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The Toyota Production System’s ‘Kanban System’
Hi, this is Mike Negami, Lean Sigma Black Belt. In the last video, I said that the ‘Kanban System’ is a tool for achieving ‘Just In Time’. If you haven’t watched the video, please click the i-shaped icon in the upper-right corner and watch the video.
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Taiichi Ohno who is called as “the father of the Toyota Production System” said:
“The Kanban System is important, but it is simply an operational method to realize ‘Just In Time’, so if you imitate only Kanban in a factory, your people will be confused.
Before starting the ‘Kanban System’, you have to make a proper operational flow throughout the factory. Also, without understanding the concept of Toyota Production System, there is no point in using the ‘Kanban System’.”
Nikkei Business Digital http://business.nikkeibp.co.jp/atcl/NBD/15/041800014/101700030/ (Translated by Mike Negami)
Let’s discuss the Kanban System while grasping this point.
Taiichi Ohno – What to obtain from his US Tour
Kiichiro Toyoda, the founder of Toyota Motor Company, had the concept of ‘Just In Time’, but he was in the middle of the road to find a definitive method to realize it. During that time, Taiichi Ohno was appointed to establish process reform to realize ‘Just In Time’, and went to the United States for factory tours to Ford and GM.
However, when he gained a hint for reform, it was not from their factories, but from a supermarket. He says in his books as follows:
“The hint obtained from the supermarket was to see a prior process step in the production line as a supermarket, and the post-step as a customer buying the necessary items at the necessary time in the necessary amounts from the prior step.
Then, the prior step immediately replenishes the amount that the post-step took. We thought that, in doing so, we could achieve our major goal, ‘Just In Time’.
In 1953, we applied this concept to our flagship machinery factory.”
From “Toyota Production System: Beyond Large-Scale Production” by Taiichi Ohno
“Push System” and “Pull System”
Production methods at that time were to produce as much as possible if there were materials and necessary parts available for each process. In other words, the information flow of the factory was from prior steps to post steps. We call it the ‘Push System’. With that method, workers did not need to think much, worked if there were materials, and increased work-in-process inventory.
However, the new system made the information flow in the opposite direction. Then, workers in a prior step work while looking at the flow of the post step. In other words, the new system broadened their horizons and reduced the work-in-process inventory along the work line. At that time, Toyota called that system the ‘Supermarket System’. Now, we call it the ‘Pull System’.
Explanation with Illustrations of the Kanaban System
At the time, the good flow of the new system had increased, but a new problem occurred. Post steps sometimes used more inventory than the prior steps expected, and many steps ran out of inventory.
Because of this situation, the ‘Kanban System’ was invented. ‘Kanban’ is a card that describes when, where, what, and how much was used.
This is a conceptual diagram of the Kanban System that Toyota made. There are two kinds of kanban (card), ‘the production instruction kanban’ and ‘the parts retrieval kanban’.
Let’s see the “Operational Flow of Parts Retrieval Kanban A” first. 1) The parts retrieval kanban is removed when operator uses parts brought from the prior step. 2) The operator carries the Kanban to retrieve replacement parts. 3) The operator removes the production instruction kanban and replaces it with a parts retrieval kanban. 4) Parts displaying the parts retrieval kanban are transported to the next process.
Next is “Operational Flow of Production Instruction Kanban A”. 1) Production instruction kanban is removed when an operator retrieves parts. 2) Only the exact number of parts indicated on the kanban are produced. 3) The kanban is attached to the newly produced parts, ready for the next process. These two kinds of kanban flow all over the plant.
That was the explanation of the ‘Kanban System’. You may not use kanban in service operations, but the idea of the “Supermarket System” or the “Pull System” most certainly can be applied.
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