SMED changeover study: measure last good to first good

A changeover study should measure the production interruption that matters to the next order. “Machine stopped” to “machine restarted” can omit the trial pieces, adjustments and quality release that delay good output. Define the boundary as last accepted good unit of the outgoing product to first accepted good unit of the incoming product, unless your site deliberately uses another definition.

FIG. 03At the inspection gate

Observe before proposing shortcuts

Use the SMED observation worksheet to record each task, its start and finish, responsible role, whether it requires a stopped machine, and what prevents preparation beforehand. Record concurrent tasks on separate rows rather than summing their durations into elapsed time.

An illustrative 40-minute changeover contains ten minutes finding tooling, eight minutes installing it, twelve minutes adjusting and ten minutes validating output. Preparing verified tooling before the stop may remove much of the search interval. It does not eliminate installation, isolation or the approved release checks.

Internal and external are operating conditions

Internal setup requires the equipment to be stopped. External setup can be completed while the previous order runs. Moving a task outside the stop is useful only when it can be completed safely, correctly and without starving the current job of an operator or material.

SMED targets rapid setup by separating and improving these tasks. The name does not mean every process can or should achieve a sub-ten-minute changeover. Process chemistry, cleaning validation, thermal conditions and safety requirements may set a different practical boundary.

Check elapsed time and total work

A second person can shorten elapsed downtime while increasing labor minutes. That can be worthwhile, but report both. Likewise, moving cleaning to another area may shift work and exposure rather than eliminate them. Review the whole route with operators, maintenance and quality before standardizing the new method.

Measure multiple comparable changeovers after the change. Retain product pair, tooling, staffing and abnormal conditions; an easy same-family setup is not comparable with a full format and material change. Watch startup scrap and downstream holds so the apparent time saving does not reappear as quality loss.

Connect improvement to capacity

At the constraint, recovered changeover time can create capacity if demand exists. Elsewhere it may improve flexibility or reduce WIP rather than increase shipped output. Use takt and capacity to establish the boundary and the ROI calculator to test a documented benefit.

Source

Lean Enterprise Institute: single-minute exchange of die introduces the setup approach. The task breakdown above is an illustrative study plan; apply your site's approved safety and quality procedures.