Supplier quality management: part approval, evidence and what happens after an escape

Part approval is a gate on a specific part, not a verdict on the company

Approving a supplier and approving a part are separate decisions that get conflated constantly. Part approval fixes a particular component, made on named tooling and equipment at a named site, to a stated drawing revision, with dimensional results across a run large enough to show variation rather than one hand-built sample. It records who signed, what was measured, what was conditionally accepted and why. Skipping it because the supplier is long established is the standard route to discovering during a production build that their process was never shown to hold the feature that matters.

Deciding what evidence travels with each lot

The default of a certificate of conformity signed by somebody in the supplier's office proves almost nothing. Specify per part what is actually required: material certification traceable to the melt or batch, results for the characteristics you have designated as significant, process data where the property cannot be inspected afterwards, and a lot identifier that ties the paperwork to the physical containers. Then decide who reads it, because unopened certificates create liability without protection. Agreeing a shorter, genuinely reviewed evidence set beats demanding a thick pack that both parties file unexamined.

The change notification clause is the one that gets breached

Most surprise defects from an established supplier follow a change they considered minor: a different resin grade, a new sub-supplier for a coating, a move of the tool to another press or another plant, a replaced operator on a manual step, an alteration to a cleaning agent. The obligation to notify before such a change, and to obtain re-approval where it affects a designated characteristic, has to be explicit, tied to a defined list, and reinforced by asking about it during visits. Discovering an unnotified change after a failure converts a technical problem into a contractual one.

When defective material arrives, decide the disposition before the argument

The immediate questions are containment and continuity of your own build, not blame. Bound the suspect lots using the identifiers on the containers, decide whether your line is sorting to keep running and at whose cost, and agree how rejected material is returned, scrapped or reworked, with someone controlling the physical stock throughout. Recording the true cost of the event — sorting labour, line stoppage, expedited replacement, your customer's reaction — is worth more than an argument about liability, because it is the evidence that later justifies either investment in the supplier or a change of source.

Where quality evidence and commercial performance meet

Sourcing decisions, scorecards and contract negotiation sit with the commercial function, but they are only as good as the quality data feeding them. That means every rejection, escape, late corrective action and unnotified change is recorded against the supplier consistently, including the ones absorbed quietly by a production team that sorted the parts and said nothing. Undocumented tolerance is the reason a supplier can hold a strong scorecard while causing weekly disruption. The quality function's contribution to the relationship is an accurate record, delivered before the negotiation rather than after it.

Frequently asked questions

Do we need to re-approve a part when a supplier moves it to a different machine?

If the move can affect a characteristic you care about, yes, and for most forming, moulding and machining processes it can. A different press, mould base, cell or oven brings different thermal behaviour, clamping and wear. The proportionate response is a reduced approval focused on the features at risk rather than a full repeat: dimensional results from the new equipment, evidence of process stability, and confirmation that the inspection method transfers. Silence on such a move is itself a finding.

Should we inspect incoming parts from an approved supplier?

Approval justifies reducing inspection, not abandoning it. Keep verification of the characteristics whose failure would be expensive or undetectable later, verify identity and quantity on every receipt because mixed or mislabelled lots are common, and reinstate fuller checking after any change, any gap in supply, or any escape. The judgement is about consequence: a feature that assembly will catch immediately needs less incoming attention than one that only reveals itself in the customer's hands.

How do we manage quality with a supplier who has more leverage than we do?

Focus on what you can enforce without cooperation: tighten your own incoming verification for the characteristics that hurt, record every event accurately, and design the product or the process so that their variation is tolerable where possible. Where dependence is structural, the honest internal conversation is about qualifying an alternative source, which is a sourcing decision rather than a quality one — but the quality record is what makes the case for it credible.