Shedding Configuration
Looms utilize specific positioning of the warp yarns during the shedding cycle to create unequal angles in the upper and lower yarn layers. Adjusting the loom to use asymmetric shed geometry alters the physical path lengths of the top and bottom warp sheets when the shed is open. This configuration modifies the tension balance between the two layers, helping to prevent yarn-to-yarn friction during the insertion of the weft.
Mills measure these angle differences during setup and record them in the loom setting sheet.
Tension Mitigation
A common industrial configuration lowers the back rest below the normal center line to decrease the tension in the upper warp sheet during shedding. Because asymmetric shed geometry changes the yarn strain distribution, the top sheet undergoes less elongation than the bottom sheet when the loom opens. This tension difference prevents excessive stretching of fragile low-twist flax yarns in the top layer.
The reduced stress minimizes warp breakages during high-speed insertion, which is a major cause of loom stoppage. Machine operators verify these settings during the trial run of each new warp beam, noting the results on the loom setup card to ensure repeatability across different shifts.
Fabric Quality
Weaving with uneven yarn tension yields a different crimp distribution in the final linen cloth. In this process, the bottom warp sheet remains under higher tension and lies flatter, while the looser top warp sheet bends more around the weft. This disparity alters the cover factor of the fabric.
