Poka-yoke

Poka-yoke is a Japanese term meaning "mistake-proofing" or "error prevention", formalized by Shigeo Shingo as part of the Toyota Production System. It refers to mechanisms that help operators avoid mistakes by preventing, correcting, or drawing attention to errors as they occur. Originally called baka-yoke ("fool-proofing"), the name was changed to the milder poka-yoke. Examples include car interlocks requiring clutch or brake pedal depression before starting, and microwave ovens that cannot run with the door open. Shingo distinguished between inevitable human mistakes and defects, aiming to design processes that detect and correct mistakes immediately. He recognized three types: contact method (physical attributes), fixed-value method (number of movements), and motion-step method (sequence of steps). Benefits include reduced training time, elimination of quality control operations, fewer rejects, and 100% built-in quality control.