Toyota Production System

"Just-in-Time" means making only "what is needed, when it is needed, and in the amount needed." To efficiently produce a large number of products such as automobiles, which are comprised of some 30,000 parts, it is necessary to create a detailed production plan that includes parts procurement, for example.Supplying "what is needed, when it is needed, and in the amount needed" according to this production plan can eliminate waste, inconsistencies, and unreasonable requirements, resulting in improved productivity.
In the TPS, a unique production control method called the "kanban system" plays an important role. The kanban system has also been called the "Supermarket method" because the idea behind it was borrowed from supermarkets. Supermarkets and mass merchandizing stores use product control cards on which product-related information, such as product name, product code, and storage location, is entered. Because Toyota employed kanban signs in place of the cards for use in production processes, the method came to be called the "kanban system." At Toyota, when a process goes to the preceding process to retrieve parts, it uses a kanban to communicate what parts have been used.- Why use a supermarket concept?A supermarket stocks the items needed by customers when they are needed in the quantity needed, and has all of these items available for sale at any time.Taiichi Ohno (a former Toyota vice president), who promoted the idea of Just-in-Time, applied this concept, equating the supermarket and the customer with the preceding process and the next process, respectively. By having the next process (the customer) go to the preceding process (the supermarket) to retrieve the necessary parts when they are needed and in the amount needed, it was possible to improve upon the existing inefficient production system in which the preceding processes were making excess parts and delivering them to the next process.
Through continuous improvements, the kanban has evolved into the "e-kanban," which is managed using IT and increases productivity even further.
Two kinds of kanban (the production instruction kanban and the parts retrieval kanban) are used for managing parts.