Equipment efficiency is not simply the ratio of machine run time and scheduled time.
Look at the situation of a manufacturing line or process running at half speed with zero downtime. This is
truly only 50% efficient. Or, what if 10% of the product being produced does not meet your minimum quality
and must be reworked. This equates to 90% efficiency, which does not take in account the effort to rework or
losses of raw material.
There are three factors, all represented as a percentage, taken into consideration for the final OEE result:
OEE Availability is the ratio between the actual run time and the scheduled run time.
The scheduled run time does not included breaks, lunches and other pre-arranged time a production line or
process may be down.
If a line is scheduled for one 8 hour shift with two 15 minute breaks and one 30 minute lunch,
then the scheduled time is 7 hours. Determined from 8 hours - 15 minute break - 15 minute break - 30 minute
lunch. If during the production run there are 25 downtime events totaling to 45 minutes of downtime, then
the runtime is 6 hours and 15 minute. Derived from 7 hours of scheduled time - 45 minutes. The OEE
Availability is 89% and is calculated by 6 hours 15 minutes divided by 7 hours.
OEE Performance is the ratio between the actual number of units produced and the
number of unit that theoretically can be produced and is based on the standard rate. The standard rate is
rate the equipment is designed for.
If a work cell is designed to produce 10 units per minute we can calculate the theoretical
production it can produce. Taking the 6 hours and 15 minutes of actual run time for the above example, a
total of 3750 units can be produced. Calculated by taking 6 hours and 15 minutes which is 375 minutes times
10. If the actual number of units produced is 3000, then the OEE Performance is 80% calculated by 3000 /
OEE Quality is the ratio between good units produced and the total units that were
Taking the number of units produced from above of 3000, if 200 units were rejected at the
quality inspection station, then 2,800 good units are produced. The OEE Quality is 93% calculated from
2,800 divided by 3,000.