Learn How to
LEARN HOW TO CALCULATE OEE
You’ve learned why Overall Equipment Effectiveness (OEE) matters and how to calculate OEE on a basic level. Now, let’s solidify your understanding with a real example. Below you’ll learn about what common plant floor inefficiencies affect Availability, Performance, and Quality, and how to calculate each factor. Lastly, you’ll learn how to interpret the final OEE metric and what insights can be gained by measuring and monitoring OEE.
OEE Availability = Actual Run Time / Production Time
OEE Availability is the ratio between the actual run time and planned production time. Planned production time does not include breaks, lunches, and other pre-arranged time a production line or process may be down for Maintenance, Changeover, etc. Any time equipment is not running when planned, an inefficiency is reflected in OEE Availability.
For instance, machine breakdowns, starvation of product, and product bottlenecks would negatively impact OEE Availability. In addition, exceeding planned changeover or planned maintenance time would reduce your Availability score.
If a line runs for an 8-hour shift with two 15-minute breaks and one 30-minute lunch, then the planned production time is 7 hours (8 hours – 15-minute break – 15-minute break – 30-minute lunch).
During the production run, there are 25 downtime events totaling 45 minutes of downtime. Run time is 6 hours, 15 minutes (7 hours planned production time – 45 minutes unplanned downtime).
OEE Performance = Actual Number of Units Started / (Standard Rate x Actual Run time)
OEE Performance is the ratio between the actual number of units started (not the number that has been produced) and the number of units that theoretically can be processed based on the standard rate. The standard rate is the rate the equipment is designed for. OEE Performance is not based on the number of units produced, but on what the line was designed to process over a given period of time. If equipment is running slower than what it is capable of, then this inefficiency is reflected in OEE Performance.
For instance, flow obstructions, incorrect settings, and poorly maintained equipment that cause production to slow would negatively impact OEE Performance.
If a work cell is designed to process 10 units per minute, we can calculate the theoretical number of units it can process in a given amount of time. The 6 hours, 15 minutes of actual run time converts to a total of 375 minutes. Given the standard rate of 10 units per minute, a total of 3,750 units should be processed (started).
Let’s say the actual number of units processed during this shift is only 3,000. In this case, OEE Performance is 80% (calculated by 3,000 actual units / 3,750 standard units).
OEE Quality = Good Units Produced / Actual Number of Units Started
OEE Quality is the ratio between good units produced and the total units that were started. The inefficiency of out-of-spec units that could have been good units is reflected in OEE Quality.
For instance, products that are scrapped or require rework to meet quality thresholds would negatively impact your Quality Score.
The number of units produced from the example above is 3,000. If 200 units were rejected at the quality inspection station, then 2,800 good units were produced. The OEE Quality is 93% calculated from 2,800 divided by 3,000.
OEE = Availability x Performance x Quality
This is the final calculation that measures Overall Equipment Effectiveness and is a combination of all three OEE sub-values. It is important to know that the OEE sub-values are isolated from each other. If equipment is down, then only OEE Availability is affected while OEE Performance and OEE Quality remain the same. If the equipment is running slow, then only OEE Performance is affected while OEE Availability and OEE Quality remain the same, etc.
The Final Result:
Using all the numbers from our example above, 89% x 80% x 93% = 66%.
This may seem like a low number, but OEE should not be compared to 100%. Rather, the OEE result from this production run is compared to other production runs to track efficiency and quality over time. Remember, you can only improve what can be measured and monitored. Utilizing the OEE metric and objective data to guide production goals is the first step to taking a more proactive approach on the plant floor.
How Sepasoft Connect Can Help
Using OEE Cloud, you can track OEE without paper or spreadsheets, compare OEE results between production runs, and much more. Here are a few of the possibilities utilizing OEE Cloud functionality:
- Determine the root cause of unsuccessful production runs or problematic events.
- Examine which factors resulted in the most successful outcomes. In other words, what do your successful runs have in common?
- Compare OEE results between equipment, departments, facilities, operators, shifts, products, or other factors you define (e.g. raw material vendor, humidity, etc.)