In brief
Overall equipment effectiveness (OEE) is a KPI that multiplies a plant's availability, performance and quality to show its real productivity.
Contents
What is Overall equipment effectiveness?
OEE stands for overall equipment effectiveness. The KPI compares the quantity of good parts actually produced with what the equipment could theoretically have produced in the planned production time. It is closely linked to total productive maintenance and is expressed as a percentage.
It is calculated as OEE = availability × performance × quality. An example: a machine is scheduled for 480 minutes, is down for 60 of them and runs for 420 minutes; availability is 87.5 per cent. With an ideal cycle time of one minute, 420 parts would be possible, but 378 are produced; performance is 90 per cent. Of these, 360 parts are good, so the quality rate is around 95.2 per cent. This results in an OEE of 75 per cent.
The factors reflect typical types of loss: availability losses from breakdowns, changeovers and material shortages, performance losses from minor stoppages and reduced speed, and quality losses from scrap, rework and start-up losses. Missing spare parts show up directly as an availability loss.
In practice: maintenance and procurement
If the reasons for downtime are recorded properly, the OEE analysis shows what share of availability losses is due to waiting for spare parts. This figure is a solid basis for justifying stockholding or framework agreements for specific parts.
Synonyms and abbreviations: OEE · overall equipment efficiency · equipment effectiveness · plant effectiveness
Frequently asked questions
How do you calculate OEE?
OEE is the product of three factors: availability (run time divided by planned production time), performance (actual output divided by the output theoretically possible in the run time) and quality (good parts divided by parts produced). A short formula is: good parts × ideal cycle time divided by planned production time.
What is a good OEE value?
There is no universally valid target. The achievable OEE depends on the industry, product variety, batch sizes and type of equipment, and companies define planned production time differently. More meaningful than comparing with other companies' figures is the development of your own OEE over time and the question of which of the three factors is holding it back most.
What is the difference between OEE and availability?
Availability is only one of the three OEE factors. It shows how long a machine actually runs during the planned time. A machine can have high availability and still a low OEE if it runs slower than possible or produces a lot of scrap.
Which losses does OEE capture?
Losses are captured in three groups: availability losses such as breakdowns, changeover and waiting times, performance losses such as minor stoppages and reduced cycle speed, and quality losses from scrap, rework and start-up losses. In TPM these are often referred to as the six big losses.