外文翻譯--基于細(xì)分曲面生成的三軸數(shù)控切削軌跡的研究-數(shù)控設(shè)計(jì)-wenkub
2023-05-19 07:21:13 本頁面
【正文】 urface patches, . Bspline surfaces and NURBS surfaces, which are generated by CAD (Computer Aided Design) systems [2][6][7]. On the other hand it is difficult to obtain perfect modeling data using these parametric surfaces. For example, constructing a surface model with multipatches can cause gaps especially when the model is plex. A trimming operation among the patches is prone to connectivity errors. Current CAD systems cannot solve these problems automatically, and engineers have to correct them manually. It is a serious problem that NC data generated from such bad CAD models often affects the quality of products. In this research we adopt subdivision surface modeling technologies to solve these problems. The basic concept of the subdivision surface is to generate a smooth surface by repeatedly subdividing an initial polyhedron such as a triangular mesh. It has such a nice property that it can represent a plex shape in only “single” patch. Thus it is seldom required to have a multipatch structure or trimming even for a plex shape. In addition, the subdivision surface has certain continuity, for instance C2continuity almost everywhere on the surface. For these characteristics the subdivision surface has been a major representation in the field of puter animation [3]. However, in the field of CAD/CAM, it has not been used so much. One reason is that we have not yet known if subdivision surface can be applied to CAM. It is our fundamental motivation behind this research. The objective of this research is to develop an effective NC path generation method for subdivision surfaces, and get the best performance of automation and rapidity. In this research we select Loop subdivision surface [1] as our target subdivision surface. Its domain is a triangular mesh. In section 2 we introduce its basics. In our research we propose a path plan including two stages: roughcut and finishcut. The approach exploits LoD property of subdivision surface for these two stages. In other words, use a rough mesh for rough cut and a fine mesh for finish cut. The generated path plan is applied for threeaxis machining. These two stages utilize a Zmap model. In section 3 we describe the Zmap model in detail. In sections 4 and 5 we present algorithms of the roughcut path generation and the finishcut path generation. In section 6 we propose collision detection and correction for controlling machining accuracy and quality. In section 7 the implementation of cutter path generation and their machining result are demonstrated. Finally in the last section we discussed conclusions. 2. Loop Subdivision Surface In this section we briefly introduce Loop subdivision surface. More details are available in [13]. In 1987 Loop generalized the recurrence relations for boxspline to irregular meshes [1][9]. The Loop’s subdivision
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