The Capacity You Buy, and the Capacity the Line Gains

How to read this sheet

Every kilogram of gain is valued at contribution, which silently assumes it can be sold. On a mill that is capacity constrained with orders queuing that is right; on one that is demand constrained the whole answer is zero however good the payback looks, and no debottlenecking sheet can tell you which you are - that is the first question and it is not on this page. Capacities must be what a stage actually delivers onward under real running, after its own efficiency, waste and product mix, because nameplate figures make every stage look adequate and the bottleneck disappear. They are also specific to one product: a line balanced for a coarse count is not balanced for a fine one, and a mill running a range has a different constraint each week, so run the sheet per article rather than once for the plant. Where several stages sit on the constraint together the sheet upgrades them as one step, because relieving one of two equal constraints gains nothing at all - and a proposal appraised one machine at a time will report exactly that, no opportunity, on a line that has a real one. The ladder is a sequence of independent purchases and takes no account of the fact that buying four things at once is cheaper, slower and riskier than buying one; nor of commissioning time, the learning curve on the new machine, or the production lost while it is installed. Treat the ladder as the shape of the argument and the first step as the decision.