OEE Factors

Where Do We Start?

OEE analysis starts with Plant Operating Time; the amount of time your facility is open and available for equipment operation.

Plant Operating Time

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.

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

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.

Operating Time

Performance

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.

Net Operating Time

Quality

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.

Fully Productive Time

Quick Review

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.

LossOEE Factor
Planned Shutdown Not part of the OEE calculation.
Down Time Loss
  • Availability is the ratio of Operating Time to Planned Production Time (Operating Time is Planned Production Time less Down Time Loss).
  • Calculated as the ratio of Operating Time to Planned Production Time.
  • 100% Availability means the process has been running without any recorded stops.
Speed Loss
  • Performance is the ratio of Net Operating Time to Operating Time (Net Operating Time is Operating Time less Speed Loss).
  • Calculated as the ratio of Ideal Cycle Time to Actual Cycle Time, or alternately the ratio of Actual Run Rate to Ideal Run Rate.
  • 100% Performance means the process has been consistently running at its theoretical maximum speed.
Quality Loss
  • Quality is the ratio of Fully Productive Time to Net Operating Time (Fully Productive Time is Net Operating Time less Quality Loss).
  • Calculated as the ratio of Good Pieces to Total Pieces.
  • 100% Quality means there have been no reject or rework pieces.

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.

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