Andon

An andon light is one of the basic tools of Lean and is one of the most common forms of visual management that you will hear about in Lean.

In Lean, andon refers to a signal used to call for help when an abnormal condition is recognized, or that some sort of action is required. The most common andon lights you will see are those used to request assistance on an assembly line.  In the office, an andon will announce that a piece of equipment, like a fax machine, is having problems.

Andon comes from an old Japanese word for paper lantern.  An everyday example of an andon is the warning light on your car’s dashboard that indicates when the gas tank is getting close to empty.

Andons are very powerful tools if they are used correctly. The best andons are visible from at least ten feet away and they are accompanied by a clear reaction plan. 

Andons need to do more than just point to a problem. An andon must go hand in hand with a plan for action.  In the example of the car, the warning light tells you not only what the problem is, but you know exactly what you need to do to fix it (fill up at a gas station sooner rather than later.)

Andons help minimize production difficulties because they rally support when problems arise. Andon lights are also the foundation for jidoka (autonomation).

In practice, you might see the following scenario take place:

1. A worker can’t find a tool she needs to do a particular job.
2. In a well-balanced, efficient line, that worker shouldn’t have much excess time available to resolve this random difficulty. So, in order to fix this problem, she presses a button or pulls an andon cord to turn on the yellow warning light early in the takt time.
3. A supervisor or floater quickly comes over to the station and helps look for the tool.
4. Takt time starts to runs out, and the supervisor doesn’t think he can fix the problem on time. He pulls the cord or hits the button for the red light to indicate a line stop condition.
5. The engineering team and managers immediately come to the station. One of them comes up with the tool and the line gets moving again.
6. The supervisor records the problem. The tool was found, but this treated the symptom instead of the underlying problem. Part of continuous improvement is tracking what went wrong so the root cause of a problem can be determined and permanently resolved.

Just remember a few things when using andons. First, there may be a reverse ‘Boy Who Cried Wolf’ condition. What happens if a worker pulls the andon cord to signal a need for help, and nobody ever comes to the rescue? The employee stops wasting his time pulling that andon cord! And if the cord is not pulled, the leadership team misses out on the opportunity to permanently fix the problem. Plus, the lack of early warning means that there will likely be more frequent line stops.

Also remember that you can build your standard work with problem resolution in mind. Let’s say that there is a work station with an easy task and a more difficult task that is prone to problems. Obviously, you want to work towards eliminating the problems, but until then, mitigate your risk. Do the harder task first. If you fall behind, you can call for help, and have the lead/supervisor/floater do the easy task and buy the operator a few more minutes. If the tough task was last on the standard work combination sheet, there would be very little the helper could do other than cheer you on.

Finally, make sure you track the andon calls, and figure out how to prevent problems in the future.

As a side note, workers generally should not have time included in their standard work to address problems. You are better off having a floater who can cover the line than adding buffer time to the standard work. Embedding extra time hides the problem in a hidden factory and it never gets the attention it deserves.

Some common andon configurations include:

• A stack of colored andon lights
• These lights correspond to the status of a work area. Green indicates a normal condition. Yellow signifies a need for help, and red means production has stopped, or soon will. The red light is frequently accompanied by an audible alarm. Some andons are linked to computer systems to track problems, and others can stop a moving assembly line when turned on.

• An andon display or andon board
• The board shows a summary of many work stations. There are two basic uses for this type of display.
• It can be used to signal when each station on an assembly line is ready to shift. You are most likely to see this set-up for assembly lines that manually advance products.
• It can be used to show which stations have a problem. When an andon cord is pulled at a station, it also may illuminate a light on an andon display.
• An andon may be wired into a machine, signaling when there is a problem.
• These lights are often automatically triggered when there is a problem. If the sensors also stop production, the system is known as jidoka, or autonomation.
• The abnormal condition andon.
• Andon lights may take a variety of other forms. A light may be linked to a space in a queue. When the space is full, the light goes on. The ‘on air’ light in a studio is also a form of andon. The military uses red flags on disabled vehicles to signal to maintenance teams. The key it so visually signal that an abnormal condition is present and action is needed.

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