How andon works
- An abnormality occurs: a defect, a missing part, a machine fault, a safety concern, or an operator falling behind takt.
- The operator signals by pulling the andon cord or pressing a button at the station.
- The signal shows on an andon light stack at the station and on an andon board visible across the area, often with the station number and the type of problem.
- A team leader responds within an agreed time, typically before the next cycle completes.
- The line keeps running or stops depending on whether the problem is resolved in time. At Toyota the line stops at a fixed position if the leader cannot clear the signal.
- The problem is recorded so recurring andon calls can be analysed and eliminated.
Types of andon
- Andon cord or button: the operator's way of calling for help.
- Andon light: a stacked light at the station, usually green for normal, yellow for help requested, red for stopped.
- Andon board: an area display showing the status of every station, counts of calls, and often production against target.
- Digital andon: the same signals on screens and phones, with calls logged automatically.
Why it matters
Andon is the practical expression of two lean principles: stop and fix problems at the source (jidoka), and respect for people, because the operator is trusted to call a halt. It also produces data: the pattern of calls shows which stations, parts and problems need improvement.
Andon and daily management
Yesterday's andon calls are a standard item for the Tier 1 huddle: how many, where, why, and which ones are repeating. Chronic causes move into structured problem solving; the fix is verified when the calls stop.
Common failures
- Operators punished, directly or subtly, for pulling the cord, so calls stop and problems go underground.
- No response standard, so the signal is ignored.
- Calls not recorded, so the same problems recur without anyone noticing the pattern.