Kanban the important and critical tool
Taiichi Ohno developed the pull system and incorporated it in the Toyota Production System (TPS). Since that time, it has become an integral principle in any Lean implementation. The Holy Grail for a Lean Enterprise is to design a business system that is capable of single piece or continuous flow. However, in reality, many companies cannot achieve this. Many have one or more shared resources, which create a serious constraint and inhibit their ability to flow. It is because of this that they work with a less than a perfect system that is not capable of supporting continuous flow. At this point, Kanban becomes an important and critical tool. It can be used to help these companies to make the transition from a batch and queue process to a system that can improve product flow. They will not have achieved perfection from a Lean purist viewpoint, but it is a better situation than what they had before.
Understanding kanban and the seven wastes:
Taiichi Ohno clearly understood one important fact when he categorized the seven wastes, it was that overproduction is the root cause of the other six wastes. He also realized that creating too much inventory increased lead times. It is these simple understandings that lead him towards the development of the pull system, using kanban. So, where did he get the idea for a pull system? While visiting the U.S. he observed a worker in a supermarket replenishing the goods on the shelves after the customers had removed them. This was the seed of the idea that eventually became what we today know as a “pull system”.
The purpose of a kanban is to send a signal
Kanban is a Japanese word which translates into “card or signal”. It becomes an important element when implementing a pull system. The purpose of a kanban is to send a signal to the person responsible for material replenishment. At each operation, there is a predefined number of products, which are being withdrawn and these will need to be replenished. For example, if a process is using a kanban quantity of 20 units, the replenishment signal could be placed at the minimum number of five units. When the kanban is uncovered, it will activate the material replenishment process to reorder the units. This minimum kanban quantity will be dependent upon the replenishment cycle time, which is the total time required to purchase or produce the 20 items and deliver them. Once they are received, they will be used to replenish the kanban quantity to it predetermined level of 20 units. This process will be repeated every time the kanban reorder quantity of five units is reached. An ideal kanban quantity is one, but it can be any number of units, e.g. 10, 12, 20, 50,100, etc. The pull system must maintain the necessary quantities to maintain the flow of work to meet customer demand, without overproduction.
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