The depot that stopped stocking door handles

A depot does not run out of door handles because someone forgot to order them. It runs out because the handle belongs to a carriage whose maker no longer exists, and the bin that used to hold two hundred of them was cleared to make room for something that still turns over.¹¹ The cost models in the sample sources treat the printer as already bought and the demand as smooth. A depot’s demand is a single car, on a particular road, in a particular week. The arithmetic is dull and it is the whole problem. A part used twice a year, with a lead time of months, is either a dusty box or a train waiting.

The fire rules make the dusty box harder to defend than a spreadsheet suggests. Patterns, jigs and a shelf of polymer prints are fuel, and a maintenance building already has enough of that.²² The fire note in the references is a sample, written to stand in for the real guidance a depot would have on the wall. A works manager who can show that the handle is a file, printed when a carriage comes in, has removed a pile of stock and a conversation with the insurer. That is a real saving. It is not yet a qualified part.

Printing changes the place the part waits. It does not change the question a rolling-stock engineer is paid to ask, which is whether the handle on the car is the handle on the drawing, in material and in the way it fails. The depot that stops stocking handles has not become a factory. It has become a workshop with a shorter memory, and a longer argument about what it is willing to fit.