OptimalOEE™ Wiki / The six big losses
Technical
The six big losses
Every OEE loss maps to one of six categories, each to a factor, and each to a distinct set of reliability and maintenance root causes. Naming the category is the first step from a symptom to a cause, and to the intervention that moves the number.
The six, by factor, cause and fix
| 1. Breakdowns Availability | Unplanned equipment failure in planned production. The largest category on most assets. The root cause is reliability, addressed by RCM-based maintenance strategy, condition monitoring and defect elimination. |
|---|---|
| 2. Setup and changeover Availability | Time lost to changeovers, startups and adjustment; often underreported. Addressed by SMED, standard work and equipment condition at the changeover points. |
| 3. Minor stoppages Performance | Short stops under five minutes, individually trivial and collectively large. Usually poor condition, sensor faults or material handling. They hide in the speed loss until they are logged. |
| 4. Reduced speed Performance | Running below rated speed, the silent loss, normalised over time. Caused by wear, process instability or calibration drift; recovered through condition-based maintenance and precision work. |
| 5. Process defects Quality | Quality loss in steady-state running, driven by equipment condition, process capability and material variability. |
| 6. Startup rejects Quality | Quality loss at startup and after changeover, tied to the condition at the point of startup and the maturity of startup procedures. |
How each loss lands in the number
The six map cleanly onto the three factors, which is what lets a loss waterfall attribute lost time and money to a cause:
- Availability carries breakdowns and changeover: they cut Run Time below Planned Production Time.
- Performance carries minor stops and reduced speed: the line ran, but under the ideal cycle time.
- Quality carries process defects and startup rejects: units were made, but not good first time.
This is the hidden factory: capacity that already exists in the asset and is consumed by the six losses rather than by any lack of equipment. OEE measures its size; the loss category points at how to reclaim it.
Losses are not equal
Losses follow a Pareto: a few categories carry most of the lost time. OptimalOEE™ ranks them so effort goes where the recoverable value is, not to whatever was noticed last. An illustrative shift roll-up:
Illustrative demonstration data. Bar length is relative to the largest loss.
How OptimalOEE™ surfaces them
Every stop is categorised at capture, trended over time, and drillable from the OEE number to the individual event and the raw reading behind it. A stoppage can be re-classified with a reason, and the change is recorded on the audit trail, so the loss picture is both actionable and defensible.