What OEE Actually Measures
Overall Equipment Effectiveness multiplies three separate scores, availability, performance, and quality, into a single number that reflects how much of a machine's true production potential is being captured. A machine can look busy all shift and still post a poor OEE if it's running slow or producing scrap.
Reading the Three Factors
Availability compares actual run time against planned production time, capturing the impact of downtime from changeovers, breakdowns, and stoppages. Performance compares the ideal cycle time against the actual time taken, capturing speed losses. Quality compares good parts against total parts produced, capturing scrap and rework. Multiplying all three together means a weakness in any single factor drags the overall score down.
Using OEE on the Shop Floor
Tracking OEE over time on a single machine or cell is usually more useful than comparing the absolute number between dissimilar machines, since cycle times, batch sizes, and changeover frequency vary a lot by job. Use this calculator on a shift-by-shift or job-by-job basis to spot which factor is dragging a particular run down before deciding where to focus improvement effort.