Work Units

One of the basic goals of lean is to create flow. The rationale is that the more that material sits in one place, the more waste it creates.

In most cases, this means a single piece of work moving through a connected process. This is where the term “one-piece flow” comes from. In some cases, though, it is okay for more than one item to move together.

The most common situation is when there is a set of finished goods that are used together. It could be a product with a matching pair, such as a pair of bookends. Another common case is when there is a group of parts that would be assembled together. A set of car doors may be worked on as a unit.

A final situation would be complementary parts. In most cases, these would be assembled separately and matched up at shipping, but on occasion you may see items grouped together earlier in a production process, especially if there is some sort of customization added to it. You might see a cordless phone and its charging base assembled together, for example, or a set of fireplace tools.

In these cases, where there is more than one item being worked on, they are grouped together into a single work unit. Things like takt time and cycle time would be managed in relation to that grouping rather than to the individual items.