Design of cellular manufacturing systems with assembly considerations

This research proposes incorporating assembly aspects associated with a product into the design of Cellular manufacturing System (CMS). The literature on CMS design implicitly assumes that finished part is the end product by itself. In practice, often, manufacturers produce parts which are assembled into a finished product. A cellular system exclusively designed based on processing similarities generates the advantages of Group Technology (GT) and leads to an increase in production of parts. However, ignoring the integration of production of parts with assembly operations leads to increased work-in-process inventory and material flow in the system. To overcome this weakness, we propose that the managers of individual cells should be responsible for production of subassemblies instead of part families. The production of end product needs to be coordinated using the subassemblies produced across the cells.;The methodology employs a part-subassembly matrix derived from the product structure in addition to the part-machine matrix. A mathematical programming model is developed which determines an assignment of parts, machines and subassemblies to manufacturing cells. The proposed model employs a new similarity coefficient between part, machine and subassembly. The model resulted in a nonlinear program with 0-1 variables. We have examined three groups of solution procedures. Firstly, the nonlinear 0-1 program is transformed into an exact linear 0-1 program to solve the model for optimality. A Lagrangian relaxation based heuristic is developed to obtain a heuristic solution. Secondly, two alternative decomposition approaches are proposed. Heuristic algorithms are developed based on each of the decomposition schemes. Finally, solution procedures have been developed for three different cases based on the cost structure of the parts flow due to processing and assembly.;Computational results on test problems produced significant CPU times to obtain optimal solution. Lagrangian heuristic produced quality solutions on some of the test problems which could not be solved for optimality. The decomposition heuristics are found to be computationally very efficient compared to Lagrangian heuristic and exact methods, while maintaining the quality of solutions. The computational efficiency of these heuristics makes it suitable for realistic manufacturing settings with large number of parts, machines and subassemblies. The results also indicate that the proposed formulation significantly reduces the number of exceptional elements resulting due to both process and assembly. A case study has been analyzed based on a published part-machine matrix and a randomly generated product structure. The analysis reveals that it may be required to forego some of the efficiencies of GT in order to achieve integration of assembly operations with production of parts. From a practical stand point of view it is preferred to have a system design which has a mix of GT and integration efficiencies, compared to a design which out performs on GT criteria and completely lacks integration of assembly operations with production of parts.