Where Do We Start?
OEE analysis starts with Plant Operating Time; the amount of time your facility is open and available for equipment operation.
From Plant Operating Time, you subtract a category of time called Planned Shut Down, which includes all events that should be excluded from efficiency analysis because there was no intention of running production (e.g. breaks, lunch, scheduled maintenance, or periods where there is nothing to produce). The remaining available time is your Planned Production Time.
OEE begins with Planned Production Time and scrutinizes efficiency and productivity losses that occur, with the goal of reducing or eliminating these losses. There are three general categories of loss to consider - Down Time Loss, Speed Loss and Quality Loss.
Availability takes into account Down Time Loss, which includes any Events that stop planned production for an appreciable length of time (usually several minutes - long enough to log as a trackable Event). Examples include equipment failures, material shortages, and changeover time. Changeover time is included in OEE analysis, since it is a form of down time. While it may not be possible to eliminate changeover time, in most cases it can be reduced. The remaining available time is called Operating Time.
Performance takes into account Speed Loss, which includes any factors that cause the process to operate at less than the maximum possible speed, when running. Examples include machine wear, substandard materials, misfeeds, and operator inefficiency. The remaining available time is called Net Operating Time.
Quality takes into account Quality Loss, which accounts for produced pieces that do not meet quality standards, including pieces that require rework. The remaining time is called Fully Productive Time. Our goal is to maximize Fully Productive Time.
Now that you have taken a look at how the factors that contribute to OEE Losses are developed we can quickly review the key points.
|Planned Shutdown||Not part of the OEE calculation.|
|Down Time Loss||
As you can see, the core concepts of OEE are quite simple and really help to focus on the underlying causes of productivity loss. We can delve even deeper into productivity losses by understanding the Six Big Losses.