Research And Practice On Virtual-Prototyping-Oriented 3-D Expression Technology Of Mechanical Products

With the development of technologies and the requirement of survival, the technology of virtual prototyping is been regarded as one of the key methods that can upgrade their competition ability by manufacturing enterprises. Undoubtedly the construction of digital models of products is the base of that technology. The 3-D expression of products is the mergence of different data from marketing information, existing objects and engineering drawings and construction of digital models .The thesis addresses the theory and methods of the 3-D expression of products from different data sources. The author summarizes the characteristics of Bézier and NURBS curve and surfaces, investigates the data structure of 3-D models ; The principles, methods and evaluation of the fairing of surfaces and curves are also discussed.On the fundamental theory of 3-D expression, the characteristics of engineering drawings are analyzed, with the difficulties of 3-D reconstruction based on engineering drawings; the algorithms of surface blending are investigated, as a strategy of surface blending is indicated; the methods of avoiding data distortion are presented, after the analysis of IGES and STEP format and their application in the data exchange among heterogeneous platforms; the methods and process of 3-D expression based on engineering drawing are provided .The characteristics of reverse engineering of real parts are investigated, with the methods of data acquisition; the strategies and process of surface construction based on laser-scanned point cloud are presented; the process of 3-D expression based on real parts is indicated; the methods of variant design through reverse engineering of real parts; the process of variant design based on assembly models is presented.With the project "The Construction of digital mock-up for some brand of car" supported by some automobile corporation, Ltd. and the project " The Rapid Development and Variant Design of some brand of motorcycle" supported by some motorcycle corporation, the author summarizes the experience of 3-D reconstruction for virtual prototyping, and provides sound proof for the viewpoints in the thesis.