BLOGWhat is Kanban?
The literal meaning of the word “kanban” in Japanese is “sign board” like you would see in front of a store or on an office building. In the narrow definition of kanban for Lean manufacturing it is a card that contains information about the lot size, the process, the quantity, the location, etc. of the material. Kanban are used to signal production and link disconnected processes. A kanban system is made up of a set of rules for calculation of kanban quantities, routes for withdrawal of kanban and delivery to kanban posts, the cycle of kanban collection and delivery, and the material replenishment lead-times to support production at minimum safe inventory levels.
The Four Functions of Kanban
Kanbans provide an “autonomous nervous system” for your factory. When kanban cards are withdrawn and cycle back to the production process this creates a flow of information, “parts sold”. When the production kanban is placed in the producing process it is the signal, “produce part”. Kanban cards themselves tell the process how much of which types need to be produced.
A second function is to the limit overproduction. Only kanban can start production and the quantity produced is strictly regulated by the quantity on the cards. In a properly designed and functioning kanban system overproduction does not happen.
The third function is visual management. In typical material flow and information flow in a factory, information arrives first and the material catches up later. In kanban systems the information (in the form of a kanban card) is attached to the actual parts or containers the cards are visual controls showing what is produced in what sequence.
The fourth and most important function of a kanban system is kaizen through reduction of number of cards. Each card represents a certain number of pieces of inventory in the system. Each card removed forces you to connect processes, reduce changeovers and lot sizes, improve yields, etc. to reduce inventory. This continuous reduction of kanban cards can be a good measure of your progress in Lean.
Removing kanban cards from the loop reduces. This exposes problems such as part shortages and line stops because there is less safety stock to hide them. Many organizations implement kanban but do not continuously reduce changeover times and lot sizes, improve quality, and continuously take our cards from the system. This often results in increasing inventory over time, even the addition of extra cards.
The Best Kanban is No Kanban
Where you see kanban, there is inventory. Kanban by itself is not Lean. The goal of Lean is to reduce waste by connecting all processes one-to-one. When this is not possible, kanban is a method to link lot production and one-piece production. Kanban is an enabler of flow where processes are disconnected. The best kanban is no kanban. Kanban helps you replenish material in a logical and controlled way while giving you a method of challenging inventory levels and improving the production system continuously.
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