Jidoka

Origin. Sakichi Toyoda's automatic loom (1896) that stopped when a thread broke; generalized at Toyota as "automation with a human touch."

Mechanism. Machines detect abnormalities and stop themselves. The operator is freed from monitoring and can manage multiple machines. When a machine stops, the abnormality is made visible and addressed immediately rather than producing defects continuously. The human role shifts from monitoring to problem-solving.

Procedure. Build detection into the process: when output deviates from specification, stop automatically. Signal the stoppage visibly (andon). The operator investigates, fixes the immediate problem, and addresses the root cause so the problem does not recur. Do not restart until the root cause is addressed. Never pass defects downstream.

Applies to. Manufacturing, software builds and tests (stop on failure), any automated process where undetected errors propagate.

Limitations. Stopping too often. If the detection threshold is too tight, the line stops constantly for noise rather than signal, and operators become desensitized or override the stops. The threshold must distinguish real abnormalities from acceptable variation. Also: jidoka requires the capacity to stop — just-in-time systems with no buffer cannot stop without starving downstream.