Quantifying Primary Trim Scrap in Rapier Weft Insertion
Primary rapier trim scrap depends on insertion geometry rather than fabric width, requiring exact tail length modeling to prevent yarn yield deficits.
False Selvedge
Auxiliary Structure
Temporary fabric edges are created during weaving to maintain uniform weft tension and protect the primary selvedge. The false selvedge is an auxiliary band of warp yarns located outside the main fabric body that holds the weft yarn during insertion. It is cut away during the weaving or finishing stage, leaving the main fabric with a clean edge.
This structure is common on shuttleless looms where the weft is cut on every pick.
Functional Application
Shuttleless insertion methods require an external mechanism to secure the open ends of the weft yarn. The false selvedge provides the necessary grip for the weft yarn during the beat-up and the subsequent shed change. In linen weaving, the stiff nature of flax fibres means they do not cling together easily, requiring this temporary boundary to prevent unraveling.
The auxiliary yarns are threaded through separate heald frames to create a tight weave, such as a plain or leno structure, which holds the weft ends under high tension. Once the weft is locked into the main fabric, the false selvedge is trimmed off by a heating element or mechanical shears.
Yield Management
Weaving mills must monitor the volume of yarn allocated to temporary structures to prevent excessive waste. The width and yarn density of the false selvedge are optimized to use the cheapest possible material, often using recycled or low-grade polyester yarns instead of the high-quality linen used in the warp. This reduces the overall cost of the discarded material while maintaining edge security.
Proper alignment of the trimming blades ensures that the false selvedge is removed cleanly without damaging the permanent edges.