OEE structure
Overall Equipment Effectiveness is commonly expressed as Availability × Performance × Quality. Each factor is a percentage, so the product is typically lower than any individual factor.
Time boundary matters
Availability can change dramatically depending on whether planned downtime, breaks, changeovers or lack of schedule are included. Publish the denominator definition with the KPI.
Performance assumptions
Performance requires a reference or ideal cycle rate. If standards are stale, product mix changes, or the rate is defined inconsistently, the KPI can mislead.
Quality factor
Quality should use agreed good-versus-total quantities and consistent treatment of rework and scrap.
ISO 22400
ISO 22400 provides an industry-neutral framework for manufacturing-operations KPIs and defines selected KPI formulas and characteristics. It is a useful reference for standardizing meaning before benchmarking.