Lower Layer Force
The tensile load acting on the lower layer of warp yarns during pick insertion controls the stability of the shuttle or weft carrier path. In flax weaving, the bottom shed line tension must be maintained at a level high enough to support the weight of the weft insertion element without causing the yarn to snap. This force ensures that the lower warp sheet forms a clean, straight line for the passage of the yarn carrier.
Mill operators measure this variable using hand-held tensiometers during the loom setup phase.
Friction Control
Higher tension in this layer prevents the warp yarns from sticking together, which is a common issue with hairy linen yarns that have not been sized. When the bottom shed line tension is too low, the open shed becomes indistinct and causes the rapier to catch on individual fibers. The resulting friction increases yarn breakage rates and slows down production speeds in Chinese weaving factories.
Weavers adjust the harness height to correct the line position before starting a new linen order, verifying each change against the tension log in the loom control system to maintain a stable operating environment.
Beat Up Geometry
Adjustments to the tension of the lower sheet also alter how the weft is locked into the fabric during beat-up. This setting determines the crimp ratio of the final linen fabric, directly affecting its strength and density. Production sheets include this tension limit to ensure that the fabric meets the specified air permeability standard.
