How to Measure Overall Equipment Effectiveness (OEE)
Getting the most out of your manufacturing maintenance program starts by understanding how effective it is. One of the simplest ways to determine how astute you are at maintaining assets is to gauge Overall Equipment Effectiveness (OEE). This measure isn’t difficult to calculate, and it can provide a wealth of valuable information about the efficacy of your value stream. Specifically, it can show you where you need to spend more time improving maintenance operations.
What is OEE?
OEE measures a piece of equipment’s ability to produce top-quality parts as quickly as possible, with no unplanned stops. This measurement helps identify any underlying losses, which might include failing equipment, reduction in speed, minor stops, and more. Identifying these losses allows manufacturers to determine which areas of their maintenance and upkeep program need improvement. This makes OEE a true measure of productivity, specific to each piece of equipment.
OEE is measured as a percentage of a machine’s total uptime. An OEE score of 100% is always the goal, and a score of 85% or above is considered excellent. Equipment operating with an OEE score of 60% or below indicates the need for an improved maintenance approach.
The formula for calculating OEE
The two most important factors in determining a piece of equipment’s OEE are Fully Productive Time and Planned Production Time. To find Fully Productive Time, subtract all losses from the time spend producing. Planned Production Time is fairly self-explanatory, found by subtracting All Time and Schedule Loss.
In the formula below, Good Count refers to top-quality parts produced, whereas Ideal Cycle Time is the least amount of time it takes to produce a good part.
OEE = (Good Count × Ideal Cycle Time) / Planned Production Time
Although this simple calculation is a great representation of OEE, there’s actually a much more complete equation to consider:
OEE = Availability × Performance × Quality
In this equation, you’ll need to branch out the individual formulas for each of the variables that factor into OEE:
- Availability = Run Time / Planned Production Time
- Performance = (Ideal Cycle Time × Total Count) / Run Time
- Quality = Good Count / Total Count
Either formula will get you an OEE measurement for a piece of equipment. The choice is usually manufacturer preference, dependent on the individual machine metrics you track.
OEE shows opportunities for improvement
OEE offers a true look at machine productivity beyond individual metrics such as uptime or pass-through rate. Specifically, if a piece of equipment needs improvements, the OEE score will show it. Here are a few catalysts for improvement that a low OEE score might illuminate:
- Downtime (unexpected or anticipated)
- Breaks and scheduled interruptions
- Setup and changeover time
- Production deficiencies and corrections
Knowing how these factors affect an OEE score makes it easy to determine where there’s a need for repair or a more robust maintenance approach.
Use OEE as part of maintenance planning
For a manufacturing operation to work at peak efficiency, it’s important that all machines have a high OEE score. The OEE score allows manufacturers to better determine the source of their machines’ shortcomings and to schedule and plan for preventative maintenance. When you know where a machine needs improvements, it’s easier to schedule targeted service.