Rieter

Influence on quality and economy

Index

If an assessment is based on quality alone, the drafting system is the most important part of the machine. It primarily influences the uniformity and tenacity of the yarns. The following aspects are therefore very important:

  • the type of drafting system;
  • its design;
  • precise settings;
  • choice of the correct components;
  • choice of the correct drafts;
  • maintenance and servicing, etc.

However, the drafting system also has an influence on economy, i.e. directly via ends down frequency and indirectly via degree of draft. If higher drafts can be set in the drafting system, this enables coarser rovings to be supplied. However, coarser rovings signify in turn higher production performance of the  roving frame and thus savings on roving spindles, i.e. a reduction in machines (roving frames), space, personnel, etc. However, if the draft is increased too much, this can result in a reduction in yarn quality. The following approximate upper limits for drafting have emerged in mill operations using modern drafting systems with good fiber guidance (e.g. Rieter drafting systems with  P 3.1 pressure arm):

  • carded cotton yarn up to 40
  • carded yarn blends up to 50
  • combed cotton and blended yarns
    - medium counts up to 60
    - fine counts up to 70
    - man-made fibers up to 45 (- 50).

In order to obtain optimum results, the break draft zone must be set in such a way that the roving is under tension in this zone, but only sufficiently for no real drafting to occur. This is achieved with break draft nip distances of 60 - 80 mm and break draft settings of 1.03 to about 1.3. Unfortunately, generally applicable optimum settings for every case cannot be stated, since they depend heavily on fiber material, roving count and roving twist.