Co-rotating electrochemical machining of convex structures on the inner surface of annular parts using a flexible cathode tool

Abstract

Thin-walled annular parts are widely used in the aerospace industry. There are some irregular island structures with non-periodic distribution on the inner surfaces of annular parts, which poses a significant challenge to manufacture such annular parts using conventional mechanical methods. Electrochemical machining (ECM) has exhibited good prospects for manufacturing thin-walled annular parts, with the advantages of no tool wear, no processing deformation and a high material removal rate. However, there is little research related to fabricate convex structures on the inner surfaces of annular parts, although ECM is vital to the machining of thin-walled annular parts. In this study, a flexible cathode tool was used to machine irregular convex structures on the inner surfaces of annular parts via co-rotating ECM. The complex motion of the cathode tool and conductive slider was simulated using matrix equations, and the digital simulation of the material removal process was realized based on matrix equations and Faraday's law. Based on the mathematical model, a design method for a flexible cathode tool was developed, and three main parameters were determined: the position of the window, radius of the cathode, and width of the window. Comparative experiments were performed using the flexible and conventional cathode tools. The results showed that the selective removal of convex structures was achieved by using the flexible cathode tool. The insulated sheet needed to be attached to the position where the convex structure was retained. An aero-engine casing with many irregular island structures on the inner surface was successfully machined. The height of the fabricated island structure is 6 mm. The sidewall thickness of the aero-engine casing is 1.2 mm. Therefore, co-rotating ECM with a flexible cathode tool offers excellent machining ability for irregular island structures on the inner surfaces of annular parts.