Tham khảo tài liệu 'multiprocessor scheduling part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 350 Multiprocessor Scheduling Theory and Applications satisfactorily studied and are implemented in commercial nesting software. Such dedicated software tools allow the user to generate good nestings and to determine the cutting technology automatically. Process planning for air bending As for the laser cutting process research on the bending process focuses on process planning. When a 3D sheet metal part is produced with air bending one starts from the unfolded blank of the required part Figure 5 . Gradually this 2D flat blank is transformed into a 3D final workpiece by producing the different required bend lines. Different sequences are possible for producing the bend lines. Some bend sequences will cause collisions between the part the machine and the tools while other sequences create no problems. The main goal of process planning is to determine an executable bend sequence and to select the different tools to use for each bend line the gauging positions and the punch displacements. Figure 5. Different unfoldings of a part In order to determine the bend sequence the different interactions between the part the machine and the operator need to be investigated. For this purpose a model is required representing the part during each of the consecutive process steps. If all geometric specifications topological information material characteristics and process related information would be included in such a representation model the memory requirements could become very large. Some information however is redundant and only key information needs to be included. Duflou 1999 proposes a reduced foil model that contains only specific geometric information. This model also contains information regarding the topological relationships between the flange and the bend features of a part. For this purpose the part is represented by a graph with n nodes. The nodes represent the flanges while the arcs represent the connecting features. The part can then be represented by a .