Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes. EDM process is based on thermoelectric energy between the work piece and an electrode. A pulse discharge occurs in a small gap between the work piece and the electrode and removes the unwanted material from the parent metal through melting and vaporising. The electrode and the work piece must have electrical conductivity in order to generate the spark. There are various types of products which can be produced using EDM such as dies and moulds. Parts of aerospace, automotive industry and surgical components can be finished by EDM. This paper reviews the research trends in EDM on ultrasonic vibration, dry EDM machining, EDM with powder additives, EDM in water and modeling technique in predicting EDM performances.

A review on current research trends in electrical discharge machining (EDM)

Electrical discharge machining of titanium alloy (Ti–6Al–4V)

This study investigates the influence of the machining characteristics on pure titanium metals using an electrical discharge machining (EDM) with the addition of urea into distilled water. Additionally, the effects of urea addition on surface modification are also discussed. In the experiments, machining parameters such as the dielectric type, peak current and pulse duration were changed to explore their effects on machining performance, including the material removal rate, electrode wear rate and surface roughness. Moreover, the elemental distribution of nitrogen on the machined surface was qualitatively determined by EPMA to assess the effects on surface modification. Micro hardness and wear resistance tests were performed to evaluate the effects of the reinforced surface. Experimental results indicate that the nitrogen element decomposed from the dielectric that contained urea, migrated to the work piece, forming a TiN hard layer, resulting in good wear resistance of the machined surface after EDM.

The effect in EDM of a dielectric of a urea solution in water on modifying the surface of titanium

In microelectrodischarge machining (micro-EDM), dielectric plays an important role during machining operation. The machining characteristics are greatly influenced by the nature of dielectric used during micro-EDM machining. Present paper addresses the issues of micro-EDM utilizing different types of dielectrics such as kerosene, deionized water, boron carbide (B4C) powder suspended kerosene, and deionized water to explore the influence of these dielectrics on the performance criteria such as material removal rate (MRR), tool wear rate (TWR), overcut, diameteral variance at entry and exit hole and surface integrity during machining of titanium alloy (Ti-6Al-4V). The experimental results revealed that MRR and TWR are higher using deionized water than kerosene. Also, when suspended particles, i.e., boron carbide-mixed dielectrics are used, MRR is found to increase with deionized water, but TWR decreases with kerosene dielectric. Further analysis is carried out with the help of scanning electron microscope (SEM) micrographs, and it is found that the thickness of white layer is less on machined surface when deionized water is used as compared to kerosene. Also, a comparative study of machining time has been carried out for the four types of dielectrics at different machining parametric settings. Furthermore, the investigation on the machined surface integrity and wear on microtool tip have also been done in each type of the dielectrics with the help of SEM micrographs and optical photographs. Hence micro-EDM machining on Ti-6Al-4V work material with B4C-mixed dielectrics is performed in the investigation and reported the performance criteria of the process. It can be concluded from the research investigation that there is a great influence of mixing of boron carbide additive in deionized water dielectrics for enhancing machining performance characteristics in micro-EDM during microhole generation on Ti-6Al-4V alloy.

Comparative study of different dielectrics for micro-EDM performance during microhole machining of Ti-6Al-4V alloy

A review on the use of environmentally-friendly dielectric fluids in electrical discharge machining

Influence of kerosene and distilled water as dielectrics on the electric discharge machining characteristics of Ti–6A1–4V

The machinability of KOVAR material

Electrical discharge machining characteristics of Ti-6Al-4V alloy using distilled water as a dielectric fluid

According to recent research the inferiority of electrical discharge machining performance of Ti–6Al–4V alloy was obvious. In this paper an efficient machining process, which combines electrical discharge machining and multiple ultrasonic vibration, is proposed for improving the material removal rate. The experimental results show that the materials removal rate of both SKD11 and Ti–6Al–4V alloy is remarkably improved with the proposed machining process, especially for Ti–6Al–4V alloy at small pulse duration. The improvement mechanism is assumed to be a fact that multiple ultrasonic vibration accelerates the ejection of debris out of the small gap between the facing materials, i.e., the electrode and workpiece. It is also shown that lower relative electrode wear is obtained, and the most significant effect is observed when machining with lower pulse duration or higher discharge current. Experimental result indicate that comparing with conventional electrical discharge machining, the proposed machining process produces a thinner recasting layer, although it is with slight deterioration in the finished surface.

S.L. Chen

Papers

Influence of kerosene and distilled water as dielectrics on the electric discharge machining characteristics of Ti–6A1–4V

The machinability of KOVAR material

Electrical discharge machining characteristics of Ti-6Al-4V alloy using distilled water as a dielectric fluid

超音波複合振動付加によるTi–6Al–4V合金の材料除去率の改善