How Should Changes Be Controlled Between Low-Volume Lots?
How Should Changes Be Controlled Between Low-Volume Lots?
Changes between low-volume lots should be controlled through a documented request that identifies the reason, affected revision or lot, CTQ risk, evidence required, approver, and resume condition. A material replenishment, fixture contact, tool, program, outside processor, inspection method, package, or ship date can affect acceptance even when the drawing is unchanged. The buyer should hold affected units when evidence is missing or measured in the wrong state, then release only after the approved reaction is complete.
Classify the Change Before Approval
Classify a proposed change as design, process, material, tooling, inspection, outside processing, packaging, logistics, or ownership. The classification helps identify which records and CTQs need review. A new cutting tool may affect burrs or size; a locator replacement may affect position; a coating batch may affect a mating surface; a package may affect contamination. Do not assume that an unchanged program means an unchanged delivered condition.
For a compact clamp-like assembly, a change in support or side hardware could alter how the base seats during machining or measurement. The images show the assembly from two angles but cannot prove load, material, tolerance, or function. Ask which interface is controlled, which state is measured, and whether the change applies to separate components or assembled acceptance.
Capture Risk and Evidence
Record the old and new values, effective date, affected serial or lot range, responsible owner, and impacted CTQs. Define whether a first-piece check, expanded inspection, functional test, material certificate, or outside-process record is required. If a new inspection method is proposed, state its alignment, uncertainty or limitation where supported, and equivalence approval. A new result should remain tied to the same drawing revision and unit identity.
Preserve the rejected proposal or expired temporary change so a later reviewer cannot mistake it for an approved route. If the change is urgent, define containment, expiry date, and retrospective review. A verbal agreement is not a release record. The resume condition must be measurable and assigned to an authority.
Write the Change Clause in the RFQ
Require notification and approval for material, temper, heat treatment, tool, fixture, program, route, processor, inspection method, location, packaging, label, or ownership changes. State notification timing, evidence format, deviation authority, and whether customer approval is needed before production or shipment. Ask each bidder for an anonymized change form or route example that identifies affected CTQs and hold rules.
Separate changes that require a new qualification from those that need a limited recheck. A minor packaging label correction may not require a dimensional study, while a new coating processor may require surface, masking, and mating checks. The decision should be based on documented effect, not the supplier's description of a change as routine.
Manage the Lot Boundary
| Boundary | Minimum record | Release question |
|---|---|---|
| Before change | Approved baseline route and revision | What condition is being replaced? |
| During containment | Affected units, owner, expiry, hold status | Which units cannot ship? |
| After change | Recheck results and approval | What evidence permits resume? |
| Future lots | Updated route and notification trigger | How is recurrence detected? |
Use the table to keep a lot boundary explicit. A quality inspection record plan can organize ownership, but the controlled drawing and approved change determine acceptance. Do not merge pre-change and post-change records simply because the parts look alike.
Review the Supplier Response
A credible response states how changes are detected, who reviews risk, which CTQs are rechecked, and how records are delivered. Compare responses by evidence rather than by a general claim of process control. Ask how the supplier handles a replacement locator, a tool offset correction, a material substitution, an outside-process delay, or a split shipment. The answer should identify a hold and resume rule for each meaningful event.
Keep the baseline route available when reviewing a proposed change. The comparison should show which operation, contact, state, or record changed and which assumptions did not. If no CTQ is affected, document the rationale instead of deleting the request. If the effect is uncertain, use containment and a limited recheck before treating the change as routine.
Record the review date and approver with the request. A later lot should be traceable to the exact decision, not merely to a supplier email.
Buyer Action
Issue one controlled change request, identify the affected lot, require a risk and evidence review, and record approval before production resumes. Store the final decision with the drawing, route, and inspection records. Reopen qualification when the approved trigger occurs, and do not let a low-volume schedule turn an undocumented change into a permanent process state.
