Oee Quality
OEE Quality is the third factor of Overall Equipment Effectiveness (OEE), representing the percentage of units produced that meet quality standards on the first pass without needing rework or rejection. It is calculated as Good Count divided by Total Count, also known as First Pass Yield.
In shop floor maintenance, OEE Quality is tracked within CMMS and asset reliability systems like ServiceGrid by logging reject parts and scrap during production runs to isolate Quality Loss. This metric separates process yield defects from availability or performance issues, enabling teams to target root causes such as machine drift or operator error. By focusing on first-pass yield, maintenance teams can identify and address quality losses that consume materials, energy, and labor for non-conforming parts, ultimately improving overall equipment effectiveness.
- Counting reworked parts as 'good' inflates the Quality score, masking true process yield and hiding quality losses.
- Ignoring startup scrap from warm-up, changeover, or adjustment scrap leads to an artificially high Quality rate.
- Delayed defect detection, where only immediate defects are counted while subtle issues surfacing later are ignored, underestimates quality losses.
How does OEE Quality differ from simple yield?
OEE Quality specifically excludes reworked parts; it measures First Time Right (parts passing the first time), whereas simple yield may include reworked units.
What is the impact of a 90% Quality score on a 100% Availability and 100% Performance system?
The resulting OEE is 1.0 × 1.0 × 0.9 = 90%, meaning 10% of the planned production time was wasted producing defective or reworkable parts.
Why is Quality Loss often the most expensive OEE loss?
It consumes materials, energy, and labor to produce non-conforming parts that generate no value, unlike downtime (no output) or speed loss (reduced output but still good).
Can OEE Quality be 100% if defects exist but are caught later?
No; a 100% Quality score requires zero defects, including those surfacing post-production, as any defect reduces the Good Count.