What Shrinkage Allowance to Cut a Knit Programme At

How to read this sheet

Read the window before the allowance. The tolerance window has a width, and it is very nearly independent of where you put it: twice the tightest tolerance on the sheet, expressed as a percentage of its own measurement. The fabric has a spread, which is the distance between the least and most shrinking lot. If the spread is wider than the window then some lot is outside it wherever you stand, and the sheet says so rather than pretending an allowance exists that will hold everything. That case is not a cutting problem. It goes back to whoever controls relaxation - the dyehouse, the compactor, the stenter overfeed - because no pattern card can absorb it. Why the recommendation is not the average shrinkage. Fabric costs money and less allowance means less fabric, so among the allowances that hold the same lots the cheapest is the smallest, which sits the garments at the short end of tolerance rather than in the middle of it. That is the arithmetic of the cost model and it is what a cutting room chasing yield does anyway - but it spends the whole safety margin. The sheet therefore prices the centred allowance as well, and the gap between them is what the margin costs. If the next lot might be outside the tested range, buy the margin knowingly. Why the search stops where it does. Because less allowance is always less fabric, the cost model has no interior minimum wherever the tolerance is loose - the answer would simply run to whatever bound the arithmetic was given. So the allowance is searched only inside the shrinkage the tests actually showed. Below the least-shrinking lot every garment in the programme finishes undersize and above the most-shrinking one every garment finishes over; either way the sheet has stopped trading against the measurement sheet and started deciding how the garment fits, which is not a costing question and is not one it will answer. Two lines report which direction was decided by the tolerance and which merely stopped at the edge of the evidence, and a direction in the second state is telling you the tests are the only thing holding the number - widen the log before trusting it. What the process reading is priced at. The second reading holds the cutting room still: it asks what the same programme costs if the spread narrows while the allowance stays where this sheet put it. That understates the gain a little, because the allowance could be reset again once the fabric behaves, and it keeps the comparison monotone and honest - a fabric that varies more must never look like it is worth more. What the size table is for. A tolerance quoted in centimetres and held flat across the size run is tightest, as a percentage, on the largest garment, so the allowance is decided by whichever size the buyer stopped grading at. Enter the tolerances exactly as they are written rather than as a single average, because the size that decides the number is usually not the one anyone is watching, and a lot can be out on three sizes and comfortably inside on the fourth. What is not modelled. Sewing and pressing variation is outside this sheet, which treats the garment as finishing exactly where the fabric puts it - so the reject rates it reports are a floor rather than a forecast. Skew and spirality are a separate failure and are not a matter of allowance at all; the free spirality calculator on this site handles that. Marker efficiency is assumed unchanged, which is fair for a small change in pattern dimensions and not fair for a large one. And the sheet prices one order at one fabric quality: run it again per quality, because a heavier interlock and a single jersey do not shrink alike and should never share a pattern card allowance.