This article is for plant managers, production managers, maintenance and continuous improvement leaders who have installed an andon, or are about to, and want it still to matter six months from now. It addresses a practical question: how to feed the andon with stops reported automatically by the machines, with which thresholds, and how to organize the response so that an alert triggers action instead of indifference. For the fundamentals of andon and line-stop authority, see our andon guide.
- An andon fed only by operator calls misses machine stops and short stops.
- Machine signals say when the line stops, the operator says why.
- Written yellow and red thresholds, tied to cycle time, prevent constant alarms.
- Every alert has an owner, and the OEE review handles cumulative micro-stops.
An andon is only as good as the signal behind it
Pulsa, a French industrial performance consultancy, published Andon Board : rendre les anomalies visibles en temps réel (in French) on its blog. The article explains how an andon board works, its color code (green when everything runs, yellow when a problem is reported and being handled, red when a problem blocks the line), and its benefits: visibility on where the problem is and what kind it is, accountability for the people in charge of solving it, and a history that brings recurring incidents to light. The sentence that sums up the stakes: “Placé à la vue de tous, l’Andon board permet donc d’informer en temps réel les équipes de la survenue d’un incident.” (in other words: placed in full view of everyone, the andon board informs teams in real time that an incident has occurred).
That article provides the method and the visual management logic. This one looks at what happens upstream of the screen: where the signal comes from. On many lines, the andon relies entirely on the operator’s call. That works for quality, safety or a material shortage. For machine stops it is more fragile: the operator is busy restarting, the call goes out late or not at all, and short stops are never reported. The screen stays green while the line loses time.
Which machine signals should trigger an alert
A running machine emits a simple signal: a cycle, a part, a movement. When that signal stops or slows down, you know something is happening without waiting for someone to say so. Here are the most useful signals for an andon and how to use them.
| Measured signal | What it indicates | Use in the andon |
|---|---|---|
| No cycle beyond a threshold | The machine is stopped | Turns yellow, then red if the stop lasts |
| Cycles slower than nameplate rate | Speed drift, slowdown | Yellow alert if the drift persists over a defined window |
| Repeated micro-stops | Feeding, setting or sensor problem | Alert on frequency (stops per hour), not on each micro-stop |
| Unqualified stop | No reason has been entered | Reminder to the team leader to qualify the stop |
| Operator call | Quality, safety, material, help | Stays manual: the person knows |
The principle: the machine says it has stopped, the person says why. Both sources complement each other on the same screen.
Setting duration thresholds: when a stop becomes an alert
An andon that turns red at every second of downtime becomes background noise. An andon that waits ten minutes arrives too late. Thresholds are built line by line, with a simple method.
- Start from the nameplate cycle time. It gives the basic unit: a stop is judged in lost cycles, not in absolute seconds.
- Separate micro-stops from stops. Write down the duration below which a stop counts as a micro-stop. Micro-stops do not trigger the andon one by one: you watch their frequency.
- Define the yellow threshold. Beyond the micro-stop threshold, the stop turns yellow and the first level is notified. For example, on a line running a 20-second cycle, a team might choose to turn yellow after 2 minutes of downtime.
- Define the red threshold and escalation. If the stop lasts beyond a second threshold, it turns red and the next level is called. This threshold depends on how critical the machine is: shorter on the bottleneck.
- Review the thresholds after a few weeks. If the andon goes off too often without action, the threshold is too low. If long stops pass without a response, it is too high. Thresholds are tuned on measured data, not on impressions.
Who responds, and how fast
The Pulsa article stresses accountability: a visible problem needs an owner. With stops reported automatically, that accountability can be written down in an escalation matrix. Level 1: the team leader or setter, notified at the yellow threshold. Level 2: maintenance or quality, depending on the type of stop, notified at the red threshold. Level 3: the production manager, if the stop hits the bottleneck or exceeds a defined duration.
Two times deserve tracking. Response time, between the start of the stop and the arrival of the right person. Resolution time, between the start of the stop and the restart. When the start of the stop is timestamped by the machine itself, neither depends on anyone’s memory any more. They become indicators you can review every week, shift by shift.
Avoiding the andon nobody looks at
Many andons end up as decoration. The causes are almost always the same:
- Too many alerts. Thresholds set too low turn every micro-stop into an alarm. The team learns to ignore the screen.
- Alerts without an owner. If nobody is explicitly in charge of responding to yellow, everyone waits for red.
- A screen far from the floor. An andon in an office or at the end of an aisle warns nobody at the right moment.
- Stops never qualified. Without a reason, the history is useless and the same stops come back.
- No review. If the week’s alerts are never discussed in a meeting, the andon stays a reaction tool, never an improvement tool.
The rule that works best: every alert has an owner, every long stop has a reason, and every week the team reviews the ten alerts that cost the most time.
Linking the andon to OEE and micro-stops
The andon and OEE do not answer the same question. The andon says what is happening now and who needs to move. OEE says what the line actually produced compared with what it could have produced, over a shift, a week, a month. The two feed each other: the stops that trigger the andon are the same ones that lower availability, and reported slowdowns weigh on performance.
Micro-stops are the typical case. One by one, they do not justify an alert. Added up over a shift, they can account for a large share of lost time, invisible on the andon as on manual logs. Measured OEE, with a Pareto of stops by duration and frequency, is what brings them to light and supports the decision to launch an improvement project.
This is where TEEPTRAK fits. A module wired into the electrical cabinet and an edge-mounted sensor at the line automatically detect stops, micro-stops and actual speed, with no connection to the PLC. Installation takes about one hour per machine and OEE is available within 48 hours. Timestamped stops can feed alerts and the weekly review, while the team keeps control over qualifying the causes. TEEPTRAK is deployed in more than 700 plants in more than 30 countries.
Further reading
- Andon Board : rendre les anomalies visibles en temps réel (Pulsa, in French)
- What is Andon and why is line-stop authority the core of it?
- Injection molding presses: tracking downtime and cycle time drift in real time
FAQ
Should the operator call button go once stops are detected automatically? No. The machine knows it has stopped, but only the operator knows that material is missing, that a part looks wrong or that there is a safety risk. Both sources complement each other on the same andon.
After how long should a stop trigger the andon? There is no universal value. Start from the cycle time and how critical the machine is, write down a yellow and a red threshold, then adjust them after a few weeks based on how many alerts were actually followed by action.
Should micro-stops appear on the andon? Not one by one, or the screen becomes unreadable. Watch their frequency over a time window instead, and deal with them in the OEE review, where their cumulative weight becomes visible.
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