Changeover Time
Changeover time is the total elapsed time from the last good part of one production run to the first good part of the next run, including all teardown, setup, and dial-in adjustments. In machining and shop-floor process engineering, it is considered non-value-added machine downtime, making reduction a core lean-manufacturing target.
On a CNC cell, changeover time covers the full transition between jobs: tear-down of the previous fixture, cleaning the table, tool removal and loading, workholding swap, program load, offset verification, probe routines, first-article inspection, and any final adjustments. In millwork or edgebanding, the same concept applies when switching panel profiles, edge tape, adhesive settings, feed rates, or trim packages; the machine stops while operators reconfigure guides, tooling, glue pots, and verification checks until the first acceptable piece matches the spec. The key manufacturing distinction is internal versus external work: internal steps require the machine to be stopped, while external steps can be staged while the machine keeps running—this is the basis of SMED reduction. In high-mix, small-batch environments, every minute of changeover recovered increases utilization and throughput, as the machine is occupied but not producing saleable parts.
- Boundary drift between shifts: Inconsistent measurement rules across crews hide real changeover losses and require a single boundary definition.
- Uncontrolled first-article scrap: A quick setup that yields multiple bad parts is still a long changeover; quality must be met before counting completion.
- Staging failures causing avoidable downtime: Missing tools or unprepared fixtures turn external tasks into internal downtime, wasting machine capacity.
Is changeover time the same as setup time?
In many manufacturing sources, the terms are used interchangeably, but changeover is often the broader transition from one job to the next, while setup may refer to the machine-prep activities inside that transition.
Why is the 'first good part' boundary important?
Because the job is not truly changed over until the next run is producing conforming parts, not merely cycling parts.
What is the most defensible formula?
A practical shop-floor definition is: Changeover Time = timestamp of first good piece of the new job minus timestamp of last good piece of the previous job.