Modeling and fabrication of microhole by electrochemical micromachining using retracted tip tool

Accurate microhole is a key feature for many kinds of micro parts widely used in diverse industries. But machining of microhole using traditional processes faces great challenges due to the thermal-mechanical effects. Electrochemical micromachining (EMM) is a potential technique to meet the requirement of high-quality microhole fabrication. However, the currently-used microtools suffer from some drawbacks such as stray dissolution, bell-mouth entrance and excess radial overcut. To overcome these limitations, a novel microtool with retracted tip structure is proposed in this work. A mathematical model has been developed to investigate the effect of retracted tip depth on machining accuracy. And an empirical formula is obtained based on the model to predict the diameter of the generated microhole. Experimental verification is performed on a home-made EMM system and reveals good correlation with the theoretical predictions. Using this novel microtool with optimum retracted tip depth, high-quality microholes have been fabricated on aluminum and 304 stainless steel sheets.