Andon

Andon is a lean manufacturing visual and acoustic signal that flags an abnormality on the floor in real time. The Japanese word refers to a paper lantern. On a plant it means a stack light, overhead board, cord pull, or digital alert that says this station needs help now. Operators and machines raise it for quality defects, material shortages, safety hazards, or equipment stops.

Plant teams care because the signal is only half the job. Someone still has to notice it, decide who should act, and find that person while the clock on MTTR or lost takt keeps running. Radio calls and walking the hall fill that gap. Each step adds minutes and noise. When the light is red and the right tech is two bays away, the board alone cannot close the loop.

On an operational digital twin, the andon event sits next to people, material, and mover location so the first alert can go to whoever is already closest and free. That pattern is walked under andon still starts with a signal, but the next step changes. The same join shows up when an andon wait is really a kit still in transit, as in cross-system clues on the operational twin.

Key Components

Trigger: Cord, button, HMI key, or automatic trip from a PLC or sensor when a limit is breached.

Local stack light: Color tower at the station. Green for normal, yellow for help while running, red for stop or critical fault is the common plant grammar.

Andon board: Overhead or digital display that shows which bay, how long, and often which maintenance skill is needed across the line or hall.

Escalation and response: Who gets notified, how they acknowledge, and how arrival and clear times are logged for later review.

System of record link: Feed into MES, CMMS, or a twin so the event becomes a timestamped stop, not only a light that goes out.

Applications in Manufacturing and Logistics

Discrete lines use andon to protect quality and takt. An operator who cannot finish a fastener in cycle time pulls yellow so a team lead can help before the defect rides downstream. If the issue will not clear, the line goes red and stops on purpose. That is jidoka in floor language: stop when abnormal, fix at the source.

Logistics and fulfillment adapt the same idea for material and handling. A picker flags a bad scan, damaged tote, or empty pick face. A pack station lights material shortage. Support walks less when the alert carries aisle or bay context and the live map shows who is nearby. twinzo and similar operational twins do not replace the cord or board. They shorten the hunt after the signal in production monitoring and when kit location explains an andon under internal logistics optimization.

Maintenance uses andon as the start of the response clock. Time from light to first on-station presence is often a larger share of restore time than the wrench work itself. Spares placement and tech location against andon events are covered under maintenance optimization with RTLS.

Benefits and Challenges

Benefit: fast visibility of breaks in standard work, cultural permission to stop for quality, and logged stop data for OEE and kaizen. Challenge: alarm fatigue when thresholds are noisy, blame culture that teaches people not to pull the cord, and escalation lists that ignore where people actually stand. A bright board still loses if the nearest free tech is never told.

Related Terms

Lean manufacturing is the home system. Kaizen uses andon history to find recurring stops. MES often owns the digital andon state. Work orders open when maintenance must act. MTTR measures restore time after the signal. Bottlenecks show where andons cluster. An operational digital twin places the signal next to people and material location.

Frequently Asked Questions

Does every andon pull stop the whole line? No. Many plants use yellow for help while the line still runs, and red only when the issue will not clear in remaining cycle time or when safety demands an immediate stop.

Is andon only for production? No. Logistics, maintenance, and quality stations use the same pattern whenever a local abnormality needs fast support.

Do we need sub-meter location to act on andon? Usually not. Knowing which bay raised the signal and which people or kits sit within about 1–3 m (3–10 ft) of medium-precision location is enough to pick the first responder and check material causes.

Should the twin replace the physical andon? No. Keep the cord, stack light, and board as the floor language. Use the twin to route the next person and to join andon state with kit and mover location so the cause is not guessed after a long walk.