Kanban – definition and function
Kanban is the Japanese word for card or character. Tominaga provided the following definition in 1996:
“A Kanban is a carrier of information that runs with the product through production and contains the necessary work instructions. However, a kanban can also trigger a supply of new material. There are therefore different types of kanbans. Within a system, the kanbans serve to ensure that the required goods are produced in the required quantity at the right time.”
With Kanban, on the other hand, the downstream operation only takes parts from the upstream operation in the required quantity and at the required time. If new material is required, the consumer requests the supplier to deliver via the system. When a signal arrives, e.g. a card, the supplier begins to provide the specified material and place it in a standardized container. The container with the card is then delivered to an agreed point. The recipient uses the delivered parts up to a minimum stock level and then sends the Kanban card back to the supplier.
What types of Kanban are there?
Variations of all kinds are possible because the process should be adapted to the respective circumstances. In the course of adapting to new requirements and continuously improving the system, different Kanban classes have emerged. As early as 1980, a distinction was made in Japan between the
- Material Kanban for the production and provision of material that is returned after a container has been opened
- Signal Kanban as a material Kanban, which is only returned when a certain quantity of the container has been used up
- Transport Kanban, as a request to move a specific material from a storage bin to a staging area
- Limited Kanban, as a material Kanban that is invalid after a certain production quantity
What goals does Kanban pursue?
In the meantime, there are a number of variations depending on the philosophy. However, the goals to be achieved with the introduction of Kanban are similar. Goals that are measurable and achievable with the introduction of Kanban:
- Reduction of throughput times
- Inventory reduction
- Reduction of rejects and waste
- Simplification of the organization
- Increasing flexibility
ABC analysis
The decision on the selection of a product for Kanban provision can be made using various methods. The ABC analysis is a planning and determination method that is used in materials management, among other things. It examines how strongly a certain characteristic is concentrated on the individual elements of a quantity under consideration. The ABC analysis is used to classify the material assortment into A-parts, B-parts and C-parts according to their relative value share of the total value of the procured materials. A quantity-value ratio analysis is carried out. This analysis is based on the knowledge that the material requirements structure of a company is generally characterized in such a way that a regularly low proportion of the material types used (A-parts) form the main share of the value of the total materials procured. Material types with a lower share of the total value but a higher quantity share are classified as B and C parts.
If we look at the consumption of individual materials over a longer period of time, we can see that there are materials whose consumption is almost constant, materials whose consumption is subject to certain fluctuations and materials whose consumption is completely irregular.
XYZ analysis
The materials weighted according to the ABC method could therefore also be classified according to the predictive accuracy of their consumption. The classification symbols mean the following:
X-parts: Consumption is constant with only occasional fluctuations; high prediction accuracy.
Y-parts: Consumption is subject to greater fluctuations, is trending upwards or downwards or is subject to seasonal fluctuations; average forecast accuracy.
Z-parts: Consumption is completely irregular; low prediction accuracy.
Carrying out the ABC analysis in conjunction with the XYZ analysis is the prerequisite for determining the products suitable for Kanban. The Kanban system can be used for all products with an increasing consumption pattern (X products and partly Y products). The quantitative fluctuation interval in a planning horizon of one week +/- 5% and one month +/- 30% should not be exceeded. The value of the products (ABC analysis) influences the characteristics of the kanban. Inexpensive C-articles, for example, are realized in larger container quantities with a high safety quantity as a kanban cycle. Expensive A articles are recorded individually in kanban cycles.
