Experimentation and Analysis into Micro-Hole Machining of Ti-6Al-4V by Micro-EDM Using Boron Carbide Powder Mixed De-Ionized Water

1. Introduction

With the trend of rapid development of micro-machining technology, the demand of precision miniaturized products has grown tremendously. Again, the innovation of hard-to-machine materials has thrown a challenging task to the manufacturing engineers to fabricate micro-components by micro-machining of these materials. Micro-EDM is one of the established and emerging advanced micro-fabrication processes, which are being utilized to manufacture micro-sized features in products made of hard materials like titanium superalloys, etc. Micro-EDM utilizes the spark erosion phenomenon for removing material from electrically conductive workpiece through a dielectric medium. As the material removal process is non-contact type between the micro-tool and workpiece, it produces no mechanical stresses in workpiece, thereby reducing chatter or vibration problems during machining.

Since micro-EDM process is performed into a dielectric fluid, the types of dielectric fluids influence the machining performances criteria. Typically, in EDM, generally hydrocarbon oil kerosene is used as the dielectric fluid. However, in micro-EDM, the use of kerosene dielectric creates several problems such as (1) deposition of carbide layer on workpiece surface that reduces material removal rate, (2) adhesion of carbon particles on micro-tool surface that makes the discharge inefficient and (3) formation of harmful vapours such as CO and CH₄ that create toxic environment around the machining area, etc. (Zhang et al., 2006; Chung et al., 2007). To promote better micro-machining performances and safe machining environment, experimental investigations are going on employing different non-hydrocarbon based dielectric oils. The oxygen-based fluid, i.e. de-ionized water is one of them that can be applied as dielectric liquid during micro-machining in EDM. The oxygen-based dielectrics improve the electrical discharge phenomena in the machining gap and further results in better machining efficiency in EDM (Kunieda et al., 1991; Chen et al., 1999).