Work out your OEE.
Five figures from a normal week. Nothing you do not already have somewhere.
The time the line was supposed to run, excluding breaks and planned maintenance.
Anything that stopped the line running while it should have been: breakdowns, changeovers, waiting for material.
What the machine can do per hour on this product, at nominal speed.
Everything you had to remake or throw away.
Availability times performance times quality. Each of the three is shown separately below.
- Availability
- 87.5%
- Performance
- 85.7%
- Quality
- 97.2%
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What does a higher OEE deliver?
Your figure from above is already filled in. Slide to where you want to be and you see what the gap is worth.
Two shifts, 230 days ≈ 3,680 hours.
Carried over from step 1. You can adjust it here too.
Companies moving from a gut feeling to a measured figure typically gain 5 to 12 percentage points in the first year. An indicative figure from our own projects, not a guaranteed result.
Margin or contribution per hour the line is producing. A rough estimate is fine.
Without a new machine, without an extra shift, without a square metre more floor.
- OEE
- 60% → 70%
- Production hours gained
- 380 h
An indicative calculation from your own input, not a measured result. We deliberately show no payback period: that needs a price, and the price depends on your machine park and the modules you switch on.
The formula
OEE stands for Overall Equipment Effectiveness and consists of three factors multiplied together:
OEE = availability × performance × quality
- Availability is the time the line actually ran, divided by the time it was supposed to run.
- Performance is what the line produced, divided by what it could have produced in that running time at nominal speed.
- Quality is the number of good pieces, divided by the total number produced.
Because you multiply the three, the final figure drops faster than people expect. A line with three scores that look reasonable:
0.90 × 0.85 × 0.97 = 0.742
That is an OEE of 74.2%. On 3,680 planned hours it means roughly 2,730 hours of good product actually come out, and around 950 hours disappear into downtime, running slow and scrap. None of the three factors looks alarming; together they cost you a quarter of your capacity.
The figures you need
You need four pieces of data, and they usually exist somewhere already. The real question is whether they are reliable.
| What it is | Where it usually sits | |
|---|---|---|
| Planned production time | The time the line was supposed to run, excluding breaks and planned maintenance | Shift roster or production planning |
| Downtime | Anything that stopped the line running while it should have been | Downtime logging, or a sheet at the line |
| Nominal speed | What the machine can do per hour on this product | Machine documentation or the fastest stable run |
| Good and rejected pieces | The count that left the line, split into good and scrap | Work order, weighbridge or quality registration |
Nominal speed is the figure that causes the most argument. Do you take the speed from the machine manual, or the fastest speed you stably reach in practice? Either works, as long as you are consistent: an OEE you compare against last month has to be calculated on the same basis.
What is a good OEE?
The reference most companies use comes from Nakajima's TPM work: an OEE of around 85% counts as world class, and 60% is a common figure in discrete manufacturing.
That 85% is a reference point, not a goal in itself. What your figure is worth depends on where you started and what it costs you to raise it. A line going from 52% to 60% wins more capacity than one going from 80% to 82%, even though the second sounds more impressive.
Four mistakes in the calculation
Most OEE figures we see are not calculated wrongly, they are calculated incomparably. Four things that cause it:
- Counting planned downtime as loss. Breaks, planned maintenance and hours with no order do not belong in the denominator. Counting them measures your shift roster instead of your line.
- Not recording microstops. Stops shorter than the threshold show up on no paper sheet at all, and together are often the largest item. They then appear as an unexplained low performance figure.
- Adjusting nominal speed as you go. As soon as the standard moves with reality, you are measuring nothing. Your figure stays healthy and your loss stays invisible.
- Calculating per week instead of per order. A weekly average hides which product or which shift makes the difference. Which is exactly the question you wanted answered.
From a number to an improvement
Calculating OEE is straightforward. Steering on it every day is not, because then the figure has to come out of what the machines and the operators register automatically, rather than a sheet somebody retypes afterwards.
That is what the OEE module does: registration happens at the line, the figure is recalculated per hour and per shift, and beside the number you see where it came from. What that looks like in practice is in the Moerman NV case, where the OEE calculation went from a manual exercise to real time.