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Electrical discharge machining (EDM) was developed over 70 years ago, but the knowledge of plasma channels that form during this process remain understudied. Therefore, this study systematically investigated the breakdown process and impedance characteristics of plasma channels through singe-pulse discharge experiments. The influence of discharge current and gap distance on the breakdown process and impedance characteristics of plasma channels was also analyzed. The results of this work can contribute to the existing body of knowledge of the physical nature of EDM. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is the extensively used nonconventional material removal process for machining engineering ceramics provided they are electrically conductive. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics that can be machined effectively by EDM. This paper investigates the effects of the electrical resistivity and the EDM parameters on the EDM performance of ZnO/AlO ceramic in terms of the machining efficiency and the quality. The experimental results showed that the electrical resistivity and the EDM parameters such as pulse on-time, pulse off-time, and peak current had the great influence on the machining efficiency and the quality during electrical discharge machining of ZnO/AlO ceramic. Moreover, the electrical resistivity of the ZnO/AlO ceramic, which could be effectively machined by EDM, increased with increasing the pulse on-time and peak current and with decreasing the pulse off-time, respectively. Furthermore, the ZnO/AlO ceramic with the electrical resistivity up to 3,410 Ω cm could be effectively machined by EDM with the appropriate machining condition. [ABSTRACT FROM AUTHOR]

This article proposes a high current density electrical discharge milling for machining Inconel 718. The proposed power supply comprises a pulse generator with high voltage and a DC power source with high current. The pip graphite electrode and the workpiece are connected to the negative and positive poles of the power supply, respectively. Benefiting from efficient flushing and high current density, the maximum material removal rate (MRR) achieved 15,062 mm3/min with a relative electrode wear ratio (REWR) of 1.73%. The effects of peak current and injection flushing pressure on the MRR and REWR were investigated. Experiments showed little differences between the thickness of recast layer with the peak currents of 150 A and 920 A, and the thickness was less than 50 µm. It is also evident that the microcracks within the recast layer penetrated into the base material and propagated along the grain boundar. [ABSTRACT FROM AUTHOR]

Micro-electric discharge machining (micro-EDM) has become an important issue in the fabrication of microcomponents, especially after the development of the wire electro discharge grinding (WEDG) technology. However, the fabrication of microelectrodes through the WEDG technology is very complicated and time consuming, which limits the extensive industrial application of micro-EDM. This article reports the feasibility of utilizing carbon fiber as the electrode in micro-EDM. A novel chucking method and device are developed to chunk the extremely slender carbon fiber. The experiment results show that carbon fiber is a promising material in micro-EDM. [ABSTRACT FROM AUTHOR]

Water-in-oil emulsion has been proposed as the working fluid of die-sinking electrical discharge machining in our previous research. Compared with the traditional mineral oil–based working fluid, the water-in-oil emulsion was more environmentally benign and efficiency. This study presents a new method of die-sinking electrical discharge machining that uses oxygen-mixed water-in-oil emulsion as the working fluid. Experimental results showed that the material removal rate can be highly improved, and the relative electrode wear ratio can be significantly reduced by mixing oxygen into the water-in-oil emulsion. The recast layer was much thinner with this oxygen-assisted machining method. [ABSTRACT FROM AUTHOR]

This work presents a comparative study on the performance of three types of dielectrics at different electrical discharge machining (EDM) parameter combinations favorable for generating porosity. The characteristics of the porosity formation in the recast layer formed in water/oil emulsions (W/O) were investigated by comparing them with those present in the recast layer formed in kerosene and deionized water dielectric. The results showed that the porosity characters were influenced significantly by the dielectric type. The formation mechanism of the porosity in different dielectrics is presented in this article. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) ceramic has been widely used in modern industry because of its superior mechanical properties, wear, and corrosion resistance even at elevated temperature. However, the manufacture of SiC ceramic is not an efficient process by conventional machining methods. This paper employs a steel-toothed wheel as the tool electrode to machine SiC ceramic using electric discharge milling. The process is able to effectively machine a large surface area on SiC ceramic. To further improve the process performance, three kinds of emulsion are proposed as the dielectric in this paper. The effects of dielectric, tool polarity, pulse duration, pulse interval, peak voltage, and peak current on the process performance such as the material removal rate (MRR) and surface roughness (SR) have been investigated. Furthermore, the microstructure of the machined surface is examined with a scanning electron microscope (SEM), an energy-dispersive spectrometer (EDS), and X-ray diffraction (XRD). [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) ceramic has been widely used in modern industry for its excellent physical and mechanical properties. However, SiC ceramic is difficult to machine owing to its high hardness and brittleness. This article presents a novel compound process that integrates end electric discharge (ED) milling and mechanical grinding to machine SiC ceramic. The process is able to effectively machine a large surface area on SiC ceramic with a good surface quality. The effect of tool polarity on the machining characteristics such as the material removal rate (MRR), tool wear ratio (TWR), and surface roughness (SR) has been explored. The effects of pulse on-time, pulse off-time, discharge current and open voltage on MRR, TWR, and SR have been investigated with Taguchi experimental design. The experimental data are statistically evaluated by analysis of variance and stepwise regression. The significant machining parameters, the optimal combination levels of machining parameters, and the mathematical models associated with the machining characteristics are obtained. The confirmation experiment results confirm the validity of the used Taguchi method for enhancing the machining performance and optimizing the machining parameters. [ABSTRACT FROM AUTHOR]

A novel high-speed dry electrical discharge machining (EDM) method was proposed in this study. Using this method, the material can be rapidly melted by extremely high discharge energy and flushed out of the discharge gap by high-pressure and high-speed air flow. The material removal rate (MRR) of dry EDM was significantly improved by the proposed method. The MRR of dry EDM is usually in tens mm 3 /min, whereas the MRR of the proposed method can be as high as 5162 mm 3 /min, which improves the MRR by 2nd to 3rd order of magnitude. Investigation was conducted systemically. The influences of work piece polarity, discharge current, pulse duration time, gas pressure, and electrode rotation speed on machining performance were studied. The machining mechanism of this method was thoroughly analyzed. Moreover, the re-solidified layer, surface morphology, elementary composition, and phase of AISI 304 stainless steel for high-speed dry EDM were also investigated. Theoretical and technical foundations were laid for the industry application of dry EDM. [ABSTRACT FROM AUTHOR]

Abstract: A new process of machining silicon carbide (SiC) ceramic using end electrical discharge milling is proposed in this paper. The process is able to effectively machine a large surface area on SiC ceramic with good surface quality and low cost. The effects of machining conditions on the material removal rate, electrode wear ratio, and surface roughness have been investigated. The surface microstructures machined by the new process are examined with a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and an X-ray diffraction (XRD). The results show that the SiC ceramic is removed by melting, evaporation and thermal spalling, the material from the tool electrode can transfer to the workpiece, and a combination reaction takes place during end electric discharge milling of the SiC ceramic. [Copyright &y& Elsevier]

Milling experiments on Ti6Al4V using high-speed compound machining with high-speed air dielectric were conducted in this study. The new and efficient compound machining combines arc machining and electrical discharge machining (EDM) together, both of them are working in parallel. Ti6Al4V can be quickly melted by significantly high processing energy and rapidly expelled by high-speed air flow and high-speed electrode rotation. The maximum material removal rate (MRR) of 5862 mm 3 /min was obtained, which was hundred times higher than that of conventional dry EDM. The influences of air flow rate, inner diameter of the tubular electrode, peak current of arc machining, peak voltage of EDM, and electrode rotation speed on MRR, relative electrode wear rate and surface roughness were studied. Moreover, the re-solidified layer, surface morphology and elementary composition were also investigated. This study demonstrates that high-speed dry compound machining of Ti6Al4V can be processed efficiently using the proper machining parameters. [ABSTRACT FROM AUTHOR]