OEE monitoring for a small CNC shop
Dinesh Kumar G · 1 min read · 4 October 2026
What OEE means on a CNC shop floor, how to measure availability, performance and quality without a big system, and the first losses worth fixing.
What OEE measures
Overall equipment effectiveness is availability × performance × quality:
- Availability — run time ÷ planned production time. Breakdowns, setups and waiting for material pull it down.
- Performance — (ideal cycle time × parts made) ÷ run time. Slow cycles and small stops pull it down.
- Quality — good parts ÷ parts made. Scrap and rework pull it down.
Try the numbers in the OEE calculator.
Start with the machine, not a dashboard
The cheapest reliable signal is the machine itself. On Fanuc controls the FOCAS library reports run state, alarms, part counts and the running program. Older machines can give a cycle-start or spindle-running signal through a simple I/O module. Manual logging on paper works for a week-long study, but not as a system.
Record downtime reasons
A machine that is stopped for an hour is a fact; why it stopped is what you can fix. Give operators a short reason list — tool change, setup, waiting for material, waiting for inspection, breakdown, no operator — and keep it short enough to use.
The first losses to attack
- Setup time. Usually the biggest availability loss in a job shop. Standard tool lists and pre-set tools cut it.
- Waiting. Material, programs, inspection and the crane. Program transfer over the network removes one of these.
- Small stops. Chips, coolant, gauging. They hide in performance losses.
What good looks like
Compare a machine with itself week on week rather than chasing a published benchmark. A downtime Pareto every Monday, and one loss fixed at a time, moves OEE more than any screen.