Presentation of definitions
If the word kanban is unfamiliar to you and you would like to become familiar with it, or you already know it and deepen your knowledge, then you must know first of all that it is one of the tools of the Lean Manufacturing concept.
The concept of “Lean Manufacturing”, apart from the fact that it sounds professional, is translated from English into Polish meaning “lean production”. Lean production means nothing more than using fewer factors in the production process compared to the average mass production. Thanks to the implementation of such a project, you can save:
- half the effort of employees,
- the area of the production hall,
- a cost including tools and tooling,
- working time of designers creating plans for new products that will be launched on the market in half the time.
- half of the inventory, which leads to both halving the number of defects and affects the increase in the range of products.
The word “kanban” in Japanese means “sign” or “card”. On the basis of the meaning of this word, a kanban system was created that facilitates the determination of the production volume in processes by means of inventory control cards used in a towed system. The tool aims to produce ordered products in the time and quantity specified in the order.
Types of kanban
We distinguish between kanban:
- transport indicates when the designated components should be delivered to the production line, or when they move between production processes and the assembly line. It shows information about parts, their quantity, where the elements come from and where they will be transported.
- the supplier, also known as the ordering party, orders the components necessary for assembly, sent to the materials delivering.
- internal or extractor is used to transfer the necessary parts and subassemblies between the assembly lines inside the company. They provide the source of information necessary to extract components from upstream processes. It may take the form of a container or trolley.
- production consists of instructions relating to operations in given processes.
- the production order is reminiscent of a production order and determines what and in what quantity should be produced. This type starts production to complete the taken items.
- signaling informs about the moment when conversion is necessary.
Stages of implementation
First, you need to plan the number of cards needed in the production process. Most plants produce products using repetitive operations and then the number of cards can be determined using the formula:
Number of cards = (daily production x (delivery time with a safety margin)) / container capacity
Daily production = monthly production / number of working days in a month
Delivery time = production time (both processing and storage) + time needed to get a kanban
The safety margin is zero days or the smallest number of days possible.
The capacity of the container is associated with keeping the smallest amount of goods in the container and increasing the quantity of deliveries.
In the assessment of the number of needed cards, the following questions may be helpful:
- Some products are on one pallet?
- How many parts of the product should be transported?
- What goods are transported – homogeneous or mixed?
The second stage is the creation of cards.
The card must contain:
- number of raw material, part, subassembly or assembly,
- precise description with a photo,
- the previous process,
- another process,
- external or internal supplier process,
- the order number from the customer or from the company,
- what, when and how much to take,
- which when and how much should be produced.
The third stage is the storage and circulation of cards.
Cards are stored in plastic T-shirts to improve handling, to facilitate reading and to protect them from dirt and tear. Then they are attached to containers such as pallets, boxes, trays, sets, boxes of various sizes, trolleys and cars.
The course of Kanban card circulation starts with placing appropriate transport kanban cards in the box after using the necessary parts on the assembly line. The carrier then pulls the kanban out of the box and picks up the components needed for assembly from the preceding process. The same man pulls the production kanban out of the pallet or container and places it in a box for a specific process. Production Kanban fulfills the role of an order to produce collected components. However, the transport kanban is applied to the pallet, on which there are parts to be delivered to the assembly line. Empty pallets have their designated storage place. The manufactured elements are put together with the production kanban in a designated place next to the production area, where they are easily available to the recipients in the next process. At the end, the worker of the process takes the transport kanban to an earlier process in order to supplement parts or subassemblies used to produce ingredients for the assembly line. This course is repeated, which leads to a chain reaction creating a stream to suppliers from outside.
During the kanban card cycle, remember to attach only one Kanban card to each pallet or container, which is always an inseparable addition to the material. Make sure that the amount on the card matches the amount in the container. You can not forget about the fact that the transport kanban placed in the box means that the previous process requires the completion of the material. Kanban cards are moved in boxes, both picked up and manufactured materials. Production Kanban is arranged in this container in the order in which ingredients are taken.
The main benefit of using the kanban technique is to highlight problems that create waste, ie overproduction, increasing flexibility to changes in customer demand, coordinating the production of short series of heterogeneous products, creating a simplified purchasing process and connecting all processes and linking them to the customer. It can also help in bonding information with a fixed component or product, finding simple data on the replenishment of products and instructions necessary to start production and removing unnecessary stocks between operations.
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