The most expensive thing you can do in contract manufacturing is change the design after NPI has begun. Here’s a practical rule of thumb:
| Change Timing | Typical Impact |
|---|---|
| Pre-NPI (before material buy) | Low cost — design changes are free to implement before committing materials |
| During NPI (after material buy, before build) | Medium — non-returnable components may create obsolete inventory risk |
| After pilot build (before production release) | Moderate — NPI may need to be re-run; some materials may need to be scrapped |
| After production release (ECO) | High — running ECO requires: rev update, re-kitting, process requalification, scrap/rework of WIP |
ADVICE: If you know changes are coming, hold the build. A 2-week delay to stabilize the design is almost always cheaper than an ECO against running production.