Robotics and Computer Integrated Manufacturing 17 (2001) 87}97 Scheduling manufacturing systems in an agile environment

Producing customized products to respond to changing markets in a short time and at a low cost is one of the goals in agile manufacturing. To achieve this goal customized products can be produced using an assembly-driven product di!erentiation strategy. The successful implementation of this strategy lies in e$cient scheduling of the system. However, little research has been done in addressing the scheduling issues related to assembly-driven product di!erentiation strategies in agile manufacturing. In this paper, scheduling problems associated with the assembly-driven product di!erentiation strategy in a general #exible manufacturing system are de"ned, formulated, and solved. The manufacturing system consists of two stages: machining and assembly. At the machining stage, multiple identical machines produce parts. These parts are then assembled at the assembly stage to form customized products. The products to be produced in the system are characterized by their assembly sequences that are represented by di!erent digraphs. The scheduling problem is to determine the sequence of products to be produced in the system so that the maximum completion time (makespan) is minimized for any given number of machines at the machining stage. The scheduling problems discussed in this paper have not been solved in the literature. The originality of the paper lies in de"ning and formulating the problems in the context of agile manufacturing and developing optimal and near-optimal for solving them. The heuristic algorithm solves the scheduling problem in two steps. First, an optimal aggregate schedule is determined by solving a two-machine #owshop problem. Next, the optimal aggregate schedule is decomposed by solving a simple integer programming formulationmodel. The computational experiment show