Improvement in accuracy of micro-dimple arrays prepared by micro-electrochemical machining with high-pressure hydrostatic electrolyte

Micro-dimple arrays, as a common surface texture, play an important role in improving the tribological properties and lifetimes of mechanical parts. Through-mask electrochemical micromachining (TMEMM) is an important and popular approach for fabricating micro-dimple arrays. In traditional TMEMM that uses polydimethylsiloxane (PDMS) as a mask, the accumulation and escape of the oxygen bubbles generated on each micro-dimple vary considerably, which decreases the uniformity of the electrical field and leads to poor dimensional uniformity (including diameter and depth) of the micro-dimple arrays. In this paper, high-pressure hydrostatic electrolyte was proposed in order to enhance the uniformity of the electrical field distribution on the workpiece surface. Both the dimensions and machining accuracy of micro-dimple arrays under different applied direct current (DC) voltages during high-pressure hydrostatic TMEMM were investigated experimentally. Two novel phenomena were observed: (i) the dimensions of the micro-dimple arrays were greater at low voltages than at high voltages, and (ii) the machining accuracy was high at both low and high applied voltages but was low at intermediate voltages. At 32 V DC, an array of 14,000 micro-dimples was successfully fabricated with a diameter and a depth of 105.95 and 9.79 μm, respectively, and with diameter and depth deviations of 0.59 μm and 0.21 μm, respectively.