Availability vs. Performance vs. Quality: The Three OEE Pillars

The Anatomy of OEE

An overall OEE score tells you how productive your factory is, but it doesn't give you enough detail to make improvements. To diagnose capacity limitations, you must analyze the three core pillars of OEE: Availability, Performance, and Quality.

Each pillar represents a different type of production loss. Understanding the relationship between them is critical for operational optimization.

Pillar 1: Availability (Time-Based)

Availability measures how much scheduled time your machine is actually running.

• The Question it Answers: "Was the machine running when it should have been?"
• Primary Target: 90.0% (World-Class)
• What Degrades It: Unplanned breakdowns, setups and changeovers, waiting for materials, operator changeovers.
• Calculation Example: If a machine is scheduled to run for 450 minutes, but stops for 45 minutes because of a breakdown, its Availability is 90.0% (405/450).

Pillar 2: Performance (Speed-Based)

Performance measures the speed at which your machine runs relative to its designed capacity.

• The Question it Answers: "Did the machine run as fast as it theoretically could?"
• Primary Target: 95.0% (World-Class)
• What Degrades It: Minor stops (jams, sensor issues), idling, running below maximum speed because of wear and tear, operator settings.
• Calculation Example: If your machine runs for 405 minutes and produces 24,000 parts, but theoretically could have produced 24,300 parts at full speed, its Performance is 98.7% (24,000/24,300).

Pillar 3: Quality (Yield-Based)

Quality measures the ratio of parts that pass inspection on the first run (good parts) to the total count of parts produced.

• The Question it Answers: "How many of the produced parts were actually salable and defect-free?"
• Primary Target: 99.0% (World-Class)
• What Degrades It: Defective parts, scrap, rework, parts produced during startup warmups or adjustments.
• Calculation Example: If the machine produces 24,000 total parts, but 600 are rejected as defective, the Quality score is 97.5% (23,400/24,000).

How the Pillars Interact

OEE is multiplicative. This means a low score in any single pillar will severely pull down the overall score.

Conclusion

To optimize your factory floor, do not just target the overall OEE score. Look at the three pillars independently. A plant with low Availability needs process engineering (SMED, PM schedules). A plant with low Performance needs machine calibrations or mechanical cleaning. A plant with low Quality needs materials checks or statistical process control.