Introduction

Compact spinning technology has been gaining much more interest since its first commercial introduction at ITMA-Paris in 1999. These spinning machines have been installed in several spinning facto- ries all over the world. Compact spinning is a modified ring spinning process which has special advantages, and can be used in both short- and long-staple yarn spin- ning areas. The zone between the line of contact of the pair of delivery rollers and the twisted end of the yarn is called the spinning triangle. In this zone, the fibre assembly contains no twist. Edge fibres splay out from this zone, and make little or no contribution to the yarn strength. The spinning triangle is the critical weak spot of the spinning process

[1]. The spinning triangle prevents the edge fibres from being completely incorporat- ed into the yarn body. However, in com- pact spinning, the drafted fibres emerging from the nip line of the front roller of the drafting arrangement are condensed in a line [2]. Ring-spun yarn is not perfect. If the enlarged view of ring spun yarn is exam- ined, it is easy to see that the integration of many fibres is poor, and they therefore make no contribution to yarn strength. In other words, if all fibres could be completely integrated in the yarn, both strength and elongation could in turn be further enhanced. It is thus obvi- ous that even ring-spun yarns are not yet ideal as regards yarn structure

[3]. The development of the compact spin- ning process began with the desire to achieve a significant step for yarn quality by influencing the spinning triangle (Fig- ure 1). This work is focused on achieving higher yarn strength and a reduction of yarn hairiness, especially on eliminating the longer hairs which have a particularly bad influence on the further process [4]. Many researchers have described the tech- nical principles of compact spinning and the more organised structure without pe- ripheral fibres and with a better twist dis- tribution. The compact yarn shows higher strength, reduced hairiness, and improved evenness. (Artzt, 1997 [5]; Olbrich, 2000 [4]; Stalder, 2000 [3]). M. Nicolic et al. [10,11]are among those researchers who investigated the similarities and differenc- es in the structural, mechanical/physical and texturing properties of ring-spun yarns of 20 tex, manufactured from various yarn blends (combed cotton, PET, CV, PA) from the same sliver, employing compact spinning on the Fiomax 1000 and Fiomax E1 ring-spinning machines from Suessen. According to their test results, the qualities of compact yarns are better than those of ring-spun yarns [10,11].

The compact spinning process produces a new yarn structure which approaches the ideal staple fibre yarn construction even more closely. This has positive effects on raw material use, productiv- ity, downstream processing, and on the product appearance [5]. The end breaks in spinning are approx. 50% fewer, which permits the reduction of the number of fibres in the cross-sec- tion, or to spin a finer yarn count. Reduc- ing the possibility of the number of fibres in the cross-section allows for the use of lower-priced tops with coarser fibres [6]. In compact yarns, fibres are uniformly oriented and joined into the yarn right after the end of the drafting arrangement. Therefore, better tenacity, elongation, and hairiness properties can be ensured. The better tenacity properties of compact spun yarn provide opportunities to work with lower twist coefficients, resulting in an increase in production rate, and also better handling properties of the end- product.

Another advantage of the compact spun system is the fly and dust reduction as an effect of condensation. The cleaning re- quirement is reduced when compared to conventional ring spinning frames. Compact spun worsted yarns also have the advantages of better quality proper- ties and different surface specifications, which will help to improve further processing and increase their production rate [7]. When using compact yarns, and allow- ing for the same level of warp breaks, the consumption of sizing agents can be reduced. This provides considerable cost savings in sizing and de-sizing. The same is true for warp breaks in weaving. Compact yarns permit better yarn regu- larity and the formation of a smoother yarn surface. This reduces the number of end-breaks by 30-50%, and leads to savings in the weaving department with significant improvements in efficiency, in the range of 3-5% [6]. Industrial trials of compact yarns have revealed a fly reduction of 1/3 on the knitting machine.

If one considers the number of faults due to knitted-in fly lumps as a percentage of the total fault count in knitting, there is distinct cost- reducing potential here with the use of these yarns. [5] With their increased yarn strength and reduced formation of fluff, compact yarns permit higher machine efficiency to be achieved, and therefore production on knitting machines can achieve a reduced ends-down rate, fewer interruptions and fewer fabric faults [8]. n Experimental Materials and methods In this study, we compared the yarn properties of compact yarns and the conventional ring spun yarns in terms of yarn hairiness (the number of protruding fibres on the yarn’s surface), yarn even- ness, tenacity and elongation (%).

The experimental work of this study was conducted on a Long Staple Tester PR 135 ring spinning machine by using four different raw materials. Compact spin- ning has some advantages for both weav- ing and knitting. The 100% wool and 45% wool/55% PET materials were spun with weaving twist factors, and the 50% wool/50% PAN and 100% PAN materials were spun with knitting twist factors. In the market, acrylic yarns and their blends with wool are usually preferred for knit- ting products; on the other hand, wool and wool/PET worsted yarns are usually preferred for woven products. On the ring spinning machine, the op- tion of spinning compact yarn by adding compact spinning equipments (Suessen EliTe?) was available. It was thus pos- sible to compare both the systems under identical machine conditions. Table 1 shows the experiment plan. After the spinning trials, the physical properties of each yarn sample were measured, and the measurement results of conventional ring yarns and compact yarns were compared to each other. Yarn evenness (CV%), thick & thin places, nep values and yarn hairiness values were measured with an Uster Tester 3 (the measurement length was 400 m/bobbin). Yarn tenacity (cN/Tex) and elongation at break (%) were meas- ured with a Statimat M. In addition, yarn hairiness was also measured with a Zwei- gle G565 yarn hairiness tester (the meas- urement length was 100 m/bobbin).

 Results and Discussion The compact spun yarns had better yarn property values - irregularity, thinand thick places, nep values, yarn hairiness, tenacity and elongation at break (%) - than the conventional ring spun yarns for all material types. The 100% wool yarn hairiness test results were given in Table 2 as an example. The results obtained from the laboratory testing of yarn samples were statistically evaluated by using SPSS software. Vari- ance analysis was applied, and by using F values we tried to find out if there was any statistically significant difference between the yarn quality data of conven- tional and compact yarns. (The details of the test results, statistical results and F values are found in Çelik [12]). Yarn evenness When we examined the yarn evenness of 100%-wool yarns, the Uster CV% and the thin place values of both compact and conventional yarns were found to have a statistically significant difference for a significance level of ?=0.05 for both 19 tex and 25 tex yarn counts (Figure 2)

. On the other hand, the differences of the two spinning systems in terms of the mean numbers of thick places and neps of 100% wool yarns were found to be sta- tistically significant for only the fine yarn count, 19 tex. The Uster CV%, the thin and thick place values of compact and conventional 45% wool/55% PET yarns were found to have a statistically signifi- cant difference for 19 tex (Figure 3). When we examined the yarn irregular- ity CV%, there was a statistically sig- nificant difference between the compact and conventional ring yarns which was produced with 50% wool/50% PAN for both two yarn counts, 25 tex and 36 tex, and all twist factor levels; but the differ- ences of two systems were found to be statistically significant in terms of thin and thick places for fine yarn count only, 25 tex (Table 3). The differences of compact-spun and conventionally-spun yarns which were produced with 100% PAC, in terms of the Uster CV% and I.P.I. values (thin & thick places and neps) were not found to be statistically significant, but the com-pact yarns’ Uster CV% values are lower than the conventional ones.