Weft Insertion Speed

The average weft insertion capacity of weaving looms is measured in m/min and can be calculated by multiplication of the machine speed with the fabric width. 

Weft insertion is intermittent therefore, the actual weft insertion speeds are much higher. The acceleration of the weft insertion is up to 1400 g or 14,000 m/sl The evolution of the weft insertion speed is shown in Fig. 4.26. The insertion speed could be increased by the reduction of masses. 

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In the research work of Vilfayeau (2014) and Trifigny (2013), the dynamic observation of the weaving loom kinematics at real weft insertion speed has been favoured in order to take into account the dynamic inertia of all the loom parts and their influence with respect to the longitudinal and transverse stresses applied on yams. 

The weft insertion speed on the looms is up to 1200 mmin. The working principle of a loom is shown in Fig. 6.19. 

The warp yams stored on the beam (Number 1 in Fig. 17.1) are subject to a constant tension and come into surface contact onto the whip roller (Number 2 in Fig. 17.1). The droppers (Number 3 in Fig. 17.1) apply a tension on each warp yam equivalent to the resultant force of their own weight. The warp yams inserted in the eye of each heddle (Number 4 in Fig. 17.1) have a dynamic vertical movement and perpendicular to the fabric plane to form the shed (angle formed between the two warp yam webs). The weft insertion system comes into frictional contact with the two perpendicularly warp yam plies. The warp yams are located into empty spaces, at regular intervals, of the weaving reed (Number 5 in Fig. 17.1). The weft density of the obtained fabric is then driven by the take-up roller speed (Number 6 in Fig. 17.1). 

Sequential multiphase looms provide sequential sheds in the warp direction, each for one weft insertion. This principle has been known for a long time. At ITMA1995, Sulzer-Riiti presented its sequential multiphase weaving loom M 8300 (Fig. 4.25). Despite the high production speed (up to 5000 m/min), it was no commercial success, the main reasons being the low flexibility regarding patterns and the difficulties when fixing a weft yarn break. 

The observation of the warp yams dynamic motions between areas 2 and 3 (Fig. 17.10) by the use of high-speed camera pictures has been done during the third level of weft yam insertion of architecture 1 (Fig. 17.17). 

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