There are many different measures used to indicate how well a manufacturing process is running. eg: % Utilisation, Efficiency, OPR etc, and it is common for each measure to be calculated differently by different industries and companies.
OEE is a “best practice” or “world class” measure for monitoring and improving the performance of your machine, line, or process versus it's potential capacity. It is one of the more widely used measures around the world and is gaining momentum
It is simply just a ratio of the fully productive time vs the planned production time
It takes the most common sources of manufacturing losses, and puts them into 3 categories.
Is a measure of the time the process was available to run within the planned production time.
Is a measure of how well the process or machine was running when it was running.
Is a measure of time taken to produce the good quality products. Every reject is taking the place in the process of a good product.
Like any measure or KPI, OEE can be used in the wrong way. Comparing distinctly different production lines/machines using OEE can be meaningless like comparing an orange vs a pear. eg a high complexity changeover line vs a line that runs the same product all day every day.
We recommend using OEE primarily to monitor improvement progress over time. If the tend is going in the right direction, then you are doing the right things. Just focus on doing this for each line or machine.