Rieter

Equalizing

Index

One of the main tasks of the drawframe is improving evenness over the short, medium and – especially – long term. Card slivers fed to the drawframe have a degree of unevenness that cannot be tolerated in practice, and slivers from the  comber contain the „infamous“ piecings; these must be obscured. It should be noted, however, that short-wave sliver evenness is not – as sometimes assumed – the sole criterion for evaluating the performance of the drawframe. It is true, for example, that unevenness over short lengths can be noticeably reduced, e.g. by very narrow setting of the rollers of the drafting arrangement, but this is often associated with deterioration in other quality parameters of the yarn, particularly strength.

It is also a mistake to assume that sliver evenness – especially over short lengths – can be significantly improved by using several passages. A second passage brings hardly any improvement and a third can actually lead to deterioration. In relation to settings and number of passages, therefore, it is important to find the optimum rather than seek the maximum. Equalizing is always and in any case performed by doubling, and can optionally also be performed by additional autoleveling. The draft and the doublings often have the same value and are in the range of 6 (short fibers) to 8 (medium and long fibers). When processing pure comber noil in the rotor spinning mill, however, it is usually necessary to settle for a value of 4 or to use high-performance  cards with integrated leveling devices instead of drawframes.