Shed Timing and Shaft Motion Profiles
topic
Dobby shaft motion profiles specify the angular position of shaft crossover, full open shed, and shed closure relative to the loom crank rotation cycle, with early shedding completing crossover before weft insertion to allow maximum shed dwell time for reliable weft passage, and late shedding delaying crossover until after beat-up to reduce warp stress from simultaneous shedding and beating forces, with the shed timing optimisation balancing warp break rate reduction against the weft insertion reliability that requires adequate shed opening during shuttle or rapier traversal.
Role
Governs the mechanical stress on warp yarns and the reliability of weft insertion through the shed timing that determines the sequence and overlap of the primary loom motions of shedding, picking, and beating, with optimal shed timing being particularly critical at high weaving speeds where the time available for each motion decreases and where incorrect timing causes either warp breaks from premature shed crossing or weft insertion failures from inadequate shed opening.