Rieter

Improved market prospects for plied yarns

Index

Plied yarns are seldom made from the products of new spinning processes (Repco and spin-twist processes are exceptions). Most plied yarns are made from ring-spun singles. Ply twisting is therefore usually a cost-intensive process, and folded yarn is generally significantly more expensive than single yarn. The field of application of plied yarn has thus shrunk in recent years. Nowadays, in short staple spinning, single yarns are used increasingly, although often a plied yarn would be more suitable. The PLYfiL process by the Suessen company has opened up the possibility of producing folded yarns relatively economically; ply twisting now has an opportunity to regain lost ground. The plied yarn made in accordance with this process exhibits slight differences in comparison with conventional ply-twisted yarn; it is somewhat softer, fuller, and more open. However, PLYfiL yarn has the same strength as conventional ply-twisted yarn and is very even.
The PLYfiL process is particularly suitable for medium to fine plied yarns and is therefore a direct competitor of ring spinning and twist spinning (Siro).

Principle of operation

Drawframe slivers provide the feedstock. These are passed through a five-line drafting arrangement (Fig. 32, A) with a draft of up to 350. The drafting arrangement (A) is followed by a strength-imparting unit (B). Here, as in the Murata false-twist method, an air-jet winds edge fibers and projecting fiber ends around the strand. As previously described in this volume, a bundled yarn is produced in which the core fibers are aligned in parallel while individual fibers of the envelope are wound around the body of the yarn. In contrast to other processes of the same general type, the yarn only receives sufficient strength here to enable winding up and subsequent twisting to occur. The bindings typical of jet-spun yarn are missing; they would give the yarn a rather hard character.

Two such yarns are combined at C and taken away by the take-off rollers (D). The yarn is taken up in a cheese, and this is a ready-made feedstock for the twisting stage (ring or – preferably – two-for-one twisting); the assembly-winding step is eliminated.

The wrapping fibers are detwisted during the twisting operation; in the plied yarn, all fibers lie parallel. The process differs from classical twisting in that it is not necessary to detwist turns in the single ends in order to achieve a soft plied product. The twisting step can therefore be carried out with relatively low twist factors, enabling higher delivery speeds to be achieved.

Fig. 32 – The PLYfiL spinning system