| In the beginning of 1990's, Reverse Engineering technology arises highly attention of many countries' industrial field and academic field. Especially with the development of computer and test technology, by using CAD/CAM and advanced manufacturing technology, have realized product material Reverse Engineering technology,which has become the main application field of Reverse Engineering technology.Industrial products design needs duplication , now Reverse Engineering based on the prototype applies broadly in products' duplication and copy , especially products' appearance , because of not being concerned with technical difficult problems such as complex dynamics analysis and material processing , we can realize relative easily. The digital scanning technology based on the system of CAD/CAM has offered strong support for the Prototype Reverse Engineering technology. After digital scanning and 3 D reconstruction of prototype, we can make mould fast through NC processing, eventually, pour to mould, and then get the product needed. This process has become the product development pattern of a lot of product enterprises in coastal area. However, every link of entire product development needs special technical people, and for partial products or some parts of products do not need 3 D mould reconstruction. So, aim at those parts which have simple curved surfaces and require prototype as soon as possible, the paper put forward the method which generate NC code directly by the coordinate measuring data.During the course of realizing NC code generation directly by measuring data, measuring data acquisition is the foundation of entire technology; This paper gives measuring method which aims at NC code direct generation .Now, the important tool of measuring data acquisition is 3 coordinate measuring machines, since its kinds are numerous, the data files forms are different. The paper give the method--using intermediate form file can solve the problem of different coordinate measure machine file forms.The pre-treatment technology of 3 coordinate data is the crucial technology to realize NC code generation, because it decides whether NC code is right or wrong. The pre-treatment technology includes deleting redundant data, interpolating necessary data, polishing process, distinguishing feature points, and fitting simple graphics, finally generating the data chain table that used for NC code generation.Now NC code generation directly based on measuring data has two typical algorithms: numerical loci generation based on measure data of profile modeling and numerical loci generation based on magnanimity data NC. According to those parts with relatively simple curved surfaces, the paper regard measuring route as the numerical locus, which can realize the conversion of NC code easily.Now, many CAD systems have NC code generation modular, we can put measuring datainto these CAD systems to get NC code. Since measuring data is simple data assemble, but for every CAD system, they have their own data file forms. Data file forms include graph data file, geometry model file and product model file. The own internal data pattern of every CAD system and the form of data file forms is related with their inner pattern closely, thus they are also different. Therefore user needs change between different data files' form: Can read in the file form of other systems and is read in by other systems, so, there has arisen data exchange file concept. DXF file has very strong representative as the file interface of AutoCAD series modeling software, the paper has studied conversion between measuring data and DXF files and developed viewing software to STL file form.According to the theory research result, this paper has developed system by adopting Visual C + + 6. 0 on the platform of Window NT/98. The system has realized the NC code generation directly, and the conversion of DXF files' format, and made 3 coordinate measuring data process's efficiency and quality improved obviously. |
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