Gap flow field simulation and experiment of electrochemical machining special-shaped inner spiral tube

In order to solve the problems of flow field divergence, short circuit, and poor forming precision in electrochemical machining (ECM) large-diameter special-shaped inner spiral tube with pull reverse flow-cathode structure, a pull downstream cathode structure is proposed which has the function of changing working teeth and converging electrolyte flow field. The gap flow field simulation model was established, and then comparing and analyzing the gap flow field between pull downstream cathode model and the pull reverse flow cathode model. The simulation results show that pull downstream cathode structure is better than pull reverse flow-cathode structure in the gap electrolyte velocity, pressure, and streamline under the condition of 15 m/s electrolyte inlet velocity and electrolyte outlet pressure with atmospheric pressure. We also analyzed the stress and displacement of these two different cathode structures. The simulation results show that the maximum stress is 0.350 MPa and the maximum displacement is 4.275 × 10 −5 mm with pull downstream cathode. However, the maximum stress of traditional pull reverse flow cathode is 0.428 MPa and the maximum displacement is 5.6355 × 10 −5 mm. Finally, under the conditions of 12 V, 20 mm/min cathode feed speed, 15 wt% NaCl electrolyte with temperature 30 °C, and inlet pressure 1.5 MPa, the 2000 mm qualified sample was machined stably and reliably by pull downstream cathode. It indicates that it is feasible to machining large-diameter special-shaped inner spiral tube with the new pull downstream cathode structure.