Improvement on the machining accuracy of electrochemical machining by using an insoluble auxiliary anode

A common challenge in electrochemical machining (ECM) with insulating masks is the concentration of electric field at mask edges, which leads to localized over-etching and limits machining accuracy. This paper proposes a generic solution: the use of an insoluble auxiliary anode. This component, consisting of a metal substrate coated with an insoluble conductive layer, is installed in the non-machining area at the same potential as the workpiece. It functions by redistributing the local electric field, thereby suppressing the edge concentration effect without undergoing dissolution itself. The efficacy of this method is rigorously validated through its application in counter-rotating electrochemical machining (CRECM), a precision variant of ECM used for generating convex structures on difficult-to-machine titanium alloys. Coupled multiphysics simulation confirms that the auxiliary anode reduces the peak current density at the insulating edge by 37.5%. Experimental results demonstrate that it completely eliminates root over-etching (0 mm over-etch depth versus 0.122 mm without the auxiliary anode), producing a smooth transition at the structure root and improving profile fidelity. The corresponding increase in convex structure width (by 1.52 mm) further indicates more uniform lateral dissolution. In conclusion, the insoluble auxiliary anode provides an effective and generalizable strategy to mitigate electric field concentration in ECM processes that employ insulating masks. The successful implementation in the demanding context of CRECM confirms its practical utility and suggests broad applicability for enhancing precision in electrochemical machining.