International journal of production research vol:45 issue:2 pages:369-383
Mathematical models, sometimes implemented in commercial software, allow optimization of individual machines based on specific criteria. For sheet-metal operations, cutting, punching, and air bending are the subject of extensive research, and both process planning and production planning can nowadays be automated to some extent. 2D cutting operations focus on minimization of waste material, and 3D bending operations focus on minimizing time-consuming setups. However, when integrating both processes, the benefits from separate machine optimization may disappear. Optimized nesting of parts at the laser can create additional setups at the pressbrake. In this paper, the use of OR techniques for integrated production planning for sheet-metal operations is analysed. An integrated production planning model is proposed, aimed at creating feasible groupings of parts while at the same time minimizing the number of time-consuming setups at the pressbrake. Simulation is used to confirm the applicability of the integrated approach. A case study is carried out to confirm the model's ability to generate feasible production plans. Those production plans are compared with a reference case, representing the current way of planning. An average makespan reduction of 4.11% is obtained, resulting in average yearly savings of about 10 days.