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Abstract

Processing parameters play an important role in influencing the quality of the final product in any kinds of production. The aim of this project is to observe the quality of the carded sliver and yarn by applying different flat speeds on the carding machine while the other machine parameters were fixed. Five flat speeds (200, 240, 280, 320, and 360 mm/min) have been used to produce slivers and yarns. Sliver fineness of Ne0.11 and yarn of two different counts (Ne24 and Ne30) were produced for assessing the quality. It is found that the neps, short fibers, and unevenness of sliver and yarn are reduced proportionally with the increase of flat speed, whereas the tensile properties of yarn are increased. The unevenness and tensile properties are found to be best for flat speed 360 mm/min with significant increasing of waste percentage. The Ne24 and Ne30 cotton yarns have comparable unevenness and tensile properties. The quality of yarn improved continuously as the yarn becomes finer.

Keywords

Flat speed carded sliver carding process carded yarn neps unevenness strength

Introduction

The general operations for yarn manufacturing are carding, drawing, twisting, and spinning. Carding sections are well known as the heart of a spinning mill.¹ “To card well is to spin well” is a term very extensively used by all those concerned with spinning technology. ² The purpose of carding is the individualization of every fiber by opening out the tiny lumps, flocks, or tufts thoroughly, and the cotton is no more in an entangled state. This removes most of impurities, neps, short fibers, and so on, which have escaped in the blow-room section. Finally, the well-cleaned material is processed into a compressed sliver form and lays continuously for the succeeding processes. In a carding machine, as shown in Figure 1, the first cylinder, called the taker-in, is used to introduce the lap (highly tangled fibers) into the carding machine. The hooked flat plates, known as flats, act to break down and tease tufts into individual fibers, in order to form a smooth coherent sliver.³

Figure 1.

A diagram of different parts of a carding machine.

The better quality of the carded sliver is not only dependent on trash and neps content but also on the evenness in card web (weight per unit area), fiber parallelization and fiber-to-fiber separation, and minimizing short term variation in sliver thickness.⁴ However, to obtain this quality, the setting parameters of carding machine play an important role, and a small change in the setting is enough to produce inferior sliver quality.² Normally, the quality of yarn is very much dependent on the quality of the sliver for sure.

Various improvements were observed with the cotton card for the last three decades.⁵ Peng-zi and Jing-dang⁶ studied the influence of wind flow of web cleaner in a carding machine on the quality of card sliver, and the result shows that neither too large nor too small wind flow at back plate is favorable for card sliver quality. The effect of rotor speed, rotor diameter, and tandem carding on properties of open-end (OE) yarns were examined by Manohar et al.⁷ Jing-dang also worked on the influence of yarn quality of the cotton web cleaner position in the carding machine’s back cover guard.⁸

Many researchers have studied the effect of preparatory process variables on sliver and yarn properties. Plawat et al. suggested various parameter settings of carding machines in order to get the optimum quality at carding.² There is some evidence to suggest that the improved carding is attained with reduced cylinder load, which in turn improves the yarn evenness.⁴ Vijayaraghavan and colleagues⁹ hold the same view. J. Simpson et al. investigated the effect of carding rate and cylinder speed on the spinning performance. It was found that high carding rates resulted in less noils being removed without detrimentally affecting fiber length, yarn properties, or end breakage.¹⁰ Ghosh and Bhaduri¹¹ found that the card web is influenced mainly by cylinder and doffer speeds and the hank of the delivered sliver. The influences of carding machine back stationary flat gauge and choice of taker-in speed were studied by Zhidan and Pengzi¹² and Sun Pengzi.¹³

This article has focused on the changes in carding machines’ elementary process parameters for producing better quality card sliver as well as yarn. Among many variables of the machine parameters, that is, cylinder speed, flat speed, delivery speed, chute feed speed, feed speed, and take in speed, here we worked with the effect of flat speed, while all other parameters were fixed. Flat speed is defined as the substantial speed difference between the cylinder and the flat.¹⁴

From the literature, it was revealed that all the process parameters have a significant effect on fiber carding superiority, fiber damage, reducing short fibers, and impurities. Therefore, the choice of appropriate flat speed also played an important role on sliver and yarn quality. Although some research efforts have been made on other process parameters from the above discussion, there is a lack of detailed research regarding the influence of flat speed in the carding machine. Hence, in this work, an attempt has been taken to investigate and analyze the influence of flat speed on carded sliver and yarn properties, while other process parameters remain same.

Materials and methods

Materials

Commonwealth of Independent States (CIS) cotton from Uzbekistan was used as the raw material to prepare samples of sliver and yarn. The raw cotton fiber properties were tested with the help of USTER HVI, according to the standard testing conditions¹⁵ shown in Table 1. Sliver fineness Ne0.11 and yarn of two different counts (Ne24 and Ne30) were used as samples. Both were produced by Akij Spinning Ltd.

Table 1.

Properties of raw cotton recorded from USTER HVI.

Properties	Value
SCI (spinning consistency index)	143.17
Micronaire value (µg/in)	4.30
UHML (upper half mean length)	28.20 mm
Tenacity	29.30 g/tex
Yellowness (+b)	11.78
Reflectance (Rd)	81.22
Color grade upland	12-2
Maturity index	0.82
Uniformity index (%)	81.60
Elongation (%)	7.10
Short fiber index (%)	6.77

Methods

Carding process

In this experiment, the flat of carding machine (RIETER C60) was driven at five different speeds, that is, 200, 240, 280, 320, and 360 mm/min, by keeping all other parameters unchanged. The process parameters of the carding machine are given in Table 2. Six carded slivers were produced for each flat speed to feed breaker draw frame.

Table 2.

Process parameters of carding machine.

Name of parameter	Settings
Feed speed	500 g/m
Taker-in speed	1420 r/min
Cylinder speed	850 r/min
Flat speed	200/240/280/320/360 (mm/min)
Delivery speed	220 m/min
Total number of flats in rotation	99
Cylinder to flat distance (in five different positions from back to front)	Position 1: 0.001 inPosition 2: 0.001 inPosition 3: 0.001 inPosition 4: 0.001 inPosition 5: 0.001 in

Spinning process

A ring frame machine, named Lakshmi, was used for producing yarn. Ne30 and Ne24 carded yarn were produced from Ne0.70 roving. In ring frame, roving was mounted on same spindles for each flat speed. Important process parameters for the spinning process are given in Table 3.

Table 3.

Important parameters of spinning process.

Name of parameter	Machine settings
Name of parameter	For Ne30	For Ne24
Drawn sliver hank	Ne0.11	Ne0.11
Roving hank	Ne0.70	Ne0.70
Twist per inch	19.36	18.21
Ring frame speed (RPM)	17,000	17,000
Drafting arrangement (ring frame)	3 over 3	3 over 3
Draft (ring frame)	42.85	34.28
Doubling (breaker draw frame)	6	6
Doubling (finisher draw frame)	8	8

Testing of samples

Neps and short fiber content

Short fiber content by number and weight, neps content, and neps removal efficiency (NRE%) of slivers was evaluated using USTER AFIS PRO for each flat speed alteration. For each flat speed, 10 readings were taken, and then, averages were calculated

$NRE % = \frac{\begin{array}{l} neps content of card matt - \\ neps content of card sliver \end{array}}{neps content of card matt} \times 100$ (1)

Unevenness and imperfection index

The produced carded sliver samples were tested for their uniformity using USTER TESTER-4. For sliver unevenness, five cans were selected randomly for each flat speed, and from each can, 10 readings of unevenness (U%) were noted. The mean sliver unevenness (U%) was calculated from the 50 individual readings. For yarn unevenness, eight ring bobbins were tested for each flat speed, and the average was calculated.

Unevenness percentage is the mass deviation of unit length of material and is caused by uneven fiber distribution along the length of the sliver or yarn

$Unevenness, U % = \frac{mean deviation}{mean} \times 100$ (2)

In handling large quantities of data statistically, the coefficient of variation (CV%) is commonly used to define variability. It is currently probably the most widely accepted way of quantifying irregularity

$Coefficient of variation, CV % = \frac{\begin{array}{l} standard \\ deviation \end{array}}{mean} \times 100$ (3)

IPI stands for imperfection index of yarns, which is the description for thick places, thin places, and neps in 1000 m of yarn

$\begin{array}{l} IPI = thick places (+ 50 %), thin places (- 50 %) \\ and neps (+ 200 %) \end{array}$ (4)

Fiber length

Mean length is the arithmetic mean of the length of all the fibers present in a sample. It can be calculated by the number or weight of fibers. Let us consider three fiber lengths (mm) and weights as l₁, l₂, and l₃ and w₁, w₂, and w₃, respectively

$\begin{array}{l} Mean length based \\ on number, ({ML}_{n}) = \frac{l_{1} + l_{2} + l_{3}}{3} mm \end{array}$ (5)

$\begin{array}{l} Mean length based \\ on weight, ({ML}_{w}) = \frac{w_{1} l_{1} + w_{2} l_{2} + w_{3} l_{3}}{w_{1} + w_{2} + w_{3}} mm \end{array}$ (6)

Upper quartile length (UQL) is the value of length for which 75% of all the observed values are lower and 25% higher in a test specimen.

Count and strength

Yarn count was determined using AUTO SORTER-5, which gives direct reading. EUREKA lea strength tester was used to calculate lea strength of yarn according to the ASTM (1997) method. Yarn samples were also tested in TEXTECHNO strength tester for measuring the single yarn strength

$\begin{array}{l} Bundle yarn strength, C . S . P = yarn count (Ne) \times \\ lea strength (in lb) \end{array}$ (7)

All tests were performed in standard testing conditions (temperature: 20 ± 2°C and relative humidity: 65 ± 2%).¹⁵

Flat strips

The short fibers and trash particles that are removed between the cylinder and flats are called “flat strips.” Fibers that are deeply embedded in the flats cannot be reached by the cylinder wires and also become flat strips.¹⁶ The percentage of the flat strips was calculated as following

$Flat strips percentage = \frac{\begin{array}{l} fed weight - \\ delivery weight \end{array}}{fed weight} \times 100$ (8)

Results and discussions

Neps content and NRE% of sliver

Figure 2(a) and (b) depicts the neps content per gram and NRE% of card sliver of different flat speeds, respectively. It is revealed that as the flat speed increases, the neps content per gram decreases and NRE% increases. It is found that at flat speeds 200, 240, 280, 320, and 360 mm/min, neps content per gram and NRE% was 88, 77, 71, 66, and 58 and 65, 69, 72, 74, and 77, respectively.

Figure 2.

Effects of flat speed on (a) neps per gram and (b) neps removal efficiency (NRE%) of the sliver.

One reason why neps have declined is that when flat speed is increased, more number of flats comes in contact with fiber treatment operation which promotes more reduction of neps. In addition, there is a brush roller on the top of the flat for cleaning them. So, as the flat speed increases, more number of flats per time comes in contact with the brush roller, which improves the cleanness of flats and results in better carding action.

Short fiber content of sliver

Figure 3(a) and (b) reveals that there has been a significant decrease in short fiber content of carded sliver with the increase in the flat speed. We observed that when the flat speed was 200 mm/min, short fiber content by number SFC(n) was 23.4 and short fiber content by weight SFC(w) was 8.3.

Figure 3.

Effects of flat speed on (a) short fiber content by number (SFC(n)) and (b) short fiber content by weight (SFC(w)) of the sliver.

Whereas, when the flat speed was increased to 360 mm/min, SFC(n) was decreased to 13.25% as 20.3 and SFC(w) was also decreased to 26.5% as 6.1. As the flat speed increases, more number of flats comes in contact of fiber, which results in the elimination of more number of short fibers, and thus better carding action occurs.

Fiber length of sliver

The effect of flat speed on the fiber length of sliver is shown in Figure 4(a) and (b). Here, the mean length (ML) and UQL of fiber is considered. Both the ML and UQL show similar trend in the graph as increased with the increase of flat speed. This trend is due to the elimination of more short fibers by increasing the flat speed from 200 to 360 mm/min. In Figure 3, it is clearly shown that short fiber content decreased with the increase of flat speed. As the ML and UQL are inversely proportional to the SFC, the fiber lengths, that is, ML and UQL, increased with the increase of flat speed.

Figure 4.

Effects of flat speed on (a) mean length (ML) and (b) upper quartile length (UQL) of fiber in sliver.

Unevenness of sliver

It is observed from Figure 5(a) and (b) that at flat speeds 200, 240, 280, 320, and 360 mm/min, the corresponding U% and CV% of card sliver are 3.25, 3.08, 2.75, 2.61, and 2.47 and 4.13, 4.06, 3.67, 3.46, and 3.1, respectively, which shows a decreasing trend. The U% and CV% reduces by 24% when flat speed is increased from 200 to 360 m/min.

Figure 5.

Effects of flat speed on (a) unevenness (U%) and (b) coefficient of variation (CV%) of sliver.

This is because the increase of flat speed reduces the neps content and short fiber content. Therefore, degree of parallelization of fiber becomes higher because of better carding action. As a result, the increase of flat speed reduces the irregularity of card sliver. Hence, we can conclude that the increase of flat speed of carding machine reduces the irregularity of card sliver.

Unevenness of yarn

The unevenness (U%) of two yarn count Ne24 and Ne30 are highlighted in Figure 6. In this figure, there is a clear trend of decrease in the unevenness of yarn with the increase of flat speed. It is apparent from the figure that Ne30 yarns are showing higher unevenness values than the Ne24 yarns.

Figure 6.

Effects of flat speed on (a) unevenness (U%) and (b) coefficient of variation (CV%) of yarn.

When flat speed increases, it reduces the neps content and short fiber content of sliver and increases the fiber parallelization, thus decreasing the unevenness. Irrespective of the flat speed, the yarn unevenness increases as the yarn becomes finer as expected.

Imperfections of yarn

Figure 7(a) to (d) depicts the imperfections of yarn. Here, we consider thick place, thin place, and neps. In all these cases, it is clearly shown that yarn imperfections (thick place +50%, thin place –50%, and neps +200%) reduces with the increase of flat speed for both Ne24 and Ne30. Altogether, we also investigated the IPI values and found the same results. The IPI value decreased tremendously to 55.44% and 46.34% for Ne30 and Ne24, respectively, by increasing the flat speed from 200 to 360 m/min. It was also found that finer yarn (Ne30) has more imperfections than coarser (Ne24), as expected.

Figure 7.

Effects of flat speed on (a) thick place + 50%, (b) thin place + 50%, (c) neps + 200%, and (d) IPI –50%, +50%, +200% of yarn.

The reason behind this result is simple. As we increase the flat speed of the carding machine, the carding actions (removing trash, neps, short fiber, etc.) will be more. As a result, the degree of fiber parallelization will also be more, which will reduce the variation in sliver as well as yarn thickness. Thus, the yarn imperfections (thick place, thin place, and neps) will decrease.

Strength and tenacity of yarn

Figure 8 provides a significant effect on the yarn strength with the increase of flat speed. From this graph, we observe that with successive increases in intensity of the flat speed of carding machine, the tenacity and count strength product (CSP) of the yarn increases. It shows 12% and 14% increase of CSP and 21.47% and 15.25% increase of tenacity for Ne24 and Ne30 yarn, respectively.

Figure 8.

Effects of flat speed on (a) count strength product (CSP) and (b) tenacity (cN/tex) of yarn.

Taken together, these results suggest that there is an association between flat speed and yarn strength. It is observed that yarn strength was increased with the increase of flat speed. A possible explanation for this might be that by increasing the flat speed of carding machine, short fibers and irregularity reduces. Hence, reduction of floated fiber, better twist insertion, and more fiber migration occur, which results in increasing of yarn strength.

Flat strips

Among all the positive aspects of increasing the flat speed of the carding machine mentioned above, flat strip percentage increasing is a negative aspect. Figure 9 shows the effects of flat speed on the percentage of flat strips. It is clearly shown that the flat strip increases with the increasing of speed. During this investigation, the production rate was 75 kg/hr for all the cases. The flat speed 360 mm/min shows the maximum strip of 5.36%. It also shows a significant increasing of strip percentage while increasing the flat speed from 320 to 360 mm/min as 56.72%.

Figure 9.

Effects of flat speed on flat strips percentage.

As mentioned above, the increasing of flat speed reduces the short fiber content from the sliver so that the amount of flat strips will definitely increase. Thus, the wastage percentage of the carding machine will also increase.

Conclusion

This project was undertaken to design the appropriate flat speed for carded strand production and evaluate the quality of end products. This study has identified that carded strands manufactured from higher flat speeds provide best quality. The short fiber and neps content of slivers from higher flat speeds are lower than that of other speeds. This happens due to the large difference in flat speed which leads to the better carding action. The sliver and yarn unevenness decreases along with yarn strength as the proportion of flat speed increases. The Ne24 cotton yarns are having marginally higher quality than that of Ne30 yarn, but both count showed similar trend with the increase of flat speed. The optimum flat speed is influenced by all the quality parameters investigated in this research, like neps and short fiber content, fiber length, unevenness, strength, tenacity, waste percentage, and so on. Although the flat speed 360 mm/min shows the significant improvements in sliver and yarn quality, this research recommends 320 mm/min as the appropriate flat speed because further increasing of speed causes significant fiber wastage which can increase the production cost. The main findings of this study suggest that good quality yarn in the mill can be achieved through higher flat speed. The findings of this investigation also complement those of earlier studies.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research,authorship and/or publication of this article.

Funding

The author(s) received no financial support for the research,authorship and/or publication of this article.

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