OEE reflects effective production time as a percentage of planned production time. It is calculated based on three factors: availability, performance and quality.

Availability aims to eliminate interruptions and ensure smooth operations.

Quality focuses on perfection and aims to reduce defective products.

Performance aims to prevent speed loss and maintain high efficiency.

OEE can be calculated using the following formula, where availability, performance and quality are important metrics in manufacturing.

OEE = Availability x Performance x Quality

Availability

Availability rate reflects the proportion of actual machine running time to planned running time, expressed as a percentage. Availability is calculated by dividing the actual runtime by the scheduled runtime and multiplying by 100 to get the percentage.

Availability = Actual Runtime / Scheduled Runtime

The scheduled runtime of a machine can be obtained from the production schedule. To obtain the actual runtime, all downtime is deducted from the planned runtime. By analyzing the downtime data, it is possible to reveal not only the causes of downtime, but also potential opportunities for improvement.

Performance

To determine performance, actual output is compared to the maximum output of the machine during the effective time at the highest operating speed.

Performance = Actual Performance / Target Performance

Actual performance is determined by calculating the total output including scrap. Target performance, on the other hand, is calculated by multiplying the machine's maximum output per hour with the actual running time, and the target performance reflects the potential capacity of the machine during that time period.

Quality

Quality is the third element that OEE must calculate. It is the proportion of total product that is qualified according to quality standards.

Quality = Qualified Products / Total Products

In practice, the quantity of conforming product is calculated by subtracting the quantity of rejects and reworked product from the total quantity of product produced in a given time period. This formula indicates that the quantity of total product is equal to the sum of the quantity of conforming product, scrap and rework.