MODELING OF MATERIAL HANDLING HOIST OPERATIONS IN A PCB MANUFACTURING FACILITY

This paper outlines a framework for flexible hoist scheduling that utilizes a knowledge-based simulation system to emulate multi-hoist operations in an electroplating line and derives hoist schedule to meet production demands. The selected hoist schedule is then used by the knowledge-based controller to control the material handling hoist operations in real-time. The paper describes the overall design of the knowledge-based simulator for material handling hoist operations that forms the fundamental part of the proposed framework. Most hoist schedules in industry are experimented on-line, which are costly and time consuming. The use of knowledge-based simulation will save both cost and time. The simulator aims at improving current manual approaches so that better schedules can be identified. We demonstrate the application of the simulator to bi-directional multi-hoist line configuration that is commonly found in industry today, where loading and unloading stations are on the same end of the line, and consider other more realistic system parameters than those considered in previous studies. Three new hoist scheduling heuristics are proposed and their performances are compared with four previously studied rules. To this end, we also study the effect of several system variables such as hoist speed and inter-hoist distance on productivity. The simulation models developed are based on data from actual multi-hoist electroplating lines within several PCB manufacturing facilities.