OEE, EPEI and Product Mix: Metrics for High-Mix Production

Once several products run over the same line, one cycle time per process is no longer enough. What counts then is the demand-weighted mix, the changeover time for each switch, and how often each product can be made.

OEE

Overall Equipment Effectiveness combines three losses: availability (breakdowns, changeovers), performance rate (speed losses) and quality (scrap, rework). In a value stream, all three feed into the effective cycle time.

Watch out when you move OEE data into the data box: OEE availability includes changeovers. The data box keeps them apart. Uptime covers breakdowns only, and changeover counts through changeover time ÷ batch size. If you enter an OEE availability that includes changeovers and also fill in the changeover time, you count changeovers twice.

Mix loading and EPEI

With several products, the load on a process is the sum of demand × cycle time per product, relative to the available time. The time left over is available for changeovers. EPEI (Every Part Every Interval) is the sum of all changeover times for one pass through the product sequence, divided by this changeover capacity per day: the interval in days in which every product can be made once.

With a changeover matrix (changeover time per product switch), EPEI depends on the sequence. The app searches for the sequence with the lowest changeover time across all processes.

Operator balance

The yamazumi chart stacks the work content of each operator and compares it with takt time. It shows how many operators a cell needs (total work content divided by takt time, rounded up) and where work has to be redistributed.

Frequently asked questions

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