Improvement of Wire Electrical Discharge Machining Characteristics in Machining Boron-doped Polycrystalline Diamond Using a Novel Iso-pulse Generator

This study aims to present a novel iso-pulse generator for improving machining characteristics of boron-doped polycrystalline composite diamond (BD-PCD) by wire electrical discharge machining (wire-EDM). The transistor-controlled pulse generator composed of a high-power source circuit, a low-power source circuit, a snubber circuit and a complex programmable logic device based pulse control circuit was devised to provide a high open voltage during the ignition period and a low peak current with a fixed discharge duration for sparking as well as identify gap states as normal sparks and abnormal sparks based on the duration of ignition delay time. Pulse on-time and pulse interval of each spark are regulated in real-time to achieve the stability of machining operation while preventing wire electrode from breaking according to the identified gap state. Compared to a conventional iso-frequency pulse generator, the developed iso-pulse generator can provide smaller variation of peak current and discharge duration and thus, the latter can enable the wire-EDM process to produce smaller surface damages and better surface quality than the former. Experimental results not only verify the iso-pulse generator can achieve a fine surface finish as low as R-a 0.247m on machined surface of BD-PCD through one rough and one finish machining operation, they also demonstrate that the developed system can enable a table-top wire-EDM machine to successfully sharpen the cutting edge of BD-PCD end milling tools.