A multi-objective customer orders assignment and resource leveling in make-to-order manufacturing

This paper presents integer programming formulations and compares two approaches – weighting and lexicographic – to the multi-objective, long-term production scheduling in make-to-order manufacturing, where both maximization of customer service level and best utilization of production resources are integrated in the objective function. The problem objective is to assign customer orders for various product types and with various due dates to planning periods and to select machines for assignment in every period to complete all the orders with minimum numbers of tardy and early orders and with a leveled machine assignment over a planning horizon. The two approaches are applied to optimize long-term production schedules in a flexible flowshop with parallel machines. Numerical examples modeled after a real-world flexible assembly line in the electronics industry are provided and some computational results are reported.