Overall Equipment Effectiveness breaks total loss into three independent categories — Availability, Performance, and Quality — so you know exactly which one to fix first, not just that output is low.
OEE (Overall Equipment Effectiveness) is the standard manufacturing metric — defined in ISO 22400-2 and originating from the SEMI E10/E79 equipment-performance standards — that separates total production loss into three independent, multiplicative components: Availability (is the machine running when it should be?), Performance (is it running at full speed?), and Quality (is it producing good parts?). Most plants track output volume or downtime hours separately, which hides which of the three is actually driving the loss. Because the three multiply together rather than add, a plant running at 90% on all three components is not at 90% OEE — it is at 72.9%, because each stage compounds against what the previous stage already lost. This is why isolated fixes ("reduce downtime by 10%") often produce disappointing OEE gains if Performance or Quality were the real constraint.
A line runs an 8-hour (480 min) shift with 60 min planned downtime (breaks), leaving 420 min Planned Production Time. 45 min of unplanned downtime (a jam and a short material wait) leaves 375 min Run Time — Availability = 375/420 = 89.3%. The line produces 700 units against an ideal cycle time of 30 sec/unit, meaning 350 min of theoretical run time was achieved in 375 actual minutes — Performance = 93.3%. Of those 700 units, 25 were rejected — Quality = 96.4%. OEE = 89.3% x 93.3% x 96.4% = 80.3%, not the 93%+ any single component might suggest in isolation.
Well-run manufacturing operations track all three OEE components separately per shift, not just a blended OEE percentage — because the fix for low Availability (maintenance scheduling, changeover procedure) is completely different from the fix for low Performance (speed loss, micro-stops) or low Quality (setup, tooling wear, material issues). The Ideal Cycle Time reference is reviewed periodically against actual demonstrated best-case performance, since a stale (too conservative) reference silently inflates the calculated Performance score.
Manufacturing engineering teams review the three OEE components separately every shift, investigate the single largest loss category first (rather than spreading effort evenly across all three), and re-verify the Ideal Cycle Time reference whenever tooling, material, or product specification changes — since Performance is the component most vulnerable to a stale reference value silently distorting every subsequent calculation.
Rebota's Equipment Monitoring and Daily Site Logs modules can capture shift-level run time, downtime events with cause codes, and production counts directly from the floor — feeding the same Availability/Performance/Quality decomposition used here automatically, shift over shift, without manual data entry at month-end.
