Electrochemical direct-writing machining of micro-channel array

Abstract

Bipolar plate is an important component in proton exchange membrane fuel cell. The machining of micro-channel array is a key process for the fabrication of metallic bipolar plate. This paper proposed a novel approach named electrochemical direct-writing machining for generating micro-channel array on thin metallic plate at one time, showing a high machining efficiency. In this method, an insulated mask with a row of micro through-holes was integrated to a metallic nozzle, the electrolyte ejected from the nozzle reached to the workpiece through micro through-holes, and then the micro-channel array could be generated from dots to lines by controlling the movement of workpiece. In the machining process, the non-processing zones were covered by the insulated mask, which avoided the stray corrosion. By analyzing the results of simulation and experiment, it was found that due to the accumulation of electrolytic product in the ending point, the profile of this point was different from that of the starting point. The parameters with the voltage of 20 V and pulse duty cycle of 20% were useful for preparing micro channel with good profile and low dimensional difference. And compared with other pulse frequencies, the pulse frequency of 2 kHz could obtain a deeper micro channel. With other parameters unaltered, the dimension of micro channel was decreased with the increasing moving speed of workpiece. At last, with the optimized parameters (voltage = 20 V, pulse duty cycle = 20%, pulse frequency = 2 kHz, and moving speed = 20 μm·s−1), ten micro channels with the length of 60 mm were generated at one time on a metallic plate with the thickness of 0.5 mm. The width was 302 ± 3.53 μm (Mean ± SD) and the depth was 95.9 ± 1.34 μm, showing a satisfied dimensional consistency.