OEE & Downtime in Machinery & Fabrication
Key takeaways
- Measure OEE the same way every shift and compare against your own trend first.
- Setup and waiting dominate, often more than actual cutting time.
- The big levers: setup reduction, tooling, and keeping jobs fed.
- Track utilization (TEEP) too, because idle and unscheduled time is large.
Machinery, equipment and metal fabrication is the world of high-mix, low-volume work: many part numbers, small batches, skilled labour. Here the machine spends a surprising amount of time not cutting, waiting for setup, material, tooling or a program. That makes this OEE profile all about availability, not speed.
What's a good OEE in machinery/fabrication?
We found no published OEE range for machinery and fabrication alone with a stated method. The usual reference is 85 percent world-class (traced to Nakajima, Introduction to TPM, 1988), and published plant studies found average OEE of about 55 to 65 percent (sources: Ljungberg, 1998; Hedman et al., 2016); the more useful target is your own line's trend. In a high-mix shop the OEE headline understates the loss, because so much time goes to setup and waiting. The biggest separator is setup time, and it is worth tracking TEEP too, since machines are often idle or unscheduled. Calculate your OEE.
The biggest losses in machinery & fabrication
| Loss | Why it's big in fabrication | OEE factor |
|---|---|---|
| Setup & changeover | Every small batch needs a setup; in high-mix it can exceed cutting time | Availability |
| Waiting (material / tooling / program) | Jobs stall waiting for the next input, fixture or NC program | Availability |
| Tool changes & breakage | Tool wear, breakage and indexing stop the cut, see CNC troubleshooting | Performance / Availability |
| Reduced speed | Conservative feeds and speeds to protect tools and finish | Performance |
| Rework & scrap | First-off errors and out-of-tolerance parts | Quality |
In high-mix shops, TEEP reveals idle, sellable capacity you already own.
One CNC machining shift, worked through
Illustrative numbers for one CNC machining centre in a high-mix shop, so you can check the math against your own shift. Planned production time is 450 minutes. The shift log records two setups of 40 minutes and 20 minutes waiting for a corrected NC program: 100 minutes of downtime. The programmed cycle for the part is 4 minutes, but it runs at 5 minutes because feeds were turned down after a broken tool last month. Chip clearing and re-touching tools stop it for about 25 minutes, which nobody logs. 3 parts are scrapped at first-off inspection.
| Step | Calculation | Result |
|---|---|---|
| Availability | run time 350 min (450 - 100) / 450 | 77.8% |
| Parts made | 325 running min (350 - 25 of short stops) / 5 min a part | 65 |
| Performance | 65 x 4 min ideal cycle / 350 | 74.3% |
| Quality | 62 good of 65 (3 first-off scrap) | 95.4% |
| OEE | 77.8% x 74.3% x 95.4% | 55.1% |
The log explains 100 lost minutes. The machine lost 202.0: 100 of setups and waiting, 25 of short stops, 65.0 of running a slow cycle and 12 of scrap. In a job shop the slow cycle hides best: every part still comes out, just later, and the quote assumed the 4 minutes.
Reason codes for a CNC machining cell
A short list everyone uses beats a long one nobody does. A starting set:
- Setup: fixture change, tool setting, first-off inspection
- Waiting: material, NC program, fixture, inspection, operator on another machine
- Tooling: tool change, broken tool, tool not available
- Machine: alarm, chip conveyor, coolant, door interlock
- Quality: out of tolerance, rework, scrap
- Planned: preventive maintenance, warm-up cycle
Log them in the free OEE tracker and the downtime Pareto ranks them for you; the downtime log template does the same on paper.
What a camera shows at a machining centre
A stop code tells you the machine went idle, not what was happening at it while it waited. Where cameras are fitted, Fabrico's camera-based OEE software syncs camera video with machine data, so you can replay the moment the machine stopped. Cameras also catch short stops and a machine that is switched on but not producing, the losses nobody writes down: in the shift above, that is the 25 minutes the log never saw.
What downtime costs in fabrication
Capacity is the constraint and skilled labour is expensive, so a machine waiting for setup or material is lost margin and a delayed order. Quoting accuracy and on-time delivery both depend on uptime. Estimate your downtime cost.
How leading shops improve
- Attack setup time with SMED, offline preparation and standard work, often a major lever.
- Stage material, tooling and programs so the machine never waits.
- Track tool life and reliability (MTBF/MTTR) to cut surprise stops.
The partner we recommend, Fabrico, reads stops from the machine and shows the stop on video with a suggested cause, where cameras are fitted, and lets a technician open the work order from the stop, turning setup and waiting losses into a fix list. It is EU-built, with data hosted in the AWS EU region and holds ISO 27001 / 20000-1 / 9001 (supports audit-readiness). Fabrico is a partner we recommend; the tools here are free regardless.
Is OEE useful in a job shop?
Yes, but pair it with setup time and TEEP. In high-mix work the biggest story is how much time is setup and waiting versus actual cutting.
What is the fastest win?
Usually setup reduction. Offline preparation and SMED free real capacity without buying machines. See the six big losses.
Does this cover welding and assembly?
Yes, the setup-and-waiting dynamic carries across fabrication. See welding troubleshooting and CNC.
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