Investigation of anode shaping process during co-rotating electrochemical machining of convex structure on inner surface

A novel co-rotating electrochemical machining method is proposed for fabricating convex structures on the inner surface of a revolving part. The electrodes motion and material removal method of co-rotating electrochemical machining are different from traditional electrochemical machining. An equivalent kinematic model is established to analyze the novel electrodes motion, since the anode and cathode rotate in the same direction while the cathode simultaneously feeds along the line of centres. According to the kinematic equations of the electrodes and Faraday's law, a material removal model is established to simulate the evolution of the anode profile in co-rotating electrochemical machining. The simulation results indicate that the machining accuracy of the convex structure is strongly affected by the angular velocity ratio and the radius of the cathode tool. An increase of the angular velocity ratio can improve the machining accuracy of a convex structure. A small difference in the radius of the cathode tool will cause changes in the shape of the sidewalls of the convex structure. The width of the cathode window affects only the width of the convex structure and the inclination α of the sidewall. A relation between the width of the cathode window and the width of the convex structure was obtained. The formation process for a convex structure under electrochemical dissolution was revealed. Based on the simulation results, the optimal angular velocity ratio and cathode radius were selected for an experimental verification, and 12 convex structures were simultaneously fabricated on the inner surface of a thin-walled revolving part. The experimental results are in good agreement with the simulation results, which verifies the correctness of the theoretical analysis. Therefore, inner surface co-rotating electrochemical machining is an effective method for fabricating convex structures on the inner surface of a revolving part.