Effect of Anisotropically-etched Silicon Electrode on Electrolytic Products Flow in Micro ECM

Abstract

Stray corrosion and electrolytic products deposition in the machining gap are major influence factors seriously restricting the application of micro electrochemical machining (ECM). Currently, one technical bottleneck is preparing thin and durable insulating films on electrode sidewall to restrain the stray corrosion. In previous work, we proposed an anisotropically-etched silicon electrode for micro ECM, on which silicon dioxide and silicon nitride are deposited as insulating films. The heavily doped silicon electrode body has good electrical conductivity, and the silicon-based films have excellent insulating property. The anisotropically-etched silicon electrode on (1 0 0) crystal plane has an isosceles trapezoid cross section. To get better machining performance compared with cylindrical electrode, the silicon electrode is rapidly rotated on a spindle in micro ECM process. The periodically varying lateral gap has a special effect on the electrolyte flow characteristics. A simulation model of electrolyte flow and discrete phase distribution is established by Fluent software. Simulation results indicate that the normal flow rate of electrolyte with silicon electrode is 50 times higher than that with cylindrical electrode, which is benefit for removing solid electrolytic products smoothly. The maximum concentration and residual ratio of solid electrolytic products are decreased with the rotating speed increasing. When the rotating speed is higher than 1200 rpm, the residual ratio is reduced to 13%. ECM experimental results indicate that electrolytic products on the workpiece machined by a silicon electrode are much fewer than that by cylindrical electrode. Silicon electrodes with trapezoidal cross section have a distinct advantage for reducing electrolytic products deposition.