Research On Geometrical Modeling And Layered NC Machining Method Of Closed Impeller

As a type of representative channel parts with sculptured surface, closed impellers are widely used in aviation, aerospace, nuclear power, energy power, petroleum chemical industry and so on. With distinguished feature, twisted blades, narrow channel and closed structure, the performance of closed impeller is affected by manufacturing techniques, machining precision and surface quality. So it has a great significant to carry on the research of closed impeller in NC machining.The definition of rough/finish machining strategy, tool path planning of layered NC machining and the calculation method of cutter location in5-axis NC machining are core contents in this paper. Combined with parametric curve&surface modeling technology, the research of key curve&surface geometrical modeling and5-axis NC machining were widely carried on.First of all, the ruled type blade which consisted of pressure and sunction surface, the shroud and hub surface which rotated by shroud camber and hub camber, are constructed by using B-spline interpolation technique. Through OpenGL API of VC++/MFC integrated development environment, the closed impeller model is displayed.Then, according to the structure of closed impeller, a simple algorithm which is suitable for intersection between blade and surface of revolution and a new layered milling method, using conical surface layering the channel, were presented for5-axis NC rough machining of closed impeller. The conical surface is formed by rotating the straight line of blade on meridian plane around the impeller axis. Then the contour parallel tool path, the spiral tool path and tool-axes which were suitable for layered machining, were calculated in this paper. By calculating the error between representative discrete points on spiral tool path and layered section, analyzing the continuity of spiral tool path, the feasibility of this method was tested. After trimming the hub and shroud surface on inlet side, the tool side step, tool’s forward step and iso-parametric tool path were calculated.Finally, by using VC++/MFC integrated development environment and based on binary buffer technique of OpenGL, a detailed account of dynamic simulation of closed impeller and tool under MFC environment was introduced. The geometric simulation modeling of NC machining of closed impeller was constructed. By simulating the whole process, the tool path was tested and vertified.