THE MODELING AND SIMULATION OF A PICK AND PLACE COMPUTER-INTEGRATED MANUFACTURING (CIM) CELL

This paper presents the work carried out on the modelling and simulation of a pick and place CIM cell. The CIM cell was designed to manufacture printed circuit boards (PCB) and consisted of four numerical controlled machines, two conveyor systems and a number of electronic devices all connected to an Ethernet local area network (LAN). With many companies across Europe [1] and the USA [2] now implementing Ethernet into their manufacturing environment, it is important that for time-critical CIM systems there is sufficient capacity within the Ethernet protocol so that there is no loss in production and that bottlenecks within the cell do not occur due to long message delays. This paper pays particular attention to the information processing function, the network communication protocol Ethernet. This communication protocol, although very popular, can give rise to long message delays which is not conducive to time critical CIM systems. In order to determine the maximum message delay which hitherto has not been considered has led to the development of a complete model of the pick and place CIM cell in which bath the operational and information processing functions were modelled and simulated using two independent simulation tools, SIMAN and L.NET. Results from the complete model have shown that providing the maximum message delay, within the pick and place CIM cell, is less than the smallest machine operating time, there is no loss in production and bottlenecks do not occur. The paper concludes that the approach adopted in this paper could be used for any CIM system and that determining the maximum message delay in this way gives a very important design parameter particularly for time critical CIM systems.