Mass production (MP)

Once PVT targets are met, the line ramps up. The focus shifts to consistency: incoming inspection of parts, in-process checks, end-of-line testing, outgoing quality audits (often AQL sampling) and tracking of field returns. Changes now go through formal engineering change orders because they affect inventory, tooling and certification.

Ramping usually happens in steps, because yield and supply problems surface as volume rises.

Where it bites: assuming engineering is finished. Sustaining engineering (fixing field issues, handling part obsolescence, cost-down projects) continues for the product's whole life and needs a budget and an owner.