Jidoka and Andon: stop the line when something goes wrong

In one line

Jidoka (autonomation) is automating "with a human touch": the machine or the operator detects an abnormality and stops the process instead of letting a defect pass to the next stage.

What it is

Meyers and Stephens define it as transferring human intelligence to a machine: devices are built that are capable of making judgments. In the lean system the concept is not limited to machines; it also applies to the production line and to the operators: if a problem occurs, an operator stops the line, and defects are dealt with right there, which makes it possible to investigate the situation. Niebel and Freivalds describe it as autonomous defect control, whose goal is not to let a defective unit interrupt a downstream process.

Bellon Álvarez records the origin of the concept: autonomation (autonomy plus automation) was born to tackle the problem of waste caused by improper machine operation, and it was first applied at Toyota when the company made textiles, and later in vehicle manufacturing. He also points out an organizational consequence: it encourages de-specialization and multifunctionality, which contradicts the extreme fragmentation of times and motions of Taylorism and Fordism.

Andon: the signal

Meyers and Stephens describe the andon as a light indicator board above the production line that works as a visual control: with normal operations a green light stays on; a yellow light indicates that an operator needs help or wants to adjust something; and if the line has to be stopped to solve the problem, a red light comes on. The associated "line-stop concept" demands discipline: every time there is a problem, the worker stops the line, identifies it, solves it and restores the flow as soon as possible.

The Universidad Icesi article places jidoka within the Lean implementation model as the prevention of errors in the process by redesigning equipment, operations and products: human errors (poka-yoke) and process errors are avoided, and 100 percent inspection is applied at the source, so that each operation ensures the quality of the previous ones.

How it is applied

1. Define what is "abnormal" at each workstation (a visible standard: without it nobody knows when to stop).
2. Give authority to the person at the workstation to stop the process, without asking for permission.
3. Install the signal (lights, sound, a cord) and define who responds and within how long.
4. Investigate the root cause of each stoppage, with the 5 Whys or Ishikawa, and record the action.
5. Count the stoppages: at first they go up, because hidden problems come to light; as corrections are made, they go down.

Real example

Niebel and Freivalds place jidoka alongside just-in-time among the key elements of the Toyota system, and Meyers and Stephens describe the simplest case: Toyota employees are encouraged to stop the line if there is any problem, with the light board above the line. It is the most visible application of the idea: the line stops by decision of the person who sees the problem, not by decision of a supervisor three workstations up. At the LACPRIMA dairy plant, the thesis from the Universidad del Azuay proposes the andon for quality control of raw material at receiving, where there was no procedure to verify it.

Benefits

• It cuts off the defect at the workstation where it is generated, instead of discovering it at the customer.
• It turns each stoppage into information about the process.
• It reduces rework and final inspection.

Limitations to keep in mind

• Without a culture that backs it, the operator does not stop: if stopping the line is "a problem," nobody does it. You have to protect the person who stops.
• Without root cause analysis, the andon becomes an alarm that sounds all day.
• Stopping a line has a cost: combine it with quick changeovers and reliable maintenance so that the stoppages are short.

In summary

Jidoka is error-proof quality built into the process: detect, stop, correct and prevent. Together with just-in-time, it holds up the Toyota Production System.