OEE implementation consulting and training

What is OEE?

Overall Equipment Effectiveness, or OEE, is widely used in Total Productive Maintenance (TPM). It measures equipment effectiveness through availability, performance and quality, helping an organisation identify opportunities for improvement.

Calculating OEE

• Availabilitymeasures the proportion of planned production time in which the equipment actually runs, reflecting stop-time losses.

Availability = Actual run time ÷ Planned production time × 100%.

• Qualitymeasures the proportion of output that meets the quality requirements.

Quality = Good units ÷ Total units produced × 100%.

• Performancemeasures speed losses by comparing actual output with the ideal output during run time.

Performance = Total units produced ÷ (Actual run time × Ideal production rate) × 100%.

• Overall Equipment Effectiveness combines availability, performance and quality into one indicator of equipment effectiveness.

OEE= Availability x Quality x Performance

When the factors are expressed as percentages, convert them to decimal fractions before multiplying, then express the result as a percentage. Use consistent time and production-rate units.

Applying OEE to a production line

OEE is commonly calculated for individual equipment. When applying it to a production line, define the measurement boundary, the relevant constraint, planned production time, ideal rate and output count consistently. Adapt the measurement arrangement to the process without arbitrarily changing the meaning of the factors.

The six big losses

One of the main purposes of TPM and OEE improvement is to reduce the six big lossesthat account for much of the lost production effectiveness.

Loss 1: Equipment breakdowns

Breakdowns are often the most visible loss because they interrupt production unexpectedly. Examples include damaged dies or fixtures, unplanned maintenance, mechanical or electrical failures and equipment that cannot perform its required function or meet the operating specification.
This is an availability loss in OEE.

Loss 2: Setup and adjustment

Setup and adjustment losses may be less visible because they are often accepted as a routine part of production. Examples include startup at the beginning of a shift, product changes, die or fixture changes, process-setting adjustments and material changes or shortages.

This is an availability loss in OEE.

Loss 3: Minor stops

Minor stops are short interruptions that usually do not require maintenance personnel. A threshold such as five minutes may be used locally, but it must be defined consistently. Examples include jams, blocked flow, feeding or alignment problems, incorrect materials, obstructed sensors and small downstream interruptions.

This is a performance loss in OEE.

Loss 4: Reduced operating speed

Reduced-speed losses occur when equipment runs below its defined ideal speed. Causes can include unsuitable operating conditions or materials, worn or dirty components, incorrect settings and insufficient operator competence.

This is a performance loss in OEE.

Loss 5: Startup defects

Startup or adjustment can generate defective products as well as stop time. These defects may be scrapped or reworked immediately, or they may pass to later operations and cause additional quality problems.

This is a quality loss in OEE.

Loss 6: Production defects

Production defects occur while equipment is otherwise considered to be operating normally. They include scrap, rework at the operation and defects detected later after non-conforming products have passed downstream.

This is a quality loss in OEE.