Research On The Key Technologies Of NC-Electrochemical Precision Machining Of Blade Surface Of Integral Impeller

The electrochemical machining (ECM) is one of main processes which are used toprocess integral impeller. The available NC Contour Evolution ECM methods aresuitable for the machining of the integral impeller with ruled surface or small angel twistblade. If they are used to process the free-from surface blade and the accuracy can notmeet the requirement. In order to process free-from surface blade of the integral impellerand increase its machining accuracy, stability and work efficiency, the research of the keytechnologies of the blade precision machining have been carry out. It includes: ECMprocess, shape law, cathode design, cutting path planning, process parameter selection,trouble diagnosis and the digital manufacture technology.Firstly，the blade machining process is researched, a combination ECM process forfree-from surface blade is proposed, which divides the blade process to rough and finishworking procedures, and the different method is applied to meet shape and precisiondemand. In processing of the blisk tunnel, the new method, fractional step, is applied toprocess600mm integral impeller. In the study of the finely process of the free-fromsurface blade the shape cathode is adopted. In order to verify the new process, the240mm integral turbine is selected as the test object. For this purpose, the processdevice with open structure has been developed, the pulse generator is used to achieve thesmall machining gape and the error compensation is adopted to reduce the machiningerror arise from the uniformity of the machining gap. The application of the abovemethods increases the machining accuracy of the blade.Then, the digital manufacture technology of impeller digital has been carried out.The ECM simulation method based on numerical calculation and process discretization ispresented in the paper. It uses finite element method to calculate the eclectic field,dissolution displacement and simulate the machined surface. The simulation software isdeveloped and applied to process analysis, cathode design, machining parameteroptimization in machining of the integral impeller. The component constrains anddimension drive methods are used to realize the motion simulation. The motionsimulation software is developed and applied to tool path planning, NC programming,error analysis. In the process of the integral impeller, the application of the digitalmanufacturing software increase the success rate of cathode design, the precision ofparameter selection and work efficiency. Finally, the selection method of process parameter is developed and it includes twostep, initial selection and optimization. The initial process parameter is selected by theaid of ECM database and then it is optimized by the simulation. The precise selection ofthe ECM parameter increases the accuracy of the blade. In order to improve themachining stability of integral impeller the trouble diagnosis system has been setup,which extracts the sensitive information from the machine current and electrolytepressure signals, then recognizes the machine pattern and judge the trouble. Thediagnosis system can avoid the damage caused by the trouble and protect the work piece.The research results show that the combination ECM process of the integralimpeller is feasible. The fractional-step method effectively increases the machiningprecision of blade root and blade back in machining of the blisk tunnel. The machiningaccuracy of the final machining blades increases to0.1mm. The blades have goodsurface finish and higher level of consistency.