International Conference on Industrial Engineering and Systems Management IESM 2007 May 30 - June 2, 2007 BEIJING - CHINA Real-Time Selection of Process Plan in Flexible Manufacturing Systems: Simulation Study * Ahmed HASSAM a , Zaki SARI b a Laboratory of Automatic of Tlemcen, University of Aboubekr Belkaïd, PoBox 230, Tlemcen 13000, Algeria. b Laboratory of Automatic of Tlemcen, University of Aboubekr Belkaïd, PoBox 230, Tlemcen 13000, Algeria. Abstract This paper presents the results of a simulation study of a typical flexible manufacturing system (FMS) that has routing flexibility. The objective in this study is to test the effectiveness of the modified dissimilarity maximization method (modified DMM) for real time FMS scheduling. modified DMM method is an improvement of the DMM method. Modified DMM method is an alternative process plan selection method developed for routing selection in real time FMS scheduling. A computer simulation model, which mimics a physical system, is used to evaluate the effect of DMM and Modified DMM rules on the system performance. The typical FMS employed in this study includes seven machining centres, a loading and unloading area, and six different part types. The part type has alternative routings because of the existence of identical machining centre in the system. The DMM and Modified DMM are used for selecting an incoming part and later routing it to a machining centre for its next operation. The result show that the Modified DMM outperforms DMM on system throughput in saturation case, increases utilization of the machines and increases utilization of the handling system. Key words: Flexible Manufacturing Systems, Routing, Real-time FMS control, Dispatching rules, Simulation 1 Introduction To achieve rapid response to customer demands, flexibility has become a key concept in the design and control of manufacturing systems. Flexible manufacturing systems were developed to combine the flexibility of conventional job shops and the productivity of flow lines. FMS consist of a computer controlled and an integrated configuration of numerically controlled machine tools inter-linked with automated material handling systems FMSs have been defined in a number of ways. Most of the definitions are based on the hardware used in the system. Other definitions are based on the capability or performance of the system. In a FMS each machine is quite versatile and capable of performing many different operations, therefore each part may have alternative routings in the system. The complexity due to the random part arrivals makes the real time routing selection and control problems multidimensional in nature. In this paper we present Modified DMM as an alternative process plan selection method developed for real-time alternative routings selection in Flexible manufacturing systems. * This paper was not presented at any other revue. Corresponding author A. Hassam. Tel +21343285689. Fax +21343285685. Email addresses: a_hassam@mail.univ-tlemcen.dz (Ahmed Hassam), z_sari@mail.univ-tlemcen.dz (Zaki Sari).