What are andon systems?

In ‘ancient’ Japan, Andon was a paper lantern (a handy vertically collapsible paper lampshade with an open top and a candle placed at the central section of the closed bottom). To the ancient Japanese, Andon functioned as a flashlight, a signaling device in distance, or even a commercial sign.

However, now:

Andon - is an visual (and often auditory) process cue. For example a light that signals all is well (green light), when stock is running low (or a machine is nearing time for service) (yellow light) and when a machine is down or stock is empty (red light).

An Andon system is

one of the principle elements of the Jidoka quality-control method. It gives the worker the ability to stop production when a defect is found, and immediately call for assistance. Common reasons for manual activation of the Andon are part shortage, defect created or found, tool malfunction, or a safety problem exists. Work is stopped until a solution has been found out. The alerts may be logged to a database so that they can be studied as part of a continuous-improvement program.

In fact:

Workers at the Toyota plant in Georgetown, Kentucky, pull the cord 2,000 times a week - and their care is what makes Toyota one of the most reliable, and most desired, brands in the US.In contrast, workers at Ford’s brand-new truck plant in Dearborn, Michigan, pull the cord only twice a week - the legacy of generations of mistrust between shop-floor workers and managers.