Quality in High-performance Combing

Performance Boost Through CAPD

Rieter's own CAPD (Computer Aided Process Development) program based on in-house technology experience was already used in the development of the E 62/E 72 predecessor models. This enabled the batch combing process to be made operationally reliable in technological

terms in mill operations as regards controlled detachment and layering as well as piecing of the detached and combed fiber packages, even at higher nip rates. This provided a sound basis for the E 65/E 75 machine generation. By adopting proven elements and incorporating other optimization features, the nip rate has been increased to 450 per min. in the short and medium staple range by means of CAPD ("plus"). Combing in the long staple range (> 1L'") is also performed in most cases at nip rates of 400-420 per min.

Circular Comb & Top Comb

The "Primacomb 8014" and "8015" circular combs specially developed for the E 65/E 75 generation ensure gentle, controlled fiber tuft intake and thus optimum combing action in conjunction with the motion of the circular comb and the high-precision clamping of the nippers. Key aspects here are the optimized front angle, the lengths of the tooth row segments with corresponding gap widths, and the configuration of the clothing points.

The "Ri-Q-Top" top combs newly developed by Rieter guarantee superior combing efficiency in conjunction with a low tendency to soiling due to a new point shape and newly modified tooth cross section. For example, short fibers that have been carried along; i.e., floating and unguided short fibers, are stopped by the top comb during detaching; accumulation at the tooth base is made virtually impossible by the completely new tooth cross section. Instead, these fibers are reliably disposed of in the next circular combing cycle. This results in a reduced tendency to soiling and thus improved combed sliver consistency compared to needled top combs.

New Drafting System

The slivers from the 8 separate combing heads are now fed to a 3 over 3-cylinder drafting system. (Figure 1) Synergies with proven Rieter drafting technology have been exploited in particular in geometry and subsequent web formation. In combination with variable main and break draft distances, all staple lengths can be processed further on the autoleveler drawframe while attaining superior CVm values with simultaneously adequate sliver adhesion length. The main draft peaks occurring in the spectrogram with the earlier 3 over 5-cylinder drafting systems, resulting from floating fibers, are a thing of the past thanks to precision drafting action in the two drafting zones. The band widths of the mass diagrams and the CVm value are thus decisively improved. The piecing stack characteristic of the comber does not change due to the system, but is now more clearly apparent in the spectrogram (Figure 2) due to the lower main draft peak. However, this is an advantage on the autoleveler drawframe, since this long-wave fault is clearly registered by the control system and is subsequently leveled out reliably.

Yarn Quality Gains From High-Performance Combing

Gentle and rapid combing results in a further reduction in the dwell time of fibers in the circular comb clothing compared with earlier. The yarns produced therefore display no impairment of stress-strain behavior, since over-elongation of the fibers is prevented. On the other hand, the IPI level of the yarns can be maintained and in most cases even improved by high-frequency combing compared with lower nip rates. (Figure 3) To complete the circle, the inevitable, infrequent weak places in the yarn, which are especially disturbing in downstream processing, are now mostly located at a higher stressstrain level than in production at lower nip rates. Comparisons of single-jersey knits have also shown that those made from yarns combed on the E 65 turn out more uniform than those of the preceding generation. The new drafting system plays a major role in this.