OEE explained: availability, performance, quality and a worked example

Theory: three factors, six big losses

OEE measures how much of the planned production time is fully productive: making only good parts, as fast as possible, without stops. The three factors map to the six big losses of TPM: breakdowns and setups (availability), small stops and reduced speed (performance), and start-up rejects and production rejects (quality).

Step by step

1. Take one shift or day.
2. Enter the planned time (shift length minus breaks), the downtime, the ideal cycle time, the total and the good count.
3. Read OEE and the factors.
4. Use a Pareto chart on the biggest loss.

Case study: one shift on a press line

A shift of 480 planned minutes has 47 minutes of downtime; with an ideal cycle time of 1 second the line made 19,271 parts, 18,848 good (the Load sample).

• Availability 90.2 %, performance 74.2 %, quality 97.8 %.
• OEE = 65.4 %, below the 85 % target.
• Loss in minutes: 47 downtime, 112 speed loss, 7 quality loss.

The biggest loss is performance: the line runs much slower than its ideal rate, typically because of small stops that nobody records. The team installs a stop counter and finds jams at the feeder as the main cause.

Common mistakes

• Using a slow “standard” cycle time, which hides speed losses and can push performance above 100 %.
• Excluding changeovers from downtime.
• Comparing OEE between plants with different definitions.

Frequently asked questions