Development of a Pulse Generator for Rough Cutting of Oil-based Micro Wire-EDM

摘要

This paper aims to develop a specific pulse generator for rough cutting of oil-based micro wire electrical discharge machining (wire-EDM). A two-stage current-limiting resistance power supply was presented to suppress thermal damage on the machined surface of polycrystalline diamond (PCD) while achieving stable machining by supplying high open voltage and low discharge current pulse waveforms. Tests revealed that the two-stage resistance power supply could achieve lower thermal damaged layer, better surface quality and surface finish than a conventional pulsed power supply since the former could provide smaller peak current and shorter discharge duration than the later. Experimental results demonstrate that boron-doped polycrystalline composite diamond (BD-PCD) is superior to polycrystalline diamond in the smoothness of cutting edge, surface quality and surface roughness since the former has lower specific resistance and thermal conductivity than the later. This study has indicated that the proposed power supply could enable a prototype micro wire-EDM machine to achieve a surface finish as low as 0.45 μm R a and a thermal damaged layer as small as 6 μm on the machined surface of BD-PCD after one rough machining operation.