Improvement of Accuracy in Micro-EDM of Tungsten Carbide Using Deionized Water

Abstract

Tungsten carbide is widely used as molds and dies material due to its superior strength, hardness and wear resistance. However, these characteristics also make it very difficult to be machined. Because the material is removed by spark erosion, micro-EDM has been found to be an effective machining process to machine difficult-to-cut materials such as tungsten carbide. Notwithstanding that micro-EDM using deionized water yields many advantages compared to hydrocarbon oil such as higher removal rate, lower tool wear and thinner recast layer, it has not been widely used due to the poor dimensional accuracy of machined part. This is the result of stray material dissolution caused by the slight conductivity of deionized water. This unanticipated material removal is especially severe for tungsten carbide which is highly susceptible to corrosion. This paper presents an attempt to improve the accuracy of micro-EDM using deionized water by using short voltage pulses. A short pulses generator has been in-house developed for this purpose. The effects of pulse parameters on the stray material dissolution are investigated. It is observed that the stray material dissolution is localized when short voltage pulses are used. As a result, dimensional accuracy of machined parts is significantly enhanced.