Research On NC Machining Technology Of Micro-texture For Drag Reduction On Blade Surface Of Whole Impeller

Reasonable arrangement of micro-texture on the blade can reduce the drag between blade and fluid,improve the performance of the engine.However,when the conventional NC tool path calculation of surface method is used to generate the tool path of machining micro-texture on the free-form blade of integral impeller,the tool axis will be rough and irregular,and the generation efficiency will be low.In this paper,the NC machining technology of micro-texture for drag reduction on the free-form blade of integral impeller is studied,including the design of micro-texture on the blade surface,the NC machining process of micro-texture and the NC tool path generation of micro-texture.The main contents and achievements of this paper are as follows:(1)The design of micro-texture for drag reduction on blade surface of integral impeller is studied.On the premise of ensuring the accuracy of the simulation,the flow field around the blade is analyzed.According to the hydrodynamic theory,a classification and identification method for drag reduction performance is designed.The influence of the direction and size of triangular micro-texture on drag reduction performance is investigated by using the control variable method.(2)The NC machining technology of micro-texture for drag reduction on the blade surface of integral impeller is analyzed and planned.A general micro-edge ball-end milling cutter is used to mill micro-texture.According to the characteristic parameters of impeller blades and micro texture,the appropriate cutting tools are selected,and the corresponding processing errors are calculated according to the tool parameters and the tool-moving mode.(3)A tool path calculation method for NC machining of micro-texture on the blade surface of integral impeller is designed.According to the geometrical characteristics of blade and micro-texture,the tool path curve is extracted by finding the intersection line of offset surface.According to the parameters of tool path curve and the requirement of machining accuracy,an efficient and accurate tool location generation algorithm of chord method based on dichotomy is designed.The initial tool axis vector is generated by establishing local coordinate system and reference plane at the cutter center and solving the critical tool axis vector satisfying the travel requirement of the machine tool rotation axis.The optimization model of tool axis vector is established,taking the change of milling inclination angle and machine tool rotation axis as the objective,and the swing region of tool axis as the constraint condition.A neighborhood minimal value search iteration algorithm is designed to solve the optimization model,and finally a fairer tool axis vector is obtained.(4)The simulation and experimental verification of NC machining of micro-texture for drag reduction on the blade surface of integral impeller are carried out.Using NX Open C++ secondary development technology,a tool path generation software for micro-texture NC machining of integral impeller blade surface is developed.The results before and after tool axis vector optimization are compared and analyzed,and the validity of the optimization model is verified.Processing simulation and experiments are carried out on VERICUT and five-axis NC machine respectively.The results are in line with expectations,which verify the correctness of micro-texture processing technology and tool path planning method.