Calculating Greige Fabric Yield from Loom Speed and Sett
Calculate linear greige yield by dividing net picks per hour by pick density, adjusting reed width and warp length for crimp contraction.
Weft Contraction
Loom Geometry
Dimensional changes in the filling yarn occur when it bends around the warp threads during the weaving process. The weft contraction describes the difference between the width of the yarn as it leaves the carrier and the final width of the fabric on the roll. This reduction in length is a necessary consequence of the interlacing that holds the cloth together.
Yarn Consumption
Accurate cost estimation for a linen order requires an adjustment for the extra yarn needed to cover the width reduction. If a weaver ignores the weft contraction, the mill will run out of filling yarn before the warp is fully depleted. Standard tables for different weave patterns provide the percentage of overage required for each production run.
Dimensional Stability
Tension settings on the loom must be managed to keep the shrinkage consistent across the entire length of the fabric. Variable weft contraction leads to wavy edges or an inconsistent fabric width, which can cause problems during the automated cutting of garment pieces. Regular measurements of the reed width versus the cloth width on the take-up roller allow the operator to maintain the correct geometry for the finished export goods.
The final width of the linen after scouring and bleaching also depends on the initial state of the yarn as it was laid in the shed.