– International Cotton Conference Bremen –
Known for the variety and range of topics from the cotton value chain, the International Cotton Conference Bremen is above all a specialist conference. This was demonstrated, for example, by the presentation by Dr.-Ing. Mahmud Hossain from the TUD University of Technology Dresden (TUD) during the International Cotton Conference in March 2024, which was dedicated to the further development of ring spinning.
Ring spinning is the dominant form of yarn formation technology in the world, accounting for about 80% of yarn production today. However, ring spinning is much slower than rotor spinning, two-nozzle air-jet spinning and air-jet spinning. Factors limiting speeds in ring spinning include the frictional heat between the traveler and the ring, which can reach melting points for manmade fibres, abrasion in the traveler system, frictional heat between the balloon control ring and the yarn, and incremental increases in tension as spindle speeds increase.
Machinery manufacturers are trying to overcome these limitations through changes in equipment designs, including different topologies and material combinations in the ring/traveler system.
State of the art research to reduce friction in the spinning process includes using a magnet levitating above a high-temperature superconductor cooled with liquid nitrogen to -196° C. This method, called Superconducting Magnetic Bearing (SMB), does not require expensive control or sensor units and is highly reliable at high spindle speeds. This system is also called a passive magnetic bearing system to differentiate from an active magnetic bearing system, which is activated electrically.
In his presentation, Mr Hossain described two concepts of the twisting element in a turbo ring spinning tester. In concept 1, the permanent magnet ring floats above the superconducting ring, while in concept 2, the permanent magnet ring rotates within the superconducting ring. In either case, the yarn guide is attached to the permanent magnet ring and rotates clockwise, distributing yarn onto a bobbin which is spinning inside the two rings.
Mr Hossain said that TUD has experimented with concept 1 because the magnetic force is sufficient to maintain the permanent magnet ring above the superconducting ring. The SMB system provides frictionless spinning even at speeds up to 50,000 rpm. The system has been tested with both natural and chemical fibres with fibre lengths up to 45 mm. In laboratory tests, the SMB system has been constructed within an insulated chamber using a cryogenic system with liquid nitrogen to maintain a constant -196° C. Tests were conducted with pima cotton, 36 mm in length, 44 g/tex strength, and 3.6-4.3 mic, up to 40,000 rpm.
Mr Hossain said tests indicated that the SMB system offers the possibility of producing yarn of acceptable quality at higher spindle speeds up to 35,000 rpm, double and even triple the speeds possible using traditional ring-spinning equipment.
In conclusion, Mr. Hossain reported that a special turbo ring spinning tester had been developed that could withstand spindle speeds up to 50,000 rpm. The system produced acceptable-quality 100% cotton yarns up to spindle speeds of 30,000 to 35,000 rpm. By eliminating the heat associated with friction in the traveler system, the SMB system has the potential to produce at 40,000 rpm. Work is underway to develop the system at scale.
After his presentation the speaker answered several questions. He explained that the reduction in friction resulted in a halving of the energy requirement per kg of yarn production.
Regarding yarn counts and cotton qualities used in the SMB system, Mr Hossain reported that the system is optimized for fine count yarns using longer, stronger, finer cottons.
Find the presentation here: Superconducting Turbo Ring Spinning