Andon is a visual feedback system that makes production status visible to everyone on the shop floor at a glance. In its simplest form, an andon is a light stack on a machine: green means running normally, yellow means attention needed, red means stopped. In its most developed form, andon is a culture — any operator can stop the line when they detect a problem, triggering an immediate team response.
The andon concept originated at Toyota, where operators are empowered (and expected) to pull the andon cord when they encounter a quality issue, missing part, or process abnormality. The line does not restart until the problem is addressed. This contrasts with the traditional approach of flagging the issue and sorting it out later, which allows defects to accumulate and root causes to remain hidden.
Modern digital andon systems extend beyond simple lights to real-time dashboards that aggregate machine status, production counts, downtime reasons, and quality alerts across the entire shop floor. Connected to machine monitoring systems, digital andons can automatically detect anomalies — spindle load spikes, cycle time deviations, temperature excursions — and alert operators before problems become defects.