A Group Technology Workcell Example

The cell above has the classic U-shape but it does not operate like a Toyota Cell. This cell produces about 85 different turned parts. These are shafts and shafts with integral pinions and/or splines. Arrows show the sequence for three of these many parts.

All parts have dedicated carts for handling and storage. They serve as material handling devices, containers and kanban. Perimeter carts are a kanban stockpoint.

The internal lot size (transfer batch) is one cart (16 parts). External lot size varies from 16-48 parts in multiples of 16.

Work times are highly variable and unbalanced. The hobbing machine (7-1) is extremely slow while the NC lathe is fast. The product mix was carefully selected to include some parts that require hobbing and many others that do not.

Operators schedule their work from kanban signals. They must schedule non-hobbed parts immediately after a hobbed part. If they did not, the slow hobber would bring output to a crawl. They may have 2-3 part numbers underway at the same time.

Operators stay alert because the variation in cycle time means that machines finish at unforeseen moments. Operators constantly move from one machine to another, loading and unloading. Small queues highlight temporary bottlenecks which get special attention.

Some drilling and milling might have been done on the NC lathe using special attachments. But, we chose to make these secondary operations to reduce machine time on the lathe. These operations occur internally to lathe turning and cell output increases as a result.

While the whole arrangement may seem like a recipe for chaos, it actually works quite well. It is not nearly as smooth as a classic Toyota cell but it is far better than the genuine chaos of a functional layout.

A lot depends on the operators. Here, they were skilled and experienced machinists. With kanban, we knew they could figure out what part to run.