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Electric arc machining (EAM), which shares the similar principle as electric discharge machining (EDM), has attracted extensive research interest in the area of electrical machining due to its extremely high material removal rate (MRR). However, the material removal mechanisms of this technology were rarely reported. In this paper, the energy distribution and material removal mechanisms of EAM were systematically investigated. It was found that, compared with the traditional electric discharge machining (EDM), the energy efficiency (the ratio of energy used to remove material from workpiece with regard to the total energy distributed into workpiece) and removal efficiency (the volume ratio of removed material with regard to the total melted material in the workpiece) of EAM is much higher. The removal efficiency of EAM can be as high as 90% whereas it is only about 5% in the case of traditional EDM and no more than 20% in the case of micro EDM. In this work, the energy distribution, material removal mechanisms and characteristics of EAM were deeply investigated and reasons behind the high energy and removal efficiency were explained. Some insightful views were provided by this work, such as materials were removed during the whole discharge, the thickness of recast layer was almost the same as the traditional EDM, the expansion speeds of the discharge generated bubble and ejective debris were calculated. [ABSTRACT FROM AUTHOR]

Experiments of high-throughput electrical discharge milling (HTED milling) of WC-8%Co at 600-A peak current and 4766 mm/min material removal rate (MRR) using a 12-mm-external-diameter and 4-mm-internal-diameter tubular graphite electrode were conducted. The HTED milling process parameters, including peak current, electrode rotation speed, flushing pressure, and peak voltage, were studied to evaluate the effect on MRR, relative electrode wear rate, and diameter of overcut. The cross section, surface morphology, and microhardness of WC-8%Co for HTED milling were also investigated. Peak current has proven to be a critical factor for MRR. The MRR of HTED milling at peak current 600 A can be increased by ten times compared to that of HTED milling at peak current 100 A. Faster electrode rotation speed, larger flushing pressure, and higher peak voltage are essential to achieve low relative electrode wear rate (REWR) and high MRR. This study demonstrates that, using proper HTED milling process parameters and tubular graphite electrode, the HTED milling of WC-8%Co can be processed efficiently. [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]

Abstract: This work proposed a novel method of determining the energy distribution and plasma diameter of EDM. The energy distribution and plasma diameter were determined by comparing the boundary of the melted material in the crater which was obtained by metallographic method and the isothermal curve of the thermal-physical model using finite element method (FEM). The results of this work indicated that the expansion of the plasma diameter must be taken into consideration in order to be more consistent with the actual EDM process. With this method, the energy distribution and plasma diameter in different dielectrics with different polarities were investigated. Comparison between the results of this work and the previously reports showed that the energy distributed into workpiece and plasma diameter can be determined by this new method. [Copyright &y& Elsevier]

Highlights: [•] Material removal characteristics in five different dielectrics were investigated. [•] Complete geometry of craters was precisely determined by metallographic methods. [•] Evolution of discharge generated bubble was investigated by computer simulation. [•] Material removal characteristics were significantly affected by bubble pressure. [ABSTRACT FROM AUTHOR]

The titanium (Ti) alloys are the notoriously 'difficult-to-machine' aerospace materials. Compared with the traditional mechanical cutting methods which are costly because of high tooling costs, electrodischarge machining (EDM) is an effective machining method for the Ti alloys. The energy distribution during the EDM process of Ti alloys was rarely reported, though it is a very important factor that can affect the machining performance. In this work, the energy distribution during EDM of Ti-6Al-4V has been investigated by a novel method, at different EDM parameters including interelectrode distance, pulse duration, polarity, and electrode shape. The results of this work show that energy distribution characteristics are greatly affected by the power density applied on the electrodes and more energy is distributed into the anode than into the cathode, which are in good concurrence with the results obtained by other authors. The results of this work will be helpful for further improving the technological performance of this process. [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]

The evolution of bubble generated by electrical discharge in sinking electrical discharge machining (EDM) occurs in a very short time period and in a very narrow space, thus making both observation and theoretical analysis extremely difficult. For this reason, the role of the discharge-generated bubble during the material removal process in sinking EDM has not to be understood very clearly. In this paper, the evolution process of the discharge-generated bubble was simulated in three dimensions and the influence of inter-electrode distance was studied. It was found that the evolution of the discharge-generated bubble was significantly affected by the inter-electrode distance. Smaller inter-electrode distances can contribute to a larger pressure and expansion velocity of the bubble as well as a larger force applied on the tool electrode and workpiece. The experimental results showed that the geometry characteristics of the crater were also significantly affected by inter-electrode distance. A smaller inter-electrodes distance can contribute to a larger volume of both melted and removed materials. The simulation results were discussed by relating to the results of single-pulse discharge experiments; some insightful views about the material removal mechanism of EDM were presented in this paper. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) has been wildly used in the modern manufacture industry due to its advantage over the traditional manufacture method of some hard-to-cut materials. However, compared with the traditional manufacture method, the EDM process was inefficient and environmentally hazardous due to the decomposition of the dielectrics, especially in the case of sinking EDM which used oil-based dielectric. In order to improve the EDM performance, and for the other hand, alleviate the environmental impact of the process, a new type of dielectric, water in oil (W/O) emulsion was proposed as the working fluid. This work presents a systematical study on the performance of this new type dielectric based on the orthogonal and additional single factor experiments. Statistical analysis of the results show that discharge current (I) and water content of the emulsion significantly influence the machining performance of sinking EDM. The study also analyzed the influence of the emulsion temperature and flushing condition on its EDM performance. It was observed that both MRR and EWR decrease with increasing temperature of the emulsion. Experiments results indicated that W/O emulsion can be used as the working fluid of sinking EDM and alleviated the environmental impact of the process. [ABSTRACT FROM PUBLISHER]

In this paper, a new type of sinking electric discharge machining (EDM) dielectric-water-in-oil (W/O) emulsion is proposed, and the machining characteristics of W/O emulsion are investigated by comparing with that of kerosene. In the experiments, machining parameters such as the dielectric type, peak current, and pulse duration are changed to explore their effects on machining performance, including the material removal rate (MRR), relative electrode wear rate (REWR), and surface roughness. Experimental results revealed that W/O emulsion could be used as the dielectric fluid of sinking EDM and adopting long pulse duration and large peak current could lead to obtaining higher MRR than kerosene. Compared with kerosene, W/O emulsion is observed to cause lower carbon adhered to the electrode surface. Therefore, its REWR is higher. Statistics of the discharge waveform show that more stable discharge processes can be obtained by using W/O emulsion compared with kerosene. Furthermore, W/O emulsion is more economical and more environmentally friendly than kerosene, and it could be an alternative to kerosene in sinking EDM application. [ABSTRACT FROM AUTHOR]

A novel hybrid process that integrates end electric discharge (ED) milling and mechanical grinding is proposed. The process is able to effectively machine a large surface area on SiC ceramic with good surface quality and fine working environmental practice. The polarity, pulse on-time, and peak current are varied to explore their effects on the surface integrity, such as surface morphology, surface roughness, micro-cracks, and composition on the machined surface. The results show that positive tool polarity, short pulse on-time, and low peak current cause a fine surface finish. During the hybrid machining of SiC ceramic, the material is mainly removed by end ED milling at rough machining mode, whereas it is mainly removed by mechanical grinding at finish machining mode. Moreover, the material from the tool can transfer to the workpiece, and a combination reaction takes place during machining. [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]

Abstract: Electrical discharge machining (EDM) caused a recast layer to form at the machined surface of the workpiece. The characteristics of the recast layer have a great relationship with the type of dielectric. The research work in this paper aims to acquire a profound knowledge of the recast layers of a surface machined by sinking EDM using water-in-oil (W/O) emulsion as dielectric. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrograph (EDS) and micro hardness analysis were performed. The characteristics of the recast layer formed in W/O emulsion were investigated by comparing them with those of the recast layer formed in kerosene and de-ionized water dielectric. It was found that the recast layer formed in W/O emulsion exhibited larger surface roughness, thickness and micro hardness compared with that formed in kerosene and de-ionized water. Both carbide and oxide were detected in the recast layer formed in W/O emulsion whereas only carbide was detected in the recast layer formed in kerosene. Due to the higher supersaturation of gases in the melted material, the recast layer formed in W/O emulsion was found to possess more micro-voids than that formed in kerosene and de-ionized water. [Copyright &y& Elsevier]

Silicon carbide (SiC) ceramics have been widely used in modern industry. However, the manufacture of SiC ceramics is not an efficient process. This paper proposes a new technology of machining SiC ceramics with electrical discharge milling and mechanical grinding compound method. The compound process employs the pulse generator used in electrical discharge machining, and uses a water-based emulsion as the machining fluid. It is able to effectively machine a large surface area on SiC ceramics with a good surface quality. In this paper, the effects of pulse duration, pulse interval, peak voltage, peak current and feed rate of the workpiece on the process performance parameters, such as material removal rate, relative electrode wear ratio and surface roughness, have been investigated. A L25 orthogonal array based on Taguchi method is adopted, and 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 process performance are obtained. In addition, the workpiece surface microstructure is examined with a scanning electron microscope and an energy dispersive spectrometer. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new compound machining process is proposed by combining EDM milling and arc machining. [•] The power supply contained a pulse generator and a DC power. [•] The machining could achieve high MRR and low REWE. [•] Flushing played an important role in deionizing the arc plasma channel. [ABSTRACT FROM AUTHOR]

High-speed near dry electrical discharge machining (EDM) is a novel and promising machining method, which obtains higher material removal rate, lower surface roughness and thinner width of overcut compared with that of high-speed dry EDM. Moreover, debris deposition on the machined surface and electrodes are significantly reduced and an obviously thin heat affected zone is obtained using the near dry dielectric (mist). In this study, a low-flux pump is utilized to supply deionized water at a controlled rate to the high-speed air pipe, which affords a mist dielectric to the machining process. Compared with dry EDM, the high-speed near dry EDM improves the cooling capacity and increases the dielectric strength of the dielectric. Furthermore, electrode injection flushing assisted by side flushing of high-speed mist was used to reduce debris deposition and improve cooling capacity. Comparative milling experiments of Ti6Al4V were conducted under the dry and near dry conditions using the different flushing ways. The effects of current, pressure, droplet size, electrode rotation speed, and droplet density on the material removal rate, surface roughness, width of overcut in continuous machining and material removal weight, trace length, trace width in single pulse machining were studied. In addition, scanning electron microscope, X-ray diffractometer, energy dispersive spectrometer, and micro-hardness tester were also used to study the micro-characters of the machined materials. [ABSTRACT FROM AUTHOR]