Abstract: There are many complex island-like high convex structures distributing on the thin-walled revolution part represented by the aero-engine casing. Machining such parts still remain a lot of problems such as serious tool wear, long process cycle and large machining deformation. Counter-rotating electrochemical machining (CRECM) uses a revolving electrode as the cathode tool. The anode workpiece and cathode tool rotate oppositely at the same angular velocity, and the material is dissolved layer by layer. This method holds unique advantages for the machining of thin-walled revolving part such as aero-engine casing. The anode shaping process during CRECM is simulated numerically, the equivalent kinematics model of the electrodes and an anodic material dissolution model are established, and an anode shaping law during counter-rotating electrochemical machining (CRECM) of island-like high convex structure is mastered. The simulation results indicate that the profile of the convex structure is greatly affected by both the feed depth and width of cathode window. With the increase of the feed depth, the motion orbits of the frontier points of the cathode window changes from the initial pointed-cone to spindle shape, and the sidewall taper of the convex structure is reduced accordingly, showing a variation trend from normal cone to vertical to inverted cone. The increase of the width of the cathode window will lead to a larger inclination angle of motion trajectory of the frontier point, which is beneficial for achieving a relative straight sidewall profile. The sidewall profile of the convex structure at an arbitrary width of the cathode window can be simply obtained through angular rotation bias of the profile at a certain width. Furthermore, it is found that the inter-electrode gap in CRECM is in a non-equilibrium state. On the basis of simulation analysis, a CRECM experiment is carried out. A high island-like high convex structure is fabricated successfully on the surface of thin-walled nickel-based GH4169 super alloy without any tool wear. The experimental results indicate that the CRECM method has good processing performance for the thin-walled revolving parts with high complex island-like convex structure.

Key words: electrochemical machining, thin-walled revolving part, counter-rotating motion, island-like convex structure, inter-electrode gap