Shed Symmetry and Uneven Shed Formation
topic
Shed symmetry describes the relative positions of upper and lower shed lines relative to the neutral warp plane, with symmetric shed having equal upper and lower extensions that equalise tension between ends on rising and falling shafts, while uneven shed shifts the shed line up or down from the neutral position to deliberately create unequal extension in the two shed halves, with the appropriate shed symmetry depending on the weave structure, warp yarn properties, and the asymmetric weft insertion mechanism of specific loom types that require different clearances in the two shed halves.
Role
Governs the tension balance between warp ends on opposing shaft positions that affects the relative break rate between upper and lower shed ends, with uneven shed formation being used to deliberately compensate for asymmetric warp break distributions between shaft positions or to provide the additional clearance for specific weft insertion mechanisms on one side of the shed that symmetric formation cannot provide.