THE QUESTION
Why do parts that passed inspection come back?
Propose what to do, then judge whether each action would move each root.
30 at the table (29 simulated) · 3 actions proposed against 4 root causes. Add one, then judge whether each action moves each cause.
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Score the roots first
why
The method's own practice, before any action is proposed: each root cause is scored 1–5 on how feasible it is to address, how much impact addressing it would have, and how likely it is to resolve by itself with no intervention. Priority goes to roots with high impact, high feasibility and low likelihood of fixing themselves — priority = impact + feasibility − likelihood. Scores are averaged across the group and shown with how many scored.
1 = low, 5 = high. Your own scores; the group's averages beside them.
| root cause | feasible | impact | fixes itself | priority |
|---|---|---|---|---|
| Tool wear is judged by ear | – | |||
| Rework is not counted anywhere | – | |||
| Customers changed their inspection method and never told us | – | |||
| The same operator runs the same machine for years and nobody checks the settings | – |
Would each action move each root cause?
Down the side: the actions people proposed. Across the top: the root causes the map found. Every square is one vote on one question — would this action significantly reduce that cause? One side has to reach 75% of the votes cast to settle it; short of that the square stays split.
why
Answered at 75% of votes cast, like every other question here. Split means people voted and neither side reached that bar — it is a result, not a queue, and it stays split until enough people change their minds. A square nobody settles stays undecided; it never turns into a no. Judging each pair on its own is what stops a popular action being credited with fixing things it does not touch.
| ACTION | ROOT CAUSES · does the action on the left reduce it? | |||
|---|---|---|---|---|
| Tool wear is judged by ear | Rework is not counted anywhere | Customers changed their inspection method and never told us | The same operator runs the same machine for years and nobody checks the settings | |
| Ask each customer for their inspection method and gauge list, and keep it with the drawing discuss | ✗ no, it does not 3 yes / 26 no · 22 of 29 settles it | ✗ no, it does not 3 yes / 26 no · 22 of 29 settles it | ✗ no, it does not 3 yes / 26 no · 22 of 29 settles it | ✓ yes, it reduces this 27 yes / 2 no · 22 of 29 settles it |
| Measure every returned part before it is remade, and log what was found discuss | ✗ no, it does not 7 yes / 22 no · 22 of 29 settles it | ✗ no, it does not 5 yes / 24 no · 22 of 29 settles it | ✗ no, it does not 3 yes / 26 no · 22 of 29 settles it | ✗ no, it does not 3 yes / 26 no · 22 of 29 settles it |
| Pay on right-first-time parts, not parts per hour discuss | ✓ yes, it reduces this 25 yes / 4 no · 22 of 29 settles it | ✗ no, it does not 3 yes / 26 no · 22 of 29 settles it | ✗ no, it does not 6 yes / 23 no · 22 of 29 settles it | ✗ no, it does not 5 yes / 24 no · 22 of 29 settles it |
Highest leverage so far
Ask each customer for their inspection method and gauge list, and keep it with the drawing reduces 1 of 4 root causes
Pay on right-first-time parts, not parts per hour reduces 1 of 4 root causes