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Andon (+7-min MP3)

An andon light is one of the most common forms of visual management that is in use in Lean. It is a staple in the bag of Lean tools because it is highly effective at keeping operations running smoothly.

Click the image to see how the andon process works.

Click the image to see a 4-panel series depicting how the andon process works.

In Lean, the term “andon” most often refers to a signaling system used to call for help when an abnormal condition is recognized, or that some sort of action is required. These andon lights are usually present on an assembly line as the cost of a problem is multiplied by the number of stations if there is a line stop. These signals are generally a stack of colored lights that are used to request assistance. Each color signifies a different condition and a different required response.

In the office, there are also signaling lights. For example, an andon will announce that a piece of equipment, like a fax machine, is having problems.

The term “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.

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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. The light may be connected to an andon board. In this case, a light will indicate the status of the station on the display.
  4. A supervisor or floater quickly comes over to the station and helps look for the tool.
  5. 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.
  6. The engineering team and managers immediately come to the station. One of them comes up with the tool and the line gets moving again.
  7. 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.

If you are a leader who has andons, ensure that there is a response when they are lit.

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.

Make the andons a source of information for you to drive continuous improvement.

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.

Andon Light Stack

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. Again, as I mentioned earlier regarding the fax machine error light, you can take a fairly liberal view of what constitutes an andon light. The function is the same. It is just the scale that is different.
  • The abnormal condition andon.
    • Andon lights may take a variety of…

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  • Be careful about using andon lights if you do not have a response plan in place. People will stop using them, and you will have a false sense of security.
  • Make sure people are not scared to use their andons. They should be rewarded for identifying and preventing problems. There is a tendency to look at line stops as a bad thing. Tie line stops to problem resolution, and people will be much more likely to hit their button.
  • Don’t waste the wealth of information that comes from…

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Andon lights are your friends. Use them to make your job easier. In some companies, this is easier said than done. Line stops are closely associated with turning on your signal light, and, before a company truly embraces a continuous improvement culture, there often negative feelings associated with shutting down production.

The key is to help your leadership team focus on solving the problems that you identify when you pull the cord or press the button to call for help. After each time somebody comes to assist you, be diligent about writing down the incident. Hopefully this will be part of a formal process. If not, it still pays to write down the problems that happened. This record will help you present your case for getting improvement resources.

Leaders get busy and they manage multiple stations. They won’t be able to see or recognize the patterns that you do. By documenting what is happening, you…

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