Distortion budget: how it propagates through the build

Distortion in a forge die build is not a single event at heat treat. It is a running total accumulated across rough machining, heat treat, finish machining, EDM, stress relief, and nitriding. Each step adds dimensional change of its own and releases residual stress the prior step put in. The budget propagates non-linearly, because the stress one operation locks in becomes the distortion the next operation lets out. You do not control the dimensional change at any step below a certain floor. What you control is where the changes land and which surfaces are still machinable after they happen.

The implication for the routing is that distortion has to be allocated at engineering time, not discovered at QC. Every critical dimension on the print needs a stock allowance on the upstream operations that can reclaim the expected movement, and the operations themselves have to be sequenced so each one's distortion is removed before the next one locks it in.