OEE = availability × performance × quality. Availability is the share of planned time the machine was running; performance is how fast it ran against its ideal pace; quality is the share of what it made that was good. Multiplied, they say how much of the machine's planned time turned into good product. In one line, OEE = good units × ideal minutes a unit ÷ planned minutes. A coffee roaster's 2-kilo roaster, booked for seven hours a day, roasted 116 good kilos in three shifts that could have made 168: an OEE of 69.0%. Below is each part, the three shifts, where the 52 kilos went, and a free calculator.
The short version
- Availability = run time ÷ planned time; downtime is what's lost.
- Performance = ideal minutes a batch × batches ÷ run time; slow batches and short stops are what's lost.
- Quality = good batches ÷ batches; rejects are what's lost.
- OEE = availability × performance × quality.
- Planned time is when you meant to run, such as the hours booked in a shared roastery; time you never planned to run isn't a loss.
- The biggest of the three losses is where to start.
- TaroStack records good and rejected on every batch, and on Standard plans hours for each work center. More below.
The formulas
| Part | Formula | Monday's shift |
|---|---|---|
| Availability | Run minutes ÷ planned minutes | 345 ÷ 420 = 82.1% |
| Performance | Ideal minutes a batch × batches ÷ run minutes | 15 × 19 ÷ 345 = 82.6% |
| Quality | Good batches ÷ batches | 18 ÷ 19 = 94.7% |
| OEE | Availability × performance × quality | 64.3% |
The same answer comes straight from the good batches: 18 good batches × 15 ideal minutes ÷ 420 planned minutes = 64.3%. The three parts say why.
An example: a roaster's three shifts
Pali Roasting Co., a made-up small-batch coffee roastery on Oʻahu I use in these examples, roasts on a used 2-kilo roaster in a shared roastery, booked for 420 minutes a day. A batch ideally takes 15 minutes from charge to charge, so a perfect day is 28 batches, 56 kilos.
| Shift | Planned | Downtime | Batches | Good | Availability | Performance | Quality | OEE |
|---|---|---|---|---|---|---|---|---|
| Monday, October 5 | 420 | 75 | 19 | 18 | 82.1% | 82.6% | 94.7% | 64.3% |
| Tuesday, October 6 | 420 | 40 | 23 | 23 | 90.5% | 90.8% | 100.0% | 82.1% |
| Wednesday, October 7 | 420 | 95 | 18 | 17 | 77.4% | 83.1% | 94.4% | 60.7% |
| Three shifts | 1,260 | 210 | 60 | 58 | 83.3% | 85.7% | 96.7% | 69.0% |
Monday lost 75 minutes: a 30-minute warm-up that started late, 20 minutes of chaff cleaning mid-shift, and 25 minutes waiting for green coffee to be weighed out. One batch scorched. Tuesday had the green coffee weighed the night before and ran clean. Wednesday lost 95 minutes, 45 of them to a jammed cooling tray. How a roaster's batches and stock fit together is in how to start a coffee roasting business.
Where the kilos went
| Kilos | |
|---|---|
| Could have roasted in the planned time, at the ideal pace | 168 |
| Lost to downtime: 210 minutes | 28 |
| Lost to running slow: batches that took longer than 15 minutes | 20 |
| Lost to rejects: 2 scorched batches | 4 |
| Roasted, good | 116 |
Downtime is the biggest loss, and most of it was preparation: warming up late and waiting for green coffee. Weighing the next day's green coffee the night before, as on Tuesday, is free. Running slow is next: batches that drifted to 17 or 18 minutes as the drum loaded up between cleanings. The rejects are the smallest loss in kilos and the most expensive per kilo, because a scorched batch has used its green coffee, its gas and its time. How to measure capacity across a week is in how to calculate production capacity.
What a good OEE is
Manufacturers often quote 85% as world class and 60% as typical. For a small roastery, the useful comparison is your own roaster from one week to the next, and which of the three parts moved. Tuesday's 82.1% shows what this roaster can do with the green coffee ready.
Get the calculator
Download the OEE calculator. One line for each shift: type the planned minutes, the downtime, the ideal minutes a batch, the batches run and the good batches, and availability, performance, quality and OEE fill in, with the period's totals and, at the side, where the output went: downtime, running slow and rejects. It's an ordinary Excel file with no macros, and it works in Google Sheets, LibreOffice and Numbers.
Where this stops working
OEE needs the downtime written down, minute by minute, and the batches counted with the rejects. A roaster on a busy day writes neither. And a good OEE on the roaster doesn't help if the green coffee for Thursday's orders hasn't arrived. How the week's batches are scheduled is in production schedule example.
How TaroStack does it
TaroStack records good and rejected on every batch, and on Standard plans hours for each work center.
Good and rejected on the batch. Each roast is a batch that takes its green coffee off stock and records how much came out good and how much was rejected, with the labor minutes, so the quality part of OEE and the cost of a scorched batch are there for every roast. A batch record form carries fields of your own, such as the charge temperature and the roast time.
Green coffee ready. "What could I make right now" says how many batches the green coffee on the shelf allows, and the reorder list says what to order before it runs out, with each importer's lead time.
The week against the roaster's hours. On Standard, planning sets work centers and their hours, so a week's roasting plan doesn't promise more batches than the roaster has time for. Planning is on Standard at $99 a month.
| The job | Notebook | In TaroStack |
|---|---|---|
| Good and scorched batches | Tally marks | Good and rejected on every batch |
| Roast temperature and time | A notebook by the roaster | Fields on the batch record |
| Green coffee for Thursday | Check the shelf | What could I make right now |
| A week that's too full | Found on Thursday | Capacity against work centers (Standard) |
Batches, batch records and reorder lists are on every plan, from $49 a month. The first 30 days are free, with no credit card. If you'd like a hand setting up, ask, and we'll do it with you.