Rieter

The order of fibers within the yarn

Index

Also expected is that the yarn has optimal strength. Nowadays yarns obtain their strength, almost without exception, from  twisting. Therefore the strength is, beyond doubt, highly dependent on the height of the twist, but also on a large area of fiber-contact, and that again means for the fibers:

  • high degree of stretching-out (straightening);
  • highest attainable degree of parallelism;
  • binding-in of the whole fiber, including if possible both fiber ends, into the yarn structure.

Furthermore, in yarns which have not been produced by using adhesives, the helical winding of all, or at least some (wrap yarns) of the fibers is of decisive importance, since ultimately the stability and strength of the structure are derived from the pressure towards the interior exerted by fiber windings, which are created by the twist.

One reason for the lower strength of rotor-spun yarn relative to ring-spun yarn is the lower degree of parallelization and the lower degree of straightening (fiber hooks) of the fibers in rotor-spun yarn.

Looking at the first two items, the following operations are responsible for imparting this order:

  • Carding (the high degree of longitudinal orientation obtained on the main cylinder is, however, nullified to a large extent by the doffer).
  • Combing (here, however, parallelizing is a side-effect, which is not always desired to this extent).
  • Drafting (this is the most usual method of imparting order, since each drafting of the fiber masses is accompanied by straightening).
  • Floating of individual fibers in a strong air current (for example, in the feed tube of the rotor-spinning machine).
  • Deliberate collection of fibers, e.g. in the rotor.