The Study On Precisely Cathode Design System Of Turbine Blades And Experiments In Electrochemical Machining (ECM)

Blades are the most essential parts in aero-engines and play important roles in aero-engines'in the national defense industry. One of the main manufacturing methods of blades is the electrochemical machining (ECM). The problem of cathode design is the key and difficult one should be solved first. The aim of the researches in the thesis is to design the blade's cathode efficiently and precisely, and to improve the precision of blades which are manufactured in ECM. And the study of the shape evolution and prediction in the thesis emphasizes on the theoretical analysis, it will be helpful to the ECM process control in the future.Using the compressor rotor blade of some type aero-engine as research object, according to the structure requirements and the precision requirements of the blade, the thesis has proposed the optimization criterions and optimized the feeding direction of cathode. Furthermore the distribution of space angle between the cathode's feeding direction and the normal direction of the blade shape has been analyzed, which can directly influence to cathode design.Based on the ECM shaping theories, two kinds of methods have been demonstrated in the paper: the cathode design method established on the basis of mathematics model of simplified electric field and the finite element cathode design method on the basis of mathematics model of actual electric field distribution. To improve the precision of the cathode design, a new method to remedy the cathode is proposed, which is a closed-loop control system constructed by transmiting the shape errors of the blade in experiments to the cathode.In the thesis the distribution of variable flow factors has been studied based on the hydrodynamics theories in detail for the special three-dimension inter-electrode gap space during the all-round ECM process. The thesis has used the database technology to solve the influence of variable electric current efficiency on tool cathode design, which is brought by non-linear electrolyte. All of the above studies make the cathode design be accord with the actual physics course of ECM.In the thesis the ECM process of the blade has been analysed. The analysis includes the blade shaping simulation and prediction considering of the influences of flow field factors and non-linear electrolyte, and the optimization of the cathode's feeding route during the ECM process that is primitively analyzed. Besides these researches, the prediction of the blade's shape accuracy using BP neural network has been constructed.The CAD/CAE/CAM system for cathode design of blades in ECM is developed on the UG software in this thesis. In the system a precise tool cathode according to a blade's sketch can be designed by using the CAD model, and the NC code of the cathode can be acquired in the CAM part. Furthermore the system also includes the optimization of the cathode's feeding direction, the simulation of the blade's evolution in the ECM process and the prediction of the experimental blade's accuracy.Finally a serial of experiments have been carried on the new designed three-direction feeding electrochemical machine. The experimental results are used to prove the cathode design precision and the reliability of the whole system. And the BP model trained by using the experimental results is of good accuracy and practical worth too.The cathode design system for ECM aero-engine blades combines the key technologies in the thesis with the modern CAD/CAE/CAM software. The researches will reduce the handworked times of remedying cathode, and improve the precision and efficiency of the blade in ECM. Finally it will be helpful to manufacture blades in ECM precisely.