Indian Journal of Fibre & Textile Research Vol. 17 , December 1992, pp. 255-262 An overview of spinning technologies: Possibilities, applications and limitations K R Salhotra Department of Textile Technology. Indian Institute of Technology. Hauz Khas. New Delhi 110016. India Received 12 August 1992 The new spinning technologies such as rotor, air jet and friction spinning have tremendous potential for hi gher productivity. However. at present these technologies not o nl y suffer from the problem of imparting some undesirable properties to the fabric but a lso have limited applicability due to the restricted choice of fibres and counts which can be successfully spun on them. Ring-spinning system, though having lower productivity, does not have these drawbacks. This system, therefore, with the incorporation of some recent improvements is likely to occupy the centre stage for the next few years. Keywords: Air jet spinning, Fabric hand, Friction spinning, Jet spin-assembly wind, Open-end spinning, Ring spinning, Rotor spinning, Twin spinner, Wrap spinning, Yarn properties 1 Introduction 'moire' effect in the fabric despite many modifications The ring-spinning system had remained made to the original yarn. This situation was entirely unchallenged since its introduction in the middle of different from the earlier developments from hand last century till the late 1960s. However, the spinners spinning to ring spinning when the product were becoming increasingly aware of the fact that low characteristics did not undergo any basic change in its productivity was inherent to the basic principle of structure. The systems such as hand wheel, flyer ring spinning. The system had reached a plateau in spinning, cap spinning, spinning jenny, mule regard to maximum production speeds. The breaking spinning and finally ring spinning produced yarns of this barrier required a fundamental change in the having real unidirectional twist which did not cause system offibre consolidation and winding of yarn. It any significant change in the yarn structure. These was in 1967 that the breakthrough became a successive developments led to increase in commercial possibility with the introduction of productivity without adversely affecting the yarn BD-200 Rotor Spinner which did away with the quality and fabric characteristics. concept of spindle twisting. The event created Among the new spinning technologies introdoced tremendous interest all over the world and aroused in late sixties and early seventies, only rotor spinning great expectations from this break-away technology. sustained its promise and in the years to follow, it Subsequently, many other spinning systems, which established itself as a worthy alternative to ring departed from the principle of ring spinning, kept on spinning in the coarse and medium count range. The appearing from time to time. Systems such as twistless reasons for its phenomenal growth were very high spinning, air vortex spinning and self-twist spinning productivity (around 5-8 times that of ring system) made their entry in the late sixties. However, except and amenability to automation and elimination of for self-twist spinning the,other systems could not roving and winding processes. However, along with progress beyond the stage of prototypes or these positive aspects there was a growing realization manufacture of a few commercial machines. The that the system has sectorial applicability and that main reason for their fading away appeared to be the this yarn imparts a harsh feel to the fabric. The poor quality of yarn and/or unacceptability of the techno-economic considerations restricted roto r resultant fabrics. The systems failed to provide spinning to coarse and medium counts. The search, certain desirable product attributes and flexibility. therefore, continued for other technologies for The twistless yartls produced fabrics with 'dead' and spinning finer ya rns. harsh hand. The self-twist ya rns retained their Wrap spinning, which was deve loped during thi s undesirable twist no n-uniformity and produced time, produced hybrid yarns in which a filament was 256 INDIAN J. FIBRE TEXT. RES., DECEMBER 1992 wra pped a ro und a core o f pa ra llel sta ple fibres. Two reached a n extremely hi gh level of I ,25,000 rpm fo r a other pro mincnt systcms, viz. ai r jet spinning a nd 32 mm ro to r. fri c ti o n spinning, which we re devclo ped fo r (ii) The roving a nd winding processes have been producin g 100 % sta ple ya rns came o n the sccne di spensed with. Rewinding may be resorted to onl y aro und thi s time with the promise of covering a n fo r spccific requirements. ex tended ra nge of coarse Lo tine yarns. (iii) The ro tor ya rns a re extremely regular a nd have F urther studies o n spinning techno logies bro ught much lower levels of imperfecti o ns a nd fa ults as fo rth the inherent dra wbacks of the new yarns a nd compa red to ring yam s. Such ilspects have made these thus enco uraged pa ra llel develo pments in the good ya rns q uite a ttractive for products where these old ring system. The innovati o ns whi ch have directl y aspects comma nd a premium. o r indirectl y suppo rted the ring systcm include (iv) The system is ex tremely a mena ble to linkage to winding a nd roving a nd increased spindle a uto ma ti o n. Features like a uto-piecing, a uto­ speeds. cleaning a nd a uto-doffi ng have become sta ndard The a pplications, possibilities a nd limitatio ns of fea lures of modern ro to r fra mes. ring a nd new spinning techno logies are considered here in deta il to project the future trend in the 2.2 Fibre Specifications for Optimum Results spinning secto r. For best results o n a ro to r spinner, the fibre pro perties, in o rder of impo rta nce, a re tenacity, 2 Rotor Spinning fin eness, length a nd cleanliness. This system of spinning is based o n the principle o f High tenacity fibres sho ul d no rmany be preferred o pen-end spinning in which the fibre continuity so as to reduce the strength deficiency of ro to r yarns. between the feed a nd twi sting is bro ken. The opened Use of fine r fi bres fo r spinning roto r yarns provides fi bres in the fo rm o f a stream a rc condensed to the severa l ad vantages such as increased spinning limit, required linear density a nd give n true twist. The mo re even ya rn, hi gher yarn strength a nd lower principle of working of ro to r spinning is represented o ptimum twist, a ll due to greater number o ffibres in in F ig. I·. the yarn cross-secti o n. The fa bric ha nd a lso becomes softer. However, as fi ne fibres a re pro ne to damage, 2.1 Possibilities and Merits the optimum deni er seems to be I.S (4.0 j.lg/in). The main meri ts/possibilities of ro to r spinning are The o ptimum fibre length has been fo und to be 32 as fo ll ows: mm fo r ma nmades. Lo nger fi bres no t onl y restrict (i) The production rate per positio n is 4-8 times that ro to r speed due to la rger ro to r required, but a lso of ring spinning. The maximum roto r speed has ad ve rsely affect yarn strength a nd evenness due to greater incidence of wra pper fibres a nd poor fibre o rienta ti o n. The effect of trash a nd o ther impurities o n ya rn qua lity and perfo rma nce a re well known. The feed sliver sho uld be quite free from impurities. In additio n to the a bove mentioned cha racteri stics, the IIbre crimp sho uld a lso be considered . A lower fibre crimp yield s better resuJts. The a rcs/cm sho uld lie between 3.5 a nd 5. 0. The delustrant Ti0 2 added to fibres meant for roto r spinning sho ul d be less tha n tha t no rmall y used fo r ring system. As a compro mi se between fi bre whiteness a nd wear of o pening roller, etc. a value of 0.1% seems to be the optimum. 2.3 Drawbacks and Limitations The ro to r-spinning system has the following inherent drawbacks/ limita ti o ns: (i) The rotor yarns ha ve 10-30% lower tenacity tha n the ring yarns. The strength loss is lower fo r co tto n Fig. I Principle of working of rotor spinnin g [F- f eed roller: tha n fo r ma nmade fibre yarns. The lower yarn T T ransport chan nel: P- feed pl ate; Y- Yarn : O- Openin g strength o f roto r yarn is carried into the fa bric which ro ll er: and R Rotorl shows lower tensil e a nd tear strengths. SALHOTRA: AN OVERVIEW OF SPINNING TECHNOLOGIES 257 (ii) The yarn twist required for optimum quality and cing stronger yarns. Some other recent air jet performance has to be kept around 15% higher tha n spinners, which employed only one jet, produced that for ring yarns. much weaker yarns due to less intensive wrappings. (iii) The minimum number of fibres required in the The MJS machines were in stalled in USA in large cross-section of rotor yarn is around 100-110 numbers in the early eighties for spinning polyester compared to 50 for ring yarns.