Key takeaways
- A process change can alter the part without touching the drawing, so change control has to cover both.
- Assess the impact on tooling, gauges, PFMEA, control plan, validation and the regulatory file, not just the dimension that moved.
- Interchangeability decides whether a new part number is needed or a revision can be cut in.
- Old stock and old tooling need a written decision, or they will reappear in a shipment.
What counts as a change
Change control is the discipline that keeps the drawing, the process, the inspection and the shipment describing the same part. A change is any difference that can alter form, fit, function, reliability, regulatory status or the evidence that proves the part meets the drawing.
Product changes are visible: a dimension, a material, a finish. Process changes are quieter: a new machine, a different tool, a new sub-supplier, a moved site, a changed plating bath or a new inspection gauge. A process change can leave the drawing untouched and still change the part.
The change request and the reason
Every change starts with a request that says what will change, why, which parts and processes are affected, what happens if it is not made, and when it needs to happen. The reason matters: a cost reduction, a quality fix, an obsolescence issue and a customer request take different routes.
The request should also say what is not changing. That keeps the review bounded and stops a tolerance correction from becoming a redesign with a new validation programme attached.
Impact assessment across the part and the process
Assess the impact on the part, the tooling, the gauges, the PFMEA, the control plan, the validation tests, the regulatory file and the stock. A tolerance change can move a process capability. A material change can move a RoHS or REACH statement. A site change can move the PPAP.
Ask whether the change is interchangeable. If a part made to the new revision can be mixed with the old one without a functional or safety difference, the cut-in can be simpler. If not, the part number usually has to change, because two parts that look alike but behave differently should not share an identity.
Who approves what
Approval should sit with the function that carries the risk, and with the customer where the contract or the PPAP manual requires notification. A change that is approved only by the person who benefits from it is not controlled.
The table is a starting route. Map it to your own contract, your customer-specific requirements and the criticality of the part before the first change arrives.
| Change | Typical approval | Evidence before cut-in |
|---|---|---|
| Drawing dimension or tolerance | Engineering, plus the customer where fit or function is affected | Revised drawing, capability check, first article |
| Material or sub-supplier | Quality and engineering, plus the customer where the part is qualified | Material certificate, test results, updated declarations |
| Process, tool or machine | Process owner and quality | Updated PFMEA and control plan, trial run, capability data |
| Inspection method or gauge | Quality | Gauge study, correlation with the old method, revised control plan |
| Site or line transfer | Programme and customer | PPAP or equivalent approval, layout, logistics plan |
| Packing or label | Quality and logistics | Label proof, transit trial, customer notification where required |
The exact route depends on the contract and the customer-specific requirements. Write it down before the first change.
Revisions on the drawing
The revision block should show the revision, the change note, the date, the person who approved it and the change reference. Mark the changed features on the drawing so the shop can see them without reading a separate email.
One change, one revision. Bundling unrelated changes into a single revision makes it impossible to identify which change caused a problem later, and it makes a partial approval impossible to express.
Superseded drawings should be withdrawn, not left in the folder. A printed copy at a machine is a controlled document whether the system says so or not.
Cut-in and effectivity
Effectivity can be set by date, serial number, lot or work order. Define the first article made to the new revision and inspect it before the rest of the order. Where the customer requires PPAP, the approval date sets the cut-in.
Never allow a mixed shipment without identifying the two revisions. Pack them separately with a label, or hold the old stock until the customer agrees. A mixed pallet with one label is a recall waiting for a reason.
Old stock, old tools, old documents
Count the old stock, quarantine it, and decide whether to use it, rework it, scrap it or sell it. Record the decision and who approved it. Using old stock under a new revision without a written concession is a traceability failure waiting to happen.
Old tooling and old drawings need the same treatment. Mark them obsolete, remove them from the line and keep the record. A tool that can still make the old revision will eventually be used, usually on a shift where nobody remembers the change.
Records that survive an audit
Keep the change request, the impact assessment, the approvals, the revised drawing, the validation evidence, the cut-in record and the training record together. Link them to the part file rather than to a project folder that gets archived.
The audit test is simple: pick a shipment and ask which revision it was made to, and why that revision was approved. If the answer takes more than a few minutes, the record is not complete.
A change is not finished when the drawing is signed
It is finished when the first part made to the new revision has been inspected, the old stock is controlled and the line is working to the new instruction.
Frequently asked questions
Does a process change always need customer approval?
Not always. It depends on the contract, the customer-specific requirements and whether the change can affect fit, function, durability or regulatory compliance. A new machine making the same part to the same drawing may need internal approval only, while a new site usually needs customer notification.
When does a revision need a new part number?
When the old and new parts are not interchangeable. If they can be mixed without a functional or safety difference, a revision can be enough. If they cannot, a new part number keeps the two identities separate through stock, assembly and service.
What is cut-in effectivity?
It is the point in production where the new revision starts. It can be defined by date, serial number, lot or work order. The cut-in should be recorded, and the first article made after it should be inspected before the rest of the batch is released.
How long should change records be kept?
Follow the contract, the customer requirement and the regulatory obligation for the part. The record should at least cover the production life of the part and the period in which a recall or a field question could arise. Date the record and keep it linked to the part file.
Sources and further reading
- ISO 9001:2015, clause 8.5.6, Control of changes
- IATF 16949:2016, clause 8.5.6.1, Control of changes, supplemental
- AIAG, Production Part Approval Process reference manual
Qumek Quality Desk
Quality team
The quality team responsible for first article inspection, PPAP packs, supplier audits and the records shipped with production parts.
Handling a change on a live programme?
Send the change description and the current revision. The quality desk will map the approvals, the validation and the cut-in steps.
Send the change