Overall equipment effectiveness is a maintenance KPI (opens in new tab) 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 (opens in new tab), asset performance, and production quality. Each one can tell you something different about how an asset operates.
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). Availability considers unplanned and planned stops. An availability score of 100% means the process is always running during the planned production time (which is the ideal scenario).
The OEE formula is a straightforward calculation used to determine the overall efficiency of a piece of equipment. The formula is:
Each component of the formula plays a critical role in understanding and improving equipment performance.
Consider a manufacturing plant that produces glass bottles. Here are some hypothetical values:
Using the OEE formula:
OEE = (9,000 × 0.5) / 5,000 = 0.9 or 90%
This means that the equipment is operating at 90% efficiency.
In our example above we walk through how to use the OEE formula, but it's important to understand the four main components of the OEE framework.
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 indicate 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.
In manufacturing and, consequently, in maintenance, there are six major categories of losses that impact OEE. Addressing these losses will improve OEE, they are:
OEE provides several benefits, particularly in the contexts of Lean manufacturing and Total Productive Maintenance (TPM).
Availability is one of the three key factors in the OEE framework, alongside performance and quality. The availability score specifically measures the percentage of planned production time during which the equipment is available for production. It accounts for losses due to equipment failures and set-up/adjustments.
The availability score is calculated using the following formula:
Run Time is the actual time the equipment is running and producing products. While the Planned Production Time is the total time scheduled for production, excluding planned downtime.
A machine is scheduled to run for 500 minutes (about 8 and a half hours) a day. During this time, it stops for 50 minutes unexpectedly, and 30 minutes for setup and adjustments.
Availability = 420 / 500 = 0.84 or 84%
This means that the equipment was available for production 84% of the scheduled time. High availability indicates that equipment is reliably available for production, minimizing downtime and maximizing potential output. Low availability, on the other hand, suggests frequent interruptions, which can significantly reduce production efficiency.
In this example, the availability score is at a good level but could use some improvements to increase to reach about 90% and above (which would be ideal). Some ways to improve availability include:
Availability loss refers to the time when equipment is not available for production due to unplanned downtime (i.e., breakdowns) or planned downtime (i.e., routine maintenance). Minimizing availability loss is crucial for maximizing and maintaining OEE.
Changeover time is the period required to switch from producing one product to another. Reducing changeover time is vital for improving equipment availability and overall efficiency. Techniques like SMED (Single-Minute Exchange of Die) can help streamline and reduce changeover times, enhancing OEE.
Overall equipment effectiveness can also be used to investigate the people, processes, and tools that impact how assets operate. When combined with the insight from other maintenance metrics, OEE provides a great foundation for identifying areas of an operation that can be improved and a quantifiable way to measure progress.
Leverage the cloud to work together, better in the new connected age of maintenance and asset management.