Overall Equipment Efficiency (OEE)

Total plant efficiency is a production-technical measure used to determine the value added of a plant.

An ideal machine would run continuously, always with maximum power and without scrap. In reality, of course, this does not happen. The OEE serves as a key figure for determining how close the plants are to this ideal. Time, quantity and quality are combined to make an assessment of effectiveness.

Based on the maximum available time, as an example assumed here 24 hours, the theoretically available production time is used as a starting point for the further calculations. This possible production time results from the total time in the period considered minus all planned downtimes, e.g. for upkeep, maintenance or non-occupancy of the plant due to the order situation.

For the OEE, three loss areas are distinguished:

  • Loss of availability
  • Loss of performance
  • Loss of quality

Losses of availability are caused by unplanned downtimes during the possible production time. These can be disruptions, setup processes and waiting times. After deducting the availability losses from the possible production time, the actual production time is obtained.

Power losses are the difference between the possible application of the plant based on the actual production time and the actual output. The difference arises from short downtimes, e.g. due to jammed parts, or from a reduced speed of the system.

All goods that are not faulty from the plant are counted as quality losses. Any product that needs rework or is to be counted as a scrap shall be deducted from the actual application for the calculation of the OEE.

Together, the OEE results from the multiplication of availability level (actual production time/possible production time) x power level (actual output/possible output) x quality level (impeccable products/actual application).

An example of how optimized maintenance can affect the OEE:

Example 1: High production time, lower quality

Available time (24 hrs)

– Planned standstill

Availability

A: Possible production time 95%

– Loss of availability:
Disruptions, waiting/retooling, line restrictions

B: Actual production time 80%

Performance

C: Possible application 80%

– Power losses:
Short downtimes, reduced speed

D: Actual application 70%

Quality

E: Actual deployment 70%

– Loss of quality:
– Scrap, rework

Q: Impeccable products 60%
0 % OEE
Degree of availability (B/A) x performance level (D/C) x grade (F/E)

Example 2: More planned maintenance, lower failure rate

Available time (24 hrs)

– Planned standstill

Availability

A: Possible production time 85%

– Loss of availability:
Disruptions, waiting/retooling, line restrictions

B: Actual production time 80%

Performance

C: Possible application 80%

– Power losses:
Short downtimes, reduced speed

D: Actual application 75%

Quality

E: Actual deployment 75%

– Loss of quality:
– Scrap, rework

Q: Impeccable products 70%
0 % OEE
Degree of availability (B/A) x performance level (D/C) x grade (F/E)

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