“Overall Equipment Effectiveness”, known in the jargon as “OEE”, is a composite metric which quantifies how far a factory is from its optimal performance – the performance level for which it was designed to.
OEE is an aggregation of three separate factors:
1. Availability - Represents the percentage of the scheduled time that the operation has to operate.
Formula:
Availability = Uptime / Available Time
Example:
Uptime = 450min Available Time - 60min Non-Scheduled Downtime = 390min
Availability = 390min / 450min = 86.6%
2. Productivity - The speed at which each work center works as a percentage of the optimal productivity for which it is designed to.
Formula:
Productivity = Estimated Time / Time Spent
where Estimated Time = Quantity Produced * Operation Cycle Time / Operation Quantity Ratio
Example:
Operation Cycle Time = 1H15m
Operation Quantity Ratio = 5
Quantity Produced = 10
Time Spent = 2H44m
Productivity = (10 * 1H15 / 5) / 2H44 = (10* 75 / 5) / 164 = 91.5%
3. Quality - The good units produced as a percentage of all the units produced.
Formula:
Quality = Units OK Produced / (Units OK Produced + Units NOK Produced)
Example:
Units OK Produced = 221
Units NOK Produced = 21
Quality = 221/(221+21) = 91.3%
OEE calculation:
In these examples:
OEE = Availability * Productivity * Quality = 86.6% * 91.5% * 91.3% = 72.3%
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