An andon board is a visual display system that communicates the real-time status of a production line or process to everyone in the area. When a problem occurs, the board signals it immediately. Everyone can see the issue, its location, and its severity without delay. No one has to search for a supervisor or wait for a report. The problem is visible the moment it starts.
The andon board is one of the most enduring tools of the Toyota Production System. Its origins trace back to the early twentieth century. Its principles apply today in manufacturing, healthcare, software development, and logistics.
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Meaning of Andon Board
An andon board is a visual management tool used in Lean manufacturing to display the real-time status of a production line or process. It uses a color-coded signal system — typically green for normal operation, yellow for an issue requiring attention, and red for a line stoppage — to make problems immediately visible to all workers and supervisors on the floor.
The andon board originated at Toyota as part of the Jidoka principle, which calls for detecting abnormalities immediately and stopping work to address them. Toyota’s own corporate history records that andon boards were installed at the Kamigo Plant in 1966, completing what Toyota describes as “line automation with a human touch.”
Key Takeaways
- The word “andon” (行灯) is Japanese for a traditional paper-covered lantern. In manufacturing, it was repurposed to mean a signal that makes problems visible.
- The andon concept traces to Sakichi Toyoda’s 1896 invention of a power loom that stopped automatically when a thread broke. Once a machine could detect its own abnormality, a system was needed to make that abnormality visible to humans.
- Toyota’s official corporate history records that andon boards were installed at the Kamigo Plant in 1966, described as completing “line automation with a human touch.”
- Taiichi Ohno, creator of the Toyota Production System, identified the andon board’s ability to show “the location and nature of trouble situations at a glance” as its key function.
- The andon system is a direct application of Jidoka, one of the two pillars of the Toyota Production System alongside Just-in-Time. Jidoka means detecting an abnormality, stopping work, and signaling for help before the problem travels downstream.
- Standard andon boards use three colors: green (normal), yellow (attention needed), and red (line stopped).
- Andon systems exist in manual form (a worker pulls a cord or pushes a button) and automated form (sensors detect the abnormality and trigger the signal without human input).
- In Lean Six Sigma, andon boards support the Control phase of DMAIC by providing real-time visual signals that trigger a documented response before defects compound.
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What Is an Andon Board?
An andon board is a physical or digital display that shows the operational status of a production line or process in real time. It sits in a visible location — typically overhead or on a large wall display — where every worker and supervisor in the area can see it without moving from their station.
The board’s fundamental purpose is to eliminate delay between when a problem occurs and when the right people know about it. In a factory without an andon system, a problem might occur at one workstation and go unnoticed until defective parts reach final inspection, or until a supervisor does a floor walk. By then, hundreds of defective units may have been produced.
The andon board makes that delay impossible. The moment a problem is detected, the board signals it. The response begins immediately.
Toyota’s official corporate history describes the principle precisely: “Problem notification devices known as andon boards and andon lights are installed on each line in positions that are highly visible to supervisors, and when a problem occurs, andon are lit up — either manually or automatically — so a supervisor can immediately come to the source of the problem and address it.”
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The Origin of the Andon Board
Sakichi Toyoda and the Automatic Loom
The word “andon” means paper lantern in Japanese — a simple light that makes something visible in the dark. The manufacturing use of the term follows the same logic: the andon makes problems visible on the production floor.
The concept has roots in the work of Sakichi Toyoda, the founder of what would become the Toyota Group. In 1896, Toyoda invented an improved power loom with an automatic thread-breakage stopping device. When a thread broke, the loom stopped itself immediately. Before this invention, a thread breakage caused the loom to keep running and produce meters of defective fabric before an operator noticed the problem.
Toyoda’s loom solved two problems at once. It detected the abnormality automatically. And it stopped production before the defect multiplied. The Lean Enterprise Institute traces the origins of Jidoka directly to this 1896 invention.
Taiichi Ohno and the Toyota Production System
After World War II, Taiichi Ohno developed the Toyota Production System through years of testing and refinement at Toyota’s Honsha Machinery Plant. Ohno built the system on two pillars: Just-in-Time and Jidoka.
Jidoka — sometimes called “autonomation” or “automation with a human touch” — is the principle of designing processes so that problems trigger an immediate stop and a visible signal. The andon board was the visual tool that completed the Jidoka principle.
Toyota’s 75-year corporate history records a specific milestone: “Andon were installed in the Kamigo Plant in 1966, completing line automation with a human touch.” This date, 1966, marks the formalization of the andon board as a standard element of the Toyota Production System.
The Art of Lean encyclopedia, one of the most thorough independent sources on TPS, notes that Ohno’s andon was “not a single invention but an evolutionary development within the broader jidoka pillar of TPS.” It developed over decades of production experience, not as a planned design specification.
How an Andon Board Works
The andon system operates on a simple, repeatable sequence.
Step 1: Detect the abnormality. A worker notices a quality problem, a parts shortage, a machine malfunction, or any condition that prevents normal operation. In an automated system, a sensor detects the condition without human observation.
Step 2: Signal the problem. The worker pulls the andon cord, pushes a button, or the automated system triggers the signal. The andon board displays the location and type of problem. The signal color changes from green to yellow or red.
Step 3: Respond within the time window. A team leader or supervisor sees the board and moves to the location. Standard andon protocols set a time limit for the yellow-light response — typically one to two minutes. If the supervisor resolves the problem within the time limit, the line continues. If not, the signal escalates to red.
Step 4: Stop the line if needed. A red signal stops the entire production line. No additional product moves downstream until the problem is resolved. This is the Jidoka principle in practice: the line does not move defective work forward.
Step 5: Investigate and fix. The team identifies the root cause. They implement a countermeasure. The line restarts.
Vorne Industries, a manufacturer of Lean tools and a recognized Lean manufacturing reference, describes this as the Andon’s core discipline: operators and supervisors “worked together to resolve the issue in a way that would prevent it from recurring.” The goal is not just to restart the line. It is to prevent the same problem from triggering the andon again.
Also Read: Six Sigma Principles in Amazon’s Operations and Reducing Wait Times
The Three-Color Andon System
The standard andon board uses three colors. Each color communicates a specific status.
Green: Normal operation. Everything on the line runs as expected. No action is required.
Yellow: Attention needed. A worker has detected a problem. The problem has not yet stopped the line. A supervisor must respond within the company’s defined time limit. In most Toyota-influenced production systems, the response time for a yellow light is one to two minutes.
Red: Line stopped. The problem exceeded the yellow-light response window, or the problem was severe enough to require an immediate line stop. Production does not resume until the root cause is addressed.
Some andon systems add a fourth color. Blue or white indicates a scheduled downtime or planned maintenance event rather than an unplanned problem. This prevents scheduled stops from appearing as quality emergencies.
Andon Cord vs. Andon Board
These two terms are often confused because they describe different parts of the same system.
| Term | What It Is |
| Andon cord | The physical trigger mechanism — a rope or cord that workers pull to signal a problem. Pulling the cord activates the signal on the andon board. Also called the andon pull cord or andon rope. |
| Andon board | The visual display that shows the status of the line. The board receives the signal from the cord or sensor and displays it to everyone in the area. |
| Andon system | The complete system combining the trigger mechanism (cord, button, or sensor), the display (board or lights), and the response protocol. |
Toyota itself began replacing the traditional overhead andon cord with waist-high buttons in some plants from 2014 onward, removing overhead clutter and improving ergonomics. The Art of Lean encyclopedia records this change explicitly. The cord changed form. The principle did not.
Types of Andon Systems
Manual Andon
A worker physically activates the signal by pulling a cord, pressing a button, or touching a screen. Manual andon requires workers to recognize the problem and choose to signal it. This requires a culture where workers feel empowered to stop production without fear of blame.
Toyota’s official process at many plants states that operators are encouraged to pull the andon any time they observe a problem. According to Vorne, this cultural dimension is what separated Toyota from competitors: workers were treated as the primary source of quality detection, not as interchangeable parts of the machine.
Automated Andon
Sensors, cameras, or machine monitoring systems detect abnormalities automatically and trigger the andon without human intervention. An out-of-tolerance dimension, a missed assembly step, or a machine parameter deviation can all trigger an automated andon signal.
The Kaizen Institute describes this as the full realization of Jidoka: “implement anomaly detection mechanisms using sensors and monitoring devices to identify process instabilities in real time.” When both detection and signal are automated, human intervention is needed only to fix the problem, not to find it.
Digital Andon
Digital andon systems replace physical boards with network-connected displays and dashboards. They track alerts, response times, resolution times, and recurring problems across an entire facility or multiple locations. Management teams can monitor line status from any screen.
Amazon’s “Virtual Andon” operates on this principle at a supply chain scale. When a customer reports a defective product or an inaccurate product listing, an automated system flags the issue and alerts representatives. If the problem persists, the system can halt shipments of the affected product — a digital version of stopping the line.
Andon Boards and Lean Six Sigma
Andon boards are a Lean tool, and Lean and Six Sigma are frequently combined in practice. The two frameworks serve different functions. Together they cover both the detection of problems and the systematic elimination of their root causes.
The andon board supports the Control phase of DMAIC. After a Six Sigma project identifies and eliminates the root causes of a defect in the Analyze and Improve phases, the Control phase builds the mechanisms to detect if the problem returns. The andon board is one of those mechanisms.
A completed control plan specifies what triggers an andon signal, what color that signal activates, who responds, within what time limit, and what investigative steps follow. When the andon board signals a problem that the DMAIC project was designed to prevent, the response plan addresses it before the defect rate climbs back toward the pre-project baseline.
Andon boards also connect to Six Sigma’s broader philosophy of building quality into the process rather than inspecting it out at the end. The andon stops production at the point where the defect occurs. It does not wait for the defect to reach final inspection. This is the Jidoka principle applied at production speed, and it aligns directly with Six Sigma’s goal of reducing defects at the source.
Frequently Asked Questions: Andon Board
Q: What is an andon board?
A: An andon board is a visual display system used in Lean manufacturing to show the real-time status of a production line or process. It uses a color-coded system — green for normal, yellow for a problem requiring attention, and red for a line stoppage — to make abnormalities immediately visible to all workers and supervisors.
The andon board originated at Toyota as part of the Jidoka principle and was formally installed at Toyota’s Kamigo Plant in 1966, according to Toyota’s official corporate history.
Q: Where does the word “andon” come from?
A: “Andon” (行灯) is a Japanese word for a traditional paper-covered lantern used for lighting in homes and businesses. The word was adopted in manufacturing because the andon system serves the same basic function as the lantern: making something visible. Just as a lantern illuminates a dark room, an andon board illuminates problems on the production floor. Taiichi Ohno and Toyota’s production engineers repurposed the term within the Toyota Production System.
Q: What is the difference between an andon board and an andon cord?
A: An andon cord (also called a pull cord or andon rope) is the trigger mechanism — the physical means by which a worker signals a problem by pulling the cord or pressing a button. The andon board is the visual display that shows the resulting signal to everyone in the area. Together with the response protocol, the cord and board form the complete andon system. Toyota began replacing traditional overhead cords with waist-high buttons in some plants from 2014 onward.
Q: What do the three colors on an andon board mean?
A: Green means normal operation — the line runs without problems. Yellow means a problem has been detected and a supervisor must respond within a set time limit, typically one to two minutes. Red means the line has stopped because the yellow-light window expired without resolution, or the problem was severe enough to require an immediate stoppage. Some systems add a fourth color, blue or white, for planned maintenance or scheduled downtime.
Q: How does an andon board connect to Jidoka?
A: Jidoka is one of the two pillars of the Toyota Production System. It means detecting an abnormality, stopping the process, and signaling for help before the defect travels downstream.
The andon board is the visual tool that completes the Jidoka cycle: once a machine or worker detects a problem and stops production, the andon board makes that problem immediately visible to supervisors so they can respond. Without the andon board, Jidoka stops the line but does not communicate the problem. The board provides the visibility.
Q: How does an andon board fit into a Lean Six Sigma project?
A: The andon board is primarily a Control phase tool in a DMAIC project. After the Analyze and Improve phases identify and eliminate root causes of a defect, the Control phase builds mechanisms to detect if the problem returns. The andon board provides real-time visual signaling when a control limit is breached.
The control plan specifies what triggers each andon signal, who responds, within what time, and what investigation follows. The andon system ensures that a process improvement does not quietly erode after the project team moves on.
Q: What is a virtual or digital andon system?
A: A digital andon system replaces physical boards with network-connected displays and dashboards. It tracks alerts, response times, and resolution data across multiple production areas or locations.
Management can monitor line status remotely in real time. Amazon’s Virtual Andon is a well-known example: it detects customer-reported product defects or inaccurate listings and automatically alerts representatives, with the ability to halt shipment of affected products — a digital version of stopping the production line.
Andon Training in Lean Six Sigma
The andon board is one of the visual management tools introduced in Lean and Six Sigma training. Yellow Belt programs introduce it as a basic visual factory concept. Green Belt programs connect it to the Lean 5S methodology and the Control phase of DMAIC. Black Belt programs address how andon data feeds into Statistical Process Control and how alert patterns identify recurring root causes that require a new improvement project.
At Six Sigma Development Solutions Inc, visual management tools including the andon system are taught in the context of real DMAIC projects and Lean implementation scenarios.
We offer training in three formats:
- Onsite training — delivered at your facility, often including a live visual factory assessment using your current visual management systems.
- Live virtual training — instructor-led sessions online, covering Lean tools including andon boards and their integration with Six Sigma’s DMAIC framework.
- Online training — self-paced Yellow Belt, Green Belt, and Black Belt certification programs covering all IASSC-testable Lean and visual management content.
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