Investigation on the profile of microhole generated by electrochemical micromachining using retracted tip tool

Electrochemical micromachining (EMM) is becoming an effective technology to manufacture microparts due to its multiple advantages of almost no tool wear, almost forceless machining, no heat effect and relatively high removal rate, etc. However, accuracy controlling is the key issue which limits the industrial application of EMM. From the current theory and industrial practice, traditional side-insulated flat tip tool often causes bell-mouth profile at entrance and exit, rough surface on the top and bottom of workpiece, and excess radial overcut due to the dispersed distribution of electrical field. To improve the machining accuracy, a novel tool structure with retracted electrode tip is proposed for EMM of microhole in the present work. The effect of the novel tool structure on machining accuracy was studied with both simulation and experiments. Simulation results show that electrical field distribution with retracted tip tool is increasingly confined to the electrode region compared to the flat tip tool throughout the EMM process. Experiments were carried out to verify the advantages of the retracted tip tool and investigate the effect of tip retracted depth on machining accuracy. The critical criterions, including depth average radial overcut (DAROC), entrance profile, exit profile, and surface quality at the entrance and exit were measured to evaluate the machining accuracy. The experimental results show that high-quality microhole with sharp entrance and exit profile, smooth surface, and small DAROC can be successfully manufactured using a retracted tip tool with the optimum tip retracted depth of 71 mu m.