A Study on Pulse Generator for Micro WEDM of Polycrystalline Diamond

Abstract

This paper presents a new pulse generator for cutting of polycrystalline diamond (PCD) by micro wire-EDM. Three pulse control methods (AC power supply pulse control method, fixed pulse width modulation pulse control method and improved AC power supply pulse control method) have been proposed to achieve high frequency and low energy discharge pulses. The improved AC power supply pulse control method enables the pulse generator to provide a period of 20 μs off duty cycle followed by a period of duty cycle for reionization of the dielectric in the spark. Compared to the other two methods, the improved AC method can provide smaller peak current and discharge duration and thereby achieve a smaller slit width and better surface finish. Tests revealed that the developed power supply using anti-electrolysis circuitry and a digital signal processor-based pulse control circuit can provide very low discharge energy pulses with a frequency of 200 KHz, discharge duration of 0.75 μs and a peak current of 3 A. Experimental results demonstrate that the proposed pulse generator can achieve a feed rate of 0.4 mm/min, a surface finish of 0.53 μm Ra and a damaged layer of 5 μm on PCD surface through proper machining settings.

Electrical discharge machining of polycrystalline diamond: A review

“…41 To further improve surface roughness, new power generators working on new principles were developed to optimize peak current and pulse duration. 80,114,[116][117][118] Non-electrical factors. The dielectric plays a critical role in improving SR.…”

“…59 The electrode materials also contribute to the thickness and distribution structure of the metamorphic layer, and structure dense electrode materials such as copper and cupronickel were more suitable for reducing the thickness of the metamorphic layer than the graphite electrode. 100,128 Using variable resistance 84 and digital signal control circuits 117,118 could reduce the thickness of the metamorphic layer by applying different discharge currents in different discharge stages. Usually, reconditioning of sintered PCD is carried out by ECM or grinding with special WC (green grit Carbide) to minimize HAZ and associated defects.…”

“…41 To further improve surface roughness, new power generators working on new principles were developed to optimize peak current and pulse duration. 80,114,116–118…”