Study on nesting scheduling for sheet metal processing (Improvement of nesting method by parts reallocation)

Abstract

In recent years, manufacturing industries are required to provide various kinds of products in a short time. They are also required to reduce the effects on the environment. In sheet metal processing, to achieve these requirements, process planning and production planning should be managed suitably. For process planning, nesting is done in order to design the optimal layout for sheet metal in terms of reduction of waste material. Scheduling is done in order to satisfy the due date of products. Nesting and scheduling are affected with each other and there occurs a certain trade-off between them. Therefore, those problems should be considered simultaneously in order to increase the efficiency of entire manufacturing activity. Under such understanding, we propose an integrated method of scheduling and nesting. In its procedure, scheduling is firstly executed by using dispatching rule. Then, based on the result of scheduling, nesting is executed by using bottom left algorithm. Moreover, to update the nesting result, the layout is redesigned by reallocating parts in each sheet metal according to its size. Finally, in order to validate the effectiveness of proposed method, we implemented prototype of nesting scheduling system and carried out computational experiments. The results are compared to a conventional method in terms of total tardiness and the number of sheet metal. To validate the effectiveness of reallocation, yield rate is also compared between the proposed method with and without reallocation.