Tooling release checklist

The questions to answer before you cut steel. After release, a change is measured in weeks and tens of thousands of euros.

Before you release hard tooling

• Thermal has been simulated and then measured on real hardware under worst-case conditions.
• Tolerances in the drawings can be held by a real production process (checked with the mould maker).
• The assembly sequence was walked through with the factory, step by step, with no manual rescue steps.
• Every component in the design can be sourced at volume, not just for prototypes.
• EMC pre-scan has been done on hardware that matches the final layout.
• Fit and function are proven on production-intent parts, not hand-made ones.
• The design is frozen: changes after this point need written approval and a cost estimate.
• The cost of a change after release is written down and signed off by the person paying.
• A named person has signed: "I would stake my own budget on this release."

Examples from the book

What was skipped	What it cost
Thermal was not resolved before committing to hard tooling.	A €80,000 tooling modification nobody had planned for.
Tolerances were set too tight in CAD, which looked fine on screen.	Specialised tooling in production; about €40k of re-work found at DVT.
Assembly sequence was not reviewed with the factory.	Manual intervention on 40% of units, invisible on a bench, a crisis at 10,000 units per week.
Component chosen because it was available for prototypes.	Single-source risk, locked in before anyone noticed.

Decision

Released?	Date	Approved by	Open issues accepted (with cost of leaving them)

Why: steel can be cut away but never put back. Releasing tooling because the schedule says so, instead of because the evidence says so, is the most expensive habit in hardware.

From The Hardest Hardware Lessons · thehardesthardwarelessons.com · Free to use and share with attribution.