Changeover time

Last Updated on 10 September 2023

The changeover time of a process is how long it takes to change from one product to another or one batch to another. This usually involves reconfiguring the machinery and retooling.

It’s often a hidden cost to the company, as a lot of effort is put into improving the speed of producing the product, but the time to retool is ignored. The cost can be huge though, as it can be many minutes longer than it needs to be, when you are running up costs but getting no ‘value add’.

It’s important that you don’t think that you are improving changeover time just because your product mix is changing. It is to be expected that the time to change from one batch to another, where only a small branding change is required can be a lot smaller than changing to a completely different product type. A minor change may just be replacing one raw material with another, but a major change could require cleaning all of the machinery to not contaminate the next product.

Where there is a large variation in what the purpose of this time is, you are better off calculating your figures per type, at very least including a major change / minor change split.

Number of changeovers

You can usually reduce your total changeover time by reducing the number of times you rearrange your production. This won’t affect your time per incident, but can lead to some very large time (and therefore cost) savings. This can be achieved by rearranging your production so that the manufacture of similar product is grouped together.

SMED

The most common method used to improve it is probably Single Minute Exchange of Die, more commonly known as SMED. The aim is to reduce your changeover time to a single number (so less than 10) of minutes.

Internal and external

A lot of the improvements come from separating your tasks into internal and external:

• Internal tasks can only be performed while the machinery is stopped.
• External tasks can be done while the machinery is still running, letting you continue production.

It’s common that most of the time of the changeover can on analysis either be removed or performed during production, saving huge amounts of time.