A kanban card is a method used for signalling requirements for replenishment of material in a just-in-time production and procurement systems. It is a means of authorising and communicating start of communication and production activities.
separate kanban cards are made for each stage of manufacture or procurement of each product or component. In the entire chain of manufacturing and procurement operations each link or work center requiring material from previous links or work centers, instructs and authorises them to manufacture and supply the required material by sending them the kanban cards. These cards are returned with the material supplied by the supplying department. For each item of material required by a work centers, different sets of kanban cards are made. The number of cards in each set is closely controlled to keep the work in progress to the minimum.
The system of kanban ensures that a work station starts manufacturing a component only when it is asked by the next work station in the process sequence. Also a work center cannot ask for replenishment of material till the material ordered has been processed the kanban card returned with the material.
The exact content and format of the kanban card can vary considerably. However the kanban card mus include some minimum information. This includes the description of the product or component to be supplied or manufactured. Quantity of the item in each supply lot, identification of supplying work center, identification of receiving work center, Reference number of the card, identification of persons preparing the card.