1. Historical Background of Toyota’s Production System
Kanban System was found by the Vice-President of Toyota Motor Company Taiichi Ohno in the middle of the 20th century. The idea behind Kanban System came from US supermarkets and this system is about producing only the necessary products, at the necessary time, in necessary quantity (Sugimori et al., 1977).
The starting point of Kanban was the recognition of diversity of Japan’s features and the idea is developed by considering the two distinct characteristics of this culture : (1) lack of resources in Japan, (2) Japanese working culture (Sugimori et al., 1977).
After World War II, Japan was affected excessively - insufficient and ...view middle of the document...
(Sugimori et al., 1977) To understand Kanban, one must be aware of pull systems. A pull system controls the flow of resources in production by replacing only what is consumed. To illustrate, let’s assume that an order is received from the final customer. Next, pull system is activated with a message which is sent to a plant to complete products to be scheduled. Then, the company gives related raw material information to its suppliers in order to start production of the order. When materials and/or subassemblies arrive to the plant, assembly of the products starts with considering due date of the order. At the end, orders exit the production line and are supplied to the final customer who orders them. Actually, they are already sold at the very beginning.
JIT is based on a pull system and Toyota was applied its JIT system with kanbans. Kanban production control system includes the usage of cards that manage the production of parts and delivery in plant. Therefore, there are basicly two types of kanbans : (1) production kanban which is used to order production of the portion withdrawn by the succeeding stage and (2) transport kanban (T-kanban) which is carried when going from one stage to the preceding stage (Huang C. & Kusiak A., 1996).
Literally, Kanban production control system connects two consecutive stages of production, that are isolated in terms of time, through buffer stocks (Mertins & Lewandrowski, 1999). Since the objective of the Kanban system is to deliver the parts to the production stages by JIT and to pass information to the preceding stage about what, when and how much to produce, it works as shown in the Figure 2.1.
Figure 2.1. General overview of Kanban system: (1) Demand from stage i+1 originate, kanbans are withdrawn and placed on dispatching board. (2) Production starts and demand is sent to stage i-1 when demand exists at stage i. (3) Finished parts and kanbans are sent to stage i+1.
First of all, when parts are processed and demand from stage i+1 occurs in stage i, the production Kanban is removed from a container and then it is placed on stage i’s dispatching board which shows production schedule. Next, transport kanban from stage i+1 takes the place of the production kanban and container. This container and transport kanban are sent to stage i+1 for further processing.
At that time, in stage i, the produciton activity starts when production kanban and container with transport kanban are available. Production kanban takes the place of transport kanban which is sent back to stage i-1 to start production at stage i-1. This creates a production chain (Huang C. & Kusiak A., 1996).
In addition, there are other kanban cards using in production : (1) Supply kanban works between storage or warehouse to production plant, (2) procurement kanban travels from outside of a company to receiving area, (3)...