OEE

What it means

OEE, overall equipment effectiveness, is a measure that multiplies three components: a machine's availability, its performance and the share of defect-free output. The result shows what part of its theoretical capacity a company actually uses to produce good-quality products.

Availability captures losses from stoppages such as breakdowns or changeovers. Performance captures slow running and minor stops. Quality captures scrap and rework. With availability of 90%, performance of 90% and quality of 95%, OEE is about 77%, meaning almost a quarter of capacity is lost.

The measure comes from TPM, total productive maintenance, and is a standard part of lean manufacturing. A value of around 85% is often cited as world class, but most companies achieve considerably less, so production holds hidden reserves.

How it works in practice

Measuring OEE requires recording planned production time, stoppage time and its causes, the number of units produced and the number of defective units. Smaller firms can manage with manual records, while larger ones collect data automatically from machines and production systems.

The value is most useful as a tool for finding losses. Breaking it into its three components shows whether the main problem is breakdowns, slow running or quality. Improvement then uses tools such as preventive maintenance, quick changeovers or kaizen teams focused on a specific loss.

Raising OEE can replace investment in a new machine. If a company improves utilisation of an existing line by ten percentage points, it gains capacity it would otherwise have to pay for. Capacity planning should therefore be based on actual OEE, not nominal capacity.

What to watch out for

The measure is easy to manipulate, for example by leaving breaks or planned downtime out of planned time. Comparing OEE between plants or companies only makes sense with the same calculation method; otherwise the figures mean nothing.

Chasing a high OEE regardless of demand can lead to overproduction and unnecessary inventory. The aim is not to keep machines running constantly but to produce efficiently what customers need. OEE should therefore be assessed together with order fulfilment and the cost of quality.