“Kanban” is a Japanese word, which means “Visual Card”. It was implemented by Taiichi Ohno in Toyota Production System. He got this idea from a grocery store, where he saw that keeper restocked the store based on inventory and not on the basis of supply from a supplier. He used that concept to maintain the inventory with demand. It is used as a signal in the manufacturing process, where workers will send what they need and in which amount they need to a warehouse by just writing in a kanban card. It is simply a card, which gives complete information about the product in a much simpler way5. An example of kanban card is shown in the figure below.
Figure 2. Kanban Card 6
There are 4 basic principles of Kanban5:
1) Get the idea about the process – this means you first understand the process that is existing. Kanban does not say to change the current process without knowing it;
2) Agree to small changes – this means that whenever there is a small change due to Kanban, support it. The reason is, Kanban is a tool that clears problem or guide you to the success through small changes rather than abrupt changes;
3) Respect the current scenario – when one implements Kanban in the current process, it does not tell you to change the whole process, but to make the small changes in the current process which does not add value to the process. And it does not tell you to change the steps that adds value to the process. Thus, one must respect the current process, roles and responsibilities of the whole system;
4) Encourage all – since it is a tool of improvement and it involves all, ideas must flow from all directions and they must be respected. Ideas can come from any of the team members rather than just the management team.
Ø Additionally, 6 general practices of Kanban were elaborated7:
1) Visualize the work flow
– Break down every step from beginning to the end of the process and create a column or line (lane) for each step;
– Write down tasks separately on a physical card;
– Differentiate the types of tasks for easier visualization with the help of the colour codes;
– Work flows from left to do to right done as shown in figure below.
Figure 3. Visualize the workflow8
2) Limit the work flow
– Do not do such task which cause harm to your process efficiency at a single time. There needs to be a limit, where only a particular task needs to be done to reduce waste and improve the efficiency;
– Put limits on columns in which work is being performed;
– The goal of WIP limits are smooth workflow and waste elimination.
3) Manage Flow
– Improvement should always be based on measurements, so find and apply methods;
– Use the gathered data to adjust your process to maximize flow and efficiency.
Using these steps, you will be able to identify where your tasks needs to be adjusted, and what works best for you and your team.
4) Make policies explicit
– The team must form the basic rules on the flow of different items, when and how to note;
– This needs to be marked on the board.
– For the continuous improvement, meetings must be carried out weekly or at the end of the shift to check whether work flow is going as per the flow or not;
– Feedback is necessary as it will indicate if anything needs the improvement or is going well.
6) Collaborate for improvement
– It requires the involvement of all departments, rather than just one;
– It is a team effort.
Ø Rules of Kanban by Toyota Production System: –
There are 6 rules defined by the Toyota production system9:
1) Downstream processes withdraw the items in the exact amount mentioned by Kanban;
2) Upstream produces items in precise amounts and sequences given by Kanban;
3) No items should be moved or produced without Kanban;
4) Kanban cards must accompany each and every time with the parts;
5) Defects and incorrect amounts should never be sent to the next downstream process;
6) The number of kanban cards is reduced carefully to minimize inventory and find the problems.
Ø Nowadays, different types of kanban cards exist. There are two principal types of Kanban cards10:
1) Withdrawal Kanban. Withdrawal kanban cards, also known as “move cards”, are used to indicate when a part is ready to move from one lane to another lane in the manufacturing areas. The card is attached with a prescribed number of parts, which are moved to the work area that needs them. Once the parts are used, the card is returned as a signal to send the same number of the same part back. An example of withdrawal kanban card is shown on figure 4;
Figure 4. Withdrawal kanban card 11
2) Production Kanban. Kanban that contains a comprehensive list of everything the part requires in order to be completed is called the production kanban card. It includes the parts required, the materials required and the information included on withdrawal Kanban. Importantly, a production kanban card orders the production system to start with the production of parts required in the production area. An example of production kanban card is shown on figure 5.
Figure 5. Production kanban card 11
Ø In addition, other types of existing kanban cards are:
1) Express Kanban. Express kanban cards come into use when the shortages of parts occur, to signal the need for more of a particular part or material so that the manufacturing process does not get stopped and work flows smoothly. These are also sometimes known as signal Kanbans. Essentially, they are used to trigger purchases;