Changeover time

Changeover time starts with the last good part of the old job and ends with the first good part of the new one. It therefore covers more than swapping the tool: cooling down, disconnecting, removal, transport, installation, connecting, adjusting, start-up and the parts scrapped until release.

During this time the machine stands still. The cost results from the downtime multiplied by the machine hourly rate – and from what long changeovers force: large batches, high stock and little flexibility.

The method for reducing changeover time, known as SMED, begins with a distinction. Internal setup is everything that can only be done with the machine stopped. External setup can be done while the machine is still or already producing: staging the tool, preheating it, fetching aids, taking the old tool away.

The first step moves as much as possible to the outside. The second shortens what remains inside – with quick clamps, uniform connections and handling that does not wait.

With heavy tools, rolls and fixtures, transport is often the longest internal item.

A handling unit that belongs to the machine is available when the changeover happens. A load handling attachment matched to the tool does away with slinging. A guided movement allows one person to bring the tool in from the side and position it without swinging.

A calculation with assumed figures: if 15 minutes of waiting are eliminated per change and tools are changed three times a day on 220 days, that is 165 machine hours a year. The value this represents follows from the hourly rate of your own machine.

Changeover is a special operating mode with its own hazards: heavy parts, hot surfaces, open guards, time pressure. A procedure that is faster because a safeguard is skipped is not a reduction. Good changeover concepts are faster because they remove travel and waiting.