What do I do when a supplier's parts don't match the drawing?
Contain the parts first: tag them and keep them out of any build. Then find out why they don't match, the wrong revision or out of tolerance on the right one, and decide what happens to them: use as is, rework, return to the supplier or scrap. Record the decision in a one-line nonconformance report.
Two different problems
Parts that don't match the drawing usually come from one of two causes, and they need different fixes.
- Wrong revision. The supplier built correct parts to a drawing that is no longer current. The parts may be fine to an old revision and wrong for yours.
- Out of tolerance. The supplier built to the right revision and missed a dimension. One engineer we spoke with said this happens far more often than wrong-revision builds.
The first question decides which one you have, and it also decides whose problem it is.
Worked example: 130-0207 motor mount bracket
Twenty machined brackets arrive for a pilot build. The first one won't bolt up: the four-hole pattern is 3 mm off. The current drawing is Rev C. The team keeps a short log in the part's folder:
/130-0207 Motor mount bracket/
/released/
130-0207_RevC.pdf
130-0207_RevC.step
/quality/
NCR-log.csv
NCR-012_photos/
NCR-012_inspection.pdf
Step 1: Contain. Move all 20 to a separate shelf and tag them before anyone tries to make them fit. A published nonconforming-material procedure from the Ocean Observatories Initiative puts it the same way: move nonconforming material to a location designated for it, and attach a nonconforming label to it (OOI procedure). Check whether any already went into an assembly.
Step 2: Find the revision they built to. Compare the packing slip, the supplier's inspection report and the PO line. Here the PO says Rev C, but the inspection report is against Rev B, where the hole pattern sat 3 mm further out. The supplier built to the old drawing. If the PO had said Rev B, the parts would be exactly what you ordered.
Step 3: Check the rest of the part. Measure a few brackets against Rev C, not just the feature that failed. A wrong revision often means more than one difference.
Step 4: Decide what happens to them. The same procedure lists four outcomes: return to supplier, use as is, rework and scrap. It requires rework instructions and re-inspection for reworked material, and a deviation or waiver before using a nonconforming purchased item as is. For 130-0207, the holes can't be moved, so the team returns all 20 and asks for a rush rebuild to Rev C.
Step 5: Log it. One line is enough:
| NCR | Part | Rev ordered | Rev built | Qty | Problem | Cause | Disposition | Closed |
|---|---|---|---|---|---|---|---|---|
| NCR-012 | 130-0207 | C | B | 20 | Hole pattern 3 mm off | Supplier had the Rev B file | Return, rebuild to C | When Rev C parts pass |
Step 6: Fix the cause. Here the supplier still had Rev B in their system. Send the Rev C PDF and STEP as a matched pair, get written confirmation of the revision, and update your register, as in How do I keep track of which revision each supplier has?
Ways to deal with parts that don't match
| Disposition | Good for | Main risk |
|---|---|---|
| Use as is | A miss that doesn't affect fit, form or function | Parts on the shelf that don't match the drawing; needs a written, approved deviation |
| Rework | A feature you can fix, such as an undersized hole | Needs written instructions and re-inspection; can create a new defect |
| Return to supplier | Their mistake, or a feature that can't be fixed | Lead time for the rebuild |
| Scrap | Cheap parts, or parts that can't be fixed or returned | Cost, and nothing learned unless it's logged |
When this stops working
- The NCR log has repeat entries for the same part or supplier.
- Parts that don't match are found during assembly, not at receiving.
- Nobody can say who decided to use a part as is, or why.
- Arguments about who pays come down to which email was sent last.
At that point you need inspection at receiving and a clear record of which revision each supplier has. Preventing the wrong revision in the first place is covered in How do I make sure my supplier builds the right revision?
FAQ
Who pays for supplier parts that don't match the drawing?
It depends on your PO terms and on which revision the PO named. If the PO named the current revision and the parts don't match it, you have a strong case to return them; if it named an old revision, the parts may be exactly what you ordered.
What is a nonconformance report?
A short record of a part that doesn't meet its requirements: what was wrong, how many, why, and what was done about it. On a small team, one line in a shared log is enough if it's filled in every time.
Can I use parts that don't match the drawing?
Yes, if the difference doesn't affect fit, form or function and someone with authority approves it in writing. Record it as a deviation so the drawing stays correct and the decision can be found later.
How do I stop suppliers building the wrong revision?
Put the revision on the PO line, send the PDF and STEP from the same revision, and ask for written confirmation of the revision before they start. Keep a register of which revision each supplier has.
Internal links
- How do I make sure my supplier builds the right revision?
- How do I keep track of which revision each supplier has?
- How do I approve a supplier deviation from the drawing?
Sources
- Ocean Observatories Initiative, Nonconforming Materials Procedure (2011): https://oceanobservatories.org/wp-content/uploads/2011/03/3101-00054_Nonconforming_Materials_Procedure_2011-01-01_ver_1-00.pdf
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