% 0.17 0.18 0.44 0.43 TAct(Table T95% =2.101) 19.17 2.19


4.14.2 Microlyocell fibres

Table 4.11 gives the results on the effect of carding delivery speed

on cutting ratio, combing ratio and orientation index of microlyocell fibres.

There is no pronounced change in combing ratio in both the directions.

Cutting ratio seem to decrease with an increase in doffer speed, the backward

162

direction is showing a significant decrease. This is in agreement with the

findings of Ghosh and Bhaduri (1968). Whereas there is an increase in

orientation index in the backward direction, a decrease is noticed in the

forward direction. The differences between CRF and CRB, CutF and CutB OIF

and OIB are also given for the sliver samples. Where there is no difference, it

means that the number of leading and trailing hooks is almost similar.

Table 4.11 Effect of carding delivery speed on cutting ratio, combing

ratio and orientation index for microlyocell fibres

Fibre Microlyocell Fibre fineness(dtex) 1 Sliver hank (Ne) 0.200 Fibre length (mm) 34 Carding delivery speed(mpm)

120 160 120 160


Mean 0.74 0.73 0.75* 0.72 CRF- CRB -0.01 0.01 CV% 2.202 2.23 1.09 1.13 TAct(Table T95% =2.101) 1.37 8.22

Cutting ratio Mean 0.1 0.08 0.12* 0.05 CutF-CutB -0.02 0.03 CV% 20 25 13.58 32.6 TAct(Table T95% =2.101) 1.83 9.59

Orientation index Mean 90 91.1 87.7 94.8*

OIF-OIB 2.3 -3.7 CV% 0.45 0.44 0.46 0.43

TAct(Table T95% =2.101) 2.66 38.8 * Indicates statistical significance

163

4.14.3 Micropolyester Fibres


on cutting ratio, combing ratio and orientation index of micropolyester. The

results show that with an increase in doffer speed, the differences between

CRF and CRB decreases showing that the hooks have reduced. Cutting ratio

difference CutF-CutB shows an increase implying that the fibre disorder has

increased. Orientation index between the forward and backward directions

show an increase which again demonstrates the fibre disorder.

Table 4.12 Effect of carding delivery speed cutting ratio, combing ratio

and orientation index for micropolyester fibres

Fibre Micropolyester Fibre fineness(dtex) 1


speed(mpm) 120 160 120 160


Mean 0.85* 0.74 0.71 0.75* CRF- CRB 0.14 -0.01

CV% 1.92 2.20 1.15 1.09 TAct(Table T95% =2.101) 15.12 10.95

Cutting ratio Mean 0.09* 0.08 0.10 0.05

CutF-CutB -0.01 0.04 CV% 9.1 10.25 9.77 16.4

TAct(Table T95% =2.101) 2.74 10.83 Orientation index

Mean 91* 90.7 89.5 94.6* OIF-OIB 1.5 -3.9

CV% 0.09 0.09 0.2 0.17 TAct(Table T95% =2.101) 8.22 67.61


164

4.14.4 Polyester Cotton Blend


on cutting ratio, combing ratio and orientation index of micropolyester-cotton

blends. While the difference between CRF and CRB does not show any change

with increase in doffer speed, difference between the cutting ratios in the

principal directions shows a decrease. Cutting ratio found to be a sensitive

indicator than combing ratio by Simpson (1967). Difference between the

orientation index shows a decrease with an increase in the doffer speed, which

indicates that fibre disorder has increased. In general, it is noticed that with

increase in doffer speed, fibre disorder has shown an increase.

Table 4.13 Effect of carding delivery speed cutting ratio, combing ratio

and orientation index for micropolyester-cotton blends

Fibre Micropolyester/cotton Fibre fineness(dtex) 1


speed(mpm) 120 160 120 160


Mean 0.7 0.8* 0.74 0.76 CRF- CRB -0.04 0.04

CV% 1.52 1.33 2.91 3.4 TAct(Table T95% =2.101) 20.8 1.6

Cutting ratio Mean 0.12* 0.09 0.06* 0.08

CutF-CutB 0.06 0.01 CV% 9.58 19.16 14.37

TAct(Table T95% =2.101) 5.8 3.8 Orientation index

Mean 87.4* 90 93.1 91.8 OIF-OIB -5.7 -1.8

CV% 0.14 0.11 0.12 TAct(Table T95% =2.101) 18.68 26.41


165

Figures 4.41, 4.42 and 4.43 show the effect of carding delivery rate on cutting ratio, combing ratio and orientation index for micromodal,

microlyocell, micropolyester and micropolyester-cotton blends processed in high production cards.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Com

bing

ratio

Micromodal 0.74 0.72 0.76 0.71

Microlyocell 0.74 0.73 0.75 0.72

Micropolyester 0.85 0.74 0.71 0.75

PC blend 0.7 0.8 0.74 0.76

120F 160F 120R 160R

Figure 4.41 Effect of carding delivery speed on combing ratio of microfibres

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Cut

ting

ratio

Micromodal 0.075 0.092 0.067 0.06

Microlyocell 0.1 0.08 0.12 0.05

Micropolyester 0.09 0.09 0.1 0.05

PC blend 0.12 0.09 0.06 0.08

120F 160F 120R 160R

Figure 4.42 Effect of carding delivery speed on cutting ratio of microfibres

Com

bing

rat

io

Cutti

ng ra

tio

166

82

84

86

88

90

92

94

96

Orie

ntat

ion

inde

x

Micromodal 92.4 91 93.3 93.7

Microlyocell 90 91.1 87.7 94.8

Micropolyester 91 90.7 89.5 94.6

PC blend 87.4 90 93.1 91.8

120F 160F 120R 160R

Figure 4.43 Effect of carding delivery speed on orientation index of microfibres

4.15 SLIVER COHESION

The results of the sliver cohesion for micromodal, microlyocell, micropolyester and micropolyester-cotton blend normalized to tex are given in Tables 4.14, 4.15, 4.16 and 4.17. While there is no trend in micro modal, in respect of micro lyocell at higher doffer speed, the sliver static cohesion shows an increase. In case of micro polyester sample, higher doffer speed had led to a drop. The blended material shows an increase in cohesion with increase in doffer speed. Sliver cohesion which has been normalized by dividing the cohesion by the tex value of the sliver, gives an idea of hooks, spin finishes, inter fibre friction and drafting force. This is due to the removal of crimp in fibres following an increase in doffer speed. The removal of hooks would also have contributed to the increase in sliver cohesion. All the samples observed show a significant difference in sliver cohesion values at low and high carding speeds. Figures 4.44 - 4.45 show the stress strain curves for card sliver for micromodal.microlyocell, micropolyester and micropolyester-cotton blends for carding delivery speeds at 120 mpm and 160 mpm. That there are differences in sliver cohesion from the peak values of different fibres can clearly be seen.

Ori

enta

tion

inde

x

167

Table 4.14 Effect of carding delivery speed on cohesion of micromodal

carded sliver

Fibre Micromodal Fibre fineness(dtex) 1 Sliver hank (Ne)/ktex 0.180/3.28 Fibre length (mm) 34 Carding delivery speed(mpm) 120 160 Mean value of sliver cohesion(g/tex)

0.07 0.067*


Table 4.15 Effect of carding delivery speed on cohesion of microlyocell

carded sliver

Fibre Microlyocell Fibre fineness(dtex) 1 Sliver hank (Ne)/ktex 0.180/3.28 Fibre length (mm) 34 Carding delivery speed(mpm) 120 160 Mean value of sliver cohesion 0.067 0.092*


Table 4.16 Effect of carding delivery speed on cohesion of

micropolyester carded sliver

Fibre Micropolyester Fibre fineness(dtex) 1 Sliver hank (Ne)/ktex 0.180/3.28 Fibre length (mm) 34 Carding delivery speed(mpm) 120 160 Mean value of sliver cohesion 0.101 0.085*


168

Table 4.17 Effect of carding delivery speed on cohesion of

micropolyester-cotton carded sliver

Fibre Micropolyester-cotton blend

Fibre fineness(dtex) 1 Sliver hank (Ne)/ktex 0.180/3.28 Fibre length (mm) 34 Carding delivery speed(mpm) 120 160 Mean value of sliver cohesion 0.039 0.075*


It is evident from Figures 4.44 and 4.45, that there is a considerable

diference on sliver cohesion between the different microfibres at different

doffer speed can be noticed. Thus sliver cohesion test is a sensitive indicator

of fibre configuration, fiber finish and inter-fibre friction.

Figure 4.44 Stress strain curves of card slivers at a delivery speed of

120 mpm

gf/te

x

Strain %

169

Figure 4.45 Stress strain curves of card slivers at delivery speed of

160mpm

4.16 CONCLUSION

The following conclusions may be drawn from the above study:

1. Carding variables such as doffer speed, delivery hank and flat

speed have a significant effect on mean length, short fibre

content and neps of card sliver.

2. An analysis of the mean length in card sliver shows that

microfibre follows different statistical distributions.

3. An increase in doffer speed has led to higher fibre disorder.

4. Cutting ratios for micromodal, microlyocell, micropolyester

and micro polyester-cotton blend at a speed of 160 mpm were

unchanged implying that hooks are independent of the fibres

used.

5. Sliver cohesion was affected by doffer speed irrespective of

micro modal, micro polyester-cotton blend and micro lyocell

fibres. Differences due to inter-fibre friction and spin finishes,

hooks and fibre contacts are apparent.

gf/te

x

Strain %

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