| Closed impellers are a type of representative complex curved surface parts. The design of the working surface relates to several subjects such as aerodynamics, fluid mechanics and so on, so machining methods, machining precision and machining quality of the surface all have large effects on the capability parameters. With the integral structure connected by axis tray, cover tray and blades, closed impellers have a near closed cavity and are machined with more difficulty. So it has great significance to carry on the research of closed impellers in five-axis NC machining.Tool-path planning and cutter shaft vector ascertainment are main contents in this paper, and the NC machining of closed impellers is comparatively overall discussed. Firstly, with the assistance of UG software, a three dimensional solid modeling of closed impellers is finished, which is the foundation of NC machining. And a processing technology plan towards closed impellers is established, which brifely introduces the selection of NC milling cutters. And then according to the configuration feature and the research of the complex curved surface NC machining tool-path planning before, tool-path planning, step by step layers scan method which is suitable for closed impellers is proposed. Feed and anti-feed patterns, tool path patterns, shift patterns and clean-up machining are detailedly described in this tool-path planning, and the calculation method of cutting step length and optimal row spacing is introduced.In order to avoid interference during machining processes, there is a region division and regional analysis of the flow channel, and point towards control pattern is adopted. In this pattern, non-interference cutter shaft effective motion interval is finally confirmed by constructing aided constraint surface to restrict cutter shaft's motion range.At the end, selection principles and selection methods of cutting parameters are briefly introduced, and the tool path generation process of rough machining, semifinishing and finishing is described in detail. And the result of simulation in the machining module of UG software has proved that tool path planning in this paper is feasible. |
