Key takeaways
- The six big losses are the standard way to break down why OEE is below 100%.
- They map onto the three OEE factors: two each for Availability, Performance and Quality.
- The performance losses - minor stops and speed loss - are the most commonly underestimated.
- Attack the loss behind your lowest OEE factor first.
If OEE tells you how much productivity you're losing, the six big losses tell you where. Coined in Total Productive Maintenance (TPM), they're the six categories every OEE loss falls into - and the right starting point for improvement, because each has a different fix.
The six losses, mapped to OEE
| OEE factor | Loss | What it is | How to cut it |
|---|---|---|---|
| Availability | 1. Breakdowns | Unplanned equipment failures and stops | Preventive + predictive maintenance, root-cause analysis, spares readiness |
| 2. Setup & adjustments | Changeovers, warm-up, tooling, calibration | SMED / quick changeover, standard work, fewer adjustments | |
| Performance | 3. Idling & minor stops | Micro-stops - jams, misfeeds, sensor trips cleared in seconds | Automatic stop detection, true-cause analysis, mistake-proofing (poka-yoke) |
| 4. Reduced speed | Running below nameplate / ideal rate | Find the bottleneck, restore design speed, tune the process | |
| Quality | 5. Process defects | Scrap and rework in steady-state production | SPC, process control, root-cause on defect modes |
| 6. Reduced yield (startup) | Rejects during warm-up, changeover, startup | Stabilise startup, reduce changeover variation, first-article checks |
The loss everyone underestimates
Breakdowns get attention because they're dramatic and logged. The quiet killers are #3 and #4 - minor stops and reduced speed. They don't trip a work order, so they hide inside the Performance factor as a vague gap. On many packaging, filling and assembly lines they cause 5–20% performance loss all by themselves. If your OEE looks acceptable but output doesn't match, this is almost always why - see the hidden factory.
How to prioritise
- Calculate OEE and look at the three factors separately.
- Find your lowest factor - that points to which pair of losses to attack.
- Get the true cause for that loss before spending money. "Performance loss" is not a cause; "the capper jams on warped caps" is.
- Fix, then verify the loss actually fell - don't assume.
Calculate OEE and see your weakest factor, then size the micro-stop loss behind it.
Why the true cause is the hard part
Most of the six losses are easy to name and hard to attribute. A line logs "minor stop" 400 times a shift with no reason attached. Cutting the loss means knowing which 400 - and that needs automatic detection plus a way to see what happened. That's exactly what does: it reads every stop from the machine and shows the true cause on video, so each of the six losses becomes a specific, fixable list.
Are there really only six?
The six big losses are the classic TPM framework. Some models add an eighth or split losses differently (e.g. adding management and operator-motion losses), but the six map cleanly onto OEE's three factors, which is why they're the standard.
How do the six losses relate to the eight wastes of lean?
They overlap but aren't identical. The six big losses are equipment-focused (they explain OEE); the eight wastes (TIMWOODS) are process- and flow-focused. Both are useful; the six losses are the right lens for machine effectiveness.
What's the fastest win?
Usually reducing minor stops, because they're frequent, cheap to fix once you know the cause, and large in aggregate. Size yours here.