A mixed integer programming model for a two line CONWIP-based production and assembly system

In this paper, a nonlinear mixed integer programming model was developed for a CONWIP-based production system where an assembly station is fed by two parallel fabrication lines. Raw materials are processed through the two fabrication lines. The processed parts are assembled to produce final products at the assembly station. The performance of the production system is measured by the total set-up time and the work load balance on the fabrication lines. The developed model is a nonlinear integer programming model consisting of two travelling salesman problem (TSP) sub-models. The nonlinear terms in the model was partially linearized and solved by enumerating a series of solutions of the TSP sub-problems. Optimal part assignment, production sequence and lot sizes are simultaneously determined by solving the problem. Optimal solutions of small size problems were obtained and are presented to illustrate the developed model.