Quality is the share of total output that was good the first time through. Quality = Good Count ÷ Total Count. Total count is everything the line produced during run time, including the bottles that were rejected. Good count is what passed every inspection without rework or reprocessing.
The reason OEE insists on first-time-good is that rework hides loss. A bottle with a low fill that is emptied, rinsed and refilled consumed filler time twice. If you count it as good because it eventually shipped, your Quality figure looks fine while the machine's real output is lower than it appears. Count it as a reject in the OEE calculation and track the rework separately as a cost.
Common reject causes on a bottling line are underfill, overfill, cap torque out of range, cocked caps, crooked or missing labels and damaged bottles. Each should be tallied by reason, because the Quality factor alone tells you how many were lost but not why.
Standard Procedure
- 1Take total count from the same counter used for Performance so both factors share one denominator.
- 2Tally every reject by reason code at the point it is removed from the line.
- 3Subtract total rejects (including units sent to rework) from total count to get good count.
- 4Divide good count by total count.
- 5Sort the reject reasons from largest to smallest before deciding what to fix.
Lesson Summary
- ✓Quality uses total count as its base and treats reworked units as not good.
- ✓Reject tallies by reason turn a percentage into an action list.