A supplier quality inspection should not begin when a finished shipment is waiting at the factory door. Effective inspection is planned from the drawing and process risk, then applied at the points where defects can be prevented, detected and contained most efficiently.
Define measurable acceptance criteria
Start with the released drawing, material, finish, standards, critical characteristics and functional tests. Replace subjective requirements with measurable criteria or approved visual samples.
State the drawing revision and required records in the purchase order. Inspection cannot resolve an ambiguous specification.
Use a risk-based inspection plan
Rank characteristics by consequence of failure, process capability and detectability. Critical features may require 100% control or capability monitoring. Stable low-risk features may use sampling.
ISO 2859 provides systems for acceptance sampling by attributes, but a sampling plan must fit the lot type and risk. AQL is not a promise that every delivered item is conforming.
Inspect before production starts
Review material certificates, process plans, tooling, gauges and qualifications before the first batch. For special processes, verify procedures and personnel.
Early review prevents an entire lot from being produced with the wrong revision, material or method.
Approve a production-relevant first article
The first article should use the intended process, tooling, material, site and sub-suppliers. Require a dimensional report, certificates and functional evidence appropriate to the product.
Record every deviation and disposition. Conditional approvals should be limited in scope and duration.
Place checks at process control points
Incoming material, first-off, in-process and final inspections serve different purposes. Inspect characteristics before they become hidden by assembly or coating. Verify process parameters where final inspection cannot prove the result.
Quality should be built into the process, not inspected into the finished product.
Confirm measurement capability
Gauges must be calibrated, suitable for the tolerance and used by competent personnel. Define datums and measurement methods for critical features. Consider measurement-system capability when tolerances are close to equipment uncertainty.
Perform pre-shipment inspection
For overseas or high-risk supply, verify quantity, workmanship, dimensions, records, packaging and labels before dispatch. This prevents defects from consuming freight, customs and recovery time.
TOS provides independent quality control and reporting at the source.
Control documents and traceability
Inspection reports should identify part number, revision, lot, material batch, quantity, equipment and inspector. Certificates must be matched to the shipped batch.
Retain records for the period required by product, customer and regulatory risk.
Manage non-conformance
Define segregation, notification, concession and rework authority. Suspect parts should be contained across finished goods, work in progress and previous shipments.
Corrective action should identify root cause, implement prevention and verify effectiveness. Repeated sorting without process correction is not a sustainable control.
Adjust inspection using performance
New suppliers and processes need increased control. Inspection may be reduced after stable evidence, but it should increase again after changes or failures. Use supplier performance data rather than habit.
Inspection plan checklist
- Current drawing and measurable acceptance criteria
- Critical-characteristic and process-risk review
- First-article evidence and approval status
- Incoming, in-process and final control points
- Sampling method and acceptance numbers
- Measurement method and calibration
- Pre-shipment document and packaging release
- Non-conformance and corrective-action process
The inspection plan should be part of supplier qualification and ongoing performance management. Review quality control for overseas manufacturing, European supplier quality requirements and supplier qualification. Contact us to set up a product-specific inspection plan.
Frequently asked questions about supplier inspection
Does an AQL plan guarantee zero defects?
No. Acceptance sampling limits the decision risk for a defined lot; it does not inspect every item. Safety-critical features may need 100% control, process monitoring or error-proofing.
Who should prepare the inspection plan?
Engineering defines functional and critical requirements, quality defines verification and sampling, and the supplier confirms process feasibility. All three views are needed.
What should happen after a failed inspection?
Contain the lot, assess previous and in-process material, decide disposition and require root-cause corrective action. Re-inspection alone does not prevent recurrence.