Rieter

Interrelationships in spinning technology

Index

Feedstock

Drawframe sliver is suitable as feedstock. Three passages should be used in order to obtain adequate parallelization of the fibers in the yarn. On account of the maximum draft of 200 in the drafting arrangement, relatively fine strands are needed. The sliver mass is in the region of 3 g/m (3 ktex).

Drafting arrangement

Four-line double-apron drafting arrangements are used, which permit drafts of 65 - 220. Both the upper and lower aprons are short. The fiber strand is not opened out into individual fibers but merely attenuated. The advantage of this is that it is not necessary to reassemble the fibers, which exhibit a higher degree of parallelization than fibers in open-end spinning, for example.

Twist jets

The two nozzle air-jet spinning principle uses two jets in sequence. The twist level in the yarn is dependent upon both the throughput speed and the air pressure in the jets. The latter is usually in the range of 4 - 6 bar. The air vortex rotates with a speed of 1 to more than 2 million rpm, the speed being somewhat lower in the first jet than in the second. The yarn takes up about 6 - 12% of the revolutions of the vortex.

Binding-in the fibers

Coarse yarns cannot be produced by two nozzle air-jet spinning. This is due to the geometrical ratio between the surface area of a yarn and its cross-section. The coarser the yarn, the lower the ratio, i.e. it becomes steadily more difficult for the wrapping fibers on the surface to bind the increasing number of core fibers together effectively.
Influence can be exerted on the binding action, the spinning conditions, and the yield primarily via:

  • the raw material;
  • the width of the fiber strand leaving the drafting arrangement;
  • the spinning draft;
  • the spinning tension (yarn tension) between the front roller and the take-off rollers;
  • the air pressure in the jets; and
  • the twist relationship between the first and second jets.

These parameters are adjustable within limits.