What a Kilogram of Waste Costs, Stage by Stage

How to read this sheet

Read the destroyed column rather than the waste percentages. The percentages say where the mass goes and they are the wrong ranking for everything: the biggest waste bill in a combed mill is the comber, which is also the stage where a kilogram of waste destroys the least value, because comber noil has cost a great deal to make and sells for two thirds of raw cotton. The dearest kilogram is at the winding, where the fibre has been through every machine in the building and the waste is a handful of soft ends. Those two facts want completely different responses and a realisation report cannot tell them apart. Extract early is a rule about trash, not about money. It is right where the waste is worth little at both stages and wrong wherever taking the fibre later means selling it for more. On the seeded mill two stages want extraction moved later rather than earlier, and the sheet says which and by how much - a point at a time, because that is how extraction settings actually move. On the unavoidable column. It is the difference between a sheet somebody acts on and a sheet somebody dismisses. Comber noil is chosen: a mill that combs sixteen per cent has decided what yarn it is selling, and telling it that sixteen per cent of its fibre is an opportunity is worse than useless. Fill the column honestly, and expect the avoidable total to be a fraction of the gross - on the seeded mill it is under a third. That fraction is the number worth taking to a meeting. Why the machine list understates the conversion cost. Every rate on it is per kilogram processed at that machine, and the blowroom processes every kilogram of cotton while the winding processes only the yarn you sell. Adding the rates gives a cost per kilogram of nothing in particular. The sheet spreads each rate over the mass that machine actually handles and divides by the yarn at the end, which on the seeded mill is nine per cent higher than the machine list says. Any mill costing yarn from a machine list is quoting below its own cost by about that much. What is not modelled. Waste is treated as fibre of uniform value at each point, where in truth the good fibre and the trash leave together and the mix changes with the setting - a card set to drop more will drop worse waste, not the same waste in greater quantity. Reprocessed and re-fed waste is handled only through the price you put on it, so a mill that re-feeds card strip into a coarse mix should enter what it displaces rather than a scrap value. Nothing here says what a setting change does to yarn quality, which is the other half of every extraction decision and the reason the unavoidable column exists.