An overview of yarn formation technologies

 During the 1970s, there appeared to be a myriad of spinning systems, such as twistless spinning, self-twist spinning, fasciated yarns, composite yarns, wrap-spun yarns, pot spinning, continuously felted yarns; and the many possible variants in open-end spinning such as rotor, electrostatic, friction spinning, and vortex spinning (the original “Polish” system). At the same time, there were continued developments in ring spinning, with ventures into rotating ring and traveler systems, individual spindle drives, high draft systems, modified travelers, double roving spinning, and hybrid systems. A look at today’s industry reveals that while some systems have established a successful but small niche — wrap spinning for fancy yarns, and friction spinning for specialty industrial markets — very few systems have survived. Indeed, this is also true of the manufacturers of these machines.

It is evident that, when judged from the perspective of the number of installed spindles, ring spinning is still the most dominant spinning system — there are about three times more spindles than installed rotors. If judgment is based on the quantity of yarn produced, it is clear that even though there are only one-third as many positions of rotors installed, rotor spinning produces three times more yarn than ring spinning.

Ring Spinning

The technology behind ring spinning has remained largely unchanged for many years, but there have been significant refinements. Changes, which on their own offered only slight advantages, provided the following synergies when combined: • The introduction of longer frames reduced the relative costs of automatic doffing. • The combination of spinning frame and winding (link winders) further enhanced the adoption of automation. •

The introduction of automatic doffing meant that doffing time was reduced and thus package (and ring) size was less critical. • The introduction of splicing on the winder meant that yarn joins became less obtrusive — again offering the potential of smaller package. • Smaller rings meant that for a limiting traveler velocity (40 meters per second [m/s]), higher rotational speeds (and hence twisting rates) could be achieved. These combinations meant that the potential maximum speed of ring spinning was raised from about 15,000 to 25,000 revolutions per minute. There also have been several other proposed developments that have met with mixed success. Drafting systems: While double apron drafting dominates, the system can be tweaked to enable higher drafts. Recent exhibitions have featured machines operating at potential drafts of 70 to 100.

The use of high drafts has significant impact on the economics of the total system. Individual spindle drives: Several manufacturers demonstrated this possibility in the 1980s. While the concept offered advantages with respect to lower energy requirements, less noise and better control of speed, it suffered higher initial costs and bigger spindle gauge. Ring Design Several approaches to reducing the limitations of traditional rings and travelers have been proposed. Orbit ring: This development from Rieter was aimed at increasing heat dissipation from the traveler. Ceramic rings (Ceratwine system): The combination of a ceramic ring and ceramic-coated traveler offered the promise of significantly better wear resistance, which translates into long traveler life. More consistent yarn quality and shorter break-in time are other claimed benefits. Rotating rings: This idea was tried by several ring frame manufacturers in the 1970s.

 Other ventures into this area included systems such as Cerifil, Magnetic Spinning and Super Traveler Spinning. The problem with these types of devices is, while they appear to operate at lower spinning tensions, and thus potentially offer lower end breakage rates, they suffer the drawbacks of short duration and high- magnitude tension peaks because of the inertia of the twisting element, which is significantly higher than a traveler.

Spindle identification (Schlafhorst, Barco): The tracking of spindles from the ring frame has great potential for process quality control. This enables the identification of those spindles on the ring frame that are responsible for producing defective yarns, as assessed on the winding frame. It is believed this type of system will result in improvements not only in yarn quality, but also in efficiency, by more readily indicating faulty positions on the spinning frame. Longer machines: Improvements in the drives used on spinning frames have enabled the number of spindles per machine to be further increased up to 1,488 (Zinser). This has a positive impact on the cost per spindle. Additionally, as indicated above, longer machines favor the use of automation, particularly link-winding. Compact spinning: Systems that use additional drafting components and pneumatics to create yarns that are less hairy and stronger are available from several machinery makers. The many claims made for these systems are usually mutually exclusive in that one can either have a stronger yarn or spin at higher production speeds with lower twist. Moreover, there is a significant increase in the cost of these machines, and the yarn thereby produced, when compared to traditional spinning frames. While the use of compact spinning machines is claimed to have made significant inroads in Europe, the system has not been well-received in the United States. It is evident that several other machinery makers will venture into this market, such as Marzoli and Cognetex, and this added competition may result in reduced machinery costs.