Home › Resources › Glossary › Andon
Glossary

What is an Andon System?

The visual management tool that stops defects at the source — from Toyota's assembly line to your digital shopfloor.

Andon (行灯 — Japanese for "paper lantern") is a visual management system from the Toyota Production System (TPS). It communicates the real-time operational status of a production line using light signals: green (running normally), yellow (assistance needed), red (line stopped). Any operator who detects a problem can trigger the Andon — preventing defects from flowing downstream.

The Three Andon States

🟢
Green — Running
Production is proceeding normally. No action required.
🟡
Yellow — Caution
Operator needs assistance. Team leader responds before line stops.
🔴
Red — Stop
Line has stopped. Quality or safety issue. Immediate intervention required.

History: The Andon Cord at Toyota

In the original Toyota Production System, Andon was implemented as a physical cord or rope running along the assembly line. Any worker could pull the cord at any time to signal a problem — triggering the yellow light and a musical tone. A team leader would immediately respond to the problem zone.

If the issue was not resolved before the assembly line advanced to the next station, the line stopped automatically (red light). This embodied Toyota's jidoka principle — "intelligent automation with a human touch" — building quality into the process rather than inspecting it at the end.

In 2007, Tesla famously abolished the Andon cord in favour of digital equivalents — though they later reinstated the concept after quality issues. Today every major automotive, electronics, and aerospace manufacturer uses some form of Andon signalling.

Physical vs Digital Andon Boards

FeatureTraditional Light StackDigital Andon Board
Display typePhysical light column (stacklight)TV screen / tablet / web dashboard
Data richnessStatus only (3 colours)OEE, cycle time, downtime reason, alert history
Trigger methodManual cord pull or buttonAutomatic from OPC UA / PLC signal OR manual
Alert routingVisual + audio in areaScreen + email + SMS + push notification
Data loggingNoneFull history — time, duration, category, resolution
IntegrationStandaloneIntegrated with OEE, maintenance, shift handover

Andon and OEE Availability

Every red Andon event is an OEE unplanned downtime event — directly reducing Availability. Digital Andon systems that log the start time, end time, and coded reason for every stop provide the data needed to calculate both MTBF and MTTR.

The insight goes further: yellow Andon events (near-misses) identify quality risks before they become red stops. Tracking yellow events feeds Six Sigma DMAIC projects — the Measure and Analyse phases — without requiring additional data collection.

Frequently Asked Questions

What is jidoka and how does it relate to Andon?
Jidoka (自働化) is one of the two pillars of the Toyota Production System (alongside Just-in-Time). It means "automation with a human touch" — giving machines and workers the authority to stop the line when a defect is detected. Andon is the visual and alerting mechanism that makes jidoka visible. Without Andon, jidoka has no communication channel; without jidoka, Andon is just a light.
Can Andon be triggered automatically?
Yes — modern digital Andon systems receive signals directly from PLCs and CNC controllers via OPC UA. The machine reports its own state (running, idle, fault, toolchange) and the Andon board updates automatically. Automatic triggers eliminate manual entry delay — the board turns red the moment the machine stops, before any operator reports it.
What is the difference between Andon and SCADA?
SCADA (Supervisory Control and Data Acquisition) is a control-room system for monitoring and controlling industrial processes — primarily used by engineers and process technicians. Andon is a production-floor visual management tool — designed for operators, team leaders, and supervisors walking the shopfloor. SCADA collects the signals; Andon presents the status. Both can be fed from the same OPC UA data source.

Real-Time Andon Board for Your Shopfloor

Shopfloor Copilot's digital Andon board automatically displays line status, cycle time vs target, and active alerts — fed directly from OPC UA signals. No light stacks. No manual updates.

See the Andon Board →