Concurrent design of cell formation and scheduling with consideration of duplicate machines and alternative process routings

Concurrent design of cell formation and scheduling is an effective method for better implementing cellular manufacturing. To address the integrated cell formation and scheduling problem, a nonlinear mixed integer programming mathematical model is developed in this paper. This newly proposed model features the simultaneous consideration of many design attributes, such as duplicate machines, alternative process routings, reentrant parts and variable cell number. Several linearization techniques are proposed to transform it into a mixed integer linear programming formulation. An improved genetic algorithm (IGA) is developed to solve large-scale problems efficiently. To remove redundancy between two chromosomes, a cell renumbering procedure is applied in IGA. An illustrative example problem is solved and the results show that the integration of cell formation and scheduling can remarkably reduce the flowtime of cellular manufacturing systems. A set of thirteen test problems with various scale is used to further evaluate the performance of IGA. Comparison of the results obtained by IGA with those obtained by Lingo and CPLEX reveals the better effectiveness and efficiency of IGA.