Research On The Large Diameter Integral Impeller With Numerical Control Electrochemical Machining

Numerical Controlled Electrochemical Machining (NC-ECM) is a new kind of technology which combined the advantages of Electrochemical Machining (ECM) with Numerical Control technology. By using generating motion of simple cathode, this technology can solve the problems in machining complex-shaped components which are made of high-strength and heat-resistant alloys. Through years of research and testing, this technology is becoming mature. Based on the previous relevant researches and literatures, the study took the passage processing and finishing machining of large-diameter integral impeller as the research object, and carried out technological experiments.To begin with, three-dimensional geometry model of blade was built according to the point cloud data based on Bicubic B-spline Surfaces, thus design of cathode, calculation of the displacements in eccentric clamping, and programming of NC-ECM manufacturing program were studied. Besides, the overcut, which caused by width of cathode's machining edge and the twist phenomenon of the blade, and its solutions were discussed. Then ECM technological experiments were carried out using DC-power and Pulse power in terms of designed cathode, which contributed to the later discussion the light spots having appeared in DC-power ECM experiments. Accordingly, Pulse power was proposed to be used in machining surfaces of the blade.Moreover, with reference to flow field of cathode, the steps of numerical simulation are explained on grounds of Computational Fluid Dynamics (CFD). Numerical simulations were carried out to solve the problems caused by local insufficient of electrolyte and the effect of structure of cathode's inner channel on velocity of electrolyte. These results provided theoretical basis for perfecting the design of cathode.Furthermore, large-diameter integral impeller waiting to be processed exceeds the machining range of ECM machine, the misalignment between the center of workpiece and rotation centre of ECM machine was put forward to widen the machining range.Eventually, using this fixturing method, experiments were conducted to perfect NC electrochemical machining large-diameter integral impeller. More importantly, the problems, including the overcut of blade root and dispersion corrosion of blade surface, were discussed and the solution was proposed. The factors affecting machining accuracy were analyzed as well. Based on all these results, the sample of large-diameter integral impeller was machined electrochemically.