Effective Tool-Path Generation in NC Machining of 3D Sculpture Surfaces

• Main Authors: Chang, Cheng-Chang, 張振彰
• Other Authors: Hong-Tzong Yau
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/80336084967613282881

碩士 === 國立中正大學 === 機械工程學系 === 85 === Introduction Traditionally, most of the CAD/CAM systems would approximate the surface with many small linear segments to construct the NC code. When high accuracy is demanded for the resulting machined surface, the NC code will become very large which will extend the machining hours. The surface machined by linear NC segments is very "rough" that would take a lot of time to polish the resulting surface and the accuracy can not be controlled easily. To improve the problems mentioned above, this research proposes the method of combining circular and linear machining segments for replacing the traditional linear machining mode. Recently, due to the development of laser scanning and high speed measuring systems, reverse engineering of physical models such as dies and molds caught great attentions. The digitized data of the physical models scanned by these systems can be NC machined directly. Gouging can be avoided by lifting the cutter when the data points interfere with the cutting tool. The problem of this method is the difficulty of determing the "uncut" area caused by gouge protection. We propose a method to determine the "uncut" section by curvature change analysis, and then use a cutter with smaller radius to machine the "uncut" section. Lastly, in order to satisfy the accurency requirement, we use surface profile tolerance to adjust the step-length and the distance between two NC paths. The result of this research is implemented in an NC code generation system that can take input data either from a complex CAD surface model, laser scanner and CMM, or even other G01 based NC code, and create a highly efficient NC code that combines both linear and circular cutting segments, and this system has achieved the goal of shortening the machining time, cutting down the NC code and improving the resulting surface quality.