When custom hardware structural parts arrive with incorrect dimensions, there are two reactions to avoid at all costs: simply returning the goods without documenting the issue, or silently mixing the non-conforming parts into the production line. The standard practice within industry quality systems follows the sequence of “isolate, document, formally assess, and implement closed-loop corrective action.”
This article outlines the proper handling process for dimensionally non-conforming parts based on ISO 9001 non-conforming product control logic.
1.
Step One: Isolation and Documentation
Upon discovering dimensional discrepancies, immediately isolate the affected batch to prevent the parts from entering production and causing assembly accidents. Preserve the parts in their “as-received” state and re-measure the disputed dimensions by comparing them against the released drawings and the inspection methods agreed upon by both parties; the measurement method must align with the drawing specifications, otherwise the values cannot be compared.
Simultaneously, issue a formal Non-Conformance Report (NCR) to the supplier, including high-resolution photos (showing both the measuring tool and the measured area in the same frame), the purchase order number, the batch number, and the specific deviation values and measurement methods used.
Industry experience shows that photographic evidence and batch records form the basis for subsequent assessments and claims; the more complete the documentation, the more compelling the case.
II. Step 2: Select a Disposition Method Based on Defect Severity
There are seven standard methods for disposing of non-conforming products; the choice depends on the severity of the defect:
- Rework: Reprocessing the product to restore it to the original standard (e.g., remachining parts with dimensional deviations). After reworking, the product must be re-inspected against the original standard and found compliant before proceeding;
- Sorting: Conducting a 100% inspection to separate conforming products from defective ones, with the defective items handled separately; this is suitable when defects are concentrated in specific batches;
- Concession Acceptance (Special Acceptance): Used when the deviation does not affect subsequent processes or final functionality; the part is used “as-is” despite the deviation, subject to written approval from authorized personnel or the customer;
- Downgrading: Used when the part cannot meet the original standard even after repair but is released for a specific application with the customer’s written consent (e.g., downgrading a high-precision part to a standard-precision part);
- Scrapping/Rejection: Direct scrapping or returning to the supplier in cases of severe non-conformity or when repair is not cost-effective.
Regardless of the method chosen, the disposition plan must be agreed upon in writing with the supplier beforehand;
one must not modify parts before discussing liability.
III.
Step 3: Root Cause Attribution and Corrective Action Loop
Root causes for dimensional non-conformity generally fall into three categories: mold wear or design errors, process parameter drift, or unreasonable drawing tolerances. Suppliers are required to submit a root cause analysis and a Corrective and Preventive Action (CAPA) plan, specifying a deadline for rectification.
In accordance with industry supplier quality agreements, the first piece of every stamping batch must undergo CMM (Coordinate Measuring Machine) inspection, and the first, middle, and last pieces must be verified using inspection fixtures. If two consecutive sampled pieces fail to match the standard master sample, all previously produced parts must be quarantined and sorted, with non-conforming parts either reworked or scrapped.
If the issue stems from the supplier’s manufacturing process, the supplier bears the costs of rework, sorting, and scrapping, with debit notes issued for claims if necessary; if the issue arises from drawing design, both parties must re-evaluate tolerances and, where required, initiate mold or drawing modification procedures.
IV.
Step 4: Re-inspection and Traceability
Any batch subjected to rework, sorting, or concession acceptance must be resubmitted for quality inspection against original or concession-specific standards; release to inventory is permitted only after compliance is confirmed. Concession-accepted parts require written customer approval, and approval records must be retained throughout the process.
The entire disposition process—including reports, review records, disposition decisions, and corrective action reports—must be archived to ensure batch traceability. Customers in sectors such as the automotive industry often require that rectification reports be factored into supplier performance evaluations, which influence future order allocation.
V.
Prevention: Stopping “Dimensional Non-conformance” Before Delivery
Frequent dimensional non-conformance often stems from a lack of process control rather than isolated batch incidents. It is recommended that the purchasing party clearly define requirements in the quality agreement—such as first-article CMM measurement, patrol inspection frequency, isolation mechanisms for out-of-tolerance parts, and approval authority for concession acceptance—and incorporate supplier inspection discipline into the contract. At the receiving end, a system for incoming material sampling and re-measurement of critical dimensions should be established, creating a dual defense line comprising “incoming material screening,” “process monitoring,” and “final inspection confirmation.”
Industry experts emphasize that the core of addressing dimensional non-conformance lies not in “how to settle the current claim,” but in “preventing recurrence.”
Documentation, root cause analysis, closed-loop management, and traceability—each step lays the foundation for long-term supply chain stability.
