OEE

OEE (Overall Equipment Effectiveness) combines the three ways a machine loses output into one number: stopping, running slower than ideal and making bad parts. An OEE of 60% means that, of the time the machine was supposed to produce, only 60% turned into good parts at the right pace.

How it works

The formula is availability × performance × quality. Availability is run time divided by planned time. Performance compares the actual cycle with the ideal cycle. Quality is the share of good parts. That is why OEE points to where to act: low availability means stops and setups; low performance means slow cycles or micro-stops; low quality means scrap and rework.

Practical example

A CNC lathe has 8 planned hours. It stood still for 1 h 30 min (availability 81%), ran parts in 2 min when the ideal was 1 min 40 s (performance 83%), and scrapped 3 in 100 parts (quality 97%). OEE = 0.81 × 0.83 × 0.97 ≈ 65%. Measured automatically on the CNC, that number shows up per shift and per stop reason, without spreadsheets.

Common mistakes

• Logging by hand at the end of the shift: operators remember big stops and forget micro-stops.
• Using calendar time (24 h) instead of planned time, mixing OEE with TEEP.
• Comparing OEE across machines with different parts and ideal cycles without adjusting the baseline.