Back Rest Position and Warp Line Angle
topic
Back rest position governs the warp line angle between beam and heddles and the back rest height relative to the shed line, with raised back rest increasing warp extension during shedding from the greater deflection angle and providing more tension equalisation between upper and lower shed halves, while lowered back rest reduces warp stress during shedding and is preferred for weak yarns, with back rest horizontal position affecting the crimp distribution between warp and weft in the woven fabric that determines the balance of mechanical properties.
Role
Controls the geometry of the warp path that determines how much the warp is stretched during shed formation, with back rest optimisation being one of the primary mechanical adjustments for managing the warp break rate and fabric structure balance, and with the interaction between back rest position, shed height, and let-off tension requiring simultaneous adjustment when optimising for a new fabric specification rather than independent single-variable adjustment.