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Conventional drilling of carbon fibre–reinforced plastic (CFRP) presents significant challenges due to the material's abrasive nature and anisotropic properties, leading to tool wear, delamination, and surface damage. To address these challenges, this study pioneers the use of wire electrical discharge machining (WEDM) to evaluate the drilling performance of thick CFRP lay-up configurations mainly unidirectional and multidirectional, marking the first application of WEDM for CFRP drilling. The study evaluates material removal rate (MRR), delamination factor (DF), and surface damage while employing an analytical solution to estimate surface temperature and heat conduction in the laminates. An eight-full factorial experimental design was employed, involving variations in ignition current (3 A and 5 A) and pulse-off time (4 µs and 8 µs). The findings revealed that the multidirectional lay-up achieved an MRR of 2.85 mm3/min, significantly outperforming the unidirectional lay-up's MRR of 0.95 mm3/min, representing a 300% increase at 5 A and 4 µs. However, the increase in discharge energy led to surface damage such as delamination, frayed fibres, and irregular circularity, especially evident in the unidirectional lay-up. For delamination, the multidirectional lay-up had the highest top DF of 1.4 at 5 A and 6 µs, while the unidirectional lay-up achieved the peak bottom DF of 1.24 at the same levels. While none of the parameters significantly affected the responses, the current exhibited the highest contribution ratios. Analytical predictions of the thermal distribution indicated a 45-µm delamination length at the laminate surface and depth, aligning closely with experimental predictions of 30–50 µm. [ABSTRACT FROM AUTHOR]

In the electrical discharge machining process (EDM), quantities of discharge craters randomly scatter the workpiece surface. However, the formation mechanism of the discharge crater has not been fully understood, which affects the application of EDM technology. In the paper, a thermal-fluid coupling model was proposed to elucidate the crater formation dynamics process utilizing COMSOL Multiphysics software. The temperature distribution, fluid flow velocity, and more changes in the crater were analyzed, aiming to deepen the understanding of the formation mechanism of the discharge crater in the EDM process. Through the comparison of experimental results and numerical simulation results, it was found that a little of the material is eroded by vaporization, while a lot of material is eroded mainly by melting. In addition, the material removal process is continuously eroded after the end of discharge due to the residual heat and the flow of molten material. Moreover, the effect of pulse on-time and peak current on the temperature field and flow field was solved. Through the experiments and numerical simulations, it was shown that the simulation results are consistent with the experimental results, verifying the applicability of the thermal-fluid coupling model in demonstrating the mechanisms of crater formation in the EDM process. [ABSTRACT FROM AUTHOR]

Electrical discharge grinding technology (EDGT) is an efficient and high precision method for machining RB-SiC ceramic materials. In this paper, the mechanism of material removal in EDGT is deeply analyzed, and the formation mechanism of surface topography under different material removal regimes affected by grinding depth is discussed. A three-dimensional heat conduction analysis model in the process of single pulse discharge was established, and the temperature field distribution in RB-SiC ceramic material under different discharge energy was obtained by numerical calculation. It is found that the simulated crater radius and depth increase with the increase of the discharge time, and the material removal amount gradually increases, but the growth rate gradually decreases. In order to give full play to the advantages of EDGT, the discharge energy and grinding depth were optimized according to the material removal mechanism. Finally, RB-SiC ceramic machining experiments were carried out using the optimized machining parameters, and a smooth surface with few discharge craters was obtained. It is found that the grinding scratches on the material surface are mainly plastic grinding, and the material surface roughness is 0.443 μm. The research results of this paper can provide guidance for engineering practice of ductile grinding RB-SiC ceramic materials. [ABSTRACT FROM AUTHOR]

Low-cost micromanufacturing technique for forming copper foils into desired micro-parts plays an important role in facilitating the widespread application of copper foil. Here, the pulsed arc plasma generated by the pulsed voltage was used as a heat source to achieve thermal stress–induced bending of copper foil in an electrical discharge machining (EDM) machine. Metallic foil with a thickness of 0.1 mm and a cylindrical rod with scanning motion were used for the first time as tool electrodes in the EDM bending of workpieces. The effect of various processing parameters, such as polarity, machining time, discharge current, duty factor, and discharge frequency, on the bending angle was investigated by optical microscopy. The main factors affecting the bending angle and their working mechanisms were analyzed in depth. Experimental results showed that the bending angle of the copper foil increases with the increase of the discharge energy, which was mainly attributed to the increasing thermal gradient along the thickness direction of the copper foil. When the copper foil was used as the anode, the carbon deposition phenomenon in the copper foil effectively reduced the material removal caused by the pulsed arc plasma, which contributes to the surface integrity and performance of the copper foil. Furthermore, several typical bend-formed parts, including curved, sawtooth, and S-shapes, were formed using pulsed arc plasma. This work proves that pulsed arc plasma is a reliable and cost-effective heat source for achieving thermal stress–induced bending of copper foil. [ABSTRACT FROM AUTHOR]

Electrode wear (EW) during the electrical discharge machining (EDM) process determines surface topography accuracy. In this paper, an automatic evaluation method is proposed by integrating image segmentation and three-dimensional (3D) registration (IS-3DR) to evaluate the EW more accurately. First, the original two-dimensional (2D) image and the 3D point cloud were derived from a laser microscope image, and the 2D worn area was determined by automatic recognition and segmentation. Then, 3D registration between the 3D point cloud and the 2D worn area was utilized to qualitatively define the 3D EW area. Finally, the 3D EW volume was obtained quantitatively through micro-element calculation based on the 3D EW area and the shape fitting of the original electrode. The results showed that the intersection over union (IOU) of image segmentation was higher than 97.5%, compared with the manually labeled image segmentation method. Compared with IS-3DR, the random error of the two-dimensional evaluation method could reach 27.08%, indicating higher reliability and stability of IS-3DR. The EDM experiment was carried out to investigate the effect of parameters on EW. The experimental results showed that the effects of current and servo voltage were most significant, followed by pulse width. [ABSTRACT FROM AUTHOR]

In electrical discharge machining (EDM), it is a much more effective method to improve working characteristics by changing the input process of pulse energy. However, it has not been investigated enough whether pulse form is the most adequate or not. In this study, the effect of superimposed pulse current waveform and its parameter on surface integrity was investigated. The surface topography, roughness, microstructure, white layer thickness, and residual stress were analyzed and discussed. Moreover, the material removal rate was also tested and compared. The results show that with the backward movement of the superimposed pulse current, the material removal rate and surface roughness decrease, while the white layer thickness, residual stress, and surface defects increase. The current waveform has little influence on microstructure. Under the same pulse discharge energy and pulse-on time, the samples processed by superimposed pulse current waveform instead of rectangular current waveform can obtain a thinner white layer, lower residual stress, fewer surface defects, and high surface roughness. With the increase of superimposed pulse-on time and current, the surface integrity becomes worse due to the increase of pulse energy. This paper provides a guide to the development and selection of EDM discharge current waveforms in EDM. [ABSTRACT FROM AUTHOR]

Electrical discharge drilling of blind holes has been a challenging task due to the inherent difficulties in removing debris from the discharging gap. This paper investigates the working mechanism and effects of new stepped electrodes which are used in conjunction with injection flushing in drilling deep blind holes. A series of theoretical simulations and comparative experiments were conducted using cylindrical electrodes and two types of stepped electrodes. Pulse waveforms were captured to analyse the discharge status. Surface topography and machining quality were analysed using scanning electron microscope (SEM) images. The machining performance was evaluated by studying the material removal rate (MRR) and tool wear ratio (TWR). Experiment results show that internal flushing caused the debris to circulate in the machining zone and led to abnormal discharges, disrupting the formation of the plasma channel. The MRR was increased by 75% and 82% when using cylindrical electrodes with pressures of 120 psi and 40 psi, respectively. In contrast, the MRR with injection flushing was about 80% of that without injection flushing when using stepped electrodes. Regardless of the type of electrode, the application of injection flushing resulted in the increase in the maximum effective machining depth. [ABSTRACT FROM AUTHOR]

A global manufacturing community is dedicatedly striving to implement the concept of NetZero in precision cutting of difficult-to-machine materials, specifically, Inconel 617 (IN617) with due consideration to environmental protocols. The fast strain hardening issue of the said alloy during conventional processing rationalizes the application of electric discharge machining (EDM). However, EDM has been criticized for its high energy consumption and limited cutting efficiency. Moreover, conventional dielectric (kerosene) employed in EDM has drastic environmental and operator health concerns. To address the abovementioned issues, waste cooking oil (WCO) has been employed in this study which enhances the reusability of resources and minimizes the cost of the dielectric. Making the process sustainable is imperative along with continuously escalating scarcity of engineering resources. Therefore, the potential of shallow and deep cryogenically treated electrodes (SCT and DCT) has been comprehensively examined against nanofilled WCO to achieve the aforementioned objective. Three different concentrations of powder (Cp) and surfactant (Cs) to uplift the machining responses are investigated through a detailed parametric experimental design. Core machining factors such as material removal rate (MRR), surface roughness (SR), and specific energy consumption (SEC) are examined through optical and electron microscopy studies and 3D surface profilometry. Hereafter, machining factors are modelled using the artificial neural network (ANN) technique. An exceptional improvement of 80%, 25.3%, and 75.16% has been achieved in MRR, SR, and SEC respectively using nanopowder-mixed WCO against SCT brass compared to the responses' values obtained against conventionally used kerosene. Furthermore, compared to kerosene, the maximum CO2 reduction of 79.97 ± 11.2% is achieved with WCO. [ABSTRACT FROM AUTHOR]

Understanding and optimizing mechanical manufacturing processes is essential for sustainable industrial development. Among unconventional machining methods, electrical discharge machining (EDM) distinguishes itself by its capability to remove material through successive electrical discharges submerged in a dielectric fluid. EDM encompasses intricate phenomena influenced by machine parameters, dielectric choice, and the materials involved. Unlike conventional machining, EDM operates with the tool electrode in close proximity to, but not in physical contact with, the workpiece, achieving material removal through localized overheating. This study focuses on monitoring EDM phenomena during the machining of AISI H13 steel, exploring variations in machining parameters and electrode materials (electrolytic copper and graphite). Acoustic emission (AE) signals and machine learning (ML) are employed for experimental characterization and data analysis. Spectral entropy is applied to AE signals, quantifying inherent signal uncertainty. The findings reveal remarkable accuracy (97.7%) and underscore the superior control achieved with graphite electrodes in managing machining phenomena compared to electrolytic copper electrodes. [ABSTRACT FROM AUTHOR]

When utilizing electrical discharge machining (EDM) for processing, the processing efficiency and quality will be significantly impacted, if the electrocorrosion residues in the gap flow field cannot be discharged in time. Numerical simulation is considered an effective means to simulate the flow field of EDM gaps. Based on simulation, this study investigates the processing time, depth, current, and dielectric (kerosene, water, and sunflower seed oil), on the movement of electrocorrosion residues within the dielectric. The simulation results demonstrate that an increase in processing time, current, or depth leads to a decrease in the escape rate of corrosion residues from the discharge gap. Compared with kerosene and sunflower seed oil, water has a higher residue escape rate, but the actual processing effect is not ideal. The escape rate of sunflower seed oil at any time was higher than that of kerosene,the highest was higher than 25%, and the average was higher than 22.21%. Sunflower seed oil can be used as a renewable dielectric to replace kerosene. Subsequently, verification experiments are conducted based on simulation results that demonstrate that the discrete phase model (DPM) fluid simulation exhibits excellent coupling with actual processing conditions. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) and electrochemical machining (ECM) are two typical unconventional processing methods for fabricating difficult-to-cut materials. Surfaces machined by EDM generally contain recast layers, whereas ECM owns low machining accuracy. EDM–ECM hybrid machining can suppress their shortcomings and combine their advantages. The working fluid is vital to realizing the combination of EDM and ECM. Conventional EDM–ECM hybrid machining commonly adopts water-based fluid, which can meet the requirements of hybrid micro-, small-hole, and milling machining. However, water-based fluid hardly maintains the stable sinking EDM that possesses a relatively large machining area and a closed machining gap; thus, it is unsuitable for hybrid sinking machining. The lack of appropriate fluid seriously hinders the promotion and application of EDM–ECM hybrid sinking machining. Here, a novel bi-characteristic fluid water-in-oil (W/O) nanoemulsion that combines electrical insulation and conductive properties is proposed, and an electrical discharge and electrochemical hybrid sinking machining (EDCSM) using W/O nanoemulsion is developed. The composition parameters (salt concentration, water content) of the W/O nanoemulsion and electric parameters (open voltage, pulse frequency) are investigated. Material removal mechanisms are also discussed. Results show that the material removal mechanisms and the strength of EDM and ECM in EDCSM can be manipulated by adjusting the investigated crucial parameters. EDCSM using W/O nanoemulsion can achieve a high-quality machined surface and good machining accuracy, demonstrating its superiority and potential in the field of sinking machining. [ABSTRACT FROM AUTHOR]

The electrode is an important component of electrical discharge machining (EDM), playing an important role in machining efficiency, surface quality and geometric accuracy. In this work, a new method combining equal channel angular pressing (ECAP), deep cryogenic treatment (DCT) and aging treatment (AT) was proposed. The ultrafine-grained Cu-0.5%Cr electrode has high strength and high electrical conductivity through this process, so as to improve the machining characteristics in EDM. The surface roughness (Ra), the workpiece corner sharpness (WCS), and the electrode wear rate (EWR) were investigated. The results showed that the treatment of the electrode with 4 passes of ECAP + DCT (12h) + AT (550℃ × 1h) can reduce the EWR and WCS by 63.6% and 49.7%, respectively. It also contributed to the enhancement of electrical conductivity and microhardness of the Cu-0.5%Cr electrode by ECAP + DCT + AT. Meanwhile, it revealed that the processing of the Cu-0.5%Cr electrode resulted in the excellent machined surface quality (Ra was reduced by 53.5%) which was confirmed by the results of the scanning electron microscopy (SEM). The ultrafine-grained Cu-0.5%Cr electrode with an excellent combination of strength and electrical conductivity has an outstanding EDM performance. [ABSTRACT FROM AUTHOR]

The titanium alloy Ti6Al4V ELI (grade 23) is widely used in biomedical industry because of its engineering attributes. However, it requires surface modifications and has processing challenges because it is difficult to machine nature. Therefore, powder-mixed electric discharge machining process is commonly applied to simultaneously machine the material and carry out surface treatment. The performance of the process is limited by both low cutting efficiency and the formation of a rough surface. In this regard, the current study evaluates SiC powder-mixed electric discharge machining of Ti6Al4V ELI using a range of tool materials such as copper, brass, graphite, and aluminum along with a comprehensive list of process parameters. The surface roughness parameters involving arithmetic roughness, the average peak-to-valley distance, and the highest peak-to-deepest valley distance along with material removal rate are comprehensively studied. Taguchi design of experiments L16 orthogonal array is used to study the process performance with parametric effect analysis, parametric significance analysis, and surface morphological analysis with a scanning electron microscope. Furthermore, the experimental results are optimized against a multi-response optimization matrix using grey relational analysis approach. An optimal compromise between surface attributes and cutting efficiency is identified by Al electrode, pulse current of 14 A, pulse on time of 75 µs, pulse off time of 75 µs, and negative polarity parametric conditions. [ABSTRACT FROM AUTHOR]

Metallic glass offers several advantages, including high strength, corrosion resistance, and low coercivity. In precision machining fields like optical devices, medical devices, and micro-electromechanical systems, Ti-based metallic glass offers more advantages than Fe- and Zr-based metallic glass. However, its current machinability poses a challenge in meeting the requirements of precision metallic glass parts. To obtain the best machining performance, a thermophysical model of the EDM drilling process was established to simulate the temperature distribution on the surface of metal glass workpiece during EDM drilling. In addition, a new systematic method is utilized to calculate the characteristics of important machining holes, such as inlet and outlet overcut and inlet and outlet edge deviation. In this investigation, the maximum relative overcut and edge deviation are 8.59% and 7.23%, respectively, relative to the electrode radius. To improve the machining quality and machining stability, the slit width should be kept at an ideal value. Therefore, the recommended discharge current is 4–5 A, pulse duration is 50 μ s, and pulse duty ratio is 0.2 - 0.3 when EDM drilling of amorphous alloy. Based on this, the EDM drilling analysis method by numerical and experimental investigation for titanium-based metallic glass is put forward, which provides scientific theoretical guidance for the EDM of drilling it. [ABSTRACT FROM AUTHOR]

Aluminum alloys with 40 to 50 wt.% silicon content are potential material candidates for the manufacturing of satellite components. These materials have excellent thermal and mechanical stabilities, but machining complex components from these alloys is facing many challenges. The present study was performed on an aluminum-high silicon alloy (50–50 wt.%) with the main aim of investigating the evolution of the microstructure with particular attention to surface and subsurface damage as a result of Electrical Discharge Machining (EDM). For this purpose, the microstructure was characterized by optical and Scanning Electron Microscopes (SEM) as well as Energy Dispersive Spectroscopy (EDS) of the machined samples. The results show the existence of melted and re-solidified zone with much finer silicon particles located in a zone on the top of the machined surface where cracks were also observed. Moreover, SEM examinations showed that the cracking damage concern the primary silicon particles. Possible mechanisms, such as the thermal shock produced by rapid cooling rate of the primary silicon particles and the presence of porosities, formed during the manufacturing process, are discussed. [ABSTRACT FROM AUTHOR]

Due to different characteristics of ceramic coatings and superalloy substrates, it is impossible to balance surface quality and machining efficiency of thermal barrier coated superalloys by using constant parameters in electrical discharge machining. In this paper, an adaptive control (AC) method is studied, which can adaptively adjust discharge parameters in real time according to the change of material types. A short circuit detection method based on statistics of the duration of the current falling edge is proposed. And by combining it with voltage detection, discharge states of high resistance and low resistance can be both identified. Based on statistics and analysis of discharge waveforms under various discharge states, a detection method is studied to distinguish metals from insulating ceramics. An adjustment strategy of parameters that has higher sensitivity to insulating ceramics is proposed. It can ensure the real-time conversion of parameters and reduce the number of high-energy pulses acting on the ceramic surface. The waveforms of discharge gap measured with an oscilloscope show that the AC method can realize the conversion between low energy pulses and high energy pulses. The experimental results show that the AC method has much shorter machining time (5.1 min) compared with the method of small energy parameters (52 min) and has smaller maximum damage distance (58.4 μm) than the method of large energy parameters (89 μm). [ABSTRACT FROM AUTHOR]

Traditional electric discharge machining (EDM) uses a Cu electrode to machine polycrystalline diamond (PCD), but it is hampered by poor machining efficiency and quality. During this study, a Cu-Ni electrode was used to machine PCD with graphene power suspended in the dielectric. The surface properties and machining mechanism of PCD under different parameters were analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The surface quality and machining efficiency were analyzed by quantifying the surface roughness (SR) and material removal rate (MRR). The results demonstrated that the MRR of the Cu-Ni electrode increased by 65% when compared with that of Cu electrode at low discharge parameters, with the MRR of Cu-Ni electrode improved by a further 87% when graphene was added to the dielectric. Raman spectroscopy and XRD analysis showed that graphitization of PCD diamond processed by the Cu-Ni electrode was greater than that of the Cu electrode, and the addition of graphene further facilitated this process. The machining efficiency and quality of PCD in EDM can be greatly improved with the use of Cu-Ni electrode and graphene suspended in the dielectric. [ABSTRACT FROM AUTHOR]

The efficiency and accuracy of conventional electrical discharge machining (EDM) are limited by the stability of the voltage between the poles. To improve the efficiency of EDM, this paper presents a machining method that combines a self-developed 5-degree-of-freedom (5-DOF) controllable magnetic levitation actuator with a conventional EDM machine tool. The stability of the interpole voltage is improved by actuator microadjustment of the electrodes of the EDM machine tool. First, an EDM control system with local current feedback and decoupling control elements is designed based on the EDM servo drive principle to improve the response speed and positioning accuracy of the actuator. Second, the actuator is connected to the spindle of a conventional EDM machine tool, and machining experiments are carried out. The experimental results show that the EDM machine tool connected to the actuator can control the electrode position more quickly, adjust the discharge state quickly, and increase the number of discharges per unit time. The average machining speed increases from 1.108 to 3.925 µm/s, which is 3.54 times as fast as conventional EDM. Finally, complex shape machining experiments are carried out, and the machining results showed that by adjusting the target value of the radial direction of the actuator, the various trajectories of the electrode can be controlled to depict arbitrary shapes. [ABSTRACT FROM AUTHOR]

Inconel 625 superalloy and stainless steel 304 are known for their significant corrosion resistance along with their high hardness and strength. Therefore, they are used in a wide range of industries, including oil and gas and nuclear. Electrical discharge machining is among the most widely used processes for machining of these metals. However, this process has limitations, such as low material removal efficiency, high surface roughness, and the formation of a recast layer. Therefore, in this study, the effective parameters on increasing the material removal efficiency and reducing recast layer thickness are investigated. These parameters include the dielectric fluid, electrode material, discharge current, and pulse duration. After performing the test matrix, the effect of each of the input parameters on the material removal rate, surface roughness, and thickness of the recast layer is evaluated using the ANOVA method. The results of this analysis showed that the type of dielectric fluid and the presence of silver oxide nanoparticles have a significant effect on output variables. When using sunflower oil fluid containing nanoparticles and the silver electrode, the recast layer and surface roughness are reduced, while the average material removal rate increases by 40% compared to the traditional mode. Also, due to the biodegradability of deionized water and sunflower oil fluids, the environmental sustainability of the process in this study is increased and while increasing productivity, it leads to the sustainable development of the EDM process. [ABSTRACT FROM AUTHOR]

The discharge current waveform affects the processing characteristics and surface integrity by affecting the process of energy input. At present, although the rectangular current waveform is widely used in electrical discharge machining (EDM), there is not enough evidence to prove that it is the most suitable. Therefore, in this study, the influence of the discharge current waveforms on processing characteristics and surface integrity was investigated and compared under similar pulse energy. Three types of discharge current waveforms including rectangular (Rec), triangular (Tri), and trapezoidal (Tra) are used for processing. The material removal amount, surface topography, roughness, phase compositions, white layer thickness, and residual stress were investigated and analyzed. The results showed that Tri could remove the most materials per pulse-on duration, followed by Tra. Compared with Rec, the size of craters and debris on the sample surface produced by the Tri and Tra was larger. The surface roughness and residual stress of samples processed by Tri were the highest. When the discharge current waveform was constant, XRD spectra of samples fabricated by EDM under different pulse energy were almost the same. Compared with Rec, the diffraction peaks of samples produced by Tri and Tra were reduced. When the pulse energy was low, the white layer of samples processed by Rec was thinner than that processed by Tri. This phenomenon was reversed when the pulse energy was high. The white layer thickness of the sample fabricated by Tra was between the samples processed by Rec and Tri regardless of pulse energy. [ABSTRACT FROM AUTHOR]

Continuous electrical discharge machining (EDM) is characterized by random discharge positions, uncertain discharge energy, extremely short discharge time, extremely narrow tool-workpiece gaps, etc. Theoretical research into the mechanisms leading to thermal erosion of material and the associated surface morphology has become urgent to allow the continued development and application of EDM technology. Firstly, multi-pulse theory and geometric optimization are utilized to derive an expression for the material removal rate and surface roughness in multi-pulse EDM. Secondly, based on the characteristics of multi-pulse discharge, a multi-pulse numerical simulation model was established to predict the material removal volume, surface roughness, and thickness of the recast layer. Finally, the results predicted by the geometric and numerical models are compared with the experimental results. Experimentally, 0.176 mg of material is removed in the multi-pulse EDM; the theoretical calculation and numerical simulation of the same produce errors of 5.11% and 11.36%, respectively. The analogous results for the surface roughness are 1.623 μm, 8.93%, and 1.23%. The experimentally determined thickness of the recast layer was 5.31 μm, which corresponds to an error in the simulation error of 7.53%. [ABSTRACT FROM AUTHOR]

In electrical discharge machining (EDM), the discharge current waveform that determines the process of energy input has an important influence on machining characteristics as the discharge voltage is constant after the dielectric is broken down. In the past, the influence of pulse-on time and current on the surface metamorphic layer under rectangular current waveform has been reported, while the influence of non-rectangular current waveform on the surface metamorphic layer is still elusive. In this study, the difference in the surface metamorphic layer of the workpiece processed by triangular current waveform and rectangular current waveform under the same pulse energy was investigated and analyzed. Compared with rectangular current waveform, surface roughness of the workpiece processed by triangular current waveform was higher. Cracks on the surface of the sample produced by rectangular current waveform always exist from 0.088 to 1.96 mJ. However, it was difficult to observe cracks on the surface of the sample processed by the triangular current waveform when the pulse energy was higher than 0.41 mJ. There is no obvious difference in the intensities of diffraction peaks α-Fe, γ-Fe, and cementite for the samples processed by rectangular current waveform with different discharge energy. However, for the workpiece fabricated by triangular current waveform, the peaks of cementite and γ-Fe increased as the pulse energy increased. When the pulse energy was low, the white layer of the sample processed by rectangular current waveform was thinner than that processed by triangular current waveform. This phenomenon is reversed when the pulse energy is high. [ABSTRACT FROM AUTHOR]

The influences of electrical and non-electrical parameters on surface integrity during the EDM process have been widely researched in past years. However, the effect of the energy input process at the same discharge energy is seldom reported. To select more suitable processing parameters according to the processing requirements, we have studied the influence of the energy input process on processing characteristics and surface properties. Two different energy input modes (high discharge current with short pule-on time (HIST) and low discharge current with long pule-on time (LILT)) are used. When the discharge energy is the same, the HIST mode has a higher material removal amount, while the sample produced by the LILT mode presents a lower surface roughness and residual stress. More surface cracks are detected on the samples processed by the LILT mode, and their dimensions in terms of length and width are greater than that of the HIST mode. The microstructure of the EDM surface is composed of α-Fe, γ-Fe, and cementite. When the discharge energy is higher than 0.24 mJ, the intensities of diffraction peaks γ-Fe and cementite on the EDM workpiece surface produced by the HIST mode are higher. The white layer thickness is related to the discharge energy and its input process. When the discharge energy is lower than 0.51 mJ, the white layer is thinner under the LILT mode. However, the white layer of the EDM sample fabricated by the HIST mode is thinner when the discharge energy is higher than 0.51 mJ. [ABSTRACT FROM AUTHOR]

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]

So far, many investigations have reported that Zr-based bulk metallic glasses (BMGs) could be precisely and flexibly shaped by electrical discharge machining (EDM). However, EDM induced crystallization and roughness is still a bottleneck. In this research, bench-mode electrochemical surface smoothing (ESS) in the NaCl-ethylene glycol (EG) electrolyte has been proposed to post-process the spark erosion treated Zr-based BMGs in order to solve the abovementioned problems. The utilization of the NaCl-EG electrolyte overcomes the difference in electrochemical dissolution mechanisms of multiple components contained in Zr-based BMGs. Taking a sort of Zr-based BMGs, Vit1 (Zr41.2Ti13.8Cu12.5Ni10.0Be22.5), as an example, voltammetry and chronoamperometry methods have been performed on the BMG surface before and after wire-EDM, respectively, in the NaCl-EG electrolyte to reveal the steady and transient electrochemical behaviors. In order to achieve high-efficiency and high-quality ESS of Zr-based BMGs, a 3D printed setup with lateral flushing has been developed, combined with the micron sized inter-electrode gap (IEG) and the pulse current. The surface morphologies after ESS have been compared to evaluate the effects of the initial surface morphologies, dwell time, and pulse parameters. The surface material properties and mechanical performance before and after ESS have also been investigated by EDS, XRD, XPS, and nanoindentation. The results suggests that the proposed ESS method is capable of quickly eliminating the crystalline layer induced by the thermal shock and reducing roughness caused by the discharge craters, which has been finally validated by fast ESS of two Zr-based BMG molds with ruled surfaces in the NaCl-EG solution. [ABSTRACT FROM AUTHOR]

To meet the increasing demand for wire electrical discharge machining (WEDM) under extreme conditions such as ultra-high thickness cutting, micro-wire cutting, micro-energy finishing, and ceramic composites machining, a concept of multichannel discharge WEDM under semiconductor characteristics was proposed. The essence of this conception is that under these extreme machining conditions, the electrode wire or workpiece — or even both of the two electrodes — cannot be treated as electrically conductive materials of the conventional WEDM due to their high electrical resistance. However, they can exhibit electrical discharge behavior like semiconductors, which is defined as semiconductor characteristics. The conventional WEDM theory and related technologies cannot be applied to extreme WEDM because conventional WEDM only has one discharge channel per pulse, whereas multiple discharge channels can be generated by each pulse in extreme WEDM. Therefore, a suitable theory needs to be developed for extreme WEDM under semiconductor characteristics. Based on the multichannel discharge behavior of semiconductors, experiments were conducted on high-efficiency machining with multichannel discharge by stacking several workpieces as an assembly with semiconductor characteristics. It was proved that the multichannel discharge WEDM is capable of achieving high machining efficiency, as well as enhanced surface quality and lower wear of electrode wire. The proposed multichannel discharge WEDM sets up the foundation for the establishment of the theoretical system of EDM under semiconductor characteristics. [ABSTRACT FROM AUTHOR]

The paper details a comprehensive experimental investigation on the influence of operating parameters and cut direction (parallel and perpendicular to fibre orientation) when wire electrical discharge machining (WEDM) unidirectional CFRP composites using zinc-coated brass wire (0.25-mm diameter). A Taguchi L18 fractional factorial orthogonal array considering four variable parameters including open voltage, ignition current and pulse-on time as well as pulse-off time was carried out for each cut direction. Results showed that a ~ 16% increase in maximum material removal rate was achieved when machining parallel to fibre direction (2.41 mm3/min) compared to cutting perpendicular to the fibres (~ 2.08 mm3/min), which was attributed to the higher electrical conductivity of the workpiece along the fibre length leading to greater discharge energies. This however resulted in relatively larger average kerf widths and poorer workpiece surface roughness (Sa) caused by the Joule heating effect. Workpieces machined parallel to fibre direction were generally free of any major edge defects, in contrast to severe delamination observed on both the top and bottom surfaces of specimens cut perpendicular to fibre orientation. High-magnification scanning electron microscopy of the machined surfaces revealed the presence of adhered resin material, fibre cracking, cavities/gaps in the matrix phase and interlayer cracks on most of the samples analysed, with damage severity dependent on the operating parameters and cut direction. [ABSTRACT FROM AUTHOR]

Closed curved and twisted channels are widely used in key parts of aerospace vehicles; however, they are difficult to process. Electrical discharge machining is a common method for machining curved and twisted channels of integral components. The electrode trajectory determines the machining quality and efficiency. We adopted a target evaluation function to distinguish between the local and global optima for an integral component with a long and narrow two-dimensional curved and twisted channel. In addition, we combined heuristic search and rapidly exploring random tree search to design and optimize the machining trajectory of the electrode. Finally, we conducted a comparative experiment between a preliminary design scheme and the proposed optimization method. The test results show that the machining efficiency and accuracy of the proposed method are higher than those of the preliminary design scheme. Furthermore, the machining trajectory generated by the proposed method satisfies the comprehensive requirements to produce two-dimensional curved and twisted channels. [ABSTRACT FROM AUTHOR]

This study fabricates a roughing electrode of electrical discharge machining (EDM) using a rapid prototyping (RP) system and investment casting technology, which reduces the overall time that is required for fabrication and the cost of the manufacturing process for a selected electrode. Pro/E (3D CAD) software is used to design the electrode prototype, which has a complex appearance, and to transform the CAD model into stereolithography (STL) format. An RP machine (Zcorp 402 3DP) is used to construct a gypsum-based powder model. After a sealing process using the permeation of resin, the water resistance and strength of the gypsum-based material are increased. The manufacturing process then involves creating a wax model with a gypsum electrode that is strengthened by resin permeation by casting a vulcanized silicone molding. The brass electrode is fabricated using investment casting technology. The results of an EDM test show that the brass electrodes with RP that are manufactured perform well and the total time that is required to machine the EDM electrode using RP is 15.8% less than the time that is required for a CNC machining process. [ABSTRACT FROM AUTHOR]

The micro-electric discharge machining (micro-EDM) process had been studied by a number of researchers incorporating the single-spark numerical simulation technique. However, due to the stochastic nature of spark generation, complexities arise in determining the precise location of sparks and exact crater overlapping. Owing to this randomness, modelling of the micro-EDM process using the multi-spark approach has not been attempted hitherto. In this research work, an endeavour has been made to propose an improved concept of occurrence of sparks based on a minimum inter-electrode gap presented by the randomly assigned surface roughness to the tool and workpiece electrodes. The inadequacies associated with the single-spark modelling of the micro-EDM process can be overcome to a larger extent by deterministic estimation of the distinct spark location. The essential crater dimensions are inferred from single-spark simulation to estimate the exact number of sparks essential for the removal of a single layer in the multi-spark simulation. Numerically simulated single-crater dimensions are validated with the experimentally determined crater. Further, multi-spark simulation is performed, and successive layers are removed from the workpiece to generate a feature with a certain depth. The effect of the thermophysical properties of workpiece materials (copper, SS-EN 24, and Ti-6Al-4V) on the linear material removal rate (MRRl) is analysed. Simulation results illustrate that among the three materials, Ti-6Al-4V and SS-EN 24 result in the highest and lowest MRRl, respectively. The multi-spark approach presented in this work essentially differs from the occurrence of multiple sparks from a single-pulse input. [ABSTRACT FROM AUTHOR]

It has been previously reported that electrical discharge machining (EDM) performance can be improved by tool electrode vibration. However, the mechanism of vibration-assisted EDM has not been clarified and the optimal vibration condition remains unknown due to the difficulty in direct process observation. In this study, direct observation of the EDM gap by using a high-speed video camera through a transparent workpiece electrode made of single-crystal 4H-SiC was attempted. It was found that tool vibration caused discharge dispersion and discharge frequency increase, and this tendency was more significant at higher amplitudes and higher frequencies. In addition, tool vibration-induced periodic discharge was observed, which prevented concentrated discharge and short-circuiting. Accordingly, the machining speed was improved and surface roughness was reduced. This study succeeded for the first time in observing the discharge behaviors in vibration-assisted EDM, thus revealed the effects of key parameters for process optimization. [ABSTRACT FROM AUTHOR]

This paper analyzes the high-performance efficiency of atomized electric discharge machining (EDM) ablation using quantitative analysis of discharge and combustion erosion. Using an argon-atomizing medium and an oxygen-atomizing medium, a comparative experiment is performed to calculate the amount of material erosion generated by discharge and combustion during EDM ablation. Then, by collecting the single-pulse discharge waveform and the discharge rate, comparative experiments are carried out between EDM and EDM ablation to study the influence of electrical parameters on the ratio of discharge to combustion erosion in EDM ablation process. The reasons for the efficiency of EDM ablation are determined to be the higher discharge probability when compared to conventional EDM and the introduced oxygen which reacts with the activated material, increasing combustion effectiveness. The results show that under different pulse width, pulse interval, and average current experimental conditions, the combustion erosion in the atomization ablation process accounts for 67–78% of the total erosion, and the efficiency of atomization EDM ablation is over 8 times that of traditional EDM. [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]

Electrical discharge machining (EDM) is a controlled metal-removal process used to remove metal by means of electric spark erosion. In this process, a high voltage is applied between two electrodes and the breakdown of the dielectric is initiated by moving the electrode towards the work piece. This movement increases the electric field in the gap until it reaches the breakdown value. When the breakdown occurs, the voltage falls and the current rises abruptly. The presence of a current is possible at this stage because the dielectric has been ionized and a plasma channel (the bubble) has been created between the electrodes. The pre-breakdown phase in the dielectric is characterized by the generation of numerous small bubbles that promote the breakdown process. In this paper a new model for the formation of the plasma channel (bubble) is proposed. This model considers a mixture gas/steam inside the bubble, the shell of the bubble (if any), and the fluid surrounding the bubble. The gas is modeled as ideal and the bubble is initially modeled only as a cavity within the fluid. It is assumed that the bubble is cylindrically symmetric and that the bubble oscillations preserve this symmetry. This assumption is made for the case of a single bubble far from any boundaries, and in a low amplitude-driving field. In these models the center point of the bubble remains stationary at the origin because of the cylindrical symmetry about the origin. The proposed model is evaluated using experimental data and existing models. [ABSTRACT FROM AUTHOR]

Water-in-oil (W/O) nanoemulsion can be an alternative working fluid to kerosene in sinking electrical discharge machining (EDM). W/O nanoemulsion can improve the material removal rate, reduce the relative electrode wear rate, and alleviate the pollution of conventional sinking EDM using kerosene. However, the mechanism of sinking EDM using W/O nanoemulsion is not fully understood. In this study, a set of comparative experiments of single-pulse discharge is conducted in W/O nanoemulsion and kerosene to clarify the discharge mechanism of W/O nanoemulsion. The main machining parameters, which are crucial in actual sinking EDM, including pulse duration, peak current, and electrode polarity, are investigated. Precise geometries of the corresponding craters generated at the critical discharge gap are determined by the combination of optical instruments and 3D-rebuilt method. The effect of the working fluid flushing on the discharge machining is also analyzed. The results demonstrate that by the introduction of nanodroplets, the critical discharge gap is enlarged in W/O nanoemulsion. Compared with kerosene, W/O nanoemulsion has higher viscosity and density, which leads to stronger restrictions to the plasma channel and the motions of bubbles; therefore, larger volumes of melted materials and craters are formed in W/O nanoemulsion. This difference between W/O nanoemulsion and kerosene rises with the increasing discharge energy. Moreover, the restriction effect from working fluid is insignificant in the case of negative electrode polarity. [ABSTRACT FROM AUTHOR]

The modern industry which widely utilized sinking electrical discharge machining (EDM) with kerosene has many problems including low processing efficiency, unsafety, unfriendly environmental impact, and poor machined surface accompanying with recast layer. In this paper, a new water-in-oil (W/O) nanoemulsion dielectric is proposed to overcome these shortcomings of conventional sinking EDM. The machining performance and mechanism of sinking EDM using W/O nanoemulsion are investigated in both rough and finishing machining by comparing with kerosene. The main characteristic parameters for evaluating machining performance, including material removal rate (MRR) and relative electrode wear rate (REWR) in rough machining, and machined surface quality in finishing machining are studied. Compared with kerosene, using W/O nanoemulsion as a dielectric in sinking EDM, a nearly 34 times higher MRR and a relatively lower REWR are obtained in rough machining, and a better machined surface with no recast layer is attained in finishing machining. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is a non-conventional machining process, widely used in the modern industry. The stochastic nature of the process and the complexity of the occurring phenomena are the major difficulties in modeling of EDM. The current study presents a novel approach on EDM modeling, by coupling a heat transfer thermal analysis with deformed geometry feature. The deformation rate was calculated proportional to the spark erosion, leading to more accurate and realistic results. To validate the simulations results, a series of experiments were carried out on AISI O1 work-steel, with changing machining parameters the pulse current and the pulse-on time. The model validation criteria were the geometry of the formed craters, the average white layer thickness, and the heat-affected zone thickness. The simulation results were in agreement with experimental ones, suggesting that deformed geometry feature is important and suitable in modeling of EDM. [ABSTRACT FROM AUTHOR]

In the orbital mode of electrical discharge machining (EDM), an electrode with a complex profile causes deviation in the cavity profile from the design objective. In this paper, electrode compensation techniques according to the envelope theory are presented to eliminate deviation errors. The succession of orbits traced out a family of electrode curves based on kinematic geometry integrated with the motion path of tool bodies and constraints. The boundary of the family of electrode curves is referred to as the orbiting profile. The deviation error between the orbiting and objective profiles can be eliminated by using a compensation electrode in the orbiting process. Thus, the generated orbiting profile conforms to the objective profile. Experimental results of the tested example for the machining profile of the compensation electrode by using the orbital process revealed that profile deviation can be eliminated to ensure that the EDM profile closely conforms to the objective profile. This compensation method for orbiting EDM provided an exact process to engineers for easy control of the machining precision of EDM. [ABSTRACT FROM AUTHOR]

Application of external magnetic field in electrical discharge machining is one of the methods to increase this process capability and decrease its limitations. In the present study, a single discharge in magnetic field-assisted electrical discharge machining has simulated using finite element method in order to obtain the temperature distribution and generated crater dimensions on the workpiece surface. A new mathematical model for plasma channel radius was also developed and used at simulation stage. Regarding good agreement between recast layer thickness obtained by numerical and experimental methods with maximum error of 8.8%, the effects of applying external magnetic fields on plasma flushing efficiency and recast layer thickness were found numerically and experimentally. Also the influences of pulse current and pulse on-time on dimensions of generated craters at magnetic field-assisted EDM were studied numerically. The results showed the positive effects of application of external magnetic field in EDM process on increasing plasma flushing efficiency and decreasing recast layer thickness. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is extensively used for machining difficult-to-machine materials and complicated shapes. Its performance in terms of material removal rate and surface roughness is usually analyzed using the process parameters such as setting voltage, setting current, pulse on time, and duty factor. It is well known that interelectrode gap condition controls the EDM performance, and it is difficult to observe the gap phenomena directly. Literature reveals that the combined influence of pulse types and their individual contributions on material removal rate and surface roughness has been ignored. In the present work, rough and finish EDM conditions are identified from a large set of 125 experiments carried out on hardened D3 die steel. From the voltage and current pulse trains in each regime, pulse characteristics and five different pulse types are assessed by a unique thresholding approach. Based on the pulse details, two new parameters such as energy expended (E) at the electrode gap over a second and a performance factor (PF) giving ratio of energy associated with the sparks to total energy expended have been proposed. It is found that a higher PF of 0.757 at a relatively lower expended energy of 113.7 J leads to a favorable condition in rough machining. A relatively lower E of 29.7 J and a higher PF of 1.00 are favorable for finish machining. Cross-sectional images of the ED machined workpieces are also included as evidences. The proposed thresholding methodology has a potential for online monitoring, analysis, and control of EDM process. [ABSTRACT FROM AUTHOR]

Wire electrical discharge machining (WEDM) is an unconventional machining method indispensable especially for the aeronautical and automotive industries. In this context, the effective manufacturing of high surface quality components from aluminum alloy 7475-T7351 requires comprehensive knowledge of the applied production procedures. We therefore performed a designed experiment comprising 33 cycles (with systematic alteration of machine setting parameters such as gap voltage, pulse on time, pulse off time, discharge current, and wire feed), enabling us to evaluate systematically the cutting speeds in the relevant samples. The machined areas were subjected to a thorough analysis involving both the surface and the subsurface layers. The actual topography was assessed using a non-contact profiler, and the entire operation concentrated on 12 parameters within the areal, profile, and basic and bearing profile categories. To observe the surface relief, we employed several instruments, including the semi-contact atomic force microscopy (AFM) technique, a digital microscope, and a non-contact 3D profiler. Another major step then consisted in examining the morphology and surface defects, a process suitably complemented with a chemical composition analysis (EDX). The distribution of individual elements within the material was investigated in detail using a lamella, whose subsequent inspection relied on a transmission electron microscope (TEM) as the principal tool. To study the subsurface layer and its defects, we prepared metallographic specimens (cross-sections) of the samples and observed them by means of light and electron microscopes. [ABSTRACT FROM AUTHOR]

Ni-Al2O3 functionally graded materials (FGMs) have become important for high-temperature applications due to a continuous change in graded layers. However, the manufacturing process of Ni-Al2O3 FGMs with the traditional pulse power is a long process because the pulse power cannot real-timely adjust machining parameters to adapt the change of graded layers. This paper designed a real-time monitoring module and a parameter adjustment module, which can identify different graded layers and actively adjust machining parameters to adapt the change of graded layers. By means of the monitoring module, four major discharge states, normal, arc, insufficiency, and long pulse discharge state have been discriminated real-timely. The 70% Ni/30%Al2O3 layer and 30% Ni/70%Al2O3 layer have been distinguished based on the quantitative analysis of insufficiency and long pulse discharge waveforms. Multi-layers of Ni-Al2O3 FGMs are machined to validate the machining performance of the parameter adjustment module. Experiment results demonstrate that by adjusting the open voltage, the machining efficiency of 30% Ni/70%Al2O3 layer has been increased by six times, resulting in more time-efficient EDM process of Ni-Al2O3 FGMs. [ABSTRACT FROM AUTHOR]

The performances of carbon nanofiber (CNF) reinforced copper (Cu) composite electrodes on the reaction-bonded silicon carbide (RB-SiC) ceramic were experimentally investigated by using electrical discharge machining (EDM). The effects of CNF content on material removal rate (MRR), electrode wear ratio (EWR), surface roughness (SR) and surface topography were examined. Results indicated that the addition of CNF to the Cu electrode increased the MRR of the workpiece. In addition, increasing the added CNF content increased the EWR of the Cu-CNF composite electrode and the SR of the machined surface. The results of one-way ANOVA indicated that the Cu-1.0 wt% CNF composite electrode exhibited the optimal MRR and EWR values, although this electrode resulted the maximum SR on the RB-SiC machined surface. [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]

Electrical discharge machining (EDM) has been recommended as the most effective way to produce an integral shrouded blisk, whereas its low machining efficiency cannot meet the batch production requirements of this component. An electrode feeding method with perturbations in the EDM process of the integral shrouded blisk is proposed, in which extra perturbations are periodically added on the original feeding path. Those perturbations are perpendicular to the original feeding path and are determined by two parameters: separation distance and perturbation factor. The optimal perturbation parameters for blisk EDM machining are experimented to be a separation distance of 2.5 mm combined with a perturbation factor of 30%. Compared with the electrode feeding method without perturbations, that with perturbations had a better discharge status. A machining time reduction of 18.45% was achieved in the EDM process of a real integral shrouded blisk by using the electrode feeding method with perturbations. [ABSTRACT FROM AUTHOR]

In the present study, an axisymmetric model for temperature distribution in single discharge of ultrasonic vibration-assisted electrical discharge machining process has been developed using finite-element method to get the dimensions of generated discharge crater on the surface of workpiece and provide a FEM model for material removal rate at this process. For this purpose, a new mathematical model for plasma channel radius was also developed and used in finite-element modeling. Then, due to good correlation between numerical and experimental results of recast layer thickness with maximum error of 6.1%, the developed finite-element model along with performed experiments was used to investigate the effects of applying ultrasonic vibrations to tool electrode on created crater dimensions, plasma flushing efficiency, and recast layer thickness at different pulse currents and durations. Also, the effects of pulse current and duration on depth, radius, and volume of created craters on machined surface at ultrasonic vibration-assisted electrical discharge machining (EDM) process was investigated. The experimental and numerical results showed that applying ultrasonic vibrations to tool electrode at EDM process increases generated crater depth and volume and plasma flushing efficiency and decreases generated crater radius and recast layer thickness. [ABSTRACT FROM AUTHOR]

This paper describes the spectroscopic measurement of arc plasma temperature and the radiation lines of different atoms in an electrical discharge machining (EDM) process under different controlling parameters: discharge current, voltage, and pulse width. The radiation lines of W, Co, and C were calibrated, and the intensities of these radiation lines, which increased with increasing discharge energy, represented the electrode wear and the material removal rate. It was found that the electrode wear and plasma temperature increased seriously with increasing discharge current, but a low electrode wear rate and high machining efficiency were obtained because of the low intensity of the radiation line of Cu and the high intensities of the C and Co lines resulting from increasing impulse width. The plasma temperature was calculated by the line-pair method, and the temperature was in the range of 5132-7758 K, which is higher than the gas/solid transition temperature of diamond at normal pressure and temperature. The results showed that some parts of the diamonds were directly transformed to a gaseous state by the high temperature generated by the discharge in the EDM process; the white layer, which consisted of some metals, covered the surface of the diamond. [ABSTRACT FROM AUTHOR]

To improve the efficiency of conventional electrical discharge machining (EDM) milling, this study proposes a highly efficient machining method that employs continuous oxygen feeding and fast-moving electrode. High-efficiency machining is achieved by the method of feeding with small thickness, allowing the electrode suspended above the workpiece to reduce short circuit and using a high discharge probability to ignite the workpiece in order to realizing high efficiency machining with great chemical energy released from metal combustion. Comparative tests for conventional EDM milling, EDM ablation milling, and ablation milling by fast-moving electrode were performed in the milling process. In this study, we analyzed the mechanism, machining efficiency, electrode relative wear ratio, and machining quality. The machining efficiency of EDM ablation milling was 6.8 times higher than that of conventional EDM milling, and the relative tool wear ratio was 20% of conventional EDM milling; the machining efficiency of ablation milling by fast-moving electrode can reach 11.2 times higher than that of conventional EDM milling, and the electrode relative wear ratio decreased by 86%. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid electrochemical discharge drilling method in which a metal tube is used as cathode tool and workpiece is used as anode. Liquid with weak conductivity flows at high speed between the metal tube and workpiece. Electrical discharge takes place mainly at the frontal gap, and electrochemical process takes place at both the frontal gap and side gap. The recast layer generated by electrical discharge at the side gap can be removed electrochemically. The machining phenomenon at the gap was observed through a designed transparent clamping fixture, voltage and current waveforms during machining were recorded, and the machining products and removal effect of recast layer were analyzed. The cross section of the hole and machining surface were analyzed, and the tool wear and machining efficiency were compared with those of other processes. Finally, the 4-mm-deep hole of 0.5-mm diameter can be produced with low tool wear and almost no recast layer. [ABSTRACT FROM AUTHOR]

In the present work, the influence of the plasma energy on the surface of the workpiece in electrical discharge machining (EDM) was investigated, using a cylindrical electrode into deionized water, applied to a heat uniform distribution which is transferred during On-time periods of 12, 20, and 28 μs. A kinetic-molecular energy model is proposed in order to determine the fraction of energy employed in material removal by evaporation and overheating on the surface of high-strength low-alloy steel. The plasma energy was determined as 1.28 × 10 and 0.760 × 10 W/m, using 25 and 15 A, for high and low discharge, respectively. Microstructural analysis of the front of machining associated with a planar heat source and the material removal rate (MRR) was carried out. Results evidence that some atomic layers of metal were removed in each cycle for different conditions of discharge energy. The planar heat distribution model to determine the MRR showed a R = 0.9753 concordance versus experimental data. The material removal mechanism was considered as a separation of sublimated metal, which in turn is mixed with steam during the heat transfer in the interface dielectric-anode and a material melt fraction is removed by drag for the EDM drilling process. It was possible to measure experimentally the resolidified layer and the heat-affected zone and accurately obtain the transferred effective energy for material removal in the range of 1 to 1.3% for a machining power of 12.1 × 10 W/m. [ABSTRACT FROM AUTHOR]