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The Six Big Losses, Mapped to OEE
Overall equipment effectiveness tells you how much of your scheduled time turned into good product. It does not tell you where the rest went. The Six Big Losses do. Here is each loss, the OEE factor it drains, and a practical way to detect and attack it.
The Six Big Losses and the three OEE factors
The Six Big Losses come from Total Productive Maintenance (TPM). They are the standard taxonomy for every way a machine wastes the time it was scheduled to run. Instead of one blended efficiency number, you get six named buckets, and each one lands under a specific OEE factor.
The mapping is worth memorizing, because it tells you which lever moves which number:
- Availability loses time to Breakdowns and to Setup & Adjustments.
- Performance loses speed to Idling & Minor Stops and to Reduced Speed.
- Quality loses good units to Process Defects and to Startup Rejects.
An OEE score of 60% tells you that four of every ten scheduled minutes produced nothing sellable. It does not tell you whether the cause was a failed drive, a slow changeover, or scrap after every start. The Six Big Losses turn that anonymous gap into six problems you can assign, measure, and close. For the OEE and TEEP math itself, see the OEE and TEEP guide.
Availability losses: Breakdowns and Setup & Adjustments
Availability is the share of planned production time the equipment was actually running. Two of the Six Big Losses drain it, and both leave a machine visibly stopped.
Breakdowns. Any unplanned stop where the equipment cannot run: a seized bearing, a tripped drive, a fractured tool, a jammed infeed that needs a technician. This is usually the most visible loss and often the largest single line on a downtime chart.
- Detect: code every stop with a reason, then build a Pareto of downtime minutes by asset and failure mode. Track mean time between failures and mean time to repair so you can see whether stops are getting more frequent or just longer.
- Attack: root cause analysis on the top failure modes, condition monitoring on the assets that hurt most (vibration, motor current, temperature), and a planned maintenance interval that replaces wear parts before they fail rather than after.
Setup & Adjustments. The clock that runs from the last good part of one job to the first good part of the next: changeovers, tool changes, material swaps, and the trial-and-error tweaks after each one. Frequent short runs make this the quiet killer of availability.
- Detect: measure changeover duration by product pair, not as a single average. The worst transitions usually hide inside a blended number.
- Attack: apply SMED. Separate internal setup, which is only possible while stopped, from external setup, which can be done while running. Move as much as possible to external, then standardize the sequence so the fast changeover repeats across every shift.
Performance losses: Idling & Minor Stops and Reduced Speed
Performance compares how fast the line actually ran against how fast it should have run while it was running. These two losses are the hardest to see, because the machine never fully stops.
Idling & Minor Stops. Brief stoppages, usually under a few minutes, that an operator clears without a tool or a work order: a misfeed, a jam, a blocked photo-eye, a part that needs a nudge. Each one is trivial. In aggregate they are often the single largest loss on a line, and they are almost always under-recorded because they never reach a downtime log.
- Detect: you cannot count these by asking operators to log them. Read the machine's own cycle signals and count every interval that runs long, including the sub-minute stops no one writes down.
- Attack: mistake-proof the failure points (poka-yoke), tune sensors and guides, improve how material is presented to the machine, and balance the line so no single station chronically starves or blocks the next.
Reduced Speed. The machine runs, but below its ideal cycle time: worn components, conservative operator overrides, poor lubrication, or a line quietly de-rated to stop it from jamming. Speed loss rarely shows on a stop report at all.
- Detect: compare actual cycle time against a validated ideal cycle time, sliced by product, shift, and operator. Persistent gaps point to a specific cause.
- Attack: establish the true ideal cycle time, then find and remove the reason the line runs under it. A line slowed to avoid minor stops is really two losses wearing one mask.
Quality losses: Process Defects and Startup Rejects
Quality is the share of parts produced that were good the first time. Rework counts against it too, because a part you had to touch twice cost you the time to make it right.
Process Defects. Defective units produced during stable, steady-state running, plus the rework to recover them. These are the defects that occur when nothing unusual is happening, which makes them a signal about the process itself rather than a one-off event.
- Detect: run statistical process control on the critical characteristics, watch first-pass yield, and Pareto defects by type and cause. A control chart tells you whether variation is normal or drifting.
- Attack: reduce common-cause variation, mistake-proof the operations that generate the top defect types, and hold the process inside its control limits instead of inspecting quality in at the end.
Startup Rejects. The scrap produced from startup until the process reaches stable output: warm-up parts, first-article checks, purge material, and the settling period after a changeover. The more often you start, the more this loss compounds.
- Detect: look at the yield curve in the minutes after every start and changeover, and tag scrap that falls inside those windows so it is counted separately from steady-state defects.
- Attack: standardize the startup sequence, shorten warm-up where the process allows, and carry proven settings across runs so the line reaches good output faster.
The losses you cannot see cost the most
Breakdowns and changeovers get logged because someone is standing at a stopped machine. Minor stops and speed loss are different. They live in the gap between scheduled time and what the manual logs capture, and a line can bleed ten or fifteen points of OEE into that gap without a single entry to explain it.
Closing that gap is a measurement problem before it is an improvement problem. You have to read the equipment directly. KaizenFlow AI connects on top of the systems a plant already runs, including MES, SCADA, ERP, and historians, through more than 43 connectors such as SAP, Siemens, Rockwell, OSIsoft PI, Ignition, Kepware, OPC-UA, MQTT, and Modbus. That gives you the high-resolution cycle and stop data the Six Big Losses actually require.
From that signal, an ensemble of AI specialists separates the losses and sizes each one. The Throughput Analyst isolates minor stops and speed loss, the Reliability Forecaster flags assets trending toward breakdown, and the Quality Sentry and Yield Modeler split steady-state defects from startup scrap. Every finding is ranked by dollar impact and confidence, so the loss that costs the most gets worked first. See how the loop fits together on the platform overview.
From a named loss to verified savings
Naming a loss is the start. The value shows up only when the fix holds and someone can prove it. KaizenFlow runs one closed loop: connect to the data, surface the ranked opportunities, decide what to work, and verify the result.
Verification is deliberately strict. Confirmed improvements land in a savings ledger that the customer's own finance team signs off on, so a downtime reduction is counted the way finance counts any other number, not as an engineering estimate.
Across the design-partner program, the modeled target ranges are 8 to 18% lower unplanned downtime, 5 to 12% less scrap, and 4 to 11% higher throughput. These are modeled ranges, not guaranteed or achieved results, and every plant starts from a different baseline. The job of the Six Big Losses is to tell you which of those ranges you have the most room to capture.
Frequently asked
What are the Six Big Losses? The Six Big Losses are the TPM framework for every way a machine wastes scheduled runtime: Breakdowns, Setup & Adjustments, Idling & Minor Stops, Reduced Speed, Process Defects, and Startup Rejects. Each one maps to one of the three OEE factors.
How do the Six Big Losses map to OEE? Breakdowns and Setup & Adjustments reduce Availability. Idling & Minor Stops and Reduced Speed reduce Performance. Process Defects and Startup Rejects reduce Quality. Multiply the three factors together and you get OEE.
What is the difference between a breakdown and a minor stop? A breakdown is an unplanned stop that needs a repair or work order, and it counts as an availability loss. A minor stop is a brief stoppage an operator clears in under a few minutes with no repair, and it counts as a performance loss. Minor stops are usually far more under-recorded.
Which of the Six Big Losses is hardest to measure? Idling & Minor Stops and Reduced Speed, because the machine keeps running and neither reliably reaches a manual downtime log. Detecting them means reading cycle-level signals from the equipment rather than trusting operator entries.
How do you reduce the Six Big Losses? Measure each loss separately, rank them by cost, then match the fix to the loss: reliability work for breakdowns, SMED for changeovers, mistake-proofing and sensor tuning for minor stops, ideal-cycle-time control for speed, and SPC for defects.
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