Q: I want to start comparing OEE’s of our machines. How should I proceed?
Arno Koch • To see what the effect of comparing OEE’s is, let’s compare two countries on how they do on Traffic. Country A has a mobility rate of 18% and Country B 13.5%. So hurray for country A, right?
So what needs to be done to get those losers from country B to get their mobility go Up? Let’s look into the situation; Country A is Great! A remarkable 40% of the time their cars are running! And the average top-speed of their cars is a wonderful 230 Km/h, and yes then you’ve got to go fast and that is what they do: on average the A’ans are cruising a wonderful 130Km/h. Of course at such speeds you may miss a curve or hit a tree, that’s in the game, but 80% of the trips go without any problem. So their mobility rate is 40% x 56% x 80% = 18%, Well done Country A!
Now let’s compare that to Country B. Only 15% of the time the cars are running; here they use a well-functioning public transportation system. And all cars are limited at 100 km/h. They are cruising on an average 90km/h and tend not to hit any trees; 99,99% of the trips have no problems. So their mobility rate is 15% x 90% x 99,99% = 13,5%.
So who is doing better here? You think this is a ridiculous comparison? YES! I also think so. And yet this is what you are asking for when you start to compare factories based on OEE… I can tell you real life stories from real companies that are even more astonishing! And yet people want to abuse OEE in this way.
Let me take a shortcut and tell you why you can’t even compare the OEE’s from ONE machine running the same product in two shifts.
The early shift runs 46% OEE and the noon shift also runs 46%. So who is best? Or are they the same?
- Shift A runs 60% of the time on 80% of the max speed, with 95% quality: 46% OEE
- Shift B runs 80% of the time (wow) on 95% speed (Hurray) producing 60% Quality (oops): 46% OEE
Now what when the machines are different, the complexity of the product, the product mix, the lot-sizes…. And still you want to put everything in ONE number to compare this to another number?? Tell me, what are you going to achieve now??
Conclusion: OEE as a number cannot be used to compare factories, machines or even shifts.
Q: Wait wait; I would build in some Weighting factors, that would solve the problem!
Arno Koch • Aha… Ok, in Country A there are 4,8 times more cars than in country B, so what would the weighting factor now? And what would the criteria be to define such factor?
Let’s assume we have a factor (I would love to join the meetings where they are established…) and as a result country A becomes 17,2% and B 19,3%.
Now what? What will the management do to improve the results?? And what will be the real effects?
It is this kind of ‘management by excel‘ that often leads to horrifying and catastrophic fail-decisions.
So before running into a huge pitfall, think twice:
- What do you really want to achieve?
- How can you really visualize where you are and where you are heading?
- How can you help the factories to move in this direction (it is the task of the management to give the direction and to govern the change in this direction, remember the speeches of Deming, if not Google for them)
My advice when a company starts comparing OEE’s: Sell shares!
This might not have been the answer you wanted but it is probably the one you need…
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