There are five principles of problem-solving which is used to investigate and eliminate the root cause of non confirming parts.
What is the problem?
A condition characterized by a discrepancy between an ideal state and an actual state.
5 Principals for Problem Solving
1- Fact-finding and situation assessment
2-Identification of cause (why-why analysis)
4-Verification of the effectiveness of measures.
5-feedback to upstream sources
1-Fact Finding and situation assessment
Start Investigation immediately
Review the fact by 5W2H
7-How much/How many
Classify information into the process and actual problem part and analyze.
Classify information into the 4M based on result of the analysis , identify the primary cause of nonconformity.
2-Identify the cause (Why-Why analysis)
Work towards to identify the root cause by repeating "why" at least 5 times, investigate both causes of occurrence and cause of non-detection.
→ Determine measures deemed most effective for the identified root cause.
→Implement measures focusing more on the elimination of cause, rather than
prevention of outflows.
4-Verification of the effectiveness of measures
→Verify the effectiveness of measures with a reasonable number of units or time period, and confirm no recurrence of problems from the same cause.
→Verify both products and processes.
5-Feeback towards to upstream sources
Incorporate measures into the quality standards, organization, and management