OEE

OEE (Overall Equipment Effectiveness) is a concept developed over years by the Institute of Plant Maintenance in Japan. It is a part of the TPM (Total Productive Maintenance) concept and takes into account the effect of losses in the production, on the overall equipment effectiveness.

The OEE of equipment can be defined as the product of three factors:

• Availability
• Performance rate
• Quality rate

The range of value lies between 0 and 1 or 0% and 100%

Availability

The factor availability is a measure of losses due to unplanned stoppages in production and can be as follows defined:

Availability = operation time / (operation time + unscheduled time)

The time available is defined as the difference between operation time and the time planed for the operation. The time planned can be formulated as the product of the shift times:

Hours x amount of shifts x amount of days/month

Machine operating time is defined as the time taken by a machine in real production (uptime). This means that time spent on stoppages etc. will be deducted from the operation time.

Performance rate (usage rate)

The performance rate is measured as the losses occurred due to deviation from the planned cycle rate through small stoppages and idle periods:

Performance rate = Production time / Planned time

Quality rate

The quality rate is defined as the time lost in the reworking of rejected and defect pieces:

Quality rate = (qty. prod. Pcs - qty. rework pcs - qty. reject pcs) / qty. prod. Pcs

Practical experiences

An OEE of 100% is practically impossible, as losses are ultimately inevitable. The OEE investigations cause at first an enormous amount of effort. Generally it is the production workers that collect the necessary data. The amount of effort required is based firstly on the schooling of the workers and secondly on the acquisition of unadulterated data.
OEE does not seek to censure workers; its aim is, through investigation and analysis of equipment and production figures, to eliminate losses and increase efficiency.
OEE is not to be equalled to equipment availability, already defined in OEE as performance rate and therefore also a part of OEE.