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- OEE Calculation
OEE Calculation
In theory, OEE is the ratio of fully productive time to planned production time. In reality, OEE is calculated in terms of its three contributing factors: availability, performance, and quality. These three factors are multiplied together in the OEE calculation to produce a percentage score. Because of this multiplication, deficiencies in any area are severly multiplied. For example, if all three factors are 90%, your overall OEE would only be 72.9%. Studies indicate that the average OEE rate in manufacturing plants is around 60% and around 85% for "world class" facilities.
OEE Calcuation Factors
As mentioned above, three factors are used in the calculation of OEE - availability, performance & quality.
Availability
Availability is a function of planned production time and actual operating time (i.e. planned minus unanticipated downtime):
Availability = [Operating Time] / [Planned Production Time]
Performance
Performance accounts for speed loss and can be calculated one of two ways - either in terms of ideal cycle time or in terms of the ideal run rate. Either way, the calculation is capped at 100% to minimize the affect of any errors in the ideal cycle time or ideal run rate.
Performance = [Ideal Cycle Time] / ([Operating Time] / [Total Pieces])
- or -
Performance = ([Total Pieces] / [Operating Time]) / [Ideal Run Rate]
Quality
Quality is simply calculated as the percentage of good parts produced:
Quality = [Good Pieces] / [Total Pieces]
OEE
Finally, OEE is calculated as the product of the other three factors:
OEE = [Availability] x [Performance] x [Quality]
Other OEE Considerations
Remember that OEE is not a magic number - just because one facility or shift has a higher OEE than another doesn't necessarily mean it is better. For example, increasing availability by 5% while decreasing quality by 3% would result in an improved OEE - but probably not a more profitable operation. This is why each of the three factors should be considered individually as well as the aggregate OEE figure.
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