4.2 Simulation models
To test the effect of the kanban size on different types of JIT manufacturing systems, two simulation models are developed using the SIMPROCESS simulation package.
There are basically two simulation models; Fig.4and5 show the systems built in the SIMPROCESS environment.
The figures show both the flow paths of materials and kanban card. Six sequential production station are built in the simulation model, between each of which a WIP buffer is allocated. Another type of buffer will be used to model the collection of kanban signal in the Pull-type manufacturing system, i.e., the kanban signal buffer. It is eorth stressing here that these kanban signal buffer are not physical buffer, but are not modelled here only for the simulation purposes. In each experiment, the kanban size can be varied by changing the capacity of the WIP buffer. This buffer is of finite capacity so that maximum level of the WIP is equal to the kanban size.
Fig.4 show a Pull-type manufacturing system where there are two type of buffer placed between the workstation, one for WIP, i.e., WP1,WP2,...,WP6, and the other one for kanban signal, i.e., m1..m5. Fig5 show a Hybrid-type manufacturing system where only a WIP buffer was placed between workstation, since there is only material flow between them but no kanban signal flow except for station 1. Therefore, only one kanban signal buffer,i.e., message, is used for receiving the feedback signal from station 6 to station 1. In fact, this signal is used to authorize the production at station 1.