A small drawing revision can disrupt an OEM project when engineering approves new geometry but the supplier continues machining from an earlier file. Tooling, inspection programs, and purchased materials may then represent different versions of the same component. The immediate risk is not just scrap: apparently acceptable parts can reach assembly with incompatible interfaces or unverified performance.

To control design changes, establish one released technical baseline and require every proposed modification to pass through a documented impact review, authorized approval, and traceable production cutover. When working with an OEM cooperation supplier, agreement on a CAD file is not enough. Both parties must confirm what changes, who approves it, which parts are affected, and what evidence allows production to resume.

Establish what the supplier is authorized to manufacture

Change control starts before the first revision request. Without a defined baseline, neither party can reliably distinguish an approved requirement from an informal suggestion. Create a controlled release package covering the part, assembly, and applicable manufacturing requirements.

• Product definition: approved drawings, CAD models, bills of materials, material specifications, and referenced technical standards.
• Acceptance requirements: critical dimensions, geometric tolerances, surface finish, inspection methods, and functional test criteria.
• Manufacturing constraints: approved special processes, tooling restrictions, and any operations or subcontractors requiring prior approval.
• Configuration identity: part numbers, revision identifiers, release status, and the agreed precedence between drawings, models, and specifications.

Document precedence explicitly. A drawing and model can disagree about a radius, thread depth, or tolerance; leaving the supplier to choose creates an uncontrolled engineering decision. The purchasing agreement should reference the released configuration rather than simply requesting parts “to the latest drawing.”

Use a controlled repository with access permissions and revision history. A shared folder can work for a small project, but released files must be distinguishable from drafts, and superseded files must be blocked from normal production use. Email attachments should not become an alternative release system.

Separate a change request from permission to proceed

A supplier’s manufacturability proposal is a request, not an authorization. Likewise, an engineer’s comment during a review meeting should not automatically release revised tooling or production. Define these boundaries in the quality agreement and purchase terms.

A practical workflow separates three decisions:

1. Request review: record the proposed change, reason, affected items, and originator. An engineering change request opens the investigation without authorizing implementation.
2. Authorize implementation: after technical and commercial review, issue an engineering change order or equivalent controlled instruction. Identify the approved revision, required actions, owners, and release conditions.
3. Verify and close: confirm that documentation, production controls, inspection evidence, and affected inventory match the approved change before closure.

Assign one coordinator to maintain the change record and chase decisions. Design authority should approve product requirements; supplier manufacturing engineering should confirm process feasibility; quality should approve verification arrangements; purchasing should authorize commercial adjustments. The project manager coordinates these decisions but should not replace technical approval with a schedule-driven instruction.

Give the supplier a named route for escalation and agree response targets based on urgency. Silence, meeting attendance, or acknowledgment of an email must not count as approval.

Review the impact beyond the edited feature

A dimensional change is rarely isolated. Increasing a shaft diameter may affect bearing fit, assembly force, available wall thickness, and inspection equipment. Changing a valve-block passage can alter pressure loss, sealing lands, cleanliness risks, or pressure-containing wall sections. Review the interfaces and operating conditions, not just the marked-up drawing.

Require an impact assessment proportional to the risk. The supplier should explain manufacturing consequences, while the design owner evaluates whether the proposed solution preserves intended function.

Ask for evidence behind statements such as “equivalent material” or “no functional impact.” Depending on the change, useful evidence may include a tolerance analysis, material-property comparison, updated risk assessment, or test proposal. A supplier should not relax a tolerance merely because its current process struggles to achieve it; first determine whether the requirement is functional and whether process improvement is feasible.

Use risk to determine the approval route

A spelling correction with no technical effect does not need the same review as a new heat-treatment specification. Define change categories, but classify them by consequence rather than by how small the edit looks.

Changes affecting safety, pressure containment, load capacity, sealing, life, or interchangeability need explicit engineering and quality review. Cosmetic or administrative changes may follow a shorter route if they cannot alter interpretation or acceptance. Where customer approvals or regulatory obligations apply, identify those dependencies before setting the implementation date.

Resolve cost and delivery before releasing the work

Technical approval does not settle the commercial impact. Before implementation, obtain a written supplier assessment covering tooling modification, programming, samples, testing, material commitments, work in progress, and obsolete inventory. Separate one-time costs from recurring unit-price changes so that approval is unambiguous.

The delivery assessment should identify the actual constraint. Is the delay caused by tool rework, replacement material, outside processing, or validation capacity? Ask for a revised sequence showing which activities can run in parallel and which depend on approval or test results. A revised shipment date alone does not explain whether the plan is credible.

Record how affected stock will be handled: use as-is under authorization, rework, return, or scrap. Responsibility for those costs should follow the agreed contract and the circumstances of the change, not an assumption that either the requester or supplier always pays.

Where technical feasibility remains uncertain, authorize a limited investigation or prototype build separately. State its quantity, spending limit, and restrictions. This allows learning without accidentally authorizing full production or shipment.

Make the production cutover identifiable

“Apply the change immediately” is usually an inadequate instruction. The supplier may have raw material, partly machined components, finished stock, and shipments in transit. Each category needs a disposition tied to the change record.

Define effectivity using a boundary the supplier can control and demonstrate: a serial number, manufacturing lot, work order, or another agreed identifier. A date can supplement that boundary, but a date alone may be ambiguous when production and shipment overlap.

• Identify the last acceptable old-revision lot and the first authorized new-revision lot.
• State whether existing stock may be consumed, requires rework, or must be quarantined.
• Decide whether changed interchangeability requires a new part number rather than only a revision.
• Require labels, packaging records, and shipping documents to preserve configuration identity where needed.
• Confirm that tooling, machine programs, work instructions, inspection plans, and supplier purchasing documents have been updated.

Request confirmation from the people controlling production and inspection, not only the supplier’s sales contact. The cutover record should show that obsolete instructions have been withdrawn from use and that any affected sub-tier processor has received the approved requirements.

Validate the changed product before routine shipment

Verification should answer a specific question: does the changed configuration still meet its requirements when made by the intended production process? A sample that looks correct is insufficient when the change affects a fit, wear surface, seal, or load-bearing feature.

Agree on the validation plan before samples are manufactured. Identify the characteristics to inspect, test methods, acceptance limits, sample rationale, and approval authority. Depending on risk and contractual requirements, evidence may include a first-article inspection, material certificates, dimensional results, capability evaluation, or functional testing.

Match the evidence to the failure mechanism. A dimensional report can verify a revised bearing housing bore, but a changed bearing fit may also require assessment across operating temperatures. A surface-treatment substitution may require thickness and adhesion checks as well as evaluation of its effect on friction or sealing. Do not substitute available measurements for the evidence actually needed.

Document the release decision against the tested configuration. Approval of prototype samples must not silently become approval of a different production material, tool, or manufacturing route. When validation fails, retain the hold, record the discrepancy, and return the proposal for revision.

Handle urgent deviations without creating a second process

A material shortage or an approaching shipment date can create pressure to accept a temporary departure. Use a controlled deviation or concession rather than changing the baseline informally. Distinguish permission to manufacture outside a requirement from acceptance of already-produced nonconforming parts; both need defined authority.

The authorization should identify the affected requirement, technical justification, risk controls, permitted quantity or lots, expiration, and product-identification method. State any additional inspection and whether downstream approval is required. Once the allowance expires, the original requirement remains in force unless a permanent change has completed normal approval.

If the supplier implements a change without permission, first contain affected stock and determine the extent of shipments. Obtain the actual manufacturing configuration and evaluate disposition through engineering and quality. Updating the drawing afterward does not, by itself, establish that previously produced parts are acceptable.

Close the record only when implementation is proven

Maintain a change register showing the owner, affected revisions, risk level, approval status, validation status, effectivity, and open actions. Use project reviews to resolve stalled decisions and conflicting dependencies, rather than merely asking whether the change is “done.”

Closure requires more than signatures. Retain the approved release package, supplier acknowledgment, commercial agreement, validation evidence, stock disposition, and cutover confirmation. Receiving inspection should be able to connect a delivered lot to the applicable configuration without reconstructing an email chain.

During early deliveries, check the changed characteristics and configuration records at a level justified by risk. If a mismatch appears, hold the affected material and determine whether the failure lies in the design, manufacturing implementation, or document handoff. Close the change only when the approved configuration is demonstrably reaching production and shipment.