Measure true OEE with three numbers
Scheduled time, good units and the ideal rate. Nothing else. If your OEE doesn’t match what actually ships, trust the lower number.
Example: 4,362 good units ÷ 4 per minute = 1,090 minutes of perfect production, in 1,830 scheduled minutes. OEE 59.6%
No ideal rate? Use the best 4 hours of your last 400. Method and example: R.C. Hansen, Overall Equipment Effectiveness.