Overall Equipment Effectiveness allows to measure current effectivenes of equipment and to identify where losses decreasing OEE come from. Inorder ti improve effectiveness it's neccessary to know what is a current situation, to know it, you have to measure it.
OEE introduces three facors used as effectivenes metrics:
- Availbility
- Performance
- Quality

OEE starts with defining of Plant Operating Time

From Plant operating Time subtract planned downtime, what covers all events which should be exlcuded from analysisi, because there was no intention to run the production (eg. breaks, trainings, planned maintenance, no customer orders). The remaining time is called Planned production time.

OEE analysis begins from Planned production time and it analyses effeciveness lesses which occur with the goal to reduce and eliminate them. There are 3 main loss categories – Downtime, Performance lose, Quality.

Availbility:

Availbility factor takes into account all downtimes, which includes all events causing production process for a certain time (usually a couple minutes or more, so the time that can be registered). For example a downtime is a failure, no material, changovers. Changeover time is counted in OEE analysis, because it is a kind of downtime. It can't be fully eliminated, but it can be minimized in majority of the cases. Time remaining after subtracting Downtimes is called Operating Time.

Performance:

Performance measures the loss of speed, what includes all factors causing production running with speed lower than maximum. Example of performance loss are reduced speed run or minor stops. The rest of the time is called Net Operating Time.

Quality:

Quality measures all losses caused by producing products which don't meet quality standards including scraps. The remaining time is called Effective Production Time.

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