Kanban - a japanese noun

Kanban Systems were first developed by Taiichi Ohno, an industrial engineer at Toyota, way back in the 1950s. Following a trip to the U.S., he was inspired by how supermarkets could order just enough stock to replenish the goods that customers had purchased, thereby keeping an oversupply of stock to a minimum.  

In the 1950s, Toyota competed with large U.S. companies Ford and General Motors. These well-established and wealthy organisations could afford to have an oversupply of stock in storage. However, Toyota could not!  They needed to find a way to maintain a steady flow of stock which arrives just at the time when it is needed, thereby reducing the need for expensive unused stock sitting in warehouses. 

This was achieved by having a physical card located within a box of parts. As the parts are consumed, and the box becomes close to empty, the card is sent “upstream” to the supplier. Written on the card is an order for another box of parts. This box is then delivered just as the old box becomes empty, therefore replenishing the box of parts “just-in-time”.

Naturally, in Japanese, a physical card that conveys some information is known as a Kanban, and so Kanban Systems were born. But there is more to it than that.  

As the card travels “upstream” in the manufacturing process, it is actually a “pull” signal indicating that the downstream part of the system is now ready for more items. So in a Kanban System, the upstream pull signal is the Kanban – it is NOT the item flowing downstream!!

Therefore, a Kanban System is a system where Kanbans (pull signals) are in circulation. And it so happens that Kanban Systems are used more often than we may think.

One of the great benefits of a Kanban System is it protects the entity that issues the Pull signal from overburden. Imagine our manufacturing process again and its box of parts. Just imagine that instead of one box arriving, twenty arrive instead.  The station consuming the parts would be “overburdened” with excessive boxes of parts. This may not be a big deal in this example, but there are other situations where the overburden is a problem.

The Palace Gardens in Tokyo is such an example. It is a walled ornamental garden which is popular with visitors.  However, in springtime, the cherry blossom attracts more visitors than the garden can accommodate.  If all these visitors were allowed into the garden, it would cause excessive damage and not be a pleasant experience. To prevent the garden (the system) from too many visitors (overburden), a simple system is in place.  As visitors arrive, they take a card from a stack of cards located at the entrance gate. The number of cards available corresponds to the number of visitors the garden can comfortably accommodate. Once all the cards have been taken, no more visitors can enter the garden until an exciting visitor relinquishes a card.

Therefore we have a Kanban System in place.  The system being protected from overburden is the garden. The cards are Kanbans because they are a Pull signal indicating the garden can take more people.