Rieter

Preparation of stock for combing

Index

The combing operation itself (feeding, nipping, combing, detaching) is a very sophisticated process which requires:

  • the best equipment;
  • optimal, stable settings;
  • excellent maintenance;
  • careful handling.

An extremely important factor besides these, however, is the preparation of the material before combing, as the raw material delivered by the card is unsuitable for combing as regards both form and fiber arrangement. If card slivers were fed to the comber, true nipping by the nipper plates (Fig. 4) would occur only on the high points, with the risk that the nippers could not retain the less firmly compressed edge zones of the slivers. These could then be pulled out as clumps by the circular combs. A sheet with the greatest possible degree of evenness in cross section is therefore required as infeed to the comber.

Good parallel disposition of the fibers within the sheet is a further prerequisite. If the fibers lie across the strand (Fig. 5), even long fibers (a) are presented to the circular combs as if they were short fibers (as shown at b) and they are eliminated as such. This represents unnecessary loss of good fibers.

Appropriate preparatory machines are needed to prepare the material so that it meets requirements. The fiber arrangement must also be taken into account, i.e. in this case the disposition of the  hooks. As explained in  Technology of Short-staple Spinning, over 50% of fibers in the card sliver have trailing hooks. If the comber is to straighten hooks, as it is intended to, then the fibers must be presented to it with leading hooks.

Because of the repeated reversal of the hook disposition during  coiling and subsequent removal from cans at the machines, an even number of  machine passages must be provided between the  card and the comber. In earlier days sliver lap and ribbon lap machines were used. During the nineteen-nineties the  sliver lap machine / rippon lap machine  process was replaced by the drawframe / sliver doubling machine process over all staple ranges.

As shown in Fig. 6, this consist mainly of:

  • the batt doubling process (classical method, outdated); and principally
  • the sliver doubling process, e.g. the Rieter UNIlap and the Marzoli Superlap SR 34.

Fig. 4 – Clamped slivers between the nipper plates

Fig. 5 – Fibers projecting from the nippers

Fig. 6 – The two preparation methods: conventional method (a, batt doubling) and new method (b, sliver doubling)