Triangular Mesh Model Based Direct NC Programming System Development

With the development of digital design and manufacturing technology and its increasingly wide range of industrial applications, the construction of digital surface models and CNC machining is becoming its core areas. More construction of surface model began in the physical model due to the complex surface functional requirements. the triangular mesh of the surface expression has been very popular and widely used for rapid prototyping. However, compared with more mature CNC machining methods of parametric surface model, the research of CNC machining system based on mesh model directly is facing a number of difficulties. In this paper, based on the STL triangular mesh models of model surfaces, we study the topological establishing of triangular mesh model and the generation of offset model, obtain intersection points of offset models using cutting plane method, the fitting of intersection points and so on, and generate NC code and system. The main work is detailed as follow:1) Investigating current research state of NC manufacturing of triangular mesh model, analyzing the key problems of this area, and proposing research work and an NC manufacturing strategy for triangular mesh model.2) Investigating generation method of offset triangular mesh model which is proposed and realized based on vertex offset. Investigating calculation method of vertex vector and judging method of interference on base of establishing reasonable data structure of triangular mesh model, and creating high precision as well as non-interference offset triangular mesh model.3) Investigating the cutting plane method based on topological after creating precision offset triangular mesh model and studying the tool path planning and manufacturing interval planning. Investigating and putting forward the improvement of calculation method of intersection points and realizing the accurate intersection method.4) Interpolating intersection points by Three times the uniform B-spline and calculating step length by iso-parameters approach, planning tool path according to the characteristics of the surface of parts and generating NC code. 5) On the basis of the above research, and through VC++6.0software and OpenGL technology, a NC manufacturing system for triangular mesh model was developed, and the feasibility and stability of the system was proved by experiment.