For the past decade, rapid technological advancements have resulted in a rise in machine productivity, allowing companies to meet increasing client demand while lowering production costs. In this regard, delivery speed of breaker draw frame has been increased at the rate of 700–1000 m/min. A number of researchers have studied the influence of preparatory process variables on yarn properties. Found that the better carding is obtained with lower cylinder load, as a result the yarn evenness improves [1]. Have also found similar observations [2,3].) The influence of draw frame variables on yarn quality [4]. The impact of higher speed of draw frame on the yarn quality and summarized that the faster the speed the higher the centrifugal force of sliver in the coiler causing an increase of fibre-to-fibre pressure thus increasing sliver tenacity [5]. High draw frame speed, the orderly sliver coiling into delivery can becomes more critical, and the intensity of fibre parallelization attained in draw frame can negatively affect yarn characteristics [6]. Increase in draw frame speed and coiler diameter of carding leads to advancement in fibre extent in yarn [7]. It has also been found that when draw frame delivery speed & coiler diameter of carding increase, mean fibre position and root-mean-square deviation decrease. The parameters listed above change slightly when the card draft increases. It is also discussed that packing characteristics behavior is also influenced by the mentioned process variables. Since draw frame speed and coiler diameter of carding increase, helix twist, helix diameter, helix angle decrease with the increase in yarn packing density. As the yarn properties are compactly related with structural parameters, the yarn quality is perhaps influenced by the process variables mentioned earlier. It should be noted that earlier researches do not expand the effect of preceding processes, such as coiler diameter and draft of carding, on the parameters of yarn manufactured at high draw frame delivery speed. In the present study, the impact of process variables i.e. coiler diameter of card, card draft and delivery speed of breaker draw frame on the rotor yarn properties has been investigated in terms of structural parameters of rotor yarn.

Materials

80% cotton fibre (mixture of Brazil 1-1/8”, USA, Chad 1-5/32” and organic cotton) and 20% wastage (dropping-1, dropping-2, flat strip, noil, pneumafil) was used as raw material for the sample preparation. The average length, strength, elongation% and micronaire of the cotton fibre were, respectively, 29.51 mm, 29.5 g/tex, 6.98 and 4.52. Three process variables i.e., delivery speed, card coiler diameter and card draft were used to prepare the samples according to Box–Behnken method[8]. After randomization, the samples were prepared for a statistical analysis that works. Tables 3 and 4 show the intensity of process variables based on the experimental design. All 15 samples of 70 grain per yard (4.92 ktex) from the finisher draw frame were passed through Rotor frame in actual running condition of the mill. Finally 10s (59.05 Tex) carded hosiery yarn was produced.

Table 1: Raw cotton properties (HVI).

Table 2: Raw cotton properties (AFIS).

Table 3: Actual values of variables corresponding to coded levels.

Methods

The unevenness and imperfection of yarn samples were tested using Uster evenness tester (UT-4). Single test per bobbin and total 10 tests per sample were executed at the testing speed of 400 m/min. The default settings used were thin (–50%), thick (+50%) and neps (+200%). Moreover, the Zweigle G 566 hairiness tester was used to measure the number of protruding hairs on the yarn surface. The hairs larger than 3 mm (S₃) affecting both the outlook and the processing performance of yarn were considered only. 400 m length yarn of each bobbin was tested at 50 m/min testing speed. The tenacity and breaking elongation were measured using Uster Tensorapid-3 at a speed of 5000 mm/min having 500 mm gauge length. Total 100 tests of each sample were performed with 0.5 cN/tex pre-tension. Uster Classimate- 3 was applied to determine the seldom-occurring faults per 100 km length of yarn. In this study, long thin faults (H₂, I₁, I₂) were considered as undesirablefaults.

The equations in relation to three process variables (breaker draw frame delivery speed, coiler diameter and card draft) with rotor yarn properties were attained through backward elimination regression method. Table 5 shows the relationship between the previously-mentioned process variables and rotor yarn characteristics.

Table 4: Rotor Yarn Properties at different process variables.

Table 5: Regression equations representing the impact of different process variables on rotor yarn properties.

It is seen from Table 4 that the influence of different process variables on rotor yarn tenacity (RKM), breaking elongation, unevenness, total imperfections, hairiness and long thin faults are significant as confirmed from higher R2values.

Yarn Tenacity

Table 4 and Figure 1(a, b) show that rotor yarn tenacity increases with the increase in breaker draw frame delivery speed and coiler diameter of carding. At lower card draft when coiler.

Figure 1(a,b): Effect of rotor yarn tenacity.

Diameter of carding increases, rotor yarn tenacity increases largely owing to the interaction effect. This increase in rotor yarn tenacity can be clarified by yarn structural changes. When draw frame delivery speed and card coiler diameter increases, total number of hooks decreases, leading to a reduction in yarn diameter and increase in fiber extent as well as packing density  and finally an increase in yarn tenacity [9]. There is also a decrease in mean fiber position and root-mean-square deviation in the yarn [9]. It can also be said that when the card draft increases, yarn tenacity decreases. This can primarily be attributed to decrease in fibre extent as well as packing density, increase in number of hooks and yarn diameter. Also there is a marginal increase in mean fibre position. Root-mean-square deviation first increases then decreases and hence overall decrease in yarn tenacity.

Breaking Elongation

It can be seen from Table 4 and Figure 2(a, b) that when draw frame delivery speed and card coiler diameter increases, the breaking elongation percentage of rotor yarn increases. The findings may be clarified by the successive increase in fibre extent, decrease in total number of

hooks including hook extent, reduction in fibre overlap index[9], as well as mean fibre position [7]. There is a reduction in mean migration intensity and increment in yarn packing density which keeps the fibers from slippage. It is also observed from the same figure that when the card draft increases, breaking elongation of rotor yarn decreases. This can be stated on the ground of reduction in fibre extent. Moreover, the effect of card draft on fibre migration parameters is marginal. So, these parameters affect the breaking elongation insignificantly.

Figure 2 (a,b): Increases in card coiler diameter and draw frame delivery speed.

Yarn Unevenness

Table 4 and Figure 3(a, b) exhibits that when draw frame delivery speed and card coiler diameter increases, the U% of rotor yarn decreases. This reduction happens due to the improvement in  fiber extent. It is also seen that when the card draft increases, U% of rotor yarn increases first and then remains same. At higher card draft, thickness of the card mat is higher. As a result, there is small penetration of wire points in the mat and less points per fiber are offered by taker-in hence less opening of the tuft and thus hooked fibers increase in the sliver[10]. As a result yarn unevenness increases.

Figure 3 (a,b): Effect on U% of rotor yarn.

Total Imperfections

It is clear from Table 4 and Figure 4(a, b) that when draw frame delivery speed and card coiler diameter increases, total imperfections of rotor yarn decreases. It is also stated that when card draft increases, the total imperfections increase first and then remains same. The explanation is similar to the yarn U%.

Figure 4 (a,b): Effect of total imperfection.

Yarn Hairiness

It is seen from Table 2 and Figure 5 (a, b) that when draw frame delivery speed and card coiler diameter increases, rotor yarn hairiness decreases. As delivery speed increases, fibre tension.

Figure 5 (a,b): Effect of rotor yarn hairiness.

Increases in the sliver. It makes more compact sliver which makes compact roving. This compactness reduces the spinning triangle of ring frame. Similar occurrence happens in case of the influence of card coiler diameter. It is also stated that when card draft increases, rotor yarn hairiness increases to a limited extent. At higher card draft, number of hooked fibres increases[10] which are not able to be straightened in the subsequent drafting stages. As a result, there is a slight increase in the yarn hairiness.

The influence of breaker draw frame delivery speed, card coiler diameter and card draft are discovered to be significant on the rotor-yarn properties. When the draw frame delivery speed and card coiler diameter increases, yarn tenacity and breaking elongation increases; on the other, U%, total imperfections, hairiness and long thin faults decreases. In a nutshell, if card draft increases in the carding machine, deterioration in yarn quality is a must.

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