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Changeover Time

Changeover time represents the elapsed time to changeover from the production/processing of one product or service to a different product or service. Admittedly, there is little math involved here. Some readers may scratch their heads and wonder why one would need a math entry at all! However, changeover time is important in the overall scheme of Lean Math and, with it, the principle of flow and pull. More specifically, internal changeover time (T∆i) is a critical driver of batch sizes, lead time, and intervals.

Neil always used to confound and shock me. He was always pursuing perfection. And I would always retort something like, “But, the real world isn’t perfect.”

Over the years, I slowly realized the value and wisdom of Neil’s mindset. It is consistent with traditional lean thinking (as long as it does not paralyze the PDCA cycle), and it helps drive innovation and the right thought process. I have found that lean thinkers not only benchmark themselves against the competition, they also benchmark themselves against perfection. This is where math can help.

Value stream analysis is conducted typically for one specific product or service family at a time. In order to identify and distinguish families, lean practitioners use what is called a product family analysis matrix (a.k.a. product quantity process matrix (PQPr)). Many times the families can be easily discerned once the matrix is populated, other times, it is more difficult. The application of a dendogram or binary sort, can be helpful in these situations. Value stream analysis and, with it, flow kaizen, is central to any lean transformation and is specific to product or service families.

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