Rieter

Components for manufacturing fancy yarns

Index

Fancy yarns account for only a very small proportion of total yarn volume, but are repeatedly in considerable demand, depending on fashion trends. Yarn effects arise from selective, controlled changes in the yarn cross-section. As a rule, these involve slub-like thick places which can be varied in shape, length, increase in cross-section, sequence and the frequency of their occurrence. The standard drives for the feed and take-off cylinders are replaced by special, processor-controlled drives in order to enable fancy yarns to be produced on the rotor spinning machine.

The thick places produced with these fancy yarn devices (see Fig. 87 and Fig. 88 ) can, however, due to the backdoubling in the rotor and in contrast to  ring-spun yarns, never be shorter than the rotor circumference! This limitation is unimportant for most types of effect. Specially developed spinning elements ( opening rollers,  draw-off nozzles) are used on the rotor spinning machine where shorter effects are essential, for example to imitate the short variations in cross-section typical of ring-spun yarns (refer to section  Fabrics made from rotor-spun yarns.
One method that is rarely employed because the extent of the effect is very limited is to vary selectively the crosssection of the drawframe slivers. The high drafts on the rotor spinning machine enable only very long changes in cross-section to be produced in the yarn in this way.

Fig. 87 – Fabric woven from rotor-spun denim yarn

Fig. 88 – Yarn effects in rotor-spun and ring-spun yarns