Andon: Visual Shopfloor Signals That Actually Work

What is Andon?

Andon is a visual signalling system that makes production problems immediately visible to everyone on the shopfloor. Originating in Toyota's production system in the 1950s, it translates a machine state or a human "I need help" into a light, a sound, or a dashboard tile that cannot be overlooked. The name comes from the Japanese word for paper lantern, and the principle is just as simple: shine a light on a problem the moment it happens, so someone can react before it turns into a bigger one.

After 25 years of rolling out MES and shopfloor systems across Germany, China, Mexico and the US, I can say this plainly: every plant has some form of Andon. The difference between plants that benefit from it and plants that have accepted it as wallpaper comes down to two things, response discipline and integration with real data. A stack light that nobody reacts to is not Andon, it is decoration.

Why Andon matters in 2026

The reason Andon survived seventy years of production philosophy fashions is that it solves a problem every manufacturing environment still has: the gap between a problem occurring and someone with the authority to fix it knowing about it. In an average German mid-size plant, that gap is typically 8 to 15 minutes when measured honestly. Andon, done right, cuts it to under 60 seconds. Multiplied across a year of production, the compounding effect on OEE and first-pass yield is substantial, usually 3 to 6 percentage points on availability alone.

The classic signal logic

Traditional Andon relies on three status colours on a stack light, one per machine or station. The meaning is standardised enough that any new operator grasps it within minutes, which is part of the reason the system works.

On top of the stack lights, two mechanisms give the system its teeth. The Andon cord, the pull rope every operator can activate to stop the line, is the most cited Toyota innovation. It deliberately moves stop authority from supervision to the worker, which is culturally harder to implement than technically. The Andon board, the plant-wide display that shows the status of every station at a glance, turns local signals into a shared operational picture.

Where classical Andon breaks down

Three failure patterns account for the majority of dead Andon systems I have walked past over the years.

1. Signal fatigue. When the warning light fires twenty times per shift for issues that never get addressed, operators stop looking at it. This is the single most common reason Andon becomes wallpaper. The fix is not more lights, it is fewer, better calibrated signals with enforced response times.

2. No data behind the light. A red light tells you something is wrong. It does not tell you what stopped, for how long, how often this same problem occurred last week, or which station is the worst offender across the plant. Without data capture behind the signal, the Pareto of actual issues stays invisible and the same problems keep recurring.

3. No escalation enforcement. If a red light goes unanswered for 90 seconds and nothing happens, the system has failed. Toyota's original TPS defined hard escalation paths with timers. Most Western adaptations drop this part, and the cultural half of Andon dies quietly.

Digital Andon and the MES connection

Modern Andon rarely lives as an isolated system. It sits inside or alongside a Manufacturing Execution System, which changes what the signal can do. A PLC alarm triggers the light automatically, without operator acknowledgement. The stop reason is captured at source and tagged with a timestamp. The same event pushes a notification to the supervisor's phone and the shift lead's dashboard. The historical record feeds a Pareto analysis that tells the plant, at the end of the week, which three stop reasons caused 60 percent of lost time.

This is how Andon moves from being a reactive tool to being a structured improvement engine. The Neoperl assembly-line case is a textbook example, automatic Andon-style stop capture combined with PLC-level alarm correlation produced 10 percent fewer stops, 8 percent higher availability, and 15 percent less scrap within the first year, not by changing the equipment but by making the signals act on themselves.

What good digital Andon looks like

A useful digital Andon implementation, from 25 years of doing this wrong and then right, covers five capabilities:

• Automatic state capture from the PLC, not manual button presses. Sub-second resolution, no missed micro-stops.
• Multi-channel escalation. Floor light for the operator, dashboard tile for the shift lead, mobile push for the supervisor if the issue persists past a defined threshold.
• Structured stop reasons attached to every event, either automatically from the alarm code or chosen from a short, maintained list.
• Response-time metrics. Mean time to acknowledge, mean time to restore, with a visible leaderboard per shift. The cultural effect of making response time a KPI is usually larger than the tool itself.
• Historical Pareto and correlation. The part of Andon that actually moves the needle month after month, not the lights themselves.

Andon, OEE and the rest of the Lean toolkit

Andon is the escalation layer of a Lean plant. It feeds availability measurement, supplies the raw event stream for OEE analysis, and connects operationally to Jidoka (the principle of stopping at the first quality defect rather than producing scrap), Kaizen (the improvement cycle that uses the Andon data), and Lean Management more broadly. Without Andon the other tools run on lagging indicators. With honest Andon data, Kaizen circles argue about facts rather than opinions.

FAQ

Is Andon the same as an alarm system?
No. An alarm tells you something is wrong; Andon is a structured system of signal, escalation and response with a defined behaviour at every level. A plant with a thousand alarms and no Andon discipline has information noise, not a management tool.

Do we need an Andon cord in 2026?
Physical pull cords are rare outside automotive assembly lines. The function matters more than the form. A mobile app button, a touchscreen tile, or a foot switch that triggers the same escalation chain serves the same purpose. What cannot be compromised is the operator's authority to stop the line.

How many Andon signals is too many?
A rough working rule: if any single station triggers warnings more than three times per shift on average, the system is miscalibrated and will produce fatigue. Thresholds should be tightened until signals are rare enough to be meaningful.

Can Andon work in small-batch and high-mix production?
Yes, but the rule set has to adapt. High-mix environments often need product-specific thresholds rather than universal ones, because the "normal" cycle time varies by SKU. A modern OEE and production metrics platform handles this automatically based on the running order.

What does digital Andon cost?
If it is a module of an existing MES, typically nothing additional beyond the base licence. As a standalone bolt-on, commercial Andon software typically runs 50 to 150 EUR per machine per month. Hardware stack lights and I/O modules add a few hundred EUR per station, one-time. The ROI is almost always measured in weeks, not years.

How long does it take to roll out?
A focused pilot on one line, two weeks. Plant-wide rollout with integration to the MES and response workflow, two to three months for a typical mid-size plant. The hardware install is the fast part, the human side (response discipline, escalation culture) takes longer and determines whether the system sticks.

Related: Lean Management Methods · Process Monitoring · Machine Availability · OEE · MES · SYMESTIC Alarms · SYMESTIC Production Metrics

About the author

Christian Fieg

Head of Sales at SYMESTIC. 25+ years in manufacturing, including Johnson Controls, Visteon, iTAC and Dürr. Six Sigma Black Belt. Led global MES rollouts across 900+ machines in China, Mexico, USA, France, Tunisia and Russia. Author of OEE: Eine Zahl, viele Lügen (2025). · LinkedIn