The Kanban method was inspired by how American supermarkets managed their stock, with small amounts of product displayed on shelves, and turning that product quickly. Like the supermarket, the material Kanban method responds to actions taken by your customer, who could be an operator on the production line. Material will be replenished not based on a fixed schedule, but on actual usage or consumption. In that way the delivery system can respond to variation in usage dynamically and automatically, as the usage changes. The Kanban system is therefore highly “self-regulating”, within limits of course.
The replenishment signals can be automated, and computers can be used in a Kanban system, but material is not “pushed” to the Point of Use based on a schedule. The actual delivery of parts will be triggered by usage, and usage can vary for an individual item.
The Material Kanban Approach
- Small line side quantities and high velocity.
- Replenish material based on consumption or usage.
- When consumption speeds up or slows down, adjustment is automatic.
- Delivery quantities are fixed, delivery frequency can vary.
- Computers can be used, but material is not “pushed”.
The replenishment of a small item stocked at a station is an example of the most basic Kanban method possible. Let's say, for example, that the item in question is a nut and bolt set, a certain number of which are held in a small bin on the bench. The operator consumes these fasteners as required, and at some point is going to need more. The fasteners’ location on the line is called a Kanban Point. The location from which you’ll be getting more is also a Kanban Point.
The location in this example is called a Kanban Supermarket. The Supermarket is a physical storage location, which contains a larger quantity of the same nut and bolt set.
At first glance, this Supermarket may look like a staging area but it has several different characteristics. Individual items in the Supermarket have assigned locations and calculated quantities, materials move to the line only as signaled by a Kanban signal, and materials are replenished into the Supermarket from a Kanban signal as well, so that the Supermarket is a Kanban Point as well.
The relationship between the Kanban Point at the Workstation and the Kanban Point in the Supermarket, is called a Kanban Link. Any movement of materials from Supermarket to the Line is based on actual consumption and demand, and is triggered by a Kanban signal. This may be an actual card, but not necessarily. It is simply a signal that could take one of several other forms, including a bar-code scan, a light, an empty bin, an automated sensor, or even a verbal signal.