Lean manufacturing focuses on the elimination of waste, formalizing a common source approach to machine design. Some general concepts to use when designing lean machines include,
- setups should be minimized or eliminated
- product changeovers should be minimized or eliminated
- make the tool fit the job, not the other way. If necessary, design a new tool
- design the machine be faster than the needed cycle time to allow flexibility and excess capacity - this does seem contradictory, but it allows better use of other resources. For example, if a worker takes a bathroom break, the production can continue with fewer workers.
- allow batches with a minimum capacity of one.
- people are part of the process and should integrate smoothly - the motions or workers are often described as dance like.
- eliminate wasted steps, all should go into making the part
- work should flow smoothly to avoid wasted motion
- do not waste motion by spacing out machines
- design "decouplers" to allow operations to happen independently.
- eliminate material waste that does not go into the product
- design the product so that it is easy to manufacture
- use methods that are obvious, so that anybody can understand - this makes workers portable and able to easily cover for others.
- design tools to reduce the needs for guards.
To achieve these principles the complexity of a machine may be increased to decrease the manual labor and setup issues. In lean manufacturing the ideal batch size is one with no switchover time.