High-Performance Combing

witzerland-based Rieter Textile Systems recently introduced the E 65/E 75 (ROBOlap)
generation of combers to the spinning market. The machines feature new and upgraded technologies
designed to enhance operation and final product quality.

Figure 1

Performance Boost Through C A P D+

Rieter’s own Computer-Aided Process Development (CAPD) program, based on in-house
technology, already was used in the development of the E 62/E 72 predecessor models. This program
enabled the batch combing process to be made operationally reliable in technological terms in mill
operations, offering 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 minute in the short- and medium-staple range by means of
CAPD+. Combing in the long-staple range (greater than 1 inch) also is performed in most cases at
nip rates of 400 to 420 per minute.

Circular Comb And Top Comb: Basic Modules For Precise Fiber

The Primacomb 8014 and 8015 circular combs specially developed for the E 65/E 75 generation
machines 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
are the optimized front angle, the lengths of the tooth row segments with corresponding gap widths,
and the configuration of the clothing points.

Rieter’s new Ri-Q-Top top combs offer superior combing efficiency and have a low tendency to
soil because of a new point shape and modified tooth cross section. For example, short fibers that
have been carried along — such as floating and unguided short fibers — are stopped by the top comb
during detaching; and the new tooth cross section prevents accumulation at the tooth base. Instead,
these fibers are disposed of in the next circular combing cycle. This results in a reduced tendency
to soiling and improved combed sliver consistency, compared to needled top combs.


New Drafting System Improves Sliver Quality

The slivers from the eight separate combing heads are now fed to a three-over-three-cylinder
drafting system
(See 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 three-over-five-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 because of the system, but is more
clearly apparent in the spectrogram
(See Figure 2) because of the lower main draft peak. However, this is an advantage on the
autoleveler drawframe, because this long-wave fault is clearly registered by the control system and
is subsequently leveled out reliably.


High-Performance Combing Versus Yarn Quality

Gentle and rapid combing results in a further reduction in the dwell time of fibers in the
circular comb clothing compared with earlier combing methods. The yarns produced therefore display
no impairment of stress-strain behavior because 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
(See 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
stress-strain 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 uniformly than those of the
preceding generation. The new drafting system plays a major role in this.

In developing the E 65/E 75 combers, Rieter also focused on defined quality in the yarn and
the final fabric — an essential factor in fulfilling the responsibility to customers as a systems

November/December 2006