The Six Big Losses in manufacturing

The Six Big Losses is a classic framework from Total Productive Maintenance (TPM) for grouping every cause of lost production time into six categories. It matters because it's the same structure OEE is built on: each of the three OEE factors — Availability, Performance and Quality — is really just two of these losses measured as a percentage.

Knowing the six losses by name makes a low OEE score actionable. Instead of "OEE is 65%", you get "changeovers and micro-stops are our biggest problem" — something a team can actually go fix.

Availability Losses

Time the machine should have been running, but wasn't. These directly reduce your Availability score.

1. Breakdowns

Unplanned equipment failures — tool breakage, mechanical faults, electrical faults — that stop production until repaired. Usually the most visible loss, and the one maintenance teams already track to some degree.

2. Setup & Changeover

Time lost switching from one product or tool to another: adjustments, calibration, and the changeover itself. Predictable and schedulable, but often longer than it needs to be — this is the loss SMED (Single-Minute Exchange of Die) programs specifically target.

Performance Losses

The machine is running, but not at its ideal rate. These reduce your Performance score.

3. Small Stops (Micro-stops)

Brief interruptions — often 5 to 30 seconds — like a jam, a misfeed, or an operator clearing a sensor. Individually trivial, collectively brutal: twenty 15-second stops an hour is 5 minutes of lost run time, every hour, and almost nobody logs them manually. This is the loss manual tracking misses entirely and automatic tracking is built to catch.

4. Reduced Speed

Running below the machine's rated or ideal cycle time — often deliberately, to avoid jams or quality issues, or simply because nobody remembers what the ideal speed actually is. Easy to miss because the machine looks like it's working fine.

Quality Losses

Parts were produced, but didn't meet spec. These reduce your Quality score.

5. Startup Rejects

Scrap produced while a process is warming up or stabilizing — after a changeover, a material change, or the start of a shift — before the machine settles into a good process window.

6. Production Rejects

Scrap or rework produced during steady-state running: out-of-spec parts, defects caught downstream, anything that has to be reworked or thrown away once the process is already stable.

How the six losses map to OEE

This is why a low OEE score is really three separate diagnoses. A weak Availability score points at breakdowns and changeovers; a weak Performance score points at small stops and speed; a weak Quality score points at rejects. See the full OEE guide for the formula and a worked example.

Which loss should you tackle first?

Track which of the six is actually costing you the most before you fix anything — it's rarely the one that feels most urgent. Breakdowns get noticed because they're dramatic; small stops get ignored because each one is trivial, even though they often add up to more lost time over a week.

Start with a simple log of stops and reasons — our free Excel template is enough to get a first Pareto view of which losses dominate. Once machine data is captured automatically, hopit sorts every stop into these categories for you, so the biggest loss is always the first thing you see.