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Weaving Calculations · Lecture 14
Fabric Production
Loom output per day from rpm, picks and efficiency; then warp and weft bags for an order, loom-days and daily yarn consumption.
Loom productionA-gradeBags per orderLoom-days
From picks per minute to metres per day
inches per minute = rpm × efficiency ÷ PPI · yards per day = in/min × 1440 ÷ 36
Then A-grade is what sells: subtract the B-grade percentage. Yarn consumption includes contraction and wastage (warp 3%, weft 5.6%) and is inflated by the B-grade rejection, because the rejected metres consumed yarn too.
| A | B | ||
|---|---|---|---|
| 1 | Construction 20×20 / 60×60, 63", plain | ||
| 2 | Warp count Ne | ||
| 3 | Weft count Ne | ||
| 4 | Ends per inch | ||
| 5 | Picks per inch | ||
| 6 | Width (in) | ||
| 7 | Warp contraction | ||
| 8 | Weft contraction | ||
| 9 | Warp wastage | ||
| 10 | Weft wastage | ||
| 11 | B-grade | ||
| 12 | Loom | ||
| 13 | Loom speed (rpm) | ||
| 14 | Efficiency | ||
| 15 | Inches per minute | 12.00 | |
| 16 | Yards per day (24 h) | 480.0 | |
| 17 | A-grade yards per day | 475.2 | |
| 18 | A-grade metres per day | 434.5 | |
| 19 | Yarn per unit of A-grade fabric | ||
| 20 | Warp lb per yard | 0.2568 | |
| 21 | Weft lb per yard | 0.2514 | |
| 22 | Warp lb per metre | 0.2809 | |
| 23 | Weft lb per metre | 0.2749 | |
| 24 | Order | ||
| 25 | Order quantity (m) | ||
| 26 | Looms allotted | ||
| 27 | Warp bags (100 lb) | 56.17 | |
| 28 | Weft bags (100 lb) | 54.98 | |
| 29 | Days to complete | 11.51 | |
| 30 | Bags consumed per day (all looms) | 9.66 | |
blue = input (edit me)grey = formula (click to see it)
Four looms at 800 rpm finish 20,000 m in 11.5 days and eat about 9.7 bags of yarn a day — a figure the yarn store needs long before the looms start (Planning III).
Original lecture material
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