Drawing managementReading time 11 min
Drawing Revisions: Catch the Change Before Production
A part made perfectly to an outdated drawing is still the wrong part. Revision control needs more than a new filename: identify what changed, where it changed and which orders are affected.
01Where revision data appears
Check revision information in the title block, change history and managed file record before production. If those sources disagree, do not guess which one is current: resolve the discrepancy and record which revision applies to the order.
| Field | Contents | Why it matters |
|---|---|---|
| Revision code | A, B, C or 01, 02 | Identifies this issue |
| Revision date | Effective date | Tells you which revision work in progress should use |
| Description of change | What changed, and in which zone | So nobody has to re-read the whole sheet |
| Zone | Grid reference on the drawing, such as B4 | Points at where on the drawing |
| Approved by | Signatures | Traceability of responsibility |
02Comparing two revisions
| Method | Approach | Strength | Limitation |
|---|---|---|---|
| Manual side by side | Two drawings side by side, checked item by item | No tools needed | Slow, easy to miss things, depends on concentration |
| Overlay | Semi-transparent, one over the other | Geometric change is obvious at a glance | Cannot show a changed dimension or note |
| CAD comparison | Compare entities inside the CAD system | Precise | Needs native files; version compatibility issues |
| Parsed comparison | Parse into structured data, then compare item by item | Covers dimensions, tolerances and notes | Depends on the drawing being parsed correctly |
An overlay can reveal moved geometry, but it may miss a narrower tolerance, a changed material note or a different datum reference. Compare the written requirements as well as the lines on the page.
03Customer-drawing pitfalls
- The file name says rev C but the title block says rev B. Which governs?
- The customer's email says only “updated version” and the attachment has exactly the same file name.
- Two versions arrive on the same day, minutes apart.
- The PDF is a scan and the revision field has been overwritten by hand.
Treat each incoming revision as a controlled handoff. Record its drawing number, revision, source and receipt date; compare it with the previous issue; then release the approved version to production. Otherwise later checks may all rely on the wrong baseline.
04The cost of a missed change
Even a small dimensional change can affect several downstream items:
- whether fixtures and gauges have to be modified
- whether tool paths (NC programs) have to be regenerated
- whether work in progress can be conceded, reworked or must be scrapped
- whether purchased downstream parts are affected
- whether inspection sheets and reports have to be reissued
- whether the customer requires a new first article inspection
In regulated work, a change to form, fit or function may also trigger a partial first-article inspection under AS9102. Review the affected characteristics and records before calling a revision minor.