What materials are used in the Kanban system to signal needs at a workstation?

In the Kanban system, physical cards are used as a fundamental element to signal needs at a workstation. These cards serve as visual indicators that communicate when a certain quantity of materials or components must be restocked or produced. The use of physical cards is critical because they provide an immediate, easily interpretable way to manage inventory levels and production flow.

When a workstation finishes using a certain part or material, the corresponding Kanban card is sent back upstream in the production process, indicating that it is time to replenish that item. This creates a smooth and continuous flow of materials, helping to prevent shortages and overproduction, which aligns with the principles of just-in-time (JIT) manufacturing.

While digital messages, visual cues, and standardized forms can all play roles in communication and efficiency within manufacturing systems, they do not embody the traditional and core function of the Kanban method as effectively as physical cards do. Physical cards provide a straightforward, tangible method for communicating workflow needs that is easily understood by all members of a production team, thereby enhancing the overall effectiveness of the Kanban system.