TeamAssurance

    What is OEE?

    Short answer

    OEE, overall equipment effectiveness, is a measure of how much of a machine's planned production time is spent making good product at its designed speed. It is calculated as availability × performance × quality, each expressed as a percentage. An OEE of 100% would mean no stops, no slow running and no defects; most operations sit well below that, which is where the improvement is.

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    The OEE formula

    • Availability = run time ÷ planned production time. It is lost to breakdowns, changeovers and other stops.
    • Performance = (ideal cycle time × total count) ÷ run time. It is lost to minor stops and slow cycles.
    • Quality = good count ÷ total count. It is lost to defects and rework, including start-up scrap.
    • OEE = availability × performance × quality.

    For example, a line planned for 480 minutes that ran for 400 (availability 83%), produced 3,600 units against an ideal of 4,000 in that time (performance 90%) and had 3,420 good units (quality 95%) has an OEE of 0.83 × 0.90 × 0.95 = 71%.

    The six big losses

    OEE was developed within total productive maintenance to make the six big losses visible:

    1. Breakdowns
    2. Set-up and adjustment
    3. Minor stops and idling
    4. Reduced speed
    5. Defects and rework
    6. Start-up losses

    Each loss maps to one of the three factors, so a falling OEE points to where the problem is.

    Using OEE well

    • Compare a machine with itself over time, not one machine with another. Different equipment has different ideal cycle times and planned schedules.
    • Look at the three factors, not only the headline. A 70% OEE from low availability needs maintenance and changeover work; the same figure from low quality needs process control.
    • Record the losses behind the numbers. OEE tells you how much time was lost; the reason codes tell you why.
    • Review it daily. Yesterday's OEE and its biggest loss belong on the Tier 1 board, with chronic losses escalated into problem solving.

    Common mistakes

    • Chasing a benchmark figure such as "world class 85%" without understanding what is in the planned time.
    • Excluding changeovers or planned maintenance to make the number look better, which hides the losses that could be reduced.
    • Treating OEE as a report for management rather than a signal for the team running the machine.

    How TeamAssurance helps

    TeamAssurance tier boards can carry OEE and its three factors as measures with targets and trends, with breakdowns, minor stops and defects logged against the asset so the losses behind the number are visible. Recurring losses move into structured problem solving, and preventive and autonomous maintenance are scheduled and tracked in the asset management capability.

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    Frequently asked questions

    What is a good OEE score?

    Figures around 85% are often quoted as world class for discrete manufacturing, and 60% is typical for operations that have only just started measuring. The useful comparison is a machine against its own history and its biggest loss.

    What is the difference between OEE and TEEP?

    OEE measures effectiveness within planned production time. TEEP, total effective equipment performance, measures it against all calendar time, so it also shows how much capacity is lost to the schedule itself.

    How is OEE related to TPM?

    OEE is the headline measure of total productive maintenance. TPM's pillars, autonomous maintenance, planned maintenance and focused improvement, each attack one or more of the six big losses that reduce OEE.

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