Kanban, or executors and containers
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Developed by the Japanese, the kanban (Japanese word for signboard) method is over 50 years old. It applies to production and supply control. The different kanban types at the various production and supply stages are the result of the use of modular systems for the construction of flow racks and assembly stations, as well as the use of various containers.
Art Smalley, author of the book “Creating Level Pull” (Lean Enterprise Institute Polska), presenting details of the design of the pull system (kanban system), the method of calculating the optimum level of stocks in production, variants of the pull system and kanban signals, divides the kanban methods into groups, due to the manner of use.
Production kanban is used to send a stream of orders to produce small quantities of a given product.
It’s basically about scheduling the final production due to stock taking or a direct signal about the need for replenishment from the customer. This first stage is usually called a production instruction kanban (also known as make kanban). It’s a signal to produce something.
The second type is a parts withdrawal kanban (also known as move kanban). It indicates that something should be retrieved from the inventory (and retrieval, in turn, starts replenishing) and moved to the process “at the bottom”.
The signal kanban is used to transfer orders for the production of large quantities to processes upstream which carry out production in batches, such as presses and injection moulding machines (the production kanban would be less efficient in these applications because a large number of such kanban cards would be needed, which would mean a long time to deal with them). The signal kanban, on the other hand, uses the batch size.
An important task is to be performed by a transport kanban, which is used to signal the need to collect (move) parts from the storage area and deliver them to the process.
In essence, the aim is to minimise the amount of stored material in the final assembly area and thus increase the space available for production (the assembly cell is frequently and regularly supplied with small quantities of material). This type of kanban is normally used together with continuous flow assembly cells that use a large number of components manufactured internally or purchased from external suppliers. A precondition for using transport kanban is the establishment of a materials market and the determination of the quantities of materials to be stored at the production line.
The supplier kanban is used to signal the need to take parts from an external supplier in order to transport them to the market of purchased parts or to the central market at the customer’s premises. It differs from the transport kanban by the fact that it is used in accordance with the external suppliers’ requirements. In advanced applications, the supplier kanban also contains information called the kanban cycle.
When short-term circumstances arise which require additional kanbans to be introduced into the system in order to ensure a smooth production process, we are dealing with a temporary kanban.
These circumstances include, for example, the need to increase stocks in order to adapt to differences in the number of working days between the customer and suppliers or to make up for lost time for the maintenance of the die or the repair of the machine. Temporary kanban, as the name suggests, is to be used only once for a certain period of time and should have a clearly stated expiry date. A good practice is to highlight temporary kanbans in colour or in some other special way so that they do not accidentally remain in the system after the intended period of use.
Kanban works well if the containers are managed consistently.
The storage location of the container at the workplace also entails costs. When selecting a container, it should be ensured that the container selected is optimal for the transport of the specific product/supply.
In the case of single container kanban, the space required is relatively small (maximum transparency). It is particularly suitable for customers with limited space and using parts that are needed permanently, but not in large quantities. Two-part containers are also used. There is a reserve at the back of the container. If the customer begins using it, an order is automatically generated. Then the goods are commissioned and sent to the customer. In the meantime, the customer is using the reserve.
The basic form of kanban means double container systems.
Both containers are always filled with the same article. The containers are placed in a special kanban rack system one after the other. Articles are always taken from the front container. When it is emptied, the order is automatically generated and the user takes the necessary parts from the second container.
In the meantime, the goods are prepared (commissioned), put into the empty container, labelled according to the customer’s needs and delivered to the customer in an agreed delivery cycle. For those who want greater comfort, full service is the choice. As part of this service, an employee of the company ensures the complete logistics of parts at the customer’s site. This type of kanban system is suitable for customers who have a relatively regular and high demand for certain articles.
An example of a holistic management system is Ferdinand Gross Kanban.
Among over a thousand customers, the majority opted for the full-service kanban system. Their own fleet of “Kanban-Express” vehicles delivers full containers and picks up the empty ones. An employee of Ferdinand Gross also takes charge of placing the goods in the kanban racks and is responsible for the monitoring (maintenance) of the racks.
Benefits for the user include:
- minimum effort,
- automatic replacement of illegible labels on kanban racks,
- the service provider keeps the racks clean,
- the owner no longer has to generate orders, the logistics specialist ensures that the company can concentrate on its core business.
The task may be facilitated by solutions for handling and storing materials. For example, there are so-called tube rack technologies for the design and construction of custom racks and structures that are not available “off-the-shelf”. A wide range of both tube-mounted and plate-mounted wheels is available for mobile racks and trolleys. Different wheel sizes are used to adapt to specific loads. Hard or pneumatic tyres can be adapted to the specific operating conditions. Particularly often used are solutions allowing to design live storage racks with inventory management according to the FIFO (First in, First out) principle.
In the kanban method, the availability of multiple integral guides is proven to ensure accurate stock separation and identification on the picking lanes. New or temporary applications can be easily adapted to process modifications. This means that the total cost of implementation and ownership is lower, as all components can be reused for new applications.