There are some common misunderstandings about Andon. The operators do not have the authority to stop the line. A red light andon stops the line immediately, but that is for an emergency like an injury. I hope such a device is included in any production line by today since it is basic safety. The yellow light is the light that indicates that an operator is calling for help. Once that yellow light is on, the team leader must come to the station, understand the situation and decide how to help. The decision by the operator to call for help is not random. The operator must follow its standardized work. There is a specific point on the shop flow where the operator can confirm the progress against the standardized work. If the operator is behind, immediately pull the andon. Andon does not have more colors than working (Green) – help (Yellow) – stop (Stop). There is no need for an operator to choose whom to call for help. A drowned man grabs a straw. We should not ask the drowned man to decide whom to come and help. My father used to call andon with many colors “Christmas tree lights,” which do not belong to the shop floor.
For the Andon system to work, the system requires thinking on developing a “help”-able process and the accessibility of the helper.
This action of “help” is something we should think about carefully. At many sites, you see multiple workers standing around a worker. One worker works. Others keep standing. Then the worker and one of the others switch positions. Switching position is not “help”; this is substitution. A team leader might come to help in many places, but if the helped operator keeps looking at what the team leader is doing, it is not “help.” “Help” must be a temporary boost of the workforce in a process so that they can catch up to the desired outcome. When the team leader comes to help, the critical decision to make is how to help. If the situation is simple, it may ask the operator to complete the task. At the same time, the team leader starts working on the next unit. If the situation is complicated, then the team leader will take over. And when they reach the end of the station, the team leader will stop the line to resolve the problem. The team leader has the final authority to stop the line.
Also, equally important to think is the start of each process. For example, suppose the connected stations are rigidly next to each other. In that case, any delay, even if the team leader helps, will impact each other and lead to loss of output. Thus, we need to design each process starting with parallel processes to overcome this, not keeping buffer stock or space. “Absorbability of processes” is the name of such process design where team leaders and andon absorb fluctuations.
For the helper to reach an area, it must go there within seconds. Otherwise, the helper will miss the moment of truth. To create such a condition, the responsible area of a helper must be at a close distance. The helper leaving the area is prohibited. The helper not responding to the Andon will destroy the entire trust. To develop these trusted relations, we need to think about the span of control. A typical belief is that the span of control only applies to white-color works. But, if the blue-color work adds many values, I think the span of control matters to the shop floor. There is no way a traditional supervisor system can provide help when one supervisor is overseeing 30 or more people. 4 – 6 operators per one team leader is a good ratio. 4-6:1 is not a fixed ratio. Instead, this is a target of Kaizen. If the process became stable, the balance should improve. Excess help is also not good. The support comes with a pull from the process. Mutal understanding that there was a problem is essential. Once the team leader provides help, then immediately work on problem-solving. A good solution will lead to trust from the shop floor.
Andon system is not just a light flashing and line stopping. It is a carefully designed system of process and people.