Tool Path Planning Research Of Cnc High Speed Machining Based On Triangular Mesh Surface

Free-form surface parts are widely used in aerospace,ship-building,automobile and mould manufacturing fields for its excellent dynamic and thermodynamic characteristics, Three-axis NC machining based on triangular mesh model has been studied deeply, however, the research on five-axis NC machining is relatively few. As a bridge of triangular mesh surface design and multi-axis machining, NC processing technology increasingly highlights its importance. Especially, for tool path planning technology, it has become a hot and difficult topic of research in this field.In the NC machining for complex triangular mesh surface, the planning of tool path's continuity is of great significance to the machining efficiency and quality of free-form surface. This paper reviews the domestic and foreign research progress for tool path planning of triangular mesh surface, researching the related core technology of five-axis NC machining for triangular mesh surface. The algorithm of the golden section method for variable step size and equal chord error and the CNC high-speed machining tool path planning algorithm based on triangular mesh surface mapping are both proposed.Simulation experiments show its obvious advantages on the aspects of the surface quality,path length and the relative error of adjacent track, compared with section method and circumcision on the machined surface.The main research works of this paper are as follows:1.Characteristics analysis of Triangular mesh surface model. It mainly uses the adaptive of triangular mesh unit topology by analyzing the cutter-contact points at different locations of the geometry composed of the triangular grid cells. it contains positional determination method of blade contacts on the triangular grid cells, normal and curvature's calculation of cut contact point on the triangular mesh cells. The research lay the foundation for the following tool path planning.2. A kind of algorithm for variable step size with equal chord error based on method of golden section is proposed. Compared with conventional calculation method with equal chord and equal step,The algorithm has the most significant feature of using the golden section method to compute the maximum chord error and variable cutter-contact points. At the same time, it avoids judgment errors caused by chord midpoint error checking method by using given symbols to determine the radius of curvature of the chord error checking methods.3. A kind of algorithm for tool path planning in CNC high-speed machining isproposed based on mapping of triangular mesh surface. Compared with algorithm of conventional tool path planning(section, circumcision etc.), it has improvement on quality and efficiency of machining. By mapping the cutter-contact points to the parameter domain, re-planning cutter-contact points in parameter domain and fitting them to helix by using NURBS method of least square. Then the helix is re-mapped to the mesh surface and finally get spiral machining trajectory which meets constant scallop-height and equal chord error.