Jet electrochemical machining of micro dimples with conductive mask

Micro dimples as a typical surface texture has been used in many fields for enhancing the functionality and performance. Electrochemical machining (ECM) is a promising approach for generating micro dimple. However, due to the isotropy of metal dissolution, the lateral undercutting of micro dimple is inevitable in ECM, which reduces the machining localization. This paper proposed a method of conductive mask jet electrochemical machining to reduce the undercutting of micro dimple and improve the machining localization. In this method, a conductive patterned mask instead of insulated patterned mask was covered on the workpiece directly during machining, which could decrease the undercutting of micro dimple by reducing the electric field intensity at the edge of micro dimple. In addition, a metallic nozzle (inner diameter of 2 mm) was employed to provide a stable columnar jet flow for enhancing the attachment between the mask and workpiece as well as the renewal of electrolyte in machining area, which was useful for generating deep micro dimple. Simulated results showed that the conductive mask could reduce the electric field identity at the edge of micro dimple effectively, and the undercutting of the profile was evidently reduced compared to that generated with insulated mask. Experimental results indicated that with conductive mask JEM, the undercutting of micro dimple was just 9 μm when the depth increased to 55 μm, the etch factor (EF) reached to 6.11, and it was four times greater than that with insulated mask. With the depth increased from 45 μm to 85 μm, the undercutting of micro dimple enlarged from 7 μm to 15 μm. The material removal rate in depth was evidently faster than that in diameter, which showed a low undercutting and high machining localization. In addition, compared with pulse current, direct current was more appropriate for generating deep micro dimple in conductive mask JEM.