Three honest questions, one number
OEE stands for overall equipment effectiveness, and the acronym scares people off a simple idea. It is just three questions multiplied together. Was the machine running when it was supposed to be? When it ran, did it run at full speed? And of what it made, how much was good the first time? Availability times performance times quality. That is the whole thing.
Availability: was it even running?
Take the time a machine was scheduled to run and subtract every minute it sat stopped: breakdowns, waiting for material, changeovers, a missing operator. What is left, divided by the scheduled time, is availability. A line scheduled for 8 hours that actually ran 6 is at 75 percent. The stops you never wrote down live here, and they are usually bigger than anyone guesses.
Performance: was it running at full speed?
A machine can be running and still losing. Performance compares how fast it actually produced to how fast it is rated to produce. Small slowdowns, short stalls, and running under the ideal rate all show up here. A line can look busy all day and quietly run at 80 percent of its real speed, and nobody notices because it never fully stops.
Quality: was it good the first time?
Of the parts it made, how many were right without rework or scrap? That is quality. A part you have to fix cost you twice and jumped the queue doing it, so it counts against you here. First-pass good parts over total parts made.
Why multiply, not average?
Multiplying is what makes OEE honest. 90 percent availability, 90 percent performance, and 90 percent quality do not average to 90 – multiplied they come to 73. Three small, forgivable-looking losses stack into one big one. That is the number that matches what you actually shipped, and it is usually a shock the first time a floor measures it.
What a good number is
World-class is often quoted as 85 percent. Most floors that have never measured land somewhere in the 40s or 50s and are stunned. That gap is not a failing – it is opportunity sitting in plain sight, and it is almost always recovered by fixing flow and changeovers, not by buying a faster machine.
The trap
OEE is a thermometer, not a cure. Chasing the number for its own sake – running a bottleneck faster to look good while piling up work in front of the next step – makes the plant worse. Use it to find where the biggest loss is, fix that, and watch the number follow. The number is the scoreboard, not the game.
If you want to know your real OEE without installing software or starting a project, a walkthrough estimates it from one walk of the floor.
Request your free walkthrough and we will find where your floor is losing the most time, no charge.
