An Overview of Spinning Technologies: Possibilities, Applications and Limitations

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. Therefore, the quality blended yarns. of rotor yarns deteriorates when finer yarns are spun The wrap spinning principle of MJS system is on this system. The techno-economics of the system shown in Fig. 2. The drafted strand coming out of the also favours spinning of coarser yarns. In India, this front rollers is subjected to ballooning and twisting limit is said to be around 24 tex for cotton yarns. In the action when it passes through the jets I and 2 rotating West, the limit is around 18 tex. in opposite directions. Such an arrangement results in delayed wrapping of edge fibres by the twisting yarn (iv) Unlike in ring spinning, longer fibres (> 32 mm) near the front nip, causing longer and extensive offer no advantage in regard to yarn quality and/or wrappings. Systems using single jet fail to delay productivity. On the other hand, very long fibres catching of edge fibres by the twisting yarn thus (>38 mm) adversely affect the yarn quality. leaving large unwrapped yarn lengths which become (v) The biggest drawback of rotor yarns is the harsh weak spots in the yarn. Fig. 2 also shows the final yarn feelll of the fabrics made out of them. This could be structure in which a core of parallel fibres is wra pped overcome by selection of suitable weaves and use of l by the edge fibres, a typical fasciated structure . certain chemical treatment such as bio-wash which On MJS, it is possible to feed in more than one has been s·uccessfully used for denims. 2 sliver. Using specially designed feeding trumpets , it (vi) The limiting rotor speed appears to be 1,25,000 can be ascertained that a majority of wrappers rpm. As the yarn quality and performance tend to originate from the designated sliver. In another deteriorate at very high speeds, the acceptable development, a 4-roller drafting system allows commercial speed generally lies around 80,000 rpm. feeding coarser sliver which makes the two-sliver technique more practical to produce good quality 2.4 Application of Rotor Yarns sheath-core yarn. Rotor spinning can be employed to spin good quality yarns from cotton, polyester blends, viscose rayon and acrylic fibres. The count range in which it Front can be successfully used lies bet ween 18-200 tex (3s to roll er 32s Ne). The products where rotor yarns are suitable Edg e include sheetings, furnishings, denims and jeans, fibres dress materials, leisure wear, towels, warp knits and knitted goods.

3 Air Jet Spinning The technological improvements in rotor spinning Core fibres resulted in phenomenal increase in spinning speeds, Jet 1 improved performance and extended spinning limit. However, towards the late seventies, it became quite clear thal this system could not go much beyond the yarn count of20 tex and-rotor speed of I ,25,000 rpm. Therefore, a great interest· aroused in finding new systems which could facilitate extension of count and speed limits. Murata Jet Spinner (MJS) introduced around 1980 fulfilled these aspirations. Jet 2 The basic principle of the system dates back to sixties when Du Pont made a prototype to produce fasciated yarns. However, this system employed only one air jet. The MJS system, on the·other hand, employs two jets rotating in opposite directions which result in longer and more numerous wrapped portions produ· Fig. 2- Wrqp-spinning principle of Murata Jet Spinner 258 INDIAN J. FIBRE TEXT. RES., DECEMBER 1992

3.1 Possibilities and Merits Yarn srength is significantly inAuenced by fibre So me of the major merits/possibilities of air jet strength in air jet ya rns; hence, in general, stronge r spinning arc as follows: fibres sho uld be preferred. However, this aspect (i) Synthetic fibres and thcir blends such as should always be considered along with fibre polyester-co tt on and polyester- viscose spr'l on this el o ngation which should be high enough to generate system givc ya rn s of ra ther good quality. Their enough wrappi ng-compressio n. I n case of polyester. strength is greater than tha t of rotor ya rns but it has been observed that fibre tenacity beyond 7.0 gpd 10-15 % lower than that of ring yarns. They are oflCrs no additional aJvantage in ya rn strength due to somewhat bulkier and have slightly higher breaking reduced fibre elongation in such super high tenacit y extension. fibres. Such fibres have hi gh o ri entation and (ii) A wide ra nge of medium and fine count ya rns can brilllcness and as such are easil y da maged during be produced . mechanical operations at fibre producer's end a nd in (iii) The yarn is more even than ring yarn as high opening and carding at the mills. The strength loss2 speed drafting on MJS produces an evenly drafted incurred in these o perations is as hi gh as 15'10. A strand due to low incidence o f fibres moving out of tougher fibre (high strength and high elongation) turn because of the inertia effect. having a uniform coating with a more wettable finish (iv) Low spinning tension allows very high can reduce the extent of such damage. production speeds reaching up to 2,50,000 rpm, which The sliver cleanliness is a crucial factor in air jet is twice that of maximum rotor speed . The maximum spinning. Any trash particle or fibrous aggregate like linear productio n speed goes up to 300 m/min (MJS neps would hinder the rotation of ya rn in the na rrow 802H). yarn tube of air jets. This leads to short-term (v) The system can produce sheath-core structures by interruption in twist insertion, creating weak places feeding two slivers. 2 and even end breaks . The machine life is also (vi) Automatic features such as auto-piecing and adversely affected by such abrasive trash particles. auto-doffing are available on these machines. In regard to inter-fibre friction, a higher value is (vii) Like in rotor spinning, roving and winding generally desirable. The increased cohesion not only processes are eliminated in this system too. helps in producing stronger yarn but also in reducing (viii) The air jet yarn fabrics are less prone to pilling end breaks. than the corresponding ring yarn fabric's, In addition to the above mentioned fibre (ix) The loom shed efficiency, using air jet yarns, is characteristics, it is helpful to use bright fibres as they much higher than that in case of ring yarns, especially cause less fibre dust during spinning and thus avoid when air jet looms are used. choking of air jet nozzle.

3.2 Fibre Specifications for Optimum Results 3.3 Drawbacks and Limitations The requirements offibre specifications for air jet The air jet spinning has the following spinning are quite different from that of other dra wbacks/limi ta tions: spinning systems. The fibre specifications in order of (i) The air jet yarns are stiffer tha n ring yarns and importance are: fineness, length, tenacity, cleanliness impart a erisp or harsh feel to the fabric. a nd inter-fibre friction. (ii) The air jet yarns show a variable texture along the As the number of fibres in the cross-section of air jet yarn length; some sections have a normal cylindrical yarn has to be greater than that for ring yarns, finer structure while others show a corkscrew fibres should be preferred. Finer fibres also help in configura tion. bringing down the bending rigidity of air jet yarns and (iii) The tenacity of MJS yarns spun from polyester increase the tightness of wrapping around the core. blends is 10-15% lower than that of the As very fine fibres result in increased nep level which corresponding ring yarns but hi gher than that of can cause plugging of nozzles, the fibre denier should rotor yarns. This system fa ils to produce strong yarns be around 1.3 dtex (1.2 den). from short fibres, such as cotton, due to shorter and In general. longer fibres should be preferred which less intensive wrappings. Such yarns are also more give longer and firm wrappings. Looking at the irregular than ring yarns. The lower strength of these problems encountered in processing long fibres at yarns is carried into the fabric. card, such as neps, it is preferable to use fibres of38 (iv) The system is better suited to medium and fine mm for polyester-cotton blends and 44 mm for countsi.e. 12tex{50s Ne)t025 tex (24s Ne). Theend polyester-viscose blends. breakage rate goes up when one tries to spin finer SALHOTRA: AN OVERVIEW OF SPINNING TECHNOLOGIES 259 yams due to the spinning triangle near the front roller DREF-3 is a core type friction-spinning system nip growing longer with finer yams. which is a development over DREF-2 for improving (v) The drafting system sets a limit to the maximum yarn quality and productivity and extending count possible production speed to around 300 m/min. range to the finer end.

3.4 Two-ply Air Jet Yarns 4.1 Possibilities and Merits A later concept in air jet spinning is the so-called The friction-spinning system offers the following "jet spin-assembly wind" used in Plyfil (Suessen) and advantages/possibilities: MJS (Murata Twin Spinner). In this system, two (i) It can spin at very high twist insertion rates of up to single air jet yams are produced which have just 3,00,000 rpm due to very low spinning tension which is enough wrappings to give tenacity.of 3-5 cN/tex so only 20% of that in ring and 14% of that in rotor 7 that they can be easily wound as a pair and then spinning • The production works out to 16 times that unwound for twisting at the two-for-one twister. of ring spinning and more than twice that of rotor Such a twisted structure would have much lower spinning (per position). rigidity and thus overcome one of the most serious (ii) Due to presence of twist in yarns and absence of drawbacks of air jet yarns. The production speed in wrappers, these yarns impart a soft hand to the this spinning system easily reaches 300 m/min. The fabric. system is well suited to production of 2-ply yarns. (iii) The yarns are bulkier than ring and rotor yaros. (iv) The system is much more versatile, in terms of 3.5 Application of Air Jet Yarns fibres used, than air jet and rotor spinning systems. It Due to the harsh feel imparted by air jet yarns can handle various types of natural and manmade (MJS) to the fabric, various ways have been devised to fibes. It can also process recycled textile wastes. mitigate this problem. Choice of proper weaves such (v) Core-spun yarns can be easily produced on as twill or sateen, suitable fabric finish and use offine DREF-3. count yams are some of the ways to improve the fabric (vi) Like rotor and air jet spinning, this system too hand. The air jet yams have also been used along with has dispensed with the roving and winding ring yarns, either as warp or weft, for the same processes. purpose. (vii) The system is amenable to automation which Some of the products where these yarns have been include automatic piecing and doffing. extensively used are bed linens, shirtings, overcoat (viii) The yarn produced is cleaner ·as the drum's fabrics, dress materials, home furnishings, towels suction removes dust and trash particles. and some industrial textiles. However, product development needs to be accelerated to exploit the 4.2 Fibre Specifications for Optimum Results unique features of these yarns. The fibre properties for optimum yarn quality, in order of importance, are: fibre friction, strength, 4 Friction Spinning fineness, length and cleanliness. Friction spinning is based on the principle of The twisting rate in friction spinning is largely open-end spinning (DREF-2 and Master Spinner). dependent upon friction between fibres and the drum The fibres are opened by an opening roller, as in rotor surface. Therefore, a high friction between the fibres spinning, and collected in a suction area between two and the drum surface is desirable. The inter-fibre drums. The twist is imparted through friction friction should also be higher as the parallel-fibre between the yarn and the drums' surface. The twisted core need to be properly bound to resist slippage. strand is drawn along the direction of the axis of the J\ f '-.' f drum. An extremely high rate of twist insertion is \'v.'I' achieved because each rotation of drums imparts about 100 turns to the yarn. Recent studies by Stalder et aJ.3 - 5 have shown, with the help of high speed photography, that the yam s y being formed is surrounded by a rotating sleeve T fonned by the fibres coming from the opening roller. The fibres arj! transferred from this sleeve to the yarn o core inside. The rotation of sleeve imparts twist to the Fig. 3--Mechanism of yam formation in friction spinning F­ yarn while fibres are being peeled from it. The Opened fibres: T-Yam tail: S-Sleeve: Y- Twisted yarn; and mechanism of yarns fonnation6 is shown in Fig. 3. D-Druml 260 INDIAN J. FIBRE TEXT. RES., DECEMBER 1992

The inherent weakness of friction yarns can be Due to all these drawbacks, friction spinning has partly overcome through use of high tenacity fibres. still not established itself as a viable spinning The minimum number offibres required in friction technology. yarn is higher. Therefore, fine denier fibres should be used for the finer range of counts. 4.4 Application of Friction Yarns The fibre length requirement in friction spinning is At present, three types of commercial friction similar to that in rotor spinning. The optimum value spinning machines are available, viz. DREF-2, lies between 32-38 mm. Longer fibres are more DREF-3 and Master Spinner. DREF-2 is meant for susceptible to damage and show tendency to lap spinning coarse yarns of 100 lex (6s Ne) to 600 tex (I's around the opening roller. While DREF-2 is meant Ne) at around ISO m/min from long-staple material. for long-staple material, DREF-3 can handle DREF-3, which is a development over DREF-2, can shorter fi bres8 . produce 33 tex (18s Ne) to ISO tex (4s Ne) yarn at The cleanliness of feed material is the fourth ISO-300 m/min from shorter fibres. Master Spinner is important requirement. Of course, this aspect is capable of spinning 2S tex (24s Ne) to 60 tex (lOs Ne) relevant only for natural fibres like cotton. An unduly yarn at ISO-300 m/min depending upon the raw high trash content would lead to frequent clogging of material. drum perforations. In general, one can say that friction spinning can be used to spin yarns from cotton, polyester, acrylic, blends and even recycled fibres. The yarns can be used 4.3 Drawbacks and Limitations There are a number of drawbacks and limitations for knit goods, terry towels, weft yarns, pile yarns, of friction spinning which are restricting its ve lvets and blankets. Some other applications acceptance as a system for producing general purpose i ncl ude carpet backi ng, wra pping cloth, furnishings, yarns. The main drawbacks/limitations are: filters and technical textiles. The core-spun yarns (i) The extremely poor fibre orientation renders the (DREF-3) are suitable for industrial textiles like fric ti on yarn very weak. The extent of disorientation beltings, tarpaUlins, etc. Friction spinning can also be and buckling is more with longer and finer fibres. The used to produce fancy yarns. yarns are weaker than rotor yarns. 5 Ring Spinning (ii) The twist variation from surface to core is quite Since its inception, ring spinning had remained high. This is another reason for the low strength of unchallenged for almost ISO years. However, its this yarn. limitation in regard to production speeds was well (iii) Due to variations in friction condition from one realized which made its position quite vulnerable. position to the other, there is a high between-position The tremendous enthusiasm to introduction of SO twist variation. 200 in 1967 was, therefore, well justified. However, in (iv) The number offibres in the sleeve reduces as the a few years time the inherent drawbacks of rotor yams count becomes finer and the incidence of holes (no were well established. The sectorial applicabi lity of fibres) in the sleeve increases6 , thereby increasing the rotor spinning became quite clear. This led to a chances of yarn tail losing contact with the sleeve thus cautious attitude on the part of spinners to any leading to higher end breakage rate. The instability in innovation which was introduced later on. They yarn formation with lower number offibres in yarn realized that any basic departure from ring spinning cross-section restricts the applicability of friction leads to changes in yarn structure which are generally spinning to coarse counts. unfavourable or unacceptable. These aspects have been discussed earlier. Subsequent to this realization, (v) The doubling of fibre layers taking place in the renewed attempts made by machinery manufacturers rotor groove is absent in this system. Periodic air led to considerable upgrading of ring spinning stream variations due to spiral clothing of opening system. The maximum production speed has roller introduce mass variations which do not get increased to 2S,000 rpm by extending the maximum evened out. This leads to periodic yarn strength . traveller speed to 45 m/s through' further variations. developments and using smaller ring diameter and (vi) The maximum production rate is limited by the bobbin lift. The subsequent problem of excessive fibre transport system and the drafting system. The material handling has been solved by linking ring maximum production rate is around 300 m/min. It is spinning frame to the winding machine. This has unlikely to go much beyond that if the above come to be known as linked ri ng spinning. The mentioned problems are not solved. problem of excessive knots due to smaller ring SALHOTRA: AN OVERVIEW OF SPINNING TECHNOLOGIES 261 package is of no consequence due to efficient splicing Air- jet systems available at winding. Another serious problem of excessive initial end breaks due to greater number of doffs has been solved by the employment of IFriction I efficient automatic piecing devices. Additionally, there are support systems such as automatic roving Rotor transport to the ring frame and automatic roving rupture if the yarn is not pieced in three successive attempts (to reduce incidence of roller lapping). Ring J I , ! ! I I I 5 10 20 50 100 200 5JO 1000 5.1 Merits of Ring-Spinning System Yarn Count, tex It would be worthwhile to briefly mention the well-known merits of ring spinning. Fig. 5- Practical count range for various spinning systems (i) Among all 100% staple-fibre spinning systems it produces the strongest yarn (Fig. 4) from various virtues of ring spinning such as versatility and wide types of fibres and their blends. range of fabric hand are given greater respect now. (ii ) This system can produce yarns with a large range Rotor spinning which has been in existence for 25 of twist density, from very low (knitting yarns) to very years now has gone through a long trial in regard to high (voile yarns). No other system can match this usage of end product, modifications in design, use of unique capability. special fibre and fabric finishes, and optimization of (iii) The ring-yarn fabrics can be imparted t:le product specifications before it could establish itself desired hand, crisp or soft, as per requirements. as a worthy successor to ring spinning for spinning coarse yarns. It had to fight against another fact that (iv) It can be used for all types of fibres and can spin there are already 200 million ring spindles in the from very coarse to extremely fine yarns. world. Any new technology can be considered only for replacement of ring spindles or addition to 6 Present Status and Future Prospects existing production capacity. The high expectations aroused by the introduction of rotor spinning in late sixties and of air jet and The air jet spinning would also have to come with friction spinning in late seventies and early eighties viable solutions to the twin problems of harsh fabric did not materialize to the full. Their sectorial feel and spinning of poor quality 100% cotton yarns. applicability, in terms of type of fibres and yarn The friction spinning has still greater technological counts, is well established. Some undesirable deficiencies such as lower yarn strength and high twist characteristics of yarns spun on these systems have variation. A viable commercial friction spinning further detracted them from their promise. The machine to spin good quality fine yams is yet to arrive. The count range which can be successfully spun on various spinning systems are given in Fig. 5. At the ~100 • • • • • present juncture, ring spinning in its new form of £ linked ring spinning supported by automatic features cc> ClI 80 such as transport of roving bobbins to ring frame, ~ V) automatic piecing and doffing reigns supreme due to c its unmatched versatility. The fact that more than 200 ~ 60 ~ million ring spindles already exist in the textile mills is ClI another factor in favour of ring spinning as far as the > 40 :.;:: • Ring next 7-10 years are concerned. ~ c Rotor ClI 0 0::: 20 Air-jet It is expected that the next decade would see lot of • Friction developments in regard to quality of yarns spun on the new systems. The problem of harsh feel of air jet Corded Combed Combed PIC PES yarn fabric would also be solved by suitable design I~ 11- ,-1- 67/33 ,00 'I. and process modifications. The new technologies 16 8 2 would become attractive as time passes on and the Fig. 4--Relative strength of yarns spun on va ri ous spinning techno-economic advantages are likely to go more systems and more in their favour. 262 INDIAN J. FIBRE TEXT. RES., DECEMBER 1992

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