Abstract:

Objective Automatic splicing of a rotor spinning machine is one of the key technologies to measure its automation level, which directly affects the efficiency and quality of spinning. At present, splicing technology used in semi-automatic rotor spinning machines is mostly concentrated on the research of splice mode. When faced with yarn breakage caused by a temporary stop or power failure, it is usually necessary for the spinning operator to carry out the operation of the piercing and splicing end by end, which consumes a lot of manpower and is inefficient. To solve this problem, this research proposes a digital control method of each process (including the feed roller, opening roller, fiber transport channel, rotor, takeoff and bottom roller, winding roller) during yarn breaking and splice and develops a continuous spinning technology of collective automatic tail yarn retention, collective automatic piercing, and collective automatic splicing.

Method Through the construction of the mathematical model of the spun yarn length of the residual fibers in the spinner after the power failure, the guidance program accurately controls the various agencies to stop in an orderly manner, so that the severed tail yarns are stopped in the lead yarn twist blocking tube, to complete the collective automatic tailing. When power is supplied, the doffing mechanism is controlled to wind the tail yarns (as seed yarns) back onto the collection groove of the rotor cup, while new fibers are fed into the collection groove, and the fiber flow is twisted to complete collective piecing and collective splicing. Through the constructed splice model of seed yarn and fiber flow, the program is guided to accurately control the overlap length and twisting time, and further realize the regulation of line density, twist, strength and other parameters of the seed yarn-fiber flow twisted body. On this basis, 30 groups of experiments were designed and the results were compared and analyzed by USTER􀳏TESTER 5, KEYENCE VHX-5000 microscope and image processing (MATLAB^® 2023b).

Results Thirty groups of verification experiments were done by manually cutting off the power supply, the results showed that. the success rate of the splice was 96.7%. The average strength of the splice was 10.435 cN/tex, which was 84.9% of the average strength of the designed normal yarn of 12.29 cN/tex; the average diameter of the splice was 0.69 mm, which is less than twice of the design normal yarn diameter of 0.361 mm. It conforms to the textile industry standards of joints quality and the single yarn breaking strength.

Conclusion This paper analyzes the mechanism of stopping the collective automatic tail yarn retention, collective automatic piecing, and collective automatic splice, constructs the corresponding mathematical model to guide the program to control the sequential movement of the relevant mechanical structure, solves the problem of how to quickly splice the yarn in the process of rotor spinning due to temporary stopping or power outage stopping the whole machine spindle position all yarn breakage, and verifies the model's accuracy through the relevant experiments. The continuous spinning technology of collective automatic tail yarn retention, collective automatic piecing, and collective automatic splice is realized, which provides a new digital jointing technology for rotor spinning broken yarn splice. However, due to the different demands for yarn post-processing in different factories, the parameters of yarn jointing, such as strength and thickness, need to be optimized and adjusted, which is also a direction that needs to be studied in depth in the future.

Key words: rotor spinning, automatic tail yarn retention, automatic piecing, automatic splice, splice model, semi-automatic rotor spinning machine, yarn quality