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Technology Refines Yarn Production

Automation and on-line monitoring are among the three advances improving quality and productivity in short-staple spinning.

By Dr. Bhuvenesh C. Goswami

S taple yarns form a very large part of the production of textiles both in the United States and around the world. In the past century, the manufacture of staple yarns has been driven by the motive to achieve desired tensile properties and aesthetics at a reasonable cost.

The achievements in accomplishing the stated goals during the last century may be discussed in terms of the developments that occurred before the second world war and those between the 1940s and late ’70s and the explosive growth that occurred in the last 20 years of this century, especially in the ’90s.

The early years saw an evolutionary change in the understanding of the properties of the raw material — one and only one cotton — and the method of production from mule spinning to ring spinning that helped the spinners to produce yarns that met the goals of quality, productivity and reduced labor cost.


Introductions Are Made

The introduction of synthetic and man-made fibers helped the technologists to enhance the availability of unique aesthetics and tensile properties either by blending or using a single component. However, the means of production were limited to one principal technology, i.e. ring spinning. In understanding of the dynamics of dafting (including fiber control), twisting and winding (including ballooning) helped advance the technology in achieving the desired yarn structure and productivity.

Even though the introduction of apron drafting systems with controlled loading of top rolls, as symbolized by the SKF technology, improved the yarn quality but the mechanical design of the roller drafting, the spindle bolster and the drive system did not allow any substantial improvement in yarn quality (evenness, hairiness, strength) with savings in energy and labor.

Nevertheless, ring spinning reached a point toward the middle of the century where the increase in productivity was marginal and would require a radical approach in making a quantum jump.

The introduction of rotor spinning in late ’60s was a welcome development. However, the yarn structure lacked the mechanical and the aesthetic properties inherent in ring-spun yarns. But this did not discourage the machinery manufacturers from introducing the monumental improvements as this technology offered increased productivity.

The recent introduction of Corobox SE 11 by Schlafhorst and R20 with AEROBOTIC technology by Rieter have made the production rates of 220 meters/minute at a rotor speed of 150,000 rpm possible.

The recent introduction of Suessen Elite Spinning Systems, where the fibers in the drafting zone are subsequently captured in a condensing zone which consists of a profile tube, the lattice apron and a delivery top roller. The geometric configuration of the apron and front roll and positioning of the condensing zone right up to the fiber delivery point, maintaining slight tension in the fibers in this zone (which allows straightening of the fibers and helps consolidation of all fibers in a compact bundle) and a slight rotation of the fiber bundle (which is very effective in the short fibers and the fiber ends being held close to the bundle), help eliminate the twist triangle.

The twist triangle geometry and the tension in the fibers in this zone in traditional ring spinning are responsible for producing hairiness and also end breaks. The new system thus produces a yarn which the manu-facturer claims to have very low hairiness and better yarn strength (due to incorporation of majority of the fibers and fiber ends in the body of the yarn) in a ring-spun yarn.

Another development introduced by Zinser (AIR-COM-TEX 700) accom-plishes the same results via air suction through a perforated surface before being twisted.

Technology Booster

rieter_769The introduction of automation via computer controls of moving parts (such as in Marzoli’s NSF-4 Ring Frame) and the monitoring of on-line yarn quality have boosted the relevance of ring spinning technology to a force to be reckoned with in the early part of the 21st Century.

Other features in the ring-spinning technology are the direct spindle drive (such as HOWA’s UAM Ring Frame) contributing to energy savings, low noise level, lower spindle vibration (lower evenness variation) and obviously lower labor costs will also be major factors in the presence of ring spinning in the textile industry.

In addition, improvements in doffing (G33 ring spinning machine by Rieter — doffing without under-winding) and machines with large number of spindles (e.g. Zinser Ring Frame 350) in a frame coupled with an efficient linking winding system will enhance the ability of ring-spinning systems to withstand competition.

The developments in ring spinning such as live rings, Orbit ring traveler system, ceramic coated rings, improved control of fibers in the drafting system, anti ballooning devices and minimization of yarn tension (a controlling factor in ends down), automatic doffing and linking system have kept this technology from being pushed out of competition.

Uniqueness Of Ring

One of the primary reasons for the sustained use of ring spinning has been the unique yarn structure that it produces. No other technology has yet been able to reproduce the mechanical properties and the aesthetic characteristics that are uniquely present in ring-spun yarns.

The rotor spinning technologies also offer the advantages of lower energy consumption and longer service life of various parts.

Some other manufacturers such as Elitex (BD-D30 New Generation Open End spinning Machine), the Suessen TT/Rotor Spinning machines need mentioning also. The new technologies in piecing, (e.g. Rieter’s Syncrotop) large yarn packages — up to 5 kg, AERO bearing, Magnetic Rotor Spinning System (offering an absolute contact-free bearing location for positioning rotors by Schlafhorst), material and design of opening roller and housing for turbulence — delivery of fibers to the rotor and foreign fiber detection systems will all contribute to not too early a demise and replacement of this yarn technology by the high speed spinning systems such as vortex, as being suggested by some futurists.

Ring spinning accommodates all types of fibers. The last part of the century has seen the introduction of air-jet and subsequently the Vortex Spinning technologies for spinning short-staple yarns. The latter technology via Murata Vortex spin-ning No. 851MVS shown at the last ITMA has ushered in a revolutionary change in the rate of production of staple yarns made from cotton.

Even though the rate of production on Vortex Spinning of 440 meters/min, which is two times, and 20 times the rates of production attainable on the rotor and ring spinning, respectively, but it is not without drawbacks. The loss of fibers during spinning is one and the appearance and the mechanical properties of the yarns are the other.

Seeing The Difference

ringspin_770The rotor spinning and the Vortex and air-jet spinning technologies rely on the direct feeding of a sliver to the combing roll and the drafting system, respectively. The sliver to spinning system in ring spinning was first introduced in the 1950s but it failed due to lack of fiber control during drafting. The system was beset with a high end-breakage rate and the uneven yarn that resulted from low fiber control. Since then, the concept of a compact spinning process where the control of fibers during drafting and the use of pneumatic devices have allowed the production of staple yarns with low hairiness.

The ring spindle speeds of 25,000 rpm have made the retention of ring spinning viable. Ring frame manufacturers Rieter, Sussen, Zinser, M.A.L., Savio, Marzolli, Howa and Lakshmi promise to stay competitive in staple yarn manufacturing in the next century.

The discussion of short spinning technologies cannot be complete without the mention of Friction Spinning. FEHRER, the only commercial manufacturer (DREF 2000 the latest introduction) has introduced some improvements in presenting individual fibers to the perforated rotating drums where the yarn is formed, will only cater to a niche market just as the Centrifugal Spinning System, AU-II-75 introduced by Techmashexport which claims to produce high-quality staple yarns at a low labor cost.

Of course the latest developments in fiber handling, yarn quality monitoring and improved yarn hairiness and strength and package winding will have to be part of the new technologies.

In the 21st century the challenge to the producers of natural fibers, vis-a-vis cotton, will be the production of clean, mature, long, fine and uniform (length and fineness) fibers. The machinery manufacturers will have to deliver the technology that offers high productivity and can handle both natural and synthetic fibers. The sliver to spinning in ring spinning will receive added attention in the near future. The other two principal technologies, i.e., rotor and vortex spinning will show incremental improvements. However, the industry will demand the reduction in the number of steps required in the production of staple yarns.

If the uniformity, both across and along the card web can be improved, the possibility of producing yarns directly from the card web can become a reality.

The interface of card to either the rotor or the vortex technology will revolutionize the next phase of the evolution of staple yarn spinning. But the ring yarn structure will occupy the supreme place in the utilization of staple yarns in weaving and knitting in the near future for obvious reasons.

Another promising area will be the expansion of the spinning of fine and medium fine plied yarns directly on the ring system (currently being used) and even perhaps its extension into the vortex technology. The plied yarn technology will definitely be a plus in reducing cost in weaving by the possibility of elimination of singeing and sizing.

Editor's Note: Bhuvenesh C. Goswami, Ph.D., is a professor of Textile Science at the Clemson University School of Textiles, Fiber & Polymer Science.

February 2000