Warp Lot with Off-Count Cotton Yarn
A handloom cooperative has accepted an order for 40 running metres of plain-weave cotton fabric, 100 cm wide, at 24 ends/cm and 20 picks/cm. The warp is to be made from 40s combed cotton. On opening the yarn store, the supervisor finds 20 bags marked 40s; wrap-reel and quadrant-balance tests on three bags give 38.6s, 31.2s and 29.4s. Lea strength tests give 2,350, 1,900 and 1,760 CSP respectively. The 29.4s bag is also 12% cheaper than the others. The cooperative has a two-roller sizing machine, a reed with 6 dents per cm and a beam that can hold 2,600 ends. The delivery date is 18 days away, and the accounts officer wants to use the cheapest bag in the warp to protect the margin. The weaver has already wound 1,200 ends from the 38.6s bag.
1. Calculate the number of warp ends, the approximate warp weight for the full order at 40s, and the weight if the 29.4s yarn were used. Explain what the difference means for beam capacity and fabric cost.
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Ends and weight. Ends = 100 cm × 24 ends/cm = 2,400. Allow 10% for take-up and loom waste: warp length = 40 m × 1.10 = 44 m. Total yarn length = 2,400 × 44 = 105,600 m. One Ne hank = 840 yd = 768.1 m, so hanks = 105,600 ÷ 768.1 = 137.5. At nominal 40s, weight = 137.5 ÷ 40 = 3.44 lb = 1.56 kg. At 29.4s, weight = 137.5 ÷ 29.4 = 4.68 lb = 2.12 kg.
Interpretation. The coarser yarn adds about 0.56 kg, or 36% more fibre, and a thicker yarn at the same 24 ends/cm raises cover factor and fabric weight. The beam can hold 2,600 ends, so 2,400 ends fit, but if the sett is increased to suit the coarser yarn the end count may exceed the beam. A lower price per kg does not guarantee lower cost per metre; calculate cost per 1,000 m at the actual count, including the extra size and breakage risk.
2. Decide how to allocate the three lots of yarn and justify your decision. Include at least one test or control that must be completed before the warp is made.
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Allocation. Use 38.6s in the warp. Its CSP of 2,350 is close to the 40s requirement and is adequate for a plain cotton warp; it is also the lot already wound. Use 31.2s in the weft, where strength demand is lower, and use 29.4s only for a separate coarser fabric or as weft in a tightly set construction after a trial.
Controls before warping. (1) Count-test every bag, not just three, using a wrap reel and balance; correct for moisture. (2) Lea-test a sample from each lot. (3) Check twist direction and twist factor; low-twist yarn is unsuitable for warp without extra sizing. (4) Size the 38.6s warp with a suitable add-on and check abrasion. (5) Segregate and label lots so the weaver cannot mix them. If the 29.4s must be used in the warp, reduce sett to about 20–21 ends/cm, recalculate the reed plan, slow the loom and accept a shorter beam. Document the substitution for the buyer.
3. The weaver proposes adding extra ends per dent to use up the coarser yarn without changing the reed. Evaluate this proposal.
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Reject the proposal as stated. A 6-dent/cm reed at 5 ends/dent gives 30 ends/cm, requiring 30 × 100 = 3,000 ends. That exceeds the 2,600-end beam and heddle capacity, so it cannot be wound as proposed. Even at a lower width, five ends per dent crowds the dent, causes yarn abrasion, poor shed formation and uneven cloth.
Correct approach. Keep 4 ends/dent for 24 ends/cm, or change to a 5-dent/cm reed with 4 ends/dent for 20 ends/cm if using the coarser yarn; recalculate ends and beam capacity. Keep the coarser lot in the weft and adjust picks/cm to balance cover. Run a 1 m trial and measure width, sett and GSM before committing the full order.