OEE : Overall Equipment Effectiveness

The OEE index has been developed by the JIPM (Japan Institute for Plant Maintenance). It is one of the pillars within the TPM method. The method distinguishes 6 loss types, and 3 categories: availability, speed losses and quality rate. The method's strength is that it makes the losses more transparent, and from experience we know that a good analysis provides a very good "picture" of the actual situation, which helps to determine both short and longer term improvement activities, including quantified benefits from each of the improvements.

Gross Available hours
Gross Available hours (#days/year: 365, 24 hours/day, 7 days/week)

Planned Downtime
For example: vacation, holidays, not 168 hours/week, not enough load.

1. Breakdowns/Machine failures
Downtime because of machine failures

2. Setup and adjustment
For example between product types, including "warmup time" after the actual changeover. Changeover time should be included here, and should not be included in the planned downtime. Changeover time can be reduced by applying the SMED System.

3. Small stops
When these have not been causes by logistics. Small stops are typically shorter than 5-10 minutes. Small stops are typically minor adjustments, for example cleaning etc. This in contrast with machinefailures, where you will usually need maintenance personnel to solve it.

4. Speed losses
Speed losses are caused when a machine runs more slowly than its optimal/maximum speed.

5. Rejects during production
This includes all rejects and repairs during normal production, so after running in/warmup phenomena.

6. Rejects during running in/ warmup
This includes all rejects and repair during startup/running in/ warmup.

Schematically it can be represented as follows:


The calculation of the OEE index is as follows:

Availability = (Planned production time - Unscheduled Downtime)/Planned production time
The Production time = Planned production time - Dwontime

The Performance = Cycle time x number of products processed/ Production time
Now remains the Net Production time (= time products are produced)

The Yield (Quality Rate) = (# processed products - # rejected products)/(# processed products)

The OEE-index = Availability x Performance x Yield

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For more information on the subject, please contact:
Ir. P. Bekkers (J.I.P.M. certified)
telephone: +31 40 211 6799, fax: +31 40 211 5719

TPM information