Precision wire electrochemical trimming of turbine slots by equalizing electric-quantity via velocity manipulation

Abstract

Efficient and cost-effective manufacturing of turbine slots has always been a challenge for aeroengine production. Wire electrochemical machining (WECM) is a feasible alternative because of its inherent characteristics. However, it readily leads to profile errors because of the uneven material removal that results from an inconsistent electric quantity when trimming complex profiles in an equidistant offset. To improve the machining accuracy of WECM for trimming turbine slots, this study proposes an electric-quantity manipulation strategy that regulates the trimming velocity of wire electrodes to facilitate equal material removal for complex profiles. The evolution of complex profiles was revealed through simulation, which led to the derivation of profile shape-dependent, regulated trimming velocities that enabled an equal electric quantity and amount of material removal. Subsequently, the electric quantity distribution, material-removal depth, and profile deviation of the turbine slot structure with and without the manipulation strategy were compared through simulations and experiments. The surface integrity of the machined turbine slots was verified. The experimental results indicate that the WECM trimming technique with the manipulating strategy prevents overcutting at convex arcs and undercutting at concave arcs, reduces the overall profile deviation of the turbine slot from ±50 to ±18 μm, and reduces the deviation of the mortise–tenon contact surface from ±30.7 to ±3.6 μm compared to that without the manipulating strategy. The fir-tree turbine slots were prepared efficiently and precisely via one-pass WECM trimming. The equalizing electric quantity strategy effectively improves the machining accuracy of WECM trimming for a complex profile.