Mixed Model - Merging Products

Mapping mixed model production systems can get tricky in practice. You typically are forced to compromise on the level of detail you can use in analyzing and planning flow, because variation between different product types can just be too much to work with. You have to figure out what products are 'close enough' to the same, and then work out their relative demands, so you can figure out how they each impact things like cycle time and inventory time.

The eVSM Mix tool extends eVSM to allow you to map these mixed model value streams, with shared resources, without having to collapse a number of products into a single flow, without needing singular cycle times and changeovers and demands. We're seeing this borne out by our users, who were able to cope before using mix, but who are now able to devote their attention to improving their value streams, and not in trying to remember what Excel file they used to calculate weighted cycle times.

As we've worked with our users, we've run into some cases where the multi-solve method eVSM Mix uses is solving a number of products which, while they impact the value stream, aren't really of interest to the study. So in these cases, it's good to go back to the old standby of averaging your products together.

I know what some of you are probably thinking, but rather than forcing you back into hand calculating weighted average cycle times, we've implemented a change in the software which allows you to merge these less-important products together, automatically. We handle all the averaging behind the scenes, and this can be undone any time, without affecting the original data. The automatic merging tool lets you specify a cumulative demand threshold, where the lowest-demand products, adding up to less than the specified percentage, get merged together. We still maintain product sets that share routings, but will add a 'merged' product where applicable, which contains the lower demand products in it.

Here's what we see on a test map I built with 50 products in two sets:

Mix Merge dialog showing merge % options


Within the dialog, you'll see a sorted list of your products, with their relative demand. You can see a '% of demand to merge' value, and see how that affects the number of product-specific solves will get done.


Mix map with merged products


You can see next to the set centers, the products in bold have not been merged, and the italicized products have been merged.

If you're interested in the mechanics of how we handle merging values like cycle time or changeover, contact us, and we can talk. If enough users want to know how it works, I can write a separate blog post detailing it a little further.

This change was ultimately done to make the analysis phase of your improvement project go a bit faster. You can access the Auto Merge dialog in eVSM v11.26 or later, within the eVSM Mix Manager dialog. It's up to you if you want to use the merge tool, and it's flexible enough you can spend some time with products merged, while you're getting the structure of your map built, and then turn off merging for your final analysis. This gives you the best of averaging and separating products, and the best part is you can still easily update data for specific products as they change, and eVSM will keep right up with you.