Fabrication of a micro-pin array with high density and high hardness by combining mechanical peck-drilling and reverse-EDM

Abstract

To fabricate circular cross-section micro-pin array with high hardness and high density in a fast and efficient way, a combined method of mechanical peck-drilling and reverse electrical discharge machining (reverse-EDM) is proposed in this research. First, a ball-cone-hole-magnet (BCHM) method is applied in high vibration cantilevered platform (HVCP) and quick release holder/jig to produce highly precise, fast and elastic positioning. Second, a micro-hole array with high density and different types of holes on a workpiece (brass material) is produced by a vibration-assisted mechanical peck-drilling (VAMPD), which includes the high vibration of workpiece created by HVCP and mechanical peck-drilling of micro-drill. This VAMPD can drill up to 1600 single-stage or multi-stage micro-holes, and the aspect ratio of the drilled one-stage micro-holes of Ø60 μm is up to ten. Finally, reverse-EDM is used to fabricate the micro-pin array made of tungsten carbide. In this process, the effects of the chip removal mechanism, the various micro-hole types, and the density of the micro-holes on the electrodes are investigated. The results indicate that the combination of multi-stage micro-hole electrodes and three chip removal methods (working fluid spraying, vibration-assisted electrode and shake-down type workpiece) can produce a 1600-micro-pin array with an average diameter below Ø30.00 μm, a length of 625.0 μm, and a pitch of 100 μm. Consequently, the proposed method of combining mechanical peck-drilling and reverse-EDM can fabricate a micro-pin array with high hardness, high density, high quantity, and uniform diameter in a fast and efficient way.