Overall Equipment Effectiveness is only as useful as your ability to act on it. A single OEE number tells you how much productive capacity you lost — the Six Big Losses framework tells you exactly where it went. Developed as part of Total Productive Maintenance (TPM) by Seiichi Nakajima, the framework gives every minute of lost production a category, a cause, and a path to reduction. This guide breaks down all six losses, shows what each one costs in real terms, and explains the specific interventions that cut them.
iFactory classifies every downtime and speed loss minute into the correct OEE category automatically — no manual logging, no guessing at the end of the shift.
How the Six Big Losses Map to OEE
OEE is calculated as Availability × Performance × Quality. Each of the Six Big Losses attacks exactly one of these three components — which is why the framework and the metric were designed together. You cannot improve OEE without reducing losses; you cannot reduce losses without knowing which category they belong to.
The Six Big Losses — Detailed Breakdown
Each loss has a precise definition, a real-world manufacturing example, a cost model, and a specific set of countermeasures. Treating all six with the same response is why most OEE improvement programs stall.
Unplanned Equipment Failures
Any unscheduled stoppage caused by equipment failure, mechanical breakdown, tooling failure, or process fault that requires intervention before production can resume. This is the most visible loss — and the most expensive per occurrence.
CNC machining center hydraulic pump fails mid-shift. Repair takes 2.5 hours. At 480 parts/hr ideal rate, that is 1,200 parts of lost output. At $8.50/part margin, the single event costs $10,200 in unrecovered throughput — before labor and parts.
Planned Stops & Setup / Changeover
Production time lost to planned stoppages — changeovers between products, scheduled maintenance windows, tooling changes, and warm-up periods. These are known in advance, which makes them reducible through engineering and process discipline. Many plants accept these as unavoidable; world-class plants treat them as waste.
An injection molding cell performs 4 mold changeovers per day averaging 45 minutes each. That is 3 hours of daily planned downtime. If SMED reduces changeover to 20 minutes, the plant recovers 100 minutes of productive time per day — roughly 42 additional shifts per year.
Slow Cycles & Reduced Speed
Any time equipment runs below its ideal or nameplate cycle time. This loss is the hardest to detect because the machine is running — it looks productive. A press running at 85% of ideal rate over an 8-hour shift loses more total output than a 30-minute breakdown, but almost never appears on a downtime report.
Stamping press ideal cycle time: 4.2 seconds/part. Actual observed cycle time: 5.0 seconds (worn die, operators compensating). Loss per hour: 48 parts. Over a 2-shift day: 576 parts. At $3.20 margin: $1,843 per day in invisible throughput loss — $460,000 per year.
Small Stops & Micro-Stoppages
Stoppages typically under 5 minutes that are cleared by the operator without a maintenance work order — jams, misfeeds, sensor faults, part blocking a chute. Each event is small enough to be ignored on a shift report. Collectively, they can account for 15–25% of total production losses in high-speed automated lines.
Packaging line experiences 18 jams per shift averaging 2.5 minutes each = 45 minutes of lost run time per shift. Because each event is cleared by the operator with no log entry, the shift report shows 95% availability. Actual availability: 84%. The 11-point gap is entirely invisible to management.
Production Rejects & Rework
Defective parts or assemblies produced during steady-state production that require rework or are scrapped. Every rejected part consumed raw material, machine time, labor, and energy — then delivered zero revenue. Reworked parts cost the operation two full cycles. This loss directly reduces the Quality component of OEE.
Welding cell with 0.8% scrap rate on 5,000 parts/shift = 40 scrapped parts. At $22 material and direct labor cost per part, daily scrap cost is $880. Across 250 production days: $220,000/year from a scrap rate that most supervisors consider acceptable.
Startup & Yield Losses
Defective parts produced from startup until the process reaches steady-state — after changeovers, shift starts, machine warm-ups, or after a breakdown restart. These parts are often written off as unavoidable startup scrap. In high-mix environments with frequent changeovers, startup losses accumulate into a significant quality drain.
Plastic extrusion line discards the first 12 minutes of output after each material changeover (4 changeovers/day) as off-spec material. At 400 lbs/hr throughput and $1.80/lb material cost: 32 lbs scrapped per changeover × 4 × 250 days = 32,000 lbs/year = $57,600 in startup scrap alone.
Calculating the Cost of Each Loss — A Worked Example
Most manufacturers know their OEE percentage. Few have translated it into a dollar figure by loss category. Here is a calculation for a mid-volume discrete manufacturing cell running a single shift to show what each loss actually costs.
| Loss Category | Time Lost / Shift | Parts Lost | Daily Cost | Annual Cost (250 days) | OEE Impact |
|---|---|---|---|---|---|
| Unplanned Failures | 48 min | 96 | $614 | $153,600 | −10 pts Avail. |
| Planned Stops / Changeover | 36 min | 72 | $461 | $115,200 | −7.5 pts Avail. |
| Slow Cycles | — (speed) | 58 | $371 | $92,800 | −6 pts Perf. |
| Small Stops | 24 min | 48 | $307 | $76,800 | −5 pts Perf. |
| Production Rejects | — (quality) | 38 | $243 | $60,800 | −4 pts Quality |
| Startup Rejects | — (quality) | 34 | $218 | $54,400 | −3.5 pts Quality |
| Total Loss | 108 min | 346 | $2,214 | $553,600 | −36 pts OEE |
Based on illustrative mid-volume cell parameters. Actual figures vary by industry, product mix, and margin structure.
iFactory connects to your machines, auto-classifies every stop and speed loss into the correct category, and shows you exactly which loss is costing you the most — updated in real time, every shift.
Priority Sequence: Which Loss to Attack First
Not all six losses are equal. The right sequencing depends on your current OEE profile — but the following decision matrix applies to most discrete manufacturing environments starting a Six Big Losses reduction program.
How iFactory Tracks the Six Big Losses
The biggest barrier to Six Big Losses reduction is visibility. Most manufacturers cannot tell you how many minutes of Loss 4 (small stops) occurred on Line 3 last Tuesday. iFactory closes that gap with automatic loss categorization from machine signal data — no manual entry, no shift-end estimates.
Automatic Loss Classification
Machine signals are interpreted in real time and every stop, speed deviation, and defect count is assigned to the correct loss category — without operators logging a single event code. Classification rules are configurable per machine type and process.
Loss Waterfall Chart per Shift
Shift supervisors see an OEE waterfall — starting from 100% ideal, stepping down through each of the six losses in sequence, landing on actual OEE. The contribution of each loss is quantified in both minutes and percentage points.
Loss Pareto Across Time Periods
Quality and production managers can rank losses by time or cost across any date range — this week, this month, by line, by product. The top loss on any line is always visible at a glance, driving prioritization decisions without manual analysis.
Maintenance & Quality Workflow Integration
Loss 1 events (unplanned failures) automatically create a maintenance work order. Loss 5 events above a threshold create a non-conformance record. Both are linked back to the originating OEE event for full traceability from loss to corrective action.
Dollar-Denominated Loss Reporting
Every loss minute is converted to a dollar figure based on your configured part margin and ideal cycle time — so plant managers and operations leaders can make decisions in business terms, not just OEE percentages.
Frequently Asked Questions
iFactory auto-classifies every loss minute across all six categories, converts them to dollars, and routes corrective actions automatically — so your team focuses on fixing losses, not logging them.
