KANBAN'S - SIMPLICITY AT IT'S BEST.

KANBAN'S - SIMPLICITY AT IT'S BEST.

BRIAN WILLCOX

ACTION MRPII

Today we have many sophisticated systems and techniques for managing our business. Is it not time we started using some of the simpler methods which are easier to control and understand. The Kanban concept provides a very simple solution to what can be a very complex subject; scheduling manufacturing.

The simple definition of a kanban is a token or indicator. It is used as a requisition for material and labour and is a works order authorisation.

In general, a kanban is a production control system for regularly used components. It resembles a two-bin system rather than the dispatch list found in an MRPII system. The kanban is simple and for it to work it requires a supply with a consistent and short lead time, a constant and not variable demand. Ideally it requires a small replenishment order quantity. There are three types of kanbans in common use, each following the same basic concepts; called the kanban square, the single card kanban and the double card kanban.

The kanban square is used on an assembly line or work cell, and is a square drawn on the bench or floor between two operators or machines. The concept is that when one operator has finished a part instead of giving it to the operator next to her, she would put it into the kanban square. The rule is, she may only make another when that one has been taken. Think about it, what would she do with it if she did make another whilst that one was still sitting there. Nobody needs it. The result is that a line keeps producing whilst there is a need for the parts, but if a problem occurs, the line will stop as nobody could use the parts if they were made. A simple but effective way of controlling the flow of material through an assembly or manufacturing process. The speed of the line is determined by the longest operation.

The single card kanban, which often is not a card at all, but a container, is a very effective way of scheduling a producing work centre that feeds an assembly line. The first rule is that when the producing work centre has produced a container of parts, it keeps them. When someone on the assembly line needs more parts, they must come and collect them, but they must bring the empty container with them. This is the instruction to the producing work centre that more are required. If no one collects any, then obviously nobody needs any, therefore no more should be made. As the producing work centre may be supplying several different parts to a number of users, the rule that the producing work centre must follow is the FIFO system. The first empty container received is the part that must be made first. Again, simple and effective. It has just done away with a complex scheduling problem and a build up of work in process.

The double card kanban system follows the same logic but is used when one company is supplying a second. In this case, the "move" card is used like the single card kanban (or container), to authorise the movement of material from the supplier to the using company. The second card, the production card is used by the supplying company to launch another batch of work into his manufacturing facility when he returns with an empty container from his customer. If when he delivers to the using company there are two empty containers for him, then that means that he must deliver two full ones tomorrow. When he returns to his company, the empty containers are the trigger for him to load two batches into his production facility. Again, a simple but effective way of controlling the flow of material into the factory.

What are the advantages of this concept?

The most important are that you only make what is needed when it is needed. You make in quantities that can be handled by the work station that needs the item, and no more.

The result is a more responsive method of satisfying a need, a simpler control system, less stock and lower WIP with shorter lead times. Typical requirements if we want to become more competitive in the market place.

If you see this as a concept all right for those in Japan but not for you, I suggest you talk to one of the many companies who are using it and obtaining the benefits.