In lean thinking, the ideal batch size is always the same—one. That is because Ohno was not trying to optimize the utilization of people and equipment in each department. When the Toyota factory was first organized, it was operating this way—like Ford's factories. But this didn't work, because Toyota could not compete with Ford's volume and economies of scale. So Ohno decided to optimize the flow of material so it would move more quickly through the factory. This meant reducing batch size. And the fastest way to achieve this was to blow up departments and "process islands" and create work
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