Lean teams use andon to surface problems while the evidence is still fresh. It makes stopping to fix a defect normal instead of risky. Over time, andon data shows which stations and causes need permanent countermeasures.
Where it comes from
Andon became part of the Toyota Production System as the visible side of jidoka. Toyota assembly lines used pull cords so any worker could flag a problem or stop the line.
At a glance
How an andon call works
Swipe sideways to see the whole diagram.
How to apply Andon
- 1
Define the trigger conditions
Agree on what counts as an abnormality: a defect, a missing part, a safety concern or falling behind takt. Make the list short and specific so operators never hesitate.
- 2
Design the signal
Choose signals that can be seen and heard from where responders work. Use consistent colors, such as yellow for help needed and red for line stopped.
- 3
Set the response rules
Name who responds to each signal and how fast. Set a response target the team can meet, so the team leader arrives in time to decide whether to fix or stop.
- 4
Train and protect the people who pull it
Explain that pulling the andon is expected, not a mark against anyone. Leaders should thank the person who raised the signal, every time.
- 5
Log every call
Record the station, time, cause and response time for each signal. Paper logs work, but digital andon makes trends easier to spot.
- 6
Review patterns and fix root causes
Review the log in daily meetings. Pick the most frequent causes and run problem solving so the same signal stops coming back.
Worked example (illustrative)
A packing cell adds a button at each station tied to a light above the line. When a carton jams, the operator presses it and the team leader arrives in under a minute on average. A week of logs shows 46 calls, and 31 of them come from one carton size, so the team adjusts the erector settings for that size. The next week brings 17 calls, with 4 from that carton.
Common mistakes
- Treating andon calls as failures, so operators stop using the system and hide problems.
- Installing lights and buttons without a defined responder or response time.
- Clearing each call without logging it, which throws away the data needed for root cause work.
When Andon is not the right tool
Andon only works if someone responds. Without a clear responder and a response target, calls go unanswered and people stop pulling the cord.
It also needs a culture where calling for help is welcomed, not blamed.
Andon cord
An andon cord is a rope or button at the workstation that any operator can pull when they see a problem. At Toyota, a pull lights a signal and calls the team leader, and the line stops at the end of the cycle if the problem is not fixed in time.
The cord only works if pulling it is safe and expected. Leaders thank people for pulling it, because each pull is a problem found early.
Andon board
An andon board is a display, often above the line, that shows the status of each station. Green means running, yellow means help called, and red means stopped. Many boards also show the shift target, actual output and downtime.
Digital andon systems send the call to a phone or watch and log each call, so the team can see which problems repeat. The andon software page lists tools for this.
Andon and jidoka
Jidoka is the principle of stopping to fix problems at the source. Andon is the signal that makes the stop visible and brings help.
Toyota describes workers being able to stop the line with a cord when they see an abnormality.
What to measure
Track calls by type, time to respond and time to resolve. A Pareto chart of call reasons shows which problems to solve first.
A falling number of calls can be good news or a sign that people have stopped calling. Check which one it is before reading it as progress.
A sample andon log and Pareto
These rows are illustrative, from the packing cell's first week. Each call records the station, time, cause, minutes to respond and minutes to resolve.
Station 3, 09:12, carton jam, 0.7, 4. Station 3, 10:40, carton jam, 0.9, 6. Station 1, 11:05, label missing, 1.2, 3. Station 4, 13:30, scale error, 0.8, 9.
Over the week, the 46 calls sort into carton jams 31, labels 8, scale errors 5 and other 2. The first bar holds two thirds of the calls, so that is where problem solving starts.
Guides on this topic
- How to measure OEE: start tracking without a big IT projectHow to measure OEE with a paper tracking sheet before buying software: what to record, how to calculate it and when OEE tracking is worth automating.Read the guide
- Lean manufacturing examples from shop floor to officePractical examples of lean in action: what the problem looked like, which lean tool was used and what changed, in factories and beyond.Read the guide
- Continuous improvement in lean: examples and strategiesContinuous improvement in lean explained: the PDCA cycle, daily kaizen and kaizen events, with practical examples and strategies that keep improvement going.Read the guide
- Gemba walk checklist: questions, form and routinesA gemba walk checklist with before, during and after steps, question sets for flow, safety and quality, a simple form layout and mistakes to avoid.Read the guide
Sources
Books and papers show their publication year. Web pages show the month we last checked them.
- 1.Jeffrey K. Liker, The Toyota Way: 14 Management Principles from the World's Greatest Manufacturer (McGraw-Hill, 2004)
- 2.Taiichi Ohno, Toyota Production System: Beyond Large-Scale Production (Productivity Press, 1988)
- 3.Toyota Motor Corporation, Toyota Production System (global.toyota, checked October 2026)