Jidoka: Building Quality into Production

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The Japanese word ji-do-ka comprises three Chinese characters. The first, ji refers to the worker herself. If she feels “something is wrong” or “I am creating a defect,” she must stop the line. Do refers to motion or work, and ka to the suffix “-action.”

Taken together Jidoka has been defined by Toyota as “automation with a human mind” and implies intelligent workers and machines identifying errors and taking quick countermeasures.

The goal of Jidoka is “zero defects”, to never pass a defective product downstream and to eliminate the risk that an undetected defect will end up in the hands of the customer.

Development of the Jidoka Concept

The Jidoka concept is very old and it goes back to the Toyoda Auto Loom Company. Mr. Sakichi Toyoda invented an automatic loom that would shut down as soon as a single thread broke. This saved a lot of wasted material and helped highlight problems as soon as one happened. That was the starting point.

Jidoka is one of the core principles of the Toyota Production System (TPS) and is highly focused on an automated production line process. It means applying the “human touch” to immediately address manufacturing problems at the moment they are detected.

The four elements of Jidoka are:

  1. Detection of a problem
  2. Stop the line
  3. Correct the immediate problem
  4. Conduct root cause analysis and develop/implement corrective action to eliminate recurrence

In addition to the specific tools of Jidoka there is also the cultural aspects. This is the empowerment of all employees to stop production when a problem is identified. A direct outcome from the Jidoka culture and practice is an improvement in product quality.

Jidoka is used at Toyota to empower every worker to stop the assembly line whenever a quality problem is detected. The worker pulls a red cord and the entire assembly line stops, idling every machine and every worker on that line until the problem is solved or a remedy is found to prevent a defect moving forward.

When the line stops, fellow workers run over to the person who pulled the red cord to help them resolve the problem. In reality, the problem resolution often takes less than a minute and the line is again up and running. In the typical Toyota plant, the line is stopped dozens of times each day.

Andon: Stop Production So That Production Never Stops.

The Japanese word andon doesn’t directly translate into English, however the andon is the name of the traditional paper lanterns seen in Japan (more so historically). In the context of Jidoka, the andon is traditionally a light signaling a problem or a line stoppage. The most common method of triggering the light is the andon cord.

The andon cord is a cord usually hung above and along a production line. The cord is similar to the old fashioned cords in trams and trains used to request the driver to stop — some were also used to apply the brakes. So it isn’t a new idea — like most of the concepts within lean.

When an operator identifies a problem on the production line they pull the cord to alert the production supervisor — in some instances the cord also stops the line, just like the old trains. Not all systems allow the operator to stop the line, however those organizations with the better and trusting cultures do allow the operators to stop the line.

chiasmus diagram showing abba pattern Figure X-2. Andon Cords at the Toyota Takaota Plant | Image by Lean BlogOpens in new window

When the cord is pulled, a light system and/or siren is triggered to alert the supervisor, some systems have an escalation process built in to alert management on subsequent pulls of the cord. If the system allows, the line is stopped to enable the immediate problem to be corrected.

The team (this may include Production Operators, Management, Engineering, Maintenance, Quality representatives) determine whether the line can be restarted or if other corrective work is required before the line is returned to normal operation.

Once the line is restarted, the team will then determine the cause of the problem through one of the root cause analysis tools. Once the root cause has been determined, the team then defines what corrective actions are required to eliminate the problem from recurring. Once again, this team could be diverse and is usually predetermined based on the problem type.

Similar systems operate in many businesses across many industries. For instance, in retail establishments, the checkout operator may have a button they press to alert the supervisor that assistance is required.

In a hospital, the patient can press a button on their bed to alert the nursing staff; hospitals have automated this in many areas now so when a patient is in distress, the alert is automated through an alarm system to the nursing station and the relevant medical team.

So why give the operators the power to stop production?

When you empower the entire team to make that call you are creating a quality culture; when something isn’t right management can trust the team to make the decision to get it right. Of course, there is a lot of training that goes into the team members to get them to the point where the correct decisions are made. The training is well worth it though.

What level of training is required?

Before you go about training you have to set the standards of quality that are expected — this expectation must be agreed and communicated across the business and to the market. This is an important step; many businesses try to improve product quality without setting or communicating a standard.

Once the standards have been set and communicated you can go about the training. The training program needs to be designed to achieve the safety, product quality, throughput/efficiency standards and should be presented by an experienced operator and trainer; it isn’t good enough to employ a smooth present if they do not have the practical experience.

If you choose to empower the staff to stop the line without this level of training you will likely encounter chaos in the production system as the line stoppages are likely to be too frequent and randomly caused. This will result in one of a couple of outcomes:

  1. The andon and possibly the lean journey may be challenged or possibly even fail as a result of the chaos created.
  2. The chaos may result in a financial loss to the organization as the relatively uncontrolled stoppage cause delays in production.
  3. Possibly the worst outcomes is if the new chaos becomes the ‘business as usual’ and could have long term and far reaching business implications.
Why do we use andon?

It is much less expensive and has far less impact on the customer when identified problems are fixed when they are identified rather than at the end of the production process. Every time a product is reworked late in the process the likelihood of extra rework (incidental rework) being required are greater.

This all adds time and money to the process and can have an impact on delivery on time. When the problem is identified and the process stopped early, the schedule can be adjusted if necessary at that time. It is still possible to make up time in later processing steps to bring the job back on schedule; or you can discuss the potential late delivery with the customer at this time rather than on or after the due date.

Another benefit of andon is the problem is fixed where it is identified. This is generally means the right people are present for rectification, root cause analysis and learning.

When inspection and rework is conducted post (after) production you will have no either employ a specialist rework team or drag the resources away from the production processes to perform the rework; this will result in the line stopping anyway. When a specialist team performs the rework the learning does not easily find its way back to the production team.

    Research data for this work have been adapted from the manuals:
  1. Jason Tisbury. Your 60 Minute Lean Business - Jidoka
  2. Jorge Luis García-Alcaraz, Aidé Aracely. Lean Manufacturing in the Developing World: Methodology, Case Studies and ...
  3. Pascal Dennis. Lean Production Simplified, Second Edition: A Plain-Language Guide to the ...