Defects, Defectives and Opportunities on a Blister Line

A blister packaging line pushes tablets into formed cavities, seals a foil lid over them and prints a lot number and expiry date on each card. Three words get confused constantly on that line, and the whole DPMO method depends on keeping them straight. A defect is a single flaw: one empty cavity, one broken tablet, one wrinkle in the seal, one smudged lot code. A defective is a unit that has at least one defect. One card with three empty cavities is three defects but one defective.

An opportunity is a place on the unit where a defect could occur. On a ten-cavity card you might define each cavity as one fill opportunity, the seal as one opportunity and the print as one opportunity, giving twelve opportunities per card. The count must be agreed before data collection and written down, because changing it later changes every number downstream.