We have several systems that determine OEE.
I agree with NED. There are several parameters.
Loading - Schedule time of operation.
Performance - Operation speeds against designed target speeds.
Availability - Time that operation was available to operate.
Quality - Acceptable produced Units.
The product i would recommend is called AMPLA. What works well is that you have down time analysis within it. So you can define additional parameters when there is a halt in production.
The downtime analysis is automated so instead of an 'operator' defining what the cause of the downtime is the system reports on this.
This streamlines the operation and makes it easy to identify problematic areas associated with the operations.
Rheinhardt