Overall Equipment Effectiveness has a reputation as a large-plant metric. The arithmetic is simple enough for any workshop, and the discipline of measuring it usually pays for itself in the first month.
The three factors
OEE multiplies three percentages:
- Availability — of the time the machine was scheduled to run, how much did it actually run?
- Performance — while running, did it run at its intended rate?
- Quality — of what it produced, how much was right first time?
Each is a fraction between zero and one. Multiply them and you have OEE. A shop at 85% availability, 90% performance and 98% quality is running at roughly 75%.
Why multiplication matters
Because the factors multiply, a weak one drags everything down regardless of how good the others are. Excellent quality cannot rescue a machine that sits idle half the shift. This is precisely why the metric is useful — it points at your actual constraint rather than the one you assumed.
Start manually
You do not need sensors to begin. A clipboard at the machine recording start time, stop time, reason for each stop, parts produced and parts scrapped will give you a usable number within a week. Buy monitoring later, once you know what question you are asking it.
Do not weaponise the number
The fastest way to kill an OEE programme is to use it to judge operators. Recorded downtime will simply stop being recorded, and you will have destroyed the data you needed. Measure the machine and the process, not the person.
A realistic target
World-class OEE is often quoted at 85%. For a job shop running high-mix, low-volume work with frequent setups, that figure is not meaningful. Compare yourself against last quarter, not against a benchmark built for mass production.