Frequently Asked Questions about OEE

Frequently Asked Questions about OEE:

Frequently Asked Questions about OEE

1) 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. Simple

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.


2) 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.


3) 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.


4) 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 Simple

OEE calculations.

5) 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.


6) Do the OEE metric calculations of a machine represent a magical


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.


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

No. If your OEE metrics (Availability, Performance, Quality, Simple

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.


8) 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.


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


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).


10) Are reworked parts counted as good or bad parts in the OEE


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.


11)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.


12)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.


13) 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 metric. 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.


14) How do I optimize my data collection to make OEE, OEE?

Automate your OEE data collection and collect your plant information in real

time by installing Live OEEs. 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