End Spinning ing Indian Raw Cotton Holger Neubauer Rieter Machine Works Ltd. Winterthur, Switzerland Harald Schwippl Rieter Machine Works Ltd. Winterthur, Switzerland ing Indian Raw Cotton Comparison of processing characteristics of cotton with a high short fiber content on Rieter s rotor and ring spinning system
Rieter. ing Indian Raw Cotton 3 Potential of rotor spinning Fig. 1 1995 Europe and America 1 automated rotor spinning machines were sold annually Today Growth market (Asia) 6 rotor spinning machines are sold annually INTRODUCTION The subject of this study is the processing of 1 1/16 cotton with a high short fiber content on Rieter rotor and ring spinning systems. The potential for processing 1% cotton on rotor spinning machines is currently still far from exhausted in the Asian countries and enormous growth potential remains. Despite the increasing consumption of textiles worldwide, an average of 6 rotor spinning machines are being installed annually in Asia. This market is forecast to double (Fig. 1). Range of application of the spinning systems, 1% cotton 1 [tons/year] Fig. 2 5 Range of ring spinning 4 5 Range of rotor spinning Range of airjet spinning 4 3 5 3 2 5 2 1 5 1 5 [mm] 23.-25.4 26.19 26.99 27.78 28.58 29.37 3.16 3.96 31.75 32.54 33.34 34.13 34.93 35.7-44.41 [inch] 29/32-1 1 1/32 1 1/16 1 3/32 1 1/8 1 5/32 1 3/16 1 7/32 1 1/4 1 9/32 1 5/16 1 11/32 1 3/8 13/32-1 3/4 short medium long extra long AFIS Autojet Commercial staple; UQL [w] [mm] Total installed [1 ] Spinning units installed worldwide 27 Installed spindles / rotor units vs. final spinning 16 14 141 269 12 1 8 6 61 62 4 2 7 7 83 Ring spinning, Ring spinning, Rotor spinning Air-jet spinning RANGE OF APPLICATION OF THE DIFFERENT END SPINNING SYSTEMS The range of application of the rotor spinning system in processing 1% cotton is restricted on economic and qualitative grounds to cotton staple lengths from 1 to 1 1/8. Depending on the short fiber and trash content of the cotton, rotor spinning technology is often the only option for manufacturing yarns economically and at the same time in the required quality. The areas of application of the different end spinning processes can therefore be allocated as a function of the staple length of the cotton (Fig. 2). 7.7 million rotor spinning units were already installed worldwide in 27. This number is small compared to the number of ring spindles installed. However, since the productivity of a rotor spinning unit exceeds that of a ring spinning unit by a factor of 6, this figure corresponds to some 3% of total yarn output. In global terms the rotor spinning system is an established technology which fulfills the high requirements for yarns in downstream processing (Fig. 3). Fig. 3
4 Rieter. ing Indian Raw Cotton Rotors installed [1 ] Fig. 4 MAIN SPHERE OF APPLICATIONS OF ROTOR SPINNING Total rotors installed 7 699 98 3 2 774 2 5 2 1 845 1 5 1 536 1 692 652 5 188 13 3 6 12 18 24 3 4 Yarn count [Ne] The yarn count range of rotor technology is Ne 3 - Ne 4, with the typical and most frequently produced yarn count being Ne 3. Yarns in this count are processed mainly in circular knitting, but also in weaving (Fig. 4). Different process sequences can be chosen for processing the fibers in rotor spinning (Fig. 5). The choice of process sequence in rotor spinning depends on the yarn count being produced and the required yarn quality. When processing 1% cotton in a yarn count of Ne 3, carding without a drawframe module and 1 or 2 subsequent drafting passages is appropriate (Fig. 6). PROCESS SEQUENCE OF THE RIETER ROTOR SYSTEM Fig. 5 Blowroom Card C 6 Blowroom Card C 6 with SB module Blowroom Card C 6 with RSB module Drawframe SB-D 4 Shorter process Shortest process Drawframe RSB-D 4 Drawframe RSB-D 4 Rotor spinning R 4 Rotor spinning R 4 Rotor spinning R 4 TEST SETUP In this trial, when processing 1% cotton, the quality of the rotor-spun yarn is analyzed in direct comparison with a ring-spun yarn. In this case the choice of raw material had to meet the processing requirements of both spinning systems. Cotton with too short a staple length has an adverse influence on drafting action in the drafting system unit on the ring spinning machine due to poor fiber guidance ( floating fibers ). coordination in rotor spinning, yarn, 1% natural fibers Raw material Cotton version Yarn count range Ne Technologically recommended process Draft / Doubling Draft SB / RSBmodule Draft SB / RSB 1. passage Draft SB / RSB 2. passage Draft SB / RSB 3. passage Doubling Draft final spinning Direct process without module - - - - - - - Direct process with RSB module 3-8 3-4.5 - - - - 4-1 CBA + drafted sliver 1 st passage 9-2 - 4-6 - - 4-6 8-2 CBA + drafted sliver 2 nd passage 9-4 - 6-8 6-8 - 6-8 8-4 SB module + drafted sliver 1 st passage - - - - - - - SB module + drafted sliver 2 nd passage - - - - - - - Fig. 6 Recommended Possible with losses
Rieter. ing Indian Raw Cotton 5 RAW MATERIAL PROPERTIES Cotton Shankar 6 origin India Micronaire: 3.86 (bale) Commercial staple : 1 1/16 Mean fiber length (n): 18.7 mm (Almeter) Strength [g/tex]: 28.4 (HVI) Neps [1/g]: 118 in bale (AFIS) Seed coat neps [1/g]: 14.2 (AFIS) Short fiber content: < 12.5 mm (n): 23.4 % (Almeter) Stickiness: not sticky (FCT) Fig. 7 SPINNING SCHEDULE, [Ne 2 + Ne 3]: A11 UNIfloc, [Ne 2 + Ne 3]: A11 UNIfloc Ring-spun, [Ne 2 + Ne 3]: A11 UNIfloc B 12 UNIclean B 7/3 UNImix Ring-spun, [Ne 3]: A11 UNIfloc B 12 UNIclean B 12 UNIclean B 12 UNIclean B 7/3 UNImix B 7/3 UNImix B 7/3 UNImix B 6 UNIflex B 6 UNIflex B 6 UNIflex B 6 UNIflex C 6 Card SB-D 15 RSB-D 4 R 4 1 kg/h Rotor C 6 Card 1 kg/h C 6 Card 8 kg/h C 6 Card 8 kg/h SB-D 15 SB-D 15 E 32 UNIlap SB-D 15 RSB-D 4 E 32 UNIlap E 65 Combing RSB-D 4 noil 14% F 15 Roving frame G 33 Ring E 65 Combing RSB-D 4 noil 16% R 4 Rotor F 15 Roving frame G 33 Ring In order to establish how the two spinning systems react to a higher short fiber content, an Indian Shankar 6 cotton with a relatively high short fiber content was used for the study. The exact raw material specifications are listed below (Fig. 7). The yarns were processed to a yarn count of Ne 2 and Ne 3 using carding and combing processes. The influence of the short fiber content on the yarn values of both yarn types was also studied. For this purpose 14% noil was extracted from the raw material in the case of the rotor spinning process and 16% in the case of the ring spinning process. Card output was adjusted according to the final spinning system; 1 kg/h for rotor spinning and 8 kg/h for ring spinning. The yarns are comparable on the basis of these appropriate adjustments (raw material, spinning schedule) (Fig. 8). The influence of rotor / spindle speed and yarn twist was also studied on both spinning systems (Fig. 9). Fig. 8 INFLUENCE OF ROTOR / SPINDLE SPEED Type of yarn Yarn [Ne] Nozzle Speed [rpm] Delivery [m/min] Twist factor [ m] 2 KS-NX 12 189 19 2 K4K 12 189 19, 2 KS-NX 12 178.7 115 2 K4K 12 178.7 115 3 KS-NX 11 142.7 19 2 KS-NX 18 7 189.2 98, 2 KS-NX 12 189.2 19 3 KS-NX 11 142.7 19 Ring-spun, 2-14 22 19 2-18 27 114 Ring-spun, 3-15 19.5 19 Fig. 9
6 Rieter. ing Indian Raw Cotton Short fiber content < 12.5 mm (n) [%] Fig. 1 Mean fiber length (n) [mm] 35. 32.5 3. 27.5 25. 22.5 2. 17.5 15. 12.5 1. 7.5 5. blowroom 23. 22.5 22. 21.5 21. 2.5 2. 19.5 19. 18.5 18. 17.5 17. 16.5 16. Short fiber content at each process stage for each yarn type 1% cotton, 1 1/16, Almeter ring-spun ring-spun rotor-spun Mean fiber length at each process stage for each yarn type 1% cotton, 1 1/16, Almeter bale after B 12 after B 6 card input card predrawframe lap sliver autoleveler drawframe roving stage rotor-spun bale after B 12 after B 6 card input card predrawframe lap sliver autoleveler drawframe roving stage RAW MATERIAL RESULTS The short fiber content of the cotton is relatively high at 22%. Short fiber content measurements rise as a result of fiber turbulence during the cleaning stages in the blowroom. This does not reflect actual shortening of the fibers. The reason is that existing measuring technology also interprets fiber turbulence as shorter fibers. The fibers are parallelized again during the carding process. The short fiber content measured in the bale should still be the same after gentle cleaning, carding and fiber parallelization by the drafting passages. This is confirmed by the fiber measurements made during the study. The short fiber content after noil extraction is 1% for the ring spinning process and 15% for the rotor spinning process (Fig. 1). The short fiber content has an impact on the mean fiber length and thus besides fiber count also on spin-out limits and yarn quality. The mean fiber length is 19 mm in applications and 2-21 mm in applications, depending on noil extraction (Fig. 11). blowroom ring-spun ring-spun rotor-spun rotor-spun Fig. 11
Rieter. ing Indian Raw Cotton 7.12.11.1.9.8.7.6.5.4.3.2.1. Ring-spun Ring-spun Trash content at each process stage for each yarn type 1% cotton, 1 1/16, ITV card lap sliver autoleveler draw frame.15 stage.14.15.73.11.19.19.19.99.54.17 The residual trash content in the feed sliver on the rotor spinning machine is an important criterion for the operating reliability of a rotor spinning machine. Contamination of the rotor groove when the trash content is too high results in ends down. Experimental evidence shows that the residual trash content of the feed sliver for the rotor spinning process should be no higher than.7 -.1% in Ne 2 - Ne 3 yarns. This requirement is just barely met by the Shankar 6 cotton in the application with.17%. With the combing process the trash content is generally reduced within a range of 6-85% (Fig. 12). Combing can thus be technologically appropriate for rotor spinning with a low noil extraction rate. Fig. 12 Number of imperfections Fig. 13 25 225 2 175 15 125 1 75 5 25 Yarn quality as a function of the spinning process 1% cotton, 1 1/16, yarn count Ne 3, m = 19, R 4 and G 33 (wound) 35 14.87 6 42 38 14.71 68 24 13.9% noil 1 15.48 217 63 Ring-spun Thin places -5% Thick places +5% Neps +28% 2 21 12.37 7 Ring-spun 16.4% noil CVm 16 15.5 15 14.5 14 13.5 13 12.5 12 11.5 11 CVm [%] In general, the adverse impact of raw material properties such as high short fiber content short mean staple length trash content of the cotton is much lower in rotor spinning than in ring spinning. YARN RESULTS IMPERFECTIONS (IPI) AND YARN IRREGULARITY Combed and rotor-spun yarns are at a similar level in terms of total imperfections with = 19 ( e = 3.6). A reduction in imperfections in rotor-spun yarn is apparent with lower twist factors and declining rotor speeds, i.e. a constant delivery speed of 189 m/min. The number of imperfections in ring-spun yarn is considerably higher than in rotor-spun yarn, despite reduced card output of 8 kg/h instead of 1 kg/h (Fig. 13).
8 Rieter. ing Indian Raw Cotton Number of imperfections Fig. 14 Total particles / 1 m Fig. 15 25 225 2 175 15 125 1 75 5 25 6 55 5 45 4 35 3 25 2 15 1 5 Yarn unevenness graded by Uster Statistics 1% cotton, 1 1/16, yarn count Ne 3, m = 19, R 4 and G 33 (wound) 5% 25% 6% 6% 246.8 65% 5% 25% 35% 13.9% noil 92.8 75% 65% 75% 6% Ring-spun Thin places -5% Thick places +5% Neps +28% 52.8 7% 4% 25% 45% Yarn particles vs. process 1% 1 1/16 cotton, yarn count Ne 3, m = 19, R 4 and G 33 (wound) 13.9% noil Ring-spun Ring-spun 16.4% noil CVm 116.1 16 15.5 15 14.5 14 13.5 13 12.5 12 11.5 11 Ring-spun 16.4% noil CVm [%] The combing process, and thus the additional extraction of short fibers, brings no advantages in the rotor spinning line in terms of yarn regularity. This result is remarkable, since the short fiber content in the ring spinning process has, in contrast, a significant influence on yarn regularity. This means that short fibers can be guided much better through the fiber guide channel in the rotor spinning process than by the drafting system in ring spinning. This can also be demonstrated very impressively by the influence of the combing process on ring-spun yarn. For this purpose a cotton yarn with approx. 16% noil extraction and a yarn count of Ne 3 was produced on the ring spinning machine. The measuring results show that due to the combing process a distinct improvement in yarn cleanliness is apparent compared to a ring-spun yarn. The yarn quality values are also better than those of a rotor-spun yarn. However, it must be borne in mind here that this improvement in quality of the ring-spun yarn could only be achieved with 16% noil extraction from the cotton (Fig. 14). In comparison (Uster Statistics), this means that the rotor-spun yarns are in a good range and the performance of ring-spun yarns is considerably poorer due to the specific raw material properties. The residual trash content of a rotor-spun yarn is much lower than in a ring-spun yarn due to trash removal at the opening cylinder in the application. Only the combing process and the associated removal of trash particles then makes a very low trash content also possible in ring-spun yarn (Fig. 15).
Rieter. ing Indian Raw Cotton 9 Strength [cn/tex] Fig. 16 Strength [cn/tex] Fig. 17 17 16 15 14 13 12 11 1 9 8 7 6 P.5 P.5 Yarn weak points (strength) vs. process 1% cotton, 1 1/16, yarn count Ne 2, noil 13.9%, R 4 and G 33 (wound) 14.22 m = 19 P.1 P.1 13.97 m = 98 P.5 P.5 14.59 m = 13 15.31 15.1 P 1. P = percentile value % Yarn weak points (strength) vs. process 1% cotton, 1 1/16, yarn count Ne 3, m = 19, R 4 and G 33 (wound) 17 16 16.3 15 14 14.16 14.6 13 12.98 12 11 1 9 8 7 6 Ring-spun Ring-spun 13.9% noil 16.4% noil P 1. m = 19 Ring-spun m = 19, after winding P = percentile value % YARN STRENGTH AND ELONGATION Compared to yarn, with an identical twist factor, the strength of rotor-spun yarn is approx. 1 cn/tex lower due to the shorter mean staple length. With an increase in twist factor from 98 ( e 3.2) to 19 ( e 3.6) an increase in yarn strength of more than 1 cn/tex is also apparent due to the improved integration of the fibers. However, ring-spun yarn displays.8 cn/tex higher strength compared to rotor-spun yarn. It is generally known that ringspun yarns display higher strength in direct comparison with rotor-spun yarns with the same raw material quality. This is related to the fiber orientation in the yarn structure, i.e. the structural assembly of the core and the covering fibers. Strength values of 1 cn/tex are normally adequate for applications in the knitting sector. The results for yarn weak points show that strength values of less than 1 cn/tex do not occur at any spin-out position (Fig. 16). Fiber strength in the bale is approx. 28.4 cn/tex. Fiber substance utilization with a twist factor of = 19 is thus: 51% in rotor-spun yarn 55% in rotor-spun yarn 54% in ring-spun yarn Experience shows that substance utilization in rotor-spun yarn is approx. 5% lower than in ring-spun yarn, due to the more random fiber orientation. Using the Ne 3 yarn count as an example, it is clearly apparent that strength increases by 2 cn/tex in absolute terms as a result of combing in the case of ring-spun yarn, and is thus higher than in and rotorspun yarns (Fig. 17).
1 Rieter. ing Indian Raw Cotton Elongation [%] 6. 5.5 5. 4.5 4. 3.5 3. 2.5 2. Yarn elongation vs. process 1% cotton, 1 1/16, yarn count Ne 2, noil 13.9%, R 4 and G 33 (wound) 5.9 5.22 5.23 m = 19 m = 98 m = 13 5.2 m = 19 4.84 Ring-spun m = 19, after winding The combing process does not have a positive effect on the elongation values of rotor-spun yarn. Carded rotor-spun yarn is at the same level as rotor-spun yarn. On the other hand, the values for ring-spun yarn are slightly poorer. The minimum requirement for knitting yarns is normally approx. 5% yarn elongation (Fig. 18). Due to the yarn structure, the good elongation values of rotor-spun yarns cannot be exceeded, even when combing is used with ring-spun yarns (Fig. 19). Fig. 18 P.5 P.1 P.5 P 1. P = percentile value % Yarn elongation vs. process 1% cotton, 1 1/16, yarn count Ne 3, m = 19, R 4 and G 33 (wound) Carded ring-spun yarn displays the lowest stretch recovery. The differences relative to rotor-spun yarn are small. Combed rotorspun yarn with the same twist factor displays the highest elongation. 6. Elongation [%] 5.5 5. 4.5 4. 3.5 3. 2.5 2. 4.82 5.1 13.9% noil 4.72 Ring-spun 4.82 Ring-spun 16.4% noil Fig. 19 P.5 P.1 P.5 P 1. P = percentile value %
Rieter. ing Indian Raw Cotton 11 Hairiness Fig. 2 1 9.5 9 8.5 8 7.5 7 6.5 6 5.5 5 4.5 4 Yarn hairiness and abrasion vs. process 1% cotton, 1 1/16, yarn count Ne 2, noil 13.9 %, R 4 and G 33 (wound) 4.89 7.88 m = 19 Hairiness 4.93 m = 98 6.32 4.76 5.76 m = 13 4.99 Abrasion [mg/1 m yarn] 5 m = 19 9.71 47.76 Ring-spun m = 19 after winding 6 5 4 3 2 1 Abrasion [mg/1 m yarn] YARN HAIRINESS AND ABRASION The yarns were processed on a circular knitting machine. The yarns were therefore waxed during the winding or rotor spinning process. Ring-spun and rotor-spun yarns differ considerably in terms of hairiness. This difference is due to the differences in yarn structure between ring-spun and rotor-spun yarns. The yarn hairiness of ring-spun yarn measured with the Uster Tester 4 is almost twice that of rotorspun yarn. The differences between and ring-spun yarns are minimal. The combing process has no effect on the hairiness values of rotor-spun yarn. The decisive factor for yarn hairiness in rotor-spun yarn is therefore primarily yarn structure rather than fiber length. Hairiness 1 9.5 9 8.5 8 7.5 7 6.5 6 5.5 5 4.5 4 Yarn hairiness and abrasion vs. process 1% cotton, 1 1/16, yarn count Ne 3, m = 19, R 4 and G 33 (wound) 4.26 9.64 6 4.5 13.9% noil 5.81 51.56 Ring-spun 7.57 26.84 Ring-spun 16.4% noil 6 5 4 3 2 1 Abrasion [mg/1 m yarn] yarns also display clear advan tages in respect of yarn abrasion. The abrasion of ring-spun yarn is higher than that of rotor-spun yarn by more than a factor of 5. It is apparent that the combing process has a positive impact on the abrasion of rotor-spun yarn (Fig. 2-21). Fig. 21 Hairiness Abrasion [mg/1 m Yarn]
12 Rieter. ing Indian Raw Cotton Rotor poorer difference in % Rotor better Rotor poorer Difference in % Rotor better Fig. 22 1 8 6 4 2-2 -4-6 1 8 6 4 2-2 -4-6 Relative comparison of ring-spun yarn 1% cotton, 1 1/16, yarn count Ne 2 7.4 8.6 1.3 CVm 3.9 5. 2.1 73.873. 89.7, m = 19 55.2 52.8 89.7 2. -5.3-6.9 strength.7-7.7 strength 5.2 7.9 3.7 14. 8.1 2.1 2.1 9.9 1.7 1.9 Relative comparison of ring-spun yarn 1% cotton, 1 1/16, yarn count Ne 3, m = 19 CVm IPI IPI elongation Yarn quality criteria, m = 19 elongation work done to break Yarn quality criteria 48.2 5.8 49.6 48.6 49.2 hairiness 8. hairiness 89.5 86.8 83.5 abrasion 88.4 81.3 47.9 5.2 5.9 82.1 81.2, m = 98 abrasion yarn particles 81.5 76.9 yarn particles The advantages of rotor spinning technology in processing Shankar 6 cotton with a relatively high short fiber content are impressive and can be summarized as follows: The quality values of rotor-spun yarn when processing Indian Shankar 6 cotton in a yarn count of Ne 2 are superior to those of ringspun yarn (Fig. 22) The quality of ring-spun yarn can be improved significantly by combing and is only then superior to rotor-spun yarn, with the exception of hairiness and abrasion resistance (Fig. 23) Micrographs showed the typical structure of rotor-spun yarn with its belly bands compared to ring-spun yarn. The greater hairiness and the associated increase in volume of ring-spun yarn are clearly apparent in the micrograph. yarn is normally distinguished from ring-spun yarn by a larger yarn diameter with the same yarn count. This results in a higher pile density in knitted fabric. However, it is apparent from these results that this effect can also be reversed as staple lengths become shorter in ring-spun yarn due to poorer fiber orientation and integration in the yarn structure (Fig. 24). Fig. 23 Ring-spun Fig. 24 1% cotton, 1 1/16, yarn count Ne 2, noil 13.9 %, R 4 and G 33 (wound), m = 19, m = 19, m = 98 Ring-spun, m = 19
Rieter. ing Indian Raw Cotton 13 Shape Fig. 25 Shape Optical shape vs. process 1% cotton, 1 1/16, yarn count Ne 2, noil 13.9 %, R 4 and G 33 (wound) 1.95.9.79.85.8.76.75.71.7.65.6.55.5, m = 19 Optical shape vs. process 1% cotton, 1 1/16, yarn count Ne 3, m = 19, R 4 and G 33 (wound) 1.95.9.85.8.8.81.75.7.69.7.65.6.55.5, m = 19, 13.9% noil Ring-spun Ring-spun, m = 19, after winding Ring-spun, 16.4% noil YARN SHAPE In addition to the orientation of the fibers in the yarn structure, yarn shape also has an influence on the refraction of light in textile fabrics. Essentially, the rounder the structure of the yarn itself, the higher the brilliance in the fabric. A ring-spun yarn is generally rounder than a rotorspun yarn. Besides yarn structure, yarn roundness can therefore have a positive impact on the brilliance of a knitted fabric (Fig. 25 + 26). PROPERTIES OF KNITTED FABRICS AND FINDINGS Besides the yarns, an appraisal of a knitted fabric before and after finishing should be conducted in order to compare the different spinning technologies. In this specific case the following typical criteria customary in practice were considered for assessing the knitted fabrics: fabric hand pile density uniformity pilling The yarns were processed into a single jersey on an ORIZIO (John/C model) circular knitting machine with a gauge of E 24. The knitted fabrics were washed, bleached and dyed in the course of the finishing process. Fig. 26
14 Rieter. ing Indian Raw Cotton Quality of knitted fabric vs. process 1% cotton, 1 1/16, yarn count Ne 2, single jersey dyed textile hand/ surface of fabric pile density 1.5 1.97 1.97 2 2.4 3 3.1 3 HAND, PILE DENSITY AND UNIFORMITY Besides different yarn structures, the different spinning processes also display different yarn diameters and roundness. In addition to yarn structure, yarn diameter affects the optical uniformity of the end product. A larger yarn diameter with the same yarn count demonstrably has a positive impact on the optical uniformity of the end product. fabric appearance/ imperfections 2.3 2.2 2.4 3.2 As was to be expected, ring-spun yarn had a softer textile hand compared to rotor-spun yarn. Fig. 27 Quality of knitted fabric vs. process 1% cotton, 1 1/16, yarn count Ne 3, single jersey dyed textile hand/ surface of fabric pile density Fig. 28 ring-spun, m = 19 rotor-spun, m = 98 fabric appearance/ imperfections ring-spun ring-spun rotor-spun, m = 19 rotor-spun, m = 19 1.7 1.8 2.1 2.1 2.6 2.8 2.6 rotor-spun 4.47 4.1 4.33 4.3 3.8 rotor-spun The greater pile density of ring-spun yarn compared to rotor-spun yarn is attributable in this case to its greater hairiness. This effect is also apparent in the fact that the pile density of ring-spun yarn deteriorates after combing. Carded ring-spun yarn results in a much poorer fabric appearance compared to rotor-spun yarn. The fabric appearance of ring-spun yarn could only be improved by combing, after which it was in the same range as that of rotor-spun yarn. No improvement in the knitted fabric was achieved by combing rotor-spun yarn. Reduction of the twist factor in rotor-spun yarn brought no improvement, either in textile hand or in the other assessment criteria (Fig. 27-32).
Rieter. ing Indian Raw Cotton 15, single jersey 1% cotton, 1 1/16, yarn count Ne 3, nozzle KS-NX, 11 rpm, m 19 Fig. 29, single jersey 1% cotton, 1 1/16, yarn count Ne 3, nozzle KS-NX, 11 rpm, m 19 Fig. 3 Ring-spun, single jersey 1% cotton, 1 1/16, yarn count Ne 3, 12 2 rpm, m 19 PILLING Most physical properties of an end product are attributable to the structure of the yarn being processed. Pilling behavior in the textile fabric, especially in knitted fabrics, is one of the most important quality criteria. End products which already form fiber pills on their surface after a short time due to stress reduce quality considerably and are unwelcome. Pilling is therefore a constant topic and can be significantly influenced and improved via low hairiness and the fiber integration structure (final spinning process). Fibers protruding from the knitted fabric are formed into pills of various sizes by mechanical stress during wearing. These pills are clearly visible, depending on their size and frequency, and have a very negative impact on the appearance of the knitted fabric. Pilling measurement is therefore very important for the qualitative assessment of knitted fabrics. Ring-spun yarn displays the poorest pilling values in all knitted fabrics studied. Carded rotor-spun yarn has the lowest pilling values, i.e. the best scores. Fig. 31 Ring-spun, single jersey 1% cotton, 1 1/16, yarn count Ne 3, 15 rpm, m 19 Fig. 32
16 Rieter. ing Indian Raw Cotton Pilling vs. type of yarn Knitted fabrics, yarn count Ne 2, Martindale Score [higher = better] Fig. 33 Space required [m 2 ] Fig. 34 6 5 4 3 2 1 5 1 15 2 25 3 35 4 45 5 55 6 65 7 75 Cycles rotor-spun, m = 19 rotor-spun, m = 19 5 45 4 35 3 25 2 15 1 5 Required space vs. process, total production ~31 kg/h 1% cotton, 1 1/16, yarn count Ne 3, basis India 4 641 4 353 ring-spun ring-spun rotor-spun, m = 98 ring-spun, m = 19 2 862 rotor-spun 3 216 rotor-spun The reason for the better pilling values of rotor-spun yarn compared to ring-spun yarn is to be found in its yarn structure with belly bands and less parallel orientation of fibers. The more random orientation of the fibers and the belly bands create resistance to the formation of pills. The results of the pilling test confirm this. It is clearly apparent that rotor-spun yarn displays poorer values than rotor-spun yarn. This can also be explained by the less random orientation of the fibers due to the different staple composition (Fig. 33). ECONOMICS AND SPHERE OF APPLICATION The rotor spinning system requires 4% less space than a ring spinning system. The yarn manufacturing costs of rotor spinning compared to ring spinning are significantly lower in the yarn count range up to Ne 3 (Fig. 34-35). CHF / kg.8.7.6.5.4.3.2.1 Cost comparison vs. process 1% cotton, 1 1/16, yarn count Ne 3, basis Thailand.1187.225.2113.1946.4637.276.38.2277.2125.562.1471.796.2846.1955 rotor-spun rotor-spun ring-spun ring-spun.6891.2572.84.394.197.727 Fig. 35 Cost of waste Cost of auxiliary material Labor costs Capital costs Energy costs
Rieter. ing Indian Raw Cotton 17 SUMMARY The subject of this study was the processing of cotton with a high short fiber content on Rieter s rotor and ring spinning systems. The trash content is reduced to a range of 6-85% by combing. Combing can certainly be technologically appropriate for the rotor spinning process with a low noil extraction rate. In the case of the ring spinning process, combing is often necessary in order to achieve the required quality values. The additional removal of short fibers is of no benefit to rotor-spun yarn as regards yarn regularity. This result is remarkable, since the short fiber content has a significant influence on yarn irregularity in the ring spinning process. This means that in the rotor spinning process short fibers can be guided better through the fiber guide channel than is possible in ring spinning by means of the drafting system. By comparison (Uster Statistics), rotor-spun yarns are in a good range and the performance of ringspun yarn is much worse due to raw material properties and the process-related influence of the drafting system. Only the use of combing for manufacturing ring-spun yarn results in a good, improved classification of ring-spun yarn again. Poorer raw material properties such as: high short fiber content low mean staple length trash content of the cotton have a much less negative impact in the rotor spinning process than in ring spinning. Depending on raw material composition and the type of downstream processing, rotor spinning can be regarded as more economical. The quality values of rotor-spun yarn with a yarn count of Ne 2 are superior to those of ring-spun yarn when processing Shankar 6 cotton. The quality of ring-spun yarn can be considerably improved by combing and is only then superior to rotor-spun yarn, with the exception of hairiness and abrasion resistance, in the case being studied. The greater hairiness and associated increase in volume of ring-spun yarn had resulted in better pile density in the knitted fabric. yarn normally features a larger yarn diameter compared with ring-spun yarn with the same yarn count. This results in higher pile density in the knitted fabric. This effect can be reversed as staple lengths become shorter as a result of the poorer fiber orientation and integration in the fiber structure. Ring-spun yarn has a softer textile hand compared to rotor-spun yarn. The combing process did not result in any improvement in the knitted fabric in the case of rotor-spun yarn. Nor does a reduction in the twist factor in rotorspun yarn result in any improvement, either in textile hand or in the other assessment criteria. Ring-spun yarn had the worst pilling values in all knitted fabrics tested. Carded rotor-spun yarn had the best pilling values.
18 Rieter. ing Indian Raw Cotton
Rieter. ing Indian Raw Cotton 19
Rieter Machine Works Ltd. Klosterstrasse 2 CH-846 Winterthur T +41 52 28 7171 F +41 52 28 832 sales.sys@rieter.com parts.sys@rieter.com Rieter India Private Ltd. Gat No 134/1, Off Pune Nagar Road, Koregaon Bhima, Taluka Shirur, District Pune IN - Maharashtra 41227 T +91 2137 253 71 F +91 2137 253 75 Rieter Textile Systems (Shanghai) Ltd. 12/F, New Town Centre No. 83 Loushanguan Road CN-Shanghai 2336 T +86 21 6236 813 F +86 21 6236 812 The data and illustrations in this brochure and on the corresponding data carrier refer to the date of printing. Rieter reserves the right to make any necessary changes at any time and without special notice. Rieter systems and Rieter innovations are protected by patents. 2285-v1 en 118 Printed in CZ www.rieter.com