DPMO can be gamed in one move: inflate the opportunity count. Count every tablet edge, every millimetre of seal, every printed character as a separate opportunity and the same 60 defects spread over a vastly bigger denominator. The sigma level climbs, the line has not changed, and the pharmacist opening a card with an empty cavity is no better off. An honest opportunity is a distinct, inspected feature that can independently fail and that the customer would notice.
A workable rule for the blister line: one opportunity per cavity (fill and tablet condition together), one for the seal, one for the print. If a defect type is never inspected, it is not an opportunity. Keep the same definition across months and across lines making similar products so trends and comparisons mean something.
Used honestly, DPMO becomes a steering tool. Split it by defect type, rank the types from largest to smallest, and put the problem-solving effort on the top one. Recalculate each week on the same definition and watch the number move. A falling DPMO that nobody can explain is luck; a falling DPMO tied to a named fix is improvement.
Standard Procedure
- 1List candidate opportunities and strike out any that are not distinct, not inspected or not noticeable to the customer.
- 2Document the final opportunity count and lock it for the reporting period.
- 3Calculate DPMO by defect type and rank the types.
- 4Assign improvement work to the top-ranked type and recalculate on the same definition after the fix.
- 5Review the opportunity definition only when the product or inspection method genuinely changes, and note the change in the records.
Lesson Summary
- ✓Padding the opportunity count raises the sigma level on paper and changes nothing for the customer.
- ✓Splitting DPMO by defect type turns a reporting metric into a prioritised action list.