Production Planning
A ninth colour costs twenty minutes of downtime and no extra running time. On short runs, colours govern the economics, not metres.
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Setup, printing and washdown together
Screens are assumed to be set one after another; machines with parallel preparation off the printer overlap much of the setup and the downtime falls accordingly, so measure your own changeover rather than summing per-screen times. Colour matching, strike-offs and first-metre approval are excluded and frequently exceed the mechanical setup on a new design. The break-even length is where printing time equals the fixed overhead, which is a useful minimum-order signal rather than a profitable one — profitability needs the paste, substrate and rejects that this does not cover.
Rotary Printing Screen Setup & Washdown Time Predictor — free, with the formula and a worked example, at Textile School.