Rieter

Introduction

Index

From a purely commercial viewpoint the drawframe is of little significance – it usually contributes less than 3% to the production costs of the yarn. However, its influence on quality, especially yarn evenness, is all the greater for this. Furthermore, if the drawframe is not properly adjusted,  yarn strength and elongation will also be affected.
There are two main reasons for the considerable influence of the drawframe on evenness. Firstly, within the sequence of machines in the short staple spinning mill, the drawframe is the definitive compensation point for eliminating errors. Inadequacies in the product leaving the drawframe not only pass into the yarn, they are actually reinforced by drafting effects following the drawframe. The yarn is never better than the drawframe sliver. Secondly, a defect arising at the drawframe itself can exert an effect of significant proportions on the overall process. High-performance drawframes currently produce over 400 kg of sliver per hour at each delivery. Very large quantities of faulty sliver will be produced in the time that elapses before discovery of the defect. It is therefore understandable that leveling drawframes are a must for every modern short staple spinning mill. It is equally clear that, of all departments in the spinning mill, the drawing section is the least suitable place for making rigorous economies. It is quite the wrong place to try to save money.

At the drawing stage for carded yarns the material rarely passes just one machine but usually two, arranged one after the other and combined to form a group. An exception is the rotor spinning mill, where often only one passage is used or even none, i.e. the sliver is fed directly from a highperformance  card, but equipped with an integrated leveling device. Normally, processing in two passages is necessary to fulfill requirements. However, a second passage after the comber is superfluous, since this does not produce any improvement in quality. On the contrary, it usually adversely affects quality due to excessive parallelization of the fibers. The drawframe used in this case, however, has then to be a leveling drawframe.

Fig. 1 – Normal processing lines; 1. card; 2. drafting module for card; 3. drawframe; 4. combing preparation, 5. combing machine; 6. roving frame; 7. rotor spinning machine, 8. ring spinning machine