Research On Tool Path Planning Method Of Impeller Machining Based On Least Squares Principle

As the core component of turbomachinery, impeller has complex structure and its manufacturing technology has been an important problem in the field of CNC machining. The CNC machining process of impeller usually contains roughing, semi-finishing, finishing and polishing processing stage from blank to production, in which the rough machining and finish machining process are the most important two stages in the impeller machining. The rough machining directly affects the production cycle and cost of impeller. The finish machining directly affects quality of impeller, while the quality has an important effect on the overall performance and mechanical efficiency of impeller. Therefore, studying the impeller CNC machining method has important application value. The semi-open integral impeller is regarded as research target, which has undevelopable ruled surface blade. On the basis of the complete impeller digital modeling of impeller, rough machining and finishing stage have been studied, the main contents are as follows:Firstly, digital model of impeller is constructed and as a basis for CNC machining research. The entire construction process of impeller model is presented, and the model is constructed under the MATLAB software and UG software environment.Secondly, the roughing tool path planning of impeller is completed. To improve the efficiency of rough machining and ensure uniform margin, this paper applied in segmentation variable axis plunge milling method. Without interference rough machining area is obtained by envelope ruled surface of blade offset surface intersecting with the offset surface of hub surface. Tool path of Plunge Milling is planned in the area. Finally, rough machining simulation is completed, which verify the theoretical feasibility.Finally, a new finishing algorithm for flanking undevelopable ruled surface is proposed. The theoretical model of flank milling non-developable ruled surface has been summarized as the best square approximation problem for the tool surface and surface designed. Motivated by the definition of the machining errors induced by tool path planning methods, a mapping curve of the tool axis of a cutter is constructed on the tool surface. The mapping curve is the typical one which can be used to express the closeness between the tool surface and the surface to be machined. Further, the least square (LS) approximation model and corresponding solving methods for the determination of the tool position have been presented. Experimental results show that the geometrical errors related to the proposed method significantly lower than that associated with the double points offset (DPO) method, three points offset (TPO) method and CNC machining module of UG. Tool path planning of finishing milling for blade surface is completed by LS method, and machining simulation is completed in UG software. Besides, the machining error of blade surface is analyzed. Tool path planning of finishing milling for hub surface and blade fillet is completed by proprietary CNC machining module of UG.