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High-intensity electrical discharges are used in the unconventional technique known as electrical discharge machining (EDM) to machine metals of any hardness. Due to their extraordinary conductivity and strength, carbon nanotubes (CNTs) have recently been explored in EDM too. However, material removal with CNT yarn (CNTY) has not been studied thoroughly. This work advocates the use of a pristine CNTY as an EDM tool. The feasibility is examined through characterization and material removal experiments. The measurements show that the CNTY (< 100 µm in diameter) has an electrical conductivity and current carrying capacity of 2.66 × 104 S/m and 1.76 × 103 A/cm2, respectively. Steel and aluminum are the workpieces for machining experiments conducted in air and hydrocarbon oil dielectrics, respectively. Significant material removal and extended tool life are obtained in the air dielectric. It is suggested that the oxidation of steel increases material removal in the air while reducing tool life. The effect of tool thickness is also investigated. Thicker (> 100 µm) multi-ply tools extend tool life and, therefore, machining time by more than 14 s in the air and nearly 2.5 s in the oil. Other factors that restrict machining include intensified discharges and the shielding effect of the carbide layer formed on the workpiece. [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]

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]

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]

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]

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]

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]

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]

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]

The aim of this research is proposing a novel and simple method to reduce the side overcut in EDM process that has a negative influence on the precision and accuracy of the work piece dimensions. Although some previous researchers applied external magnetic field for reducing the overcut, their methods were not efficient and practical, especially in the micro- and nano-EDM. The main ideas are that as the electrical filed between work piece and tool has significant effect on the occurring sparks, reducing electrical field leads to descending sparks and, as a logical result, influences EDM process factors, one of which is decreasing side overcut. In this study, it is tried to reduce side overcut by distortion of the electrical field between the side of work piece and tool. From physic rules, it is clear that adding an electric charge next to other electric charges can change the electrical filed distribution between them. Therefore, applying an electric charge close to the side of tool can strongly change the magnitude and direction of electrical field between side of work piece and tool. The results indicate that side overcut is reduced after applying an external voltage around the side of tools and also the value of overcut decreases by increasing the amount of external voltage [ABSTRACT FROM AUTHOR]

Shrouded blisk components are one of the core parts in aerospace engines. Five-axis or six-axis electrical discharge machining is once regarded as the best solution to manufacturing these components. The machining process, however, is time consuming and money cost. In this paper, an electron beam melting (EBM) and electrical discharge machining (EDM) combined method for shrouded blisks manufacturing was presented. In the new method, EBM was used to generate the near-net forming blank of the shroud blisk, and EDM was responsible for finish machining. The mechanical properties of the EBM formed Ti6Al4V blank was tested to be good enough for shrouded blisks. A visual identification method was proposed to establish the machining reference on the EBM formed blisk blank for the subsequent EDM process. The given example showed the required blade accuracy of ±0.03 mm can be achieved by the visual identification method. Through the combination of EBM and EDM method, the machining time of the shrouded blisk was greatly reduced by 54.8 %. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) are used to provide thermal insulation for superalloy components from high-temperature gas streams. Due to the insulativity of the top coat and the different physical and chemical properties of each layer, it is difficult to machine small holes in TBC-coated components. In this paper, electrical discharge machining (EDM) was used to machine small holes in high-velocity oxy-fuel-sprayed TBC-coated nickel superalloys using the assisting electrode method. The signal-to-noise (S/N) ratio of the experimental results was used to study the influence of the processing parameters on the response characteristics. Based on the S/N ratio results, the machining parameters of multiple responses were optimized using the gray relational analysis method. Experiments were conducted using an orthogonal array, and the factors selected in this study were peak current, pulse duration, duty factor, and flushing pressure. The responses (i.e., machining time (MT), electrode wear (EW), maximum falling distance of 8 %YO-stabilized ZrO (MFD-YSZ), and surface roughness (Ra)) were chosen to evaluate the effects of machining. The results showed that peak current influences MT, EW, Ra, and MFD-YSZ more than the other factors and that pulse duration is the most significant factor for multiple responses. A confirmation experiment showed that the optimal process parameters improved the gray relational grade index for the multiple responses from 0.7393 to 0.7785. [ABSTRACT FROM AUTHOR]

Ni-AlO functionally graded materials (FGMs) have become important for high-temperature applications due to a continuous change in composition. However, the manufacturing of Ni-AlO FGMs with conventional machining methods is a long and costly process because of the insulating ceramic composition. This paper presents a new method of machining Ni-AlO FGMs by self-induced electrical discharge machining (EDM). Self-induced EDM uses the conductive compositions of Ni-AlO FGMs to trigger the discharges in the insulating composition. Machining characteristics of a four-layered Ni-AlO FGMs drilled by self-induced EDM have been investigated, which include the material removal mechanisms, discharge properties, surface characteristics, material removal rate, and electrode wear ratio. It has been found that graded layers, 70 % Ni-graded layer and 30 % Ni-graded layer, are removed by dislodgement of AlO particles, in addition to conventional melting and evaporation. Pure AlO layer is melted and evaporated by utilizing conductive layer-induced discharges. The discharge properties, surface characteristics, material removal rate, and electrode wear ratio are significantly influenced by the material removal mechanisms of graded compositions. These findings demonstrate that self-induced EDM is able to effectively machine Ni-AlO FGMs. [ABSTRACT FROM AUTHOR]

Surface modification is essential to enhance the surface properties of engineering components. This may be accomplished either in the form of altering the surface chemistry or by providing a protective layer over the work surface. In this paper, the surface modification phenomenon by depositing a protective layer over the work surface by electrical discharge machining (EDM) is presented. The potential of EDM, which is otherwise a useful non-conventional machining process, has been explored for surface alteration by depositing material over work surface using tungsten-copper (W-Cu) sintered powder metallurgy tools. The photographic presentation of the EDMed surface at different parameter settings is given. The variations of mass transfer rate (MTR), deposited layer thickness (LT), and average surface roughness ( R) with various parameter combinations are presented in graphical form and their effects are discussed. A wide spectrum of MTR ranging from nearly 1 to 191 mg/min and average surface roughness values ranging from 3 to 15 μm have been achieved. A wide range of deposited layers with thickness varying from 3 to 785 μm has been achieved by various combinations of process parameters. The microstructure of the deposited layers with microhardness at different zones is presented. It has been observed that the microhardness is gradually increasing from the base material to the deposited layer and its maximum value is found to be 15.7 GPa at the hardest zone. SEM, EDX, and XRD analyses has been also performed for further characterization of the deposited layer. A quantitative analysis of the layer has been carried out by EDX and it is found that the inner part of the layer is richer in tungsten than the superficial surface. This contributed towards the higher hardness of the layer at the core. [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]