Frequently Asked Questions about OEE


Are OEE metric values subject to misinterpretation?

Yes. You should look for these OEE metrics to help you monitor the machine to minimize losses and eliminate bottlenecks in your process. OEE data does not supply you with the best decision to make an improvement or how much it will cost to make these changes. But, OEE data is very useful in your efforts to improve the process of your machine by separating data into the three metrics of Availability, Performance, and Quality.


Can OEE create political differences at the management level?

Yes. Sometimes this misinterpreted data can be used for political purposes rather than working to improve the overall productivity of the machine. The important concept to keep in mind is to produce more quality parts with reduced downtime and less waste. As with the measurement of any number, make sure you have a clear plan that will deliver a result. This will help you create a plan to incentivize your machine operators to maximize the productivity of the equipment.


Can OEE help management enable machine operators?

Yes. The real value of OEE is providing management and machine operators the ability to make systematic improvements to the process of the machine. The concept of OEE is to put this information in terms that are easily understood and keep the machine operator informed with visual data on the manufacturing plant floor.


Are OEE metric values defined in numbers of parts or units or time?

The answer is to use the unit of measure that you best understand. Availability is usually described in hours and minutes, Performance in parts per minute or hour, and quality as the ratio of good product to total production. All of these metrics are converted to the percentage (%) of the actual versus potential in the OEE calculations.


What sample time period should I use for my OEE test?

The OEE sample time period can be any period of time. Usually, it is set on the working cycle of the machine. One shift equals 8 hours or 480 minutes. Some other sample periods could include 10 hours, 12 hours, 1 day, the job or part number, or continual monitoring.


Do the OEE metric calculations of a machine represent a magical number?

No. The strength of OEE is that it gives you four metric numbers. These numbers can be used individually to make decisions as your machine process changes from day to day. The OEE metrics help you visualize the total resources of your manufacturing process as it relates to what the machine actually produced. If your machine produces these OEE metric numbers: Availability 90%, Performance 85%, Quality 99%, OEE = 76% only you can decide if these numbers are good or bad. However, if your machine produced these OEE metric numbers: Availability 98%, Performance 85%, Quality 91%, OEE = 76% are these numbers any better. The OEE metric stayed the same but is the drop in quality worth the improvement in availability. Most manufacturers always try to improve quality so they would consider this to be an unacceptable tradeoff.


Is it possible to have to have a OEE metric exceed 100%?

No. If your OEE metrics (Availability, Performance, Quality, OEE) are greater than 100%, you are not defining something in your process correctly. You are probably underestimating the capacity of a process when you input your machine parameters. Most commonly, the Performance metric has not been correctly calculated when determining your Ideal Cycle Time (Target Counter Value) of your process.


What defines if a machine is producing parts (running)?

For the purpose of measuring productivity, the OEE metric needs to know if the machine is producing product, even if this product is good or bad. If the machine is scheduled for production (not in break or planned maintenance), the production clock is running and the machine is considered producing parts.


How do you determine the Ideal Cycle Speed (Target Counter Value) of your machine?

If the “nameplate capacity” of the machine is available from the equipment manufacturer, this would give you the capacity data for that particular machine. If this data is unavailable, you should perform machine calculations to measure the cycle times and rates of the machine. These numbers will give you a starting point but may vary depending on machine age and operator training. Take measurements, experiment, and calculate your own Ideal Cycle
Speed (Target Counter Value).


Are reworked parts counted as good or bad parts in the OEE calculation?

In the OEE calculation, any part that comes out of the machine not manufactured to specifications the first time is considered a bad (reject) part. This is a production problem that exists at the machine and needs to be addressed by management. You need to implement a production practice for improving original part quality versus reworking bad parts.


If I have multiple machines in a group cell, which machine should you base my Ideal Cycle Time (Target Counter Value) on?

Your Ideal Cycle Time (Target Counter Value) should be based on the fastest machine of the group cell. Typically, most machines in a group cell are designed to produce product at the same rate. Using the fastest stage as your target, forces you to recognize the bottlenecks and work on improving the process of product flow in the machine.


If my machine is running during a scheduled break, is this break time factored into machine availability?

If the machine is producing parts, then regardless if that machine operator is or is not on break OEE considers this to be part of the machine runtime and is factored into machine availability.


Does preventive maintenance downtime penalize the OEE performance calculation?

If the preventive maintenance occurs during actual production time rather than during planned shutdown, you are interfering with machine production and should count this downtime in the OEE Performance m etric. Monitoring downtime and supplying a reason code will help us monitor and measure if this scheduled maintenance will result in less overall downtime due to fewer surprises and more efficient machines than losing production when maintenance is called to the machine.


How do I optimize my data collection to make OEE?

Automate your OEE data collection and collect your plant information in real time by installing Production Monitors. Production data is not very useful if you see it in a printout tomorrow in the production office or don’t visualize it on the plant floor. With this real time plant information, management and machine operators can react to the information and alarms displayed on the plant floor and monitor and collect the OEE metrics anywhere within your manufacturing plant.