On-machine fabrication of high-aspect-ratio micro-electrodes and application in vibration-assisted micro-electrodischarge drilling of tungsten carbide

Abstract

The concept of fabricating on-machine high-aspect-ratio micro-electrodes arises from the need to fabricate small and deep micro-holes in micro-electrical discharge machining (micro-EDM). In the present study, investigations are conducted on the fabrication of high-aspect-ratio micro-electrodes using two simple and cost-effective micro-EDM-based processes: the ‘turning-μEDM’ hybrid process and the ‘moving-electrode-block-μEDM’ process. Process descriptions and important aspects for successful fabrication of high-aspect-ratio micro-electrodes are discussed. In addition, the application of these micro-electrodes in the fabrication of deep micro-holes in tungsten carbide using normal micro-EDM and vibration-assisted micro-EDM is presented. It is found that the turning-μEDM process can generate finer micro-electrodes for easily machinable materials such as brass, but its application to the machining of deep micro-holes in tungsten Carbide is limited by the extreme tool wear of the brass electrode. The block-μEDM process can generate microelectrodes with hard, difficult-to-cut, and high-melting-point materials such as copper tungsten (alloy) and tungsten with much higher aspect ratios. However, the taper angle of the fabricated micro-electrodes is a common problem in the stationary block-μEDM process. This problem is reduced to a great extent by using block-μEDM with a moving electrode. Micro-holes with an aspect ratio of 16.7 are achieved using vibration-assisted micro-EDM with the fabricated tungsten micro-electrode machined by the moving-electrode-block-μEDM process.