Overall equipment effectiveness (OEE)
The maintenance metric that powers the manufacturing processHow to master OEE and other maintenance metrics
What is OEE?
Overall equipment effectiveness is a maintenance KPI that measures an asset’s level of productivity. OEE is a combination of three factors that tell you how efficient an asset is during the manufacturing process: asset availability, asset performance, and production quality. Each one can tell you something different about how an asset operates.
- Availability – How often does the asset function when needed?
- Performance – How much does the asset produce?
- Quality – How many high-quality items does the asset produce?
When an asset operates with an OEE of 100%, it means that every item it produces is without defect (quality), it is producing as fast as possible (performance), and it experiences no unplanned downtime (availability).
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The OEE formula is calculated by multiplying availability, performance and quality and is represented by a percentage.
Finding the OEE of an asset starts with measuring availability, which is calculated by dividing the total run time of an asset by the total planned production time of an asset. It excludes planned shutdowns for preventive maintenance, holidays, or similar scenarios.
For example, if a machine was supposed to run for 12 hours, but suffered a breakdown and only ran for 11 hours, the availability would be 0.917 or 91.7%.
Next, measure the performance of an asset by dividing the actual system throughput by its maximum possible throughput.
Let’s say that you have an asset that runs for 12 hours with a maximum production rate of 1,000 units per hour. The maximum throughput would be 12,000. But if that asset only produces 11,500 units in that time, the performance score would be 0.958 or 95.8%.
Finally, the quality of the goods produced by the asset must be determined. Quality is calculated by dividing the number of usable units produced by the total units started.
If an asset produces 12,000 units in a 12-hour production time frame, but 300 of them have defects that make them unusable, then the number of usable units is 11,700. Therefore, the quality score would be 0.975 or 97.5%.
Now that you have your three components, you can calculate OEE by multiplying them.
For example, if availability is 0.917, performance is 0.958, and quality is 0.975, the OEE measurement would be 0.857 or 85.7%.
How is OEE used?
Overall equipment effectiveness is an indicator of how efficient the manufacturing process is. It can be used to identify underperforming assets and connect poor performance with one or more of the three main factors (availability, performance and quality). Once the source of the problem is pinpointed, the underlying issues can be investigated and improved.
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What does OEE mean for maintenance?
Conducting an OEE analysis can provide insight into the way you schedule, organize and conduct maintenance tasks. Ultimately, this information can help you avoid common and critical issues with assets costing your organization time and money. Low asset availability can tell you that a machine is breaking down too often or for too long. This might mean the asset isn’t getting the proper amount of preventive maintenance, or critical spare parts aren’t available to quickly repair a problem.
Low performance could point toward issues with a specific part or preventive maintenance tasks, such as bearings that aren’t receiving enough lubrication or a belt that is too old and needs to be replaced.
A poor quality score is often the result of process failures and a lack of standardization. For example, if gauges aren’t set properly from shift to shift, or the system isn’t aligned consistently between every use, it could lead to a higher number of defects.