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Overall equipment effectiveness (OEE) is the premier standard for measuring manufacturing productivity. Read about how to calculate OEE, the six big losses, OEE benefits and more.
Overall equipment effectiveness (OEE) is a term used to evaluate how efficiently a manufacturer's operation is being used. In other words, overall equipment effectiveness helps you notice a problem in your operations, identify which percentage of manufacturing time is actually productive and fix it while giving you a standardized gauge for tracking progress. The goal for measuring your OEE is continuous improvement.
Overall equipment effectiveness is a powerful figure. It provides a lot of information in one number, so there are multiple ways OEE is used to measure manufacturing productivity. When calculated and interpreted correctly, it can significantly maximize your production. Overall equipment effectiveness is used as a benchmark to compare any given production to industry standards, in-house equipment or other shifts working on the same piece of equipment. Standard OEE benchmarks are as follows:
Overall Equipment Effectiveness is not only a great tool for managers but can have a significant impact on employees working the plant floor. Plant floor metrics can include:
Before we discuss overall equipment effectiveness further, there are some important terms to be aware of.
Before calculating overall equipment effectiveness, it's important to denote the difference between the terms effectiveness and efficiency when discussing OEE.
Effectiveness is the relationship between what could technically be produced and what is actually produced at the end of a production period. For example, if your machinery is capable of making 100 products an hour and it only makes 80, then it is 80 percent effective.
However, this doesn't tell us how efficient the machinery is because we didn't consider things like the number of operators, energy and the materials needed to reach 80 percent effectiveness. For example, if your machinery runs 60 percent effective with one employee and becomes 75 percent effective with two employees, the effectiveness increases by 25 percent, but efficiency decreases to 50 percent based on labor.
There are two main ways to calculate OEE:
Below we'll look at two examples of Preferred Calculation.
A widget-making machine with 5 percent downtime (or 95 percent availability) has an efficiency of 96 percent. (ASTM and other governing bodies help determine some machine efficiency ratings. For others, it's as simple as looking at that machine's specific production.) Two of every 100 widgets the machine makes are rejected as being out of specification (98 percent quality). Since OEE is calculated by multiplying the three factors (availability, performance and quality), your formula looks like this: OEE = 0.95 x 0.96 x 0.98 = 89.376 percent
Let's look at a more practical example. A normal shift at a bottling facility takes 480 minutes. Machine operators take three breaks during their shift totaling 50 minutes, and they do two changeovers during the shift totaling 60 minutes of machine downtime for a total of 180 minutes of lost time. To calculate the availability part of the equation, we take:
To calculate the performance part of the equation, let's assume the bottling plant produces 60 bottles per minute. Factoring in the remaining 300 minutes, the bottling system can make 18,000 bottles (300 x 60). Let's say the machines are running slower at 1.5 seconds of cycle time, slowing the maximum speed by two-thirds. This reduces the actual performance to 12,000 bottles. So, to calculate the performance part of the equation, we take:
To calculate the quality part of the equation, let's say out of the 12,000 bottles, 3,000 don't meet quality-control standards, making the quality rate of the bottles 75 percent. The quality part of the equation is calculated as:
Another way to look at it is 3,000 bottles / 60 bottles per minute = 50 minutes lost quality.
So, to calculate the overall equipment effectiveness (Availability x Performance x Quality = OEE), we'd take 62.5 percent x 66.7 percent x 75 percent = 31.25 percent OEE. This means we could technically produce 28,800 bottles, but in the end, only 9,000 bottles are cleared for sale (9,000 / 28,800) = 31.25 percent.
Perhaps the biggest goal of implementing an OEE program is to reduce or eliminate the most common causes of machine- or equipment-based productivity loss, known as the six big losses. These six losses are broken down into the three main OEE categories (availability, performance and quality).
|OEE||Six Big Losses|
|Availability Loss||Equipment Failure|
|Setup and Adjustments|
|Performance Loss||Idling and Minor Stops|
|Quality Loss||Process Defects|
Implementing an overall equipment effectiveness strategy is a powerful advantage in achieving your production targets. It allows you to take a proactive approach by tweaking manufacturing processes in real time, reducing downtime, increasing capacity, reducing costs, improving quality and increasing efficiency. Let's take a look at 10 benefits of OEE.
How do I know OEE will work for my company?
Overall equipment effectiveness is common in manufacturing plants making individual parts (discrete plants). However, it is also often used in refineries to help identify actual output.
How do I get an OEE score for my entire production line?
The best way to get an OEE score for your entire production line is to measure OEE at the piece of equipment or specific machine that handles the majority of the work. In non-balanced production lines, measure OEE at the point of constraint.
Should changeover, preventative maintenance and lunches/breaks affect my OEE score?
Changeovers are part of one of the six big losses (setup and adjustment) and should be included in OEE. Preventive maintenance and lunches/breaks will probably affect your OEE score as well because they take away time that could be used for production. Exceptions to this include preventive maintenance being done during a planned shutdown and if your machinery can produce parts regardless of whether the operator is on break.
Since a world-class OEE score is 85 percent, should this be my target?
No. While 85 percent is an admirable benchmark, most manufacturers who are new to OEE kick out an OEE score of less than 50 percent. You should set OEE goals that will show improvement over time (usually three to five months).
What's the difference between OEE and TEEP?
Total effective equipment performance (TEEP) measures how much your operation could manufacture if your plant ran 24 hours a day, seven days a week, while OEE measures your productivity during planned production time.
What period of time is used to calculate OEE?
It's up to the manufacturer's discretion, but the most common period of time is one shift. Other time frames include one job, one day or continuous monitoring.