Japanese manufacturing guru Shigeo Shingo once told Toyota assembly line workers about his clever techniques to make production processes “idiot-proof.” One of the plant’s employees burst into tears. “I am not an idiot!” she cried. A stricken Shingo quickly recanted. He scrapped “idiot-proof” in favor of declaring his initiatives essential to making assembly lines “mistake-proof.”
Shingo’s trans-idiotic design insight was poka-yoke—Japanese for “avoid mistakes.” In effect, Shingo looked for the simplest, cheapest, and surest way to eliminate foreseeable process errors. To make sure an assembler uses three screws, for example, package the screws in groups of three. The package is a poka-yoke device.