Machine downtime and OEE improvement

Learning objectives

• Compute OEE with honest ideal cycle and good count.
• Separate availability, performance and quality losses.
• Focus improvement on the constraint machine, not every machine.

Problem and CTQ

OEE = availability × performance × quality. Equipment losses reduce capacity and disrupt flow, but only losses at the constraint move throughput.

DMAIC path

• Define planned time and loss codes.
• Validate timestamps, ideal rate and good count.
• Pareto breakdown, minor stops, speed loss, setup and defects; compute MTBF and MTTR.

Improvement choices

• Autonomous and planned maintenance.
• Critical spares, centerlining, response escalation and condition checks.
• Failure-mode actions on repeat causes.

Control plan

• OEE and its three factors, downtime minutes, MTBF, MTTR, repeat failure, schedule compliance and throughput at the constraint.

Garment-factory example

A bar-tack machine at the constraint runs at 58% OEE (Availability 82%, Performance 88%, Quality 80%). A 30-minute daily condition check plus a spare-parts kit lifts OEE to 74% and adds 210 shirts/day at the same line count.

Common mistakes

• Using OEE to judge operators.
• Inflating the ideal cycle to make OEE look worse (or better).