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Electrical discharge machining (EDM) is an unconventional machining process based on removing material by successive electrical discharges. The tool electrode wear must be kept as minimal as possible to produce high-precision components. This scope proposes the development of a new technique for identifying wear on electrodes and its evolution using acoustic emission (AE) signals. Therefore, EDM tests were performed on AISI H13 steel parts with electrolytic copper tool electrodes under different conditions with concomitant AE signal measurements. In these tests, the first one has the following parameters: voltage pulse duration time (te) of 150 μs; the time interval between two successive voltage pulses (to) of 14.84 μs; electrical current of 33 A; and positive polarity electrode. For the second test: duration of the voltage pulse of 2 μs; the time interval between two successive voltage pulses of 4.90 μs; electrical current of 18 A; and negative polarity electrode. In this way, a wear rate 28.3 times higher was obtained in the electrolytic copper electrode in the first test, more aggressive due to its parameters, for the same machining time compared to the second test. Finally, the wear of the tool electrodes was related to the AE signals from machining; initially in this study, the workpiece's mass loss was not verified. These signals were analyzed using the short-time Fourier transform techniques and spectral entropy. The results showed that the signals using the new technique of relation respond to wear and are sensitive to the electrode's wear rate. [ABSTRACT FROM AUTHOR]

Nowadays, additive manufacturing (AM)-based rapid prototyping (RP) is used as a convenient route for making tool electrodes required in electrical discharge machining (EDM). AM enables direct fabrication of complex shaped EDM electrode in comparatively less time in contrast to subtractive machining processes. In this study, an EDM electrode is prepared directly by selective laser sintering (SLS) process using metal matrix composite of aluminium (Al), silicon (Si) and magnesium (Mg). To study the performance of the prepared RP tool electrode in electrical discharge machining, titanium is used as workpiece material and EDM-30 oil as dielectric medium during machining. The performance of the prepared tool electrode is compared with conventional copper and graphite tool electrodes. Experiments have been conducted changing EDM process parameters viz. open circuit voltage (V), peak current (Ip), duty cycle (τ) and pulse duration (Ton) along with three tool electrodes such as RP, graphite and copper tool electrodes. The performance measures considered during the experimental study are material removal rate (MRR), tool wear rate (TWR), average surface roughness (Ra), white layer thickness (WLT), surface crack density (SCD) and micro-hardness (MH) on white layer. SEM and EDX of the machined surface reveal that tool material is generally eroded and deposited on the machined surface with formation of metal carbides. However, tool erosion is more pronounced in case of RP tool electrode. XRD analysis reveals the formation of titanium carbides on the machined surface resulting in increase in the micro-hardness of white layer. Discharge current and tool type are found to be significant parameters influencing the performance measures considered in the study. The surface produced when machined with RP tool electrode exhibits superior surface characteristics while graphite tool electrode produces better MRR and TWR. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond (PCD) is increasingly becomes an important material used in the industry for cutting tools of difficult-to-machine materials due to its excellent characteristics such as hardness, toughness and wear resistance. However, its applications are restricted because of the PCD material is difficult to machine. Therefore, electrical discharge machining (EDM) is an ideal method suitable for PCD materials due to its non-contact process nature. The performance of EDM, however, is significantly influenced by its process parameters and type of electrode. In this study, soft computing technique was utilized to optimize the performance of the EDM in roughing condition for eroding PCD with copper tungsten or copper nickel electrode. Central composite design with five levels of three machining parameters viz. peak current, pulse interval and pulse duration has been used to design the experimental matrix. The EDM experiment was conducted based on the design experimental matrix. Subsequently, the effectiveness of EDM on shaping PCD with copper tungsten and copper nickel was evaluated in terms of material removal rate (MRR) and electrode wear rate (EWR). It was found that copper tungsten electrode gave lower EWR, in comparison with the copper nickel electrode. The predictive model of radial basis function neural network (RBFNN) was developed to predict the MRR and EWR of the EDM process. The prominent predictive ability of RBFNN was confirmed as the prediction errors in terms of mean-squared error were found within the range of 6.47E−05 to 7.29E−06. Response surface plot was drawn to study the influences of machining parameters of EDM for shaping PCD with copper tungsten and copper nickel. Subsequently, moth search algorithm (MSA) was used to determine the optimal machining parameters, such that the MRR was maximized and EWR was minimized. Based on the obtained optimal parameters, confirmation test with the absolute error within the range of 1.41E−06 to 5.10E−05 validated the optimization capability of MSA. [ABSTRACT FROM AUTHOR]

In this paper, an inexpensive auxiliary tool vibration device is described that improves the efficiency of deep groove electrical discharge machining (EDM). Titanium alloy samples (Ti-6Al-4V) were machined using two different methods: unassisted normal EDM and vibration-assisted EDM, using copper, copper-tungsten, and graphite tool electrode materials. The vibration-assisted EDM machining was done at 40, 90, and 140 Hz, and the material removal rate, tool electrode wear rate, and surface roughness of the specimens were compared. Experimental results revealed that the material removal rate with vibration-assisted EDM was better than that obtained using unassisted EDM with copper and copper-tungsten electrodes. In this study, the vibration frequency was found to have an optimum value of 90 Hz with respect to surface roughness. It was found that the machining time for a groove 10 mm deep with vibration-assisted EDM was reduced by 200% compared to unassisted EDM. This new vibration device can help in the development of a more efficient deep groove EDM. [ABSTRACT FROM AUTHOR]

To increase the performance of discharge ablation, a sintered diamond (SD) electrode is used as a machining electrode to achieve machining combined with high-efficiency ablation and mechanical grinding in this paper. A new constant pressure servo control method based on the SD electrode is proposed by gathering the mechanical grinding force during machining. Using Cr12 as the workpiece, we conducted five groups of comparative experiments in this study. They are mechanical grinding with SD electrode, inner jetted dielectric electrical discharge machining (EDM) with copper electrode, aerosol ablation with copper electrode, aerosol ablation based on voltage control with SD electrode, and aerosol ablation based on constant pressure with SD electrode. In this paper, we studied the mechanism, machining efficiency, and machining quality. The method based on constant pressure servo control with SD electrode can effectively grind the oxide layer and ensure the sustainability of machining. From these five groups of experiments, we concluded that the method based on constant pressure servo control can be efficient and stable during machining. The machining efficiency was 6.3 times that of the inner jetted dielectric EDM. The machining efficiency based on constant pressure servo control increased by 88% compared with that of the aerosol ablation with copper electrode and it increased by 62% compared with that of the aerosol ablation based on voltage with SD electrode which showed that the grinding effect of diamond based on constant pressure servo control was obvious. Compared with the other four methods, the method based on constant pressure servo control can obtain the best surface quality. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on cryogenic cooling of liquid nitrogen (LN) copper electrode in the electrical discharge machining (EDM) process. The optimization of the EDM process parameters, such as the electrode environment (conventional electrode and cryogenically cooled electrode in EDM), discharge current, pulse on time, gap voltage on material removal rate, electrode wear, and surface roughness on machining of AlSiCp metal matrix composite using multiple performance characteristics on grey relational analysis was investigated. The L orthogonal array was utilized to examine the process parameters, and the optimal levels of the process parameters were identified through grey relational analysis. Experimental data were analyzed through analysis of variance. Scanning electron microscopy analysis was conducted to study the characteristics of the machined surface. [ABSTRACT FROM AUTHOR]

Electrical discharge machining is a very accurate non-traditional manufacturing process for creating tiny apertures, complex shapes and geometries within mechanical parts and assemblies. Its performance is evaluated in terms of surface roughness, existence of cracks, voids, and recast layer on the surface of product. The high heat generated on the electrically discharged material during the electrical discharge machining (EDM) process unfortunately decreases the quality of product. In this paper, the high strength and unique electrical and thermal properties of multi-wall carbon nanotubes are used to improve the EDM performance when machining the AISI H13 tool steel, by means of copper electrodes. Material removal rate, electrode wear rate, surface roughness, and recast layer were measured in presence of carbon nanotubes in the dielectric, then compared to the outcome of traditional EDM. Experiments show that mixing multi-wall carbon nanotubes within the dielectric makes the EDM more efficient, particularly if machining parameters are set at low pulse of energy. [ABSTRACT FROM AUTHOR]

A compound process that integrates end electrical discharge (ED) milling and mechanical grinding to machine silicon carbide (SiC) ceramics is developed in this paper. The process employs a turntable with several uniformly-distributed cylindrical copper electrodes and abrasive sticks as the tool, and uses a water-based emulsion as the machining fluid. End electrical discharge milling and mechanical grinding happen alternately and are mutually beneficial, so the process is able to effectively machine a large surface area on SiC ceramic with a good surface quality. The machining principle and characteristics of the technique are introduced. The effects of polarity, pulse duration, pulse interval, open-circuit voltage, discharge current, diamond grit size, emulsion concentration, emulsion flux, milling depth and tool stick number on performance parameters such as the material removal rate, tool wear ratio, and surface roughness have been investigated. In addition, the microstructure of the machined surface under different machining conditions is examined with a scanning electron microscope and an energy dispersive spectrometer. The SiC ceramic was mainly removed by end ED milling during the initial rough machining mode, whereas it is mainly removed by mechanical grinding during the later finer machining mode; moreover, the tool material can transfer to the workpiece surface during the compound process. [ABSTRACT FROM AUTHOR]

Die-sinking electrical discharge machining is an unconventional technology that allows to machine all at least minimally electrically conductive materials regardless of their physical and mechanical properties. Despite the fact that it is not a conventional technology, the tool gets also worn out, which is a tool electrode. The wear of the electrode does not only mean its loss but also the degradation of the shapes that are transferred to the resulting workpiece. For this reason, a design of experiments was conducted with 6 input factors, 2 were categorical: the electrode material (copper, graphite) and workpiece material (steel 1.2363 and steel 1.2343ESR) and 4 were numerical: Open-voltage, Pulse current, Pulse on-time, and Pulse off-time. In the framework of this design of experiments, the wear of the used graphite and copper electrodes at their corners and edges was evaluated, which was made possible by the use of electron microscopy and the use of approximation circles. Furthermore, the eroding speed, the topography of the machined samples, and the morphology of the surfaces of the used electrodes were investigated. It has been recognized that the use of a graphite electrode will allow for more accurate workpiece shapes and less wear. [ABSTRACT FROM AUTHOR]