132 ◾ Lean Production Simplified, Third Edition
◾ A machine will not start if a work piece is incorrectly positioned. The
on switch sends a weak electric current to reference pins, and only
when the part makes contact with each pin will the machine start.
◾ A tapping machine stops because the metal sensor fails to detect a
washer at each drilling point.
A final example of the shutdown poka-yoke is the so-called full-work sys-
tem wherein a supplier process stops feeding the downstream process when
it is full (i.e., when the desired number of parts have been provided).
Warning
Warning poka-yokes alert us to abnormalities by activating a buzzer or light.
The most famous is perhaps the Toyota andon board, which alerts the group
leader to problems ...