A Study on Electrochemical Micromachining for Fabrication of Microgrooves in an Air-Lubricated Hydrodynamic Bearing

A specially built electrochemical micromachining/pulsed electrochemical micromachining (EMM/PECM) cell, a electrode tool filled with non-conducting material, a electrolyte flow control system and a small and stable gap control unit, are developed to achieve accurate dimensions for spindle recesses. Two electrolytes, aqueous sodium nitrate and aqueous sodium chloride are applied in this study. The former electrolyte has better machinability than the latter because of its ability to change appropriately to the transpassive state without forming pits on the surface of the workpiece. It is easier to control the machining depth precisely by micrometer with pulse current than direct current. This paper also presents an identification method for the machining depth by the in-process analysis of the machining current and interelectrode gap size. The interelectrode gap characteristics, including pulse current, effective volumetric electrochemical equivalent and electrolyte conductivity variations, are analysed, based on the model and experiments.