The dynamics of fabric forming on the loom at high weaving rates

Abstract

The problems arising with the increase in weaving machines outputs and their speed are discussed. The main problem is the decrease in the weavability of higher fabric densities. It is shown that the loss of weavability related to fabric is caused by an increase in the frictional and deformation work of woven-

in threads due to increase in the velocity of weft sliding into the fabric. This causes then an increase in the weaving resistance, beat-up force, lift of the reed in contact with the cloth fell, and in the angle of duration of beat-up. All these variables are functions of the time of the beat-up pulse of reed, <i>f</i>[y(<i>t</i>)]

and vary progressively with weaving speed. There exists nevertheless one parameter, the impulse of the beat-up force (or force of weaving resistance <i>R)I= </i><i>ʃ</i>(<i>T</i>_P<i> </i>)<i>R(t)·dt, </i>which remains constant for the given fabric and weave at today's usual loom speed (about 500 rpm and higher). This parameter can be taken

as the determining variable for the given weave and fabric density, and the weavability can be measured by it.<br>

The machine related problems are caused by the compliance of the light-built fast running mechanism of the loom, which may not be able to deliver the necessary 'active' impulse of the beat-up force to the fabric; the active impulse is imparted due to forces of the elastic deformation of the beat-up mechanism as of a "press", and due to its momentum as of a "hammer".

<br> Further complications arise due to the superposition of forces arising during the beat-up in the warp as a result of shedding and backrest oscillations. These forces get added to the beat-up force of the reed, but they may vary rather significantly even with small random variations in the ratio of weaving frequency to eigen frequency of the backrest system, so that the intensity of beat-up may be unstable in the course of weaving. However, the effect of backrest oscillations may be, under certain conditions, exploited

<span style="font-size:14.0pt;line-height:115%;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";mso-ansi-language:en-in;mso-fareast-language:="" en-in;mso-bidi-language:hi"="" lang="EN-IN">for improving the weavability of the given loom.</span>