Thursday, July 31, 2008

How a production line supporting multiple products with different takt times runs?

Lean implementation can be more straightforward in dedicated parts of your value stream - those places where only one product is made and where one-piece flow cells are appropriate.
But what if your value stream produces more than one product? What if it produces many products in any given month, or week or hour? Mixed Model flow is the solution you may have been looking for.
The popular way of dealing with this situation (called as the mixed-model flows) is to create product families based not just on similarities of manufacturing operations but also on the operation times.
What is Mixed-Model flow? Mixed-Model flow is making value flow by taking out the waste in your value stream so that multiple products are made in each time period.
This is accomplished by making the Mixed-Model flow part perform as if it were a dedicated asset. Each product "flows" at the rate of customer demand, even though multiple products are made there. For example, if two products A & B visit similar matching stations and the cycle time for A&B differ by over say 20% then they should "not" be lumped together in one product family. They should be handled by different manufacturing cells. Now where did this 20% come from? I have seen practitioners use some numbers such as these as a heuristic. It is not a magic number but based on experience. Any other ideas???

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