First steps
- List earlier actions and check which are still in place.
- Verify the root cause by switching it on and off.
- Spread the fix to similar lines (read across).
How to measure success
Repeat rate of the defect over 6 months. Record the value before you start, so the effect of every action can be shown.
When these methods are the wrong choice
- 8D report: Small internal issues where one person can fix the cause in a day.
- CAPA / NCR tracker: Analysing one problem in depth.
- PFMEA / DFMEA: Fixing a problem that has already happened; update it after the 8D instead.
- Layered process audit (LPA): Finding root causes.
- Hypothesis tests: Exploring causes; use it to confirm them.
- Standard work / work instruction: Processes that are still changing every week.
The methods in one line
| Method | What it is |
|---|---|
| 8D report | Team-based method for customer complaints: containment, root cause for occurrence and non-detection, verified corrective action, prevention. |
| CAPA / NCR tracker | Register of nonconformities and corrective actions with owners, deadlines and effectiveness checks. |
| PFMEA / DFMEA | Analyses how a process or design can fail, rates the risk (AP) and defines prevention and detection. |
| Layered process audit (LPA) | Short daily checks of key process controls by several management layers. |
| Hypothesis tests | Proves whether a difference (before / after, machine A / B) is real or chance. |
| Standard work / work instruction | The current best way to do a job, with key points and reasons, used for training and audits. |