What is OEE
OEE stands for Overall Equipment Effectiveness. It is a single number that measures how effectively a piece of equipment or a line is being used. OEE combines three factors: Availability, Performance, and Quality. It was developed by Seiichi Nakajima and is a core metric in Total Productive Maintenance (TPM) and Lean Manufacturing.
The OEE Formula
OEE equals Availability times Performance times Quality. Availability equals actual run time divided by planned production time. Performance equals actual output divided by theoretical output at rated speed. Quality equals good pieces divided by total pieces produced.
Practical Example 1 — Sewing Line
Planned time is 480 minutes. Downtime is 60 minutes. Availability is 420 divided by 480 equals 87.5 percent. Actual output is 800 pieces, theoretical is 1000, so Performance is 80 percent. Good pieces are 780 out of 800, so Quality is 97.5 percent. OEE is 0.875 times 0.80 times 0.975 equals 68.25 percent.
Practical Example 2 — Cutting Machine
A cutting machine runs 400 minutes out of 480. Availability is 83.3 percent. Actual output is 1200 pieces, theoretical is 1500. Performance is 80 percent. Quality is 98 percent. OEE is 65.3 percent.
Practical Example 3 — Benchmarking
World-class OEE is 85 percent. A factory at 65 percent has 20 points of hidden loss. Each point of OEE improvement usually translates into thousands of extra pieces per month.
Practical Example 4 — Focus
The factory tracks OEE weekly and finds that Performance (not Availability) is the biggest loss. Improvement focuses on speed losses: small stops and slow cycles. OEE rises from 65 to 72 percent in 3 months.
The Six Big Losses
Availability losses: breakdowns and setup/adjustments. Performance losses: small stops and slow cycles. Quality losses: process defects and startup rejects. Naming the losses makes it easier to fix them.
How to Improve OEE
Track downtime reasons daily. Address the top 3 reasons with 5 Why. Standardize setups with SMED. Train operators on basic maintenance. Monitor speed losses with real-time data. Address quality defects with inline QC.
Common Mistakes
Calculating OEE without a real baseline. Using theoretical speed that is unrealistic. Including planned downtime in availability loss. Not tracking downtime reasons. Comparing OEE across different machine types without context.
When to Use It
OEE is used in garment factories for cutting, sewing, finishing, washing, and any equipment-based process. It is especially useful in TPM-driven factories with a continuous improvement culture.