# What Is an Andon System and How Does It Work? Making Line Problems Visible in Minutes

> What is an andon system and how does it work? Light vs digital andon, a 7-step setup, response time measures and tracking downtime through MES.

Source: https://digitalbridge.com.tr/en/blog/andon-system-explained.html
Publisher: Digital Bridge Teknoloji (https://digitalbridge.com.tr)
Topic: Industry 4.0
Published: 2026-10-27 · Updated: 2026-10-27

An [andon system](https://digitalbridge.com.tr/en/glossary.html#andon) is an alert system that lets a production line operator call for help the moment they spot a problem, using a button, pull cord or terminal, and makes that call instantly visible to the right team through lights, sound and display boards. The lean principle is simple: problems are exposed where and when they happen.

## Key takeaways

- Andon is a lean manufacturing tool from the Toyota Production System; operators flag a problem instantly by button, pull cord or terminal.
- Traditional light andon only provides visibility; digital andon records the time, reason and response time of every call.
- According to a 2024 Siemens report, large plants average 25 unplanned downtime incidents and lose 27 hours of production a month.
- A sound andon needs few call types, an owner for each, target response times and an escalation rule.
- Five measures to track with andon data: call mix, time to first response, time to resolution, escalation rate and repeat calls.

## How does an andon system work?

An andon system works by shortening the path between the person who spots a problem and the team that can fix it. In traditional andon, a call is announced only by a light and a sound. Digital andon goes a step further by recording the time, reason and response time of every call, so stoppages become measurable. Once connected to an [MES (Manufacturing Execution System)](https://digitalbridge.com.tr/en/glossary.html#mes), those records are matched to work orders and products.

A typical call in a digital andon system follows five steps:

1. **Call:** the operator presses a button, pulls the cord or selects a call type on a terminal; a call can also open automatically when a machine stops.
2. **Alert:** a stack light comes on, the call appears on the line display and the relevant team receives a mobile notification.
3. **Arrival:** the owner from maintenance, quality or logistics reaches the station and takes the call.
4. **Resolution and record:** the call closes when the line runs again; call, arrival and resolution times are stored with the reason.
5. **Escalation:** if nobody arrives within the target time, the call goes to the supervisor and then the production manager.

## What happens on a line without andon? A problem nobody knows about

On an assembly line without an andon system, a component runs out, a fixture fails or a part looks suspect. The operator has two options: leave the station to find a supervisor, or try to work round the problem and slow the line down. Either way, time is lost, and usually nothing is recorded.

At the end of the shift the report says "line down for 40 minutes", but nobody knows how much of that was waiting for maintenance and how much was the fault itself. Whether the same problem recurs at the same station every day is noticed only if someone happens to be paying attention. Maintenance, quality and logistics teams, meanwhile, have no idea which call is most urgent and go wherever the loudest voice is.

Andon exists to remove that uncertainty. Installing a light is not enough, though; you also have to define who receives each call, how quickly it should be answered and what happens if it is not.

## How much do unplanned downtime and slow response cost?

The value of an andon system comes from the cost of every minute that goes unnoticed or unanswered.

> According to Siemens' The True Cost of Downtime 2024 report, an hour of unplanned downtime costs **$2.3 million** in a large automotive plant and $36,000 in fast-moving consumer goods (FMCG) plants. ([Siemens – The True Cost of Downtime 2024](https://assets.new.siemens.com/siemens/assets/api/uuid:1b43afb5-2d07-47f7-9eb7-893fe7d0bc59/TCOD-2024_original.pdf))

Nor is it only about major breakdowns. The same [Siemens report](https://assets.new.siemens.com/siemens/assets/api/uuid:1b43afb5-2d07-47f7-9eb7-893fe7d0bc59/TCOD-2024_original.pdf) found that large plants average 25 unplanned downtime incidents a month and lose 27 hours of production a month. On average that is more than one stoppage every working day, and in each one the minutes before anyone starts to respond make up a meaningful share of the total loss.

The 2024 Siemens report also estimates that the world's 500 largest companies lose almost $1.4 trillion a year to unplanned downtime, equivalent to 11% of their revenues. Your plant's numbers will be different, but without knowing your own hourly cost of downtime it is hard to decide how much to invest in andon or any other improvement. Our article on [how to calculate OEE](https://digitalbridge.com.tr/en/blog/how-to-calculate-oee.html) (Overall Equipment Effectiveness) is a good place to build that baseline.

## What is the difference between light, digital and MES-connected andon?

Andon systems are built at three levels of maturity. The table below compares traditional light andon, digital andon and MES-connected andon on how calls are raised, alerted, recorded and analysed.

| Feature | Traditional light andon | Digital andon | MES-connected andon |
|---|---|---|---|
| How a call is raised | Button or pull cord | Button, terminal, tablet | Terminal, or automatically from a machine signal |
| Who is alerted | Anyone who sees the light | The relevant team by call type (display, mobile notification) | The team and named owner by call type and station |
| Reason recorded | No | Operator selects a reason | Reason recorded with work order and product |
| Response time | Not measured | Call, arrival and resolution times logged | Same data feeds OEE and downtime reports |
| Escalation | None | Next level notified when a target is missed | Rule-based escalation and shift reports |
| Analysis | Based on memory | Call Pareto, station comparison | Root cause analysis, linked to quality and maintenance systems |

Which level suits you depends on the size of the line and how you use downtime data today. Many plants start with lights and move to digital once they need measurement, but going digital from the outset avoids reworking wiring and station hardware later. Traditional light andon provides visibility but no measurement. Digital andon turns stoppages into data, and once connected to an MES that data feeds decisions on production planning, quality and maintenance.

## How do you set up an andon system? Seven steps that work

1. **Keep call types simple.** Four or five types, such as material, maintenance, quality and production support, are enough for most lines. Too many options leave the operator deciding instead of calling.
2. **Give every call type an owner.** Who receives a maintenance call, and who is next if that person cannot be reached? If responsibility is not written down, andon becomes just a flashing light.
3. **Set target response times.** For example, "maintenance at the station within five minutes", with escalation to the supervisor and then the production manager when the target is missed.
4. **Plan visibility for the station and the centre separately.** A stack light at the station, a screen at the head of the line and in the maintenance workshop showing calls in order, and mobile notifications for managers each meet a different need. We cover the content and management side of line screens in our [digital signage guide](https://digitalbridge.com.tr/en/blog/digital-signage-guide.html).
5. **Connect machine signals where you can.** If a call opens automatically when a machine stops, the operator only has to choose a reason, and short stops are captured too. On machines with no PLC (programmable logic controller), [retrofitting legacy machines](https://digitalbridge.com.tr/en/blog/retrofitting-legacy-machines.html) provides that signal. On CNC machine tools, status and alarm codes can be read directly from the controller, as explained in [CNC machine monitoring](https://digitalbridge.com.tr/en/blog/cnc-machine-monitoring.html).
6. **Support operators, do not blame them.** The operator who pulls the cord is making a problem visible, not causing it. A rise in calls in the early weeks is a good sign: hidden problems are surfacing.
7. **Review the data every week.** The station and reason with the most calls set the order for improvement work. For recurring quality issues, the [8D problem-solving method](https://digitalbridge.com.tr/en/blog/8d-problem-solving.html) works well with andon data.

## Which measures should you track with andon data?

The real gain from a digital andon system is the trail its calls leave behind. After a few weeks of data, review these measures regularly:

- **Call volume and mix:** which stations, shifts and call types stand out? Material calls concentrated at one station point to a problem with line-side supply.
- **Time to first response:** the gap between a call opening and the team arriving. If it is long, the problem is organisational rather than technical; the team may be based in the wrong place or calls may be going to the wrong person.
- **Time to resolution:** from arrival until the line is running again. Long resolution times suggest missing spares, training or work instructions.
- **Escalation rate:** the share of calls not answered within target. If it rises, revisit either the targets or resourcing.
- **Repeat calls:** calls raised at the same station for the same reason are your list of problems still waiting for a permanent fix. If maintenance calls cluster on one machine, the next step is [predictive maintenance](https://digitalbridge.com.tr/en/blog/predictive-maintenance-guide.html). Keeping the fault and repair history of those calls against each machine is the job of [CMMS maintenance management software](https://digitalbridge.com.tr/en/blog/cmms-maintenance-management-software.html).

Read andon measures by process, not by team. The aim is not to find out who was late but to understand why waiting happens. A short weekly review of these five measures turns andon from an alert system into a continuous improvement tool. Andon is one of the quickest wins in the visibility stage of our [Industry 4.0 roadmap for SMEs](https://digitalbridge.com.tr/en/blog/industry-4-0-roadmap-smes.html), and the downtime data it builds gives [production scheduling with APS](https://digitalbridge.com.tr/en/blog/production-scheduling-aps.html) realistic input.

## How Digital Bridge builds andon systems

At Digital Bridge, we do not recommend hardware until we understand how your line flows and how your teams work. Because our software and hardware are developed by the same team, we build the whole chain, from call button to display board, in one piece.

- **Line analysis.** We work with your teams to define stations, call types, owners and target response times. Site assessments for Industry 4.0 projects are free.
- **Station hardware.** For call buttons, stack lights and operator terminals, we use off-the-shelf products where they fit and design the circuit board, embedded software and enclosure ourselves where special mounting or a harsh environment demands it. Our rugged [industrial data terminals](https://digitalbridge.com.tr/en/industrial-products/industrial-data-terminals.html) can handle operator input.
- **Andon boards.** For the head of the line, the maintenance workshop and management offices, we install [digital signage displays](https://digitalbridge.com.tr/en/industrial-products/digital-signage-displays.html) showing open calls, waiting times and daily targets. They are a live window onto the system, not a board someone has to update by hand.
- **MES integration.** We connect andon data to our [MES production management](https://digitalbridge.com.tr/en/industry-40/mes-production-management.html) system, matching stoppages to work orders, products and shifts so OEE and downtime reports build themselves. Our MES integrates with Logo, SAP, Mikro (widely used Turkish ERP packages) and bespoke ERPs. If you are unsure how MES and ERP divide the work, read our article on [MES vs ERP](https://digitalbridge.com.tr/en/blog/mes-vs-erp.html).
- **Linked to quality.** Quality calls can become nonconformance records in our [quality management system](https://digitalbridge.com.tr/en/industry-40/quality-management-system.html), so there is no gap between a suspicion on the line and the quality team's record.

In sectors with frequent customer audits, such as automotive supply, response time and root cause records carry extra weight; our approach for that sector is on the [automotive suppliers solutions](https://digitalbridge.com.tr/en/industry-solutions/automotive-suppliers.html) page. For how stoppage and waiting data is captured in line-based garment production, see [textile production tracking](https://digitalbridge.com.tr/en/blog/textile-production-tracking.html). On every project, scope, stages and cost are set out in a written proposal after a needs analysis.

To see which work order an andon call has stopped, calls need to be tied to the work order record; we cover this in our article on [production work order tracking](https://digitalbridge.com.tr/en/blog/work-order-tracking-production.html).

## Where should you start with andon?

To introduce an andon system, you do not need to equip the whole factory at once. Starting with the single line that suffers most downtime shows within weeks which call types dominate and what response times really look like, and the decision to expand can be made on that data. Share your line layout and how you record stoppages today, and we will plan a pilot together. You can reach us through our [contact page](https://digitalbridge.com.tr/en/contact.html).

For the steps beyond the line, browse [our complete Industry 4.0 guide](https://digitalbridge.com.tr/en/blog/topic/endustri-40.html).

## Frequently Asked Questions

### What does the word andon mean?

Andon is a Japanese word for a paper lantern. In lean manufacturing it refers to the alert system that announces a problem on the production line visually and audibly, so the right team can respond at once. The term spread worldwide through the Toyota Production System. Today it ranges from simple stack lights to digital boards that record the time of every call.

### Is andon only for large factories?

No. Even on a small line with a few stations, andon shortens the time it takes an operator to get help and records why stoppages happen. The system scales with the number of stations, and starting with one line is perfectly feasible. In smaller businesses the main gain is eliminating the minutes spent looking for a supervisor and the stoppages that never get recorded.

### What is the difference between andon and MES?

Andon makes a problem visible immediately and gets it to the right team. An MES records the whole of production: work orders, output, scrap and stoppages. When andon is connected to an MES, call data is matched to work orders and products and becomes part of OEE and downtime reporting. One does not replace the other; andon is often the quickest first step towards an MES.

### Can existing machines raise andon calls automatically?

In most cases, yes. By reading the machine's stop signal or its current draw, a call can open automatically the moment it stops, leaving the operator only to select a reason, so short stops are captured too. We confirm which method suits each machine, including older machines without a PLC, during the free site assessment.

### How much does an andon system cost?

There is no single price, because cost depends on the number of stations, whether call points are buttons, pull cords or terminals, the size and number of display boards, and whether the system is connected to an MES. Starting with one line keeps the first step small. We confirm scope and cost in a written proposal after the site assessment.

### What should an andon display show?

The essentials are open calls, waiting times, and the station and type of each call. Adding shift target versus actual output and a daily downtime summary helps teams see priorities. Too much information makes a display unreadable, so keep it simple enough to read from several metres away and use colours consistently.