Rotor Spinning

Rotor or open-end spinning is now a mature technology, and since the 1960s, it has seen a five-fold increase in twisting speeds. During the early stages of development, debates concerned such questions as: • Were self-pumping or evacuated systems better? • Was roller drafting feed superior to a beater opener? • Was spin through better than feed and withdrawal from the same face of the rotor? • Were twin disc bearings the best solution for higher speeds? These issues were seemingly resolved, and most modern rotor machines are very similar in layout with relatively subtle differences between machines from the major manufacturers. These differences are typically associated with the aerodynamics of the transfer tube, rotor design and navel design

 

While it is still possible to obtain low-tech rotor spinning frames, present state-of-the-art machines have significant integrated automation such as doffing, piecing, cleaning and process/product monitoring. Additionally, the machine can be part of a material handling system from sliver through to packaged yarn. It is generally accepted that, while rotor yarns are different from ring-spun yarns, they tend to offer advantages in processing through weaving and knitting. This difference is a result of structural differences introduced during yarn formation. This structure — which is responsible for the lower strength of rotor yarns, but improved hairiness and yarn abrasion — is an inherent feature of the system. While it is possible to control the formation of wrapper fibers by optimizing rotor and navel designs, it is impossible to eliminate them. Unfortunately, while smaller rotors are required for higher processing speeds, this also negatively impacts wrapper fibers, and thus higher speeds often carry the penalty of a reduction in yarn quality. Developments in rotor spinning include the use of longer machines. Additionally, there is interest in potentially using rotor technology to produce core yarns and using additional components to create effect yarns.

Fasciated Yarns

While initially there were several potential manufacturers of machines for this technology, the market has been dominated by Murata, with its jet spinning and vortex spinning systems. Murata Jet Spinning (MJS) gained a small, but significant, share in the polyester/cotton yarn market. The advantage of the system was that it offered high-speed production of finer-count yarns and thus did not directly compete with rotor spinning. Since its commercial launch as MJS, several variants have been introduced, including Murata Twin Spin (MTS) and Roller Jet Spinning (RJS). Different jets also were offered to accommodate different yarn styles. These offerings were to extend the use of jet spinning, with particular respect to fiber type and yarn count. Jet spinning has the major disadvantage of not being able to produce acceptable 100-percent cotton yarns. Furthermore, MJS is restricted to finer counts because yarn tenacity reduces as the yarn becomes coarser. For optimum processing, there also are higher quality requirements on the feed sliver with extra drawing or combing operations. Despite these limitations, and the necessity to optimize finishing in order to promote an acceptable hand, jet spinning is a viable system in the United States because of high productivity — 250 meters per minute (m/min) for the MJS 802H — and adequate yarn and fabric quality. As a bonus, the core sheath structure of the yarn tends to minimize hairiness, which in turn reduces pilling propensity, often a major problem with polyester-rich blends.

Murata Vortex Spinning

Murata Vortex Spinning (MVS) is best judged as a development of jet spinning specifically created to overcome the limitations of fiber type. The major marketing feature of MVS was that it was capable of spinning uncombed cotton slivers into acceptable yarns at speeds that were significantly higher than with any other system. The yarn structure is different from jet-spun yarn with many more wrapper fibers, and in parts the vortex yarn resembles a two-fold yarn. There were concerns that there is excessive fiber loss using this spinning machine. But, even though the fiber loss may be about 8 percent, most of this is short fiber, which would not contribute to yarn quality

MVS was introduced with a remarkable potential processing speed of 350 to 400 m/min. Successful spinning systems historically have had a significant increase in production speed within a few years of introduction. If this trend were to be true of MVS, it is possible that the industry could have a staple spinning frame capable of speeds in excess of 500 m/min. Even though it is claimed that MVS is capable of processing 100-percent cotton, it is believed that the major use of this system is in the processing of cotton-rich blends with polyester. The machine utilizes a roller drafting system working at high drafts and high speeds. There is proof that indicates these systems may give rise to unacceptable yarn variations, which become apparent in terms of fabric defects or weak spots in the yarn. This is a problem that could be addressed by using the rotor spinning beater opener. New developments likely for MVS include modifications to enable the production of coarser counts and a possible re-examination of the concept of spin assembly winding, where yarns from two spinning positions are combined onto one package that is subsequently two-for-one twisted. It is also evident, from a cursory review of patents, that other machinery makers have invested in significant research into technology similar to vortex spinning and perhaps there soon may be alternative machines available. It is clear that at the present time, there is a lull in investment in new spinning machinery in the United States. This could be explained partly by a downturn in the industry, which seems to be supported by the reduction in positions shown in Table 1, and partly by the fact that the current technologies are mature.