Overall Equipment Effectiveness (OEE) in TPM
Normally, the effectiveness of the equipment is measured in terms of availability of the same. If an equipment is not available for a certain duration then due to breakdown, it is taken as a drawback of the maintenance system. On the other hand, TPM has a way of measuring the effectiveness of the whole process or system rather than piecemeal approach.
Overall Equipment Effectiveness (OEE) is a key performance indicator that is commonly used in Total Productive Maintenance (TPM) programs. OEE is a metric that is used to measure the effectiveness of a manufacturing process by looking at the availability, performance, and quality of the equipment.
The concept of OEE was first introduced in the 1960s as a way to measure the effectiveness of the equipment in the manufacturing process. Since then, it has become an important metric for companies that are looking to improve their manufacturing processes and increase their productivity.
The formula for calculating OEE is as follows:
OEE = Availability x Performance x Quality
Availability refers to the amount of time that the equipment is available for production. This includes both planned downtime, such as maintenance and changeovers, and unplanned downtime, such as breakdowns and stoppages.
Performance refers to the speed at which the equipment is operating. This is measured by comparing the actual cycle time to the theoretical cycle time.
Quality refers to the number of good parts that are produced by the equipment. This is measured by comparing the number of good parts to the total number of parts that are produced.
By using OEE, companies can identify the areas of their manufacturing process that are causing downtime and inefficiencies. This allows them to focus their efforts on improving these areas and increasing overall equipment effectiveness. For example, if the availability of the equipment is low, the company may decide to focus on reducing downtime through preventative maintenance or by improving the efficiency of changeovers.
One of the key benefits of OEE is that it provides a clear and measurable way of evaluating the effectiveness of the manufacturing process. This allows companies to set targets for improvement and track their progress over time. OEE can also be used to compare the effectiveness of different equipment or processes, which can help companies to make informed decisions about investments in new equipment or process improvements.
In addition to providing a metric for measuring the effectiveness of the manufacturing process, OEE is also a powerful tool for engaging employees in the improvement process. By involving employees in the collection and analysis of OEE data, companies can create a culture of continuous improvement and empower employees to take ownership of their equipment and processes.
Thus OEE is a powerful tool for improving the effectiveness of the manufacturing process. By using OEE to identify areas of improvement, companies can reduce downtime, increase productivity, and improve the quality of their products. OEE is an essential metric for companies that are looking to implement a Total Productive Maintenance program and achieve world-class manufacturing performance.
Example of OEE calculation
Let’s consider an example of how to calculate OEE for a hypothetical manufacturing process.
Assume that a company operates a machine that produces widgets. The machine runs for 8 hours per day and produces 1,000 widgets per hour, for a total of 8,000 widgets per day. Over the course of a day, the machine experiences the following:
Planned Downtime:
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30 minutes for maintenance
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15 minutes for changeovers
Unplanned Downtime:
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20 minutes due to a machine breakdown
Quality:
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5% of the widgets produced are defective
To calculate OEE for this machine, we would start by calculating availability, performance, and quality.
Availability:
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Available Time = 8 hours x 60 minutes = 480 minutes
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Planned Downtime = 30 minutes + 15 minutes = 45 minutes
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Unplanned Downtime = 20 minutes
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Total Downtime = Planned Downtime + Unplanned Downtime = 45 minutes + 20 minutes = 65 minutes
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Available Time (net) = Available Time – Total Downtime = 480 minutes – 65 minutes = 415 minutes
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Availability = Available Time (net) / Available Time = 415 minutes / 480 minutes = 0.865 or 86.5%
Performance:
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Theoretical Cycle Time = 60 minutes / 1,000 widgets = 0.06 minutes/widget
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Actual Cycle Time = 65 minutes / 7,600 widgets (excluding the defective ones) = 0.0086 minutes/widget
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Performance = Theoretical Cycle Time / Actual Cycle Time = 0.06 minutes/widget / 0.0086 minutes/widget = 6.98 or 698%
Quality:
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Good Widgets Produced = 7,600 widgets (excluding the defective ones)
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Total Widgets Produced = 8,000 widgets
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Quality = Good Widgets Produced / Total Widgets Produced = 7,600 widgets / 8,000 widgets = 0.95 or 95%
Now that we have calculated availability, performance, and quality, we can calculate OEE.
OEE = Availability x Performance x Quality OEE = 0.865 x 6.98 x 0.95 OEE = 5.5 or 55%
In this example, the OEE of the machine is 55%. This means that there is room for improvement in the manufacturing process. By identifying the causes of downtime and inefficiencies, the company can take steps to improve the OEE and increase productivity.