Q: How can the Performance Rate OEE go over 100%?
The Performance of OEE can go over 100% when there was more output produced than theoretically possible according to your definition.
Arno Koch: There are three ways this could happen:
1. ‘Maximum Speed’ defined too low
The most common way to produce more output than possible according to your definition happens in cases where the defined maximum speed is lower than the real maximum speed.
This is the reason why the THEORETICAL maximum speed should be defined as the 100% value of performance. Do not use some ‘practical or actual maximum’ that is just practical for the moment but can be improved in time. If the machine CAN go faster it WILL go faster one moment or the other.
The golden rule for Maximum Speed in OEE:
The real maximum speed can only be improved by re-engineering the machine or product.
2. Making a data entry-mistake
Another possibility to have more than 100% performance is when somebody made a data-entry mistake, where the entered actual output might be higher than the maximum output (Time x Maximum Speed).
In this case the performance rate would go over 100%
3. Registering less Production time than actually happened.
Imagine someone states there was 2 Hrs mainenance performed, but actually it was just one hour. The other hour the machine was running. Now there was a production volume for two hours yet only one hour is being registered. In that case the output most probably is higher than theoretically possible in this one hour.
Whenever this occurs it is important to find out WHY this was done? What was trying to be achieved?
Consequences of a too high performance rate
- Imagine you make 20% scrap (Quality = 80%) and the machine is idling 30% of its time, (Availability = 70%) but due to a too low standard, your performance is 150%. You end up with a world class OEE of 70% x 150% x 80% = 84%. Of course that is nonsense and leading away the focus of the losses being present!
- Several graphs and analyses would get distorted, since OEE is a balanced system, with 100% as maximum.
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