Simulation of the yarn transportation dynamics in a warp knitting machine

Abstract

To date, in the textile manufacturing process of warp knitting, trouble-shooting and process optimization mainly rely on empirical knowledge and experiments. This factor limits the achievable increase in productivity and quality. On the other hand, using simulations, different phenomena that affect the quality of the knitted fabric and the knitting process can be clarified in the run-up of the experiments. Consequently, an increase in quality and flexibility can be reached with reduced experimental effort. This paper presents a process simulation of the warp thread dynamics in the thread feeding system of a warp knitting machine. For this purpose, a continuum model of the warp thread that includes the spatial dynamics of the thread and the axial transport movement has been developed.

Analysis of yarn tension based on yarn demand variation on a tricot knitting machine

“…The difference between the yarn demand and feed is the main factor causing the change of the yarn tension, but at high machining speed and high thread fineness, the properties of the yarn, which is an elastic material with mass and which creates friction, influence the process. 2 The inertia of the mass affects the fluctuation of yarn speed, causes yarn quality change, and indirectly influences the yarn tension. The inertia of a warp is due to a stick-slip phenomenon, but it is also due of the actual reaction to fast dynamic warp tension change.…”

“…In 1996, a model to simulate the warp tension in weaving processes was described in the dissertation of De Weldige, 1 in which the thread was assumed to be a linear elastic, massless, and flexible spring element, and the friction between the thread and solid bodies was neglected. 2 He presented an algorithm to calculate the warp tension based on an examination of the equilibrium of torque around the axis of a mass-spring backrest system. An additional dissertation concerning this topic was published in 1998 by Chen, 3 which made the same assumptions concerning the thread as the previous work.…”

“…An additional dissertation concerning this topic was published in 1998 by Chen, 3 which made the same assumptions concerning the thread as the previous work. 2 According to the characteristics of bearded needle warp knitting machine, researchers like Feng 4 and Zong, 5 by combining knitting yarn consumption and warp dynamic tension in the spindle in the range of 360 , theoretically analyzed the dynamic tension variation and the main influencing factors, 4 and discussed the optimization of the machine parameters. This provided a theoretical basis for the study of the positive warp let-off system, and improved tension fluctuation from the angle of the delivery.…”

“…Metzkes et al investigated the thread tension in the looping process, and developed a continuum model of the warp thread in an attempt to reduce the influence of tension fluctuation. 2 Koo used simulated knitting conditions with a newly developed test rig to study yarn tension variation, and found that the selection of gauge and the yarn feed angle should be taken into account to reduce yarn tension during knitting. 7 Now the warp knitting machine has largely adopted the positive warp let-off system, which can effectively reduce the tension fluctuation.…”

Construction and system realization of the yarn tension model of fully fashioned flat knitting fabric

“…Therefore, positive yarn feeding is difficult to achieve. 8 , 9 The deceleration and rotation acceleration of the carriage will cause part of the yarn to remain as it drives the yarn feeders to knit, thereby increasing the fluctuation of the yarn tension of feeding. Fluctuations in the feeding tension often cause loose loops at the edge of the fabric.…”