Sandwich-like electrochemical micromachining of micro-dimples

Micro-dimples have been applied to different mechanical components to improve friction and lubrication performances in various fields. Through-mask electrochemical micromachining (TMEMM) is a promising method for producing micro-dimples. In TMEMM, overcutting of micro-dimples leads to a deterioration in machining accuracy. This paper proposes a new method, sandwich-like electrochemical micromachining (SLEMM), to reduce overcutting of micro-dimples in diameter and to enhance the dimensional uniformity of micro-dimple arrays. Experimental results show that for a similar depth of 11 μm, the use of SLEMM instead of TMEMM leads to a reduction in micro-dimple diameter from 124.3 to 109.0 μm and a sharp increase in etch factor from 0.9 to 2.5, confirming that SLEMM should be able to enhance the machining localization and machining accuracy of micro-dimples. Arrays of 1500 micro-dimples were generated both by TMEMM and by SLEMM. For TMEMM, the micro-dimple diameter and depth increased from 120.8 and 11.0 μm, respectively, near the center of the workpiece surface to 130.4 and 12.8 μm, respectively, at the edge. In contrast, for SLEMM, the micro-dimple diameter and depth near the center of the workpiece surface, 109.0 μm and 11.2 μm, respectively, were almost the same as those at the edge. Thus, SLEMM can also improve the dimensional uniformity of micro-dimple arrays. Finally, different types of surface textures involving hexagons, ellipses, and squares can be fabricated using SLEMM.