Flow is at the heart of the lean message that shortening the
elapsed time from raw materials to finished goods (or
services) will lead to the best quality, lowest cost, and
shortest delivery time.
You will not see Toyota just throwing together machines and
suppliers and forcing one-piece flow where it does not fit.
Taiichi Ohno wrote that it takes time and patience to achieve
flow...inventory buffers are used judiciously where continuous
flow is not possible today. But the ideal of flow provides a
clear direction. At Toyota it means that using small lots,
having processes close together, and keeping the material
moving through processes without interruption is better than
producing large batches of stuff and having them sit and wait