Research On Surface Modeling And Nc Processing Technology Based On Loop Scheme

With the increasing demand of product complexity and diversity, subdivision surface modeling technology and processing technology based on reverse engineering have been widely studied and developed. Compared with parametric surfaces, subdivision surfaces have some advantages such as arbitrary topology and overall continuity in modeling complex free-form surface, which makes it widely used in the field of games, animation, medical image processing and multi-resolution analysis. Loop subdivision as one of the most popular subdivision methods has been widely used. But there are still many problems to be solved in extending it to engineering application. Based on reverse engineering background, this thesis mainly researches Loop subdivision and Loop subdivision surfaces in the processing of applications, including the following content:(1) The research background and reverse engineering technologies are summarized. The history, development and characteristics of the surface subdivision are briefly introduced.(2) The properties of subdivision surface are studied, and several classical subdivision schemes, such as Doo-Sabin subdivision, Catmull-Clark subdivision, Loop subdivision are introduced, and several subdivision algorithm application effect are showed. Characteristics of typical subdivision algorithms are summarized and compared.(3) A detailed introduction of Loop scheme's fundamental is given, also includes the computation of limit coordinate of vertex and its normal. The problem of rapidly increasing number of data in the processing of subdivision is studied. On the basis of the rule of dihedral angle, adaptive Loop subdivision algorithm based on vertex flatness is proposed, which solve various problems.(4) Two subdivision surfaces isometric algorithms are discussed. To keep the sharp features in the process of offsetting, a method for different sharp feature points using different ways to offset is introduced. Then, on the basis of the offset surface, finish machining strategy with section plane method is proposed. Rough machining path is generated by using layer cutting method.(5) System experiments of the adaptive subdivision algorithm, equidistant algorithm and path planning algorithm are implemented, and using conventional CNC machining and 3D printing two processing methods processes models and obtains a better quality of in-kind, which verify the effectiveness of the algorithms.