Contain the problem first, then prove the cause. “Operator error” is rarely enough by itself; the system condition that allowed the failure should be investigated and the effectiveness of the action verified.
1. Describe the nonconformity
State what requirement was not met, where it was found, quantity affected, drawing/specification reference and objective evidence. Avoid vague wording such as “quality issue”.
2. Contain
Protect the customer and the next process: segregate affected stock, stop shipment if necessary, identify work-in-process and define temporary inspection or sorting.
3. Investigate root cause
Use evidence. 5 Whys, fishbone diagrams and process mapping can help, but the output should be tested against facts. ASQ emphasizes that a proposed root cause must be verified rather than accepted because it sounds plausible.
4. Corrective action
Remove or control the verified cause. Examples may include changing tooling, error-proofing a fixture, correcting a BOM link, changing inspection sequence, revising software logic or improving supplier controls.
5. Update the system
Where applicable, update the control plan, work instruction, training, FMEA, inspection standard, ERP/BOM logic or maintenance plan so the improvement survives beyond one person’s memory.
6. Effectiveness check
Define what evidence will prove the action worked: zero recurrence over a defined batch/time, process capability, audit result, reduced defect rate or successful repeat production.
This article is general guidance for preliminary engineering and shop-floor understanding. The drawing, applicable standard, machine/tooling OEM instructions, process-specific safety requirements and qualified engineering judgment take priority.