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Micro electrical discharge drilling (ED-drilling) is a machining method used to make micro holes in hard-to-cut materials. The RC-discharge generator is often used because it creates a short and strong discharge spark. However, this method has issues such as current oscillation between tool electrode and workpiece, causing polarity changes that increase tool wear, and a low material removal rate due to long spark delay time. Furthermore, micro ED-drilling results in a large taper angle due to second discharge sparks created by debris in the narrow gap. To address these issues, the effect of adding graphite powder to the working fluid was studied. The graphite powder in kerosene created a bridge effect that reduced tool wear and taper angle, while improving MRR and surface roughness. The electrical conditions were not changed, and the machining process was improved by only altering the working fluid without modifying the existing system. [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]

Recent developments in material science have concentrated not only on the improvement in mechanical properties, but also on the machinability that was difficult for system profiles. The present research explains the machinability assessment of the part of the sintered powder metallurgy using an electric discharge machining. The ferrous clay matrix preparations are constructed from iron–carbon–copper material and bentonite clay. The selected input parameters for the measurement of machinability are wt. % of clay, current (A), pulse on time (µs) and voltage (V), whereas the electrode wear rate, material removal rate and surface roughness (Ra) are considered as performance features. Results show that the performance parameters have been optimized at three different parametric conditions. Further, to obtain single optimum condition the hybrid GRA-TOPSOS methodology has been implemented for maximum MRR with minimum EWR and low surface roughness. The single optimum condition has been found at 5% clay, current 7 A, voltage 49 V and pulse on time 400 µs. The study of micro-structure and chemical composition of machined surfaces has been carried out using scanning electron microscopy with X-ray diffraction and energy-dispersive spectrometry analysis, respectively. The SEM exposes the less recast layer and micro-cracks during electrical discharge machining of ferrous clay composite. [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]

The influence of electrical discharge machining (EDM) on thermal barrier coating (TBC) in a two-step drilling of nickel-based superalloy has been studied. The TBC was coated on the superalloy using electron beam physical vapor deposition (EB-PVD). Simulation result shows that the temperature at TBC/metal interface increases with pulse-on time and peak current. The temperature will exceed the melting point of the coating material when using relatively large pulse energy. Experimental result reveals that large pulse-on time or high peak current caused defect such as cracking at coating sidewall and delamination at the TBC/metal interface. For EDM drilling holes with inclined angle, the leading edge had worse condition of debris evacuation, and consequently caused secondary discharge which resulted in melt and spalling of the coating material. In addition, relatively larger pulse-on time and greater peak current might result in greater thermal stress gradient at the interface and subsequently lead to cracking or spalling at the coating layer. Therefore, process conditions of short pulse-on time, longer pulse-off time, and small peak current are recommended for EDM drilling of the EB-PVD coated nickel-based superalloy. [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]

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]

Wire electrical discharge machining is an on-traditional technology of machining, which is used in many industries. This technology of utilizing electrical impulses to cut material at high temperatures tends to create many types of surface and subsurface defects on machined surfaces. The occurrence of defects in the form of cracks or burned cavities may represent a significant limitation of the functionality and lifetime of the component. For this reason, the analysis of the occurrence and formation of surface and subsurface defects was carried out in this study, depending on the type of material used and the parameters setup of the machine. The object of the study was three metallic and three non-ferrous materials, three samples of which were produced with different parameters setting of the machine. The processed samples were analysed using both light and electron microscopy, and their cross sections as well. In addition, the topography of all samples was evaluated using a contactless profile meter, and the visualization of the 3D surface of the sample was performed using the semi-contact atomic force microscope technique. On the basis of the analyses performed, materials have been found in which the occurrence of defects is influenced by the parameters setup and they can, therefore, be prevented. [ABSTRACT FROM AUTHOR]

This paper proposes a machining performance prediction approach on multiple performances of wire electrical discharge machining (WEDM) on Inconel 718. Artificial neural network (ANN) is emphasized to predict the machining performances. Many efforts have been made to model the performances of WEDM using ANN. However, to obtain the best ANN model, generally the network parameters are not consistent and so far, the selection has been made in a random manner and resulted in an excessive experimental trial. Taguchi design orthogonal array L256 is implemented in the process of network parameter selection to search for the potential machining model. This approach, prescribed as OrthoANN, is simplified to avoid as much as unnecessary experimentations. Material removal rate, surface roughness (Ra), cutting speed (Vc) and sparking gap (Sg) are the machining performances considered in this study. Five machining parameters considered; pulse on time, pulse off time, peak current, servo voltage and flushing pressure. Cascade forward back-propagation neural network (CFNN) is found to be the best network type of the selected data set. One hidden layer 5-14-4 CFNN showed the most precise and generalized network architecture with very good prediction accuracy. An average of 5.16% error is generated which seems to be in superior concurrence with the actual experimental results. Confirmation test is carried out to verify the machining performances suggested by this approach. [ABSTRACT FROM AUTHOR]

In present work, micro-deep holes on AISI 304 stainless steel were drilled via electrical discharge machining (EDM) method. In the first phase of this work, the effect of test parameters on the drilling performance and the profile of drilled holes were investigated experimentally. Test parameters including discharge current, dielectric spray pressure and electrode tool rotational speed were taken and then the machining rate (MR), electrode wear rate (EWR), average over-cut (AOC) and taper angle (TA) were measured in order to assess the drillability of EDM. After experimental study, an analysis of variance was performed to identify the effect of the importance of test parameters on experiment outputs. In the second phase of this study, optimum process parameters were determined using signal-to-noise analysis and response surface methodology (RSM) for mono-optimization and multi-response optimization, respectively. In the last phase, regression analysis and artificial neural network (ANN) models for predicting the MRR, EWR, AOC and TA. As a result of experimental analysis, discharge current was the most important parameter for micro-drilling with EDM. It was found out that this parameter influenced positively MR, while it has negatively an effect on EWR, AOC and TA. Mathematical model based on ANNs exhibited a successful performance for predication of outputs. Optimum process parameters which were discharge current of 10.18 Å, dielectric liquid pressure of 58.78 bar and electrode tool rotational speed of 100 rpm for multi-objective optimization were determined through RSM with desirability function analysis in micro-deep hole EDM drilling of AISI 304 stainless steel. [ABSTRACT FROM AUTHOR]

In PM/EDM, it is known that when used electrically conductive powders, highly homogeneous alloyed layers can be formed where the gap extends slightly more than using non-conductive powders and regulates spark discharge and machining voltage more uniform. Boron element is non-conductive but when alloyed with steel, materials with high abrasion and corrosion resistance are obtained. In this study, the effects of boron oxide powders addition into dielectric fluid on microstructure and hardness of steel workpiece in electrical discharge machining (EDM) were investigated. For this purpose, by using a prismatic steel workpiece and a copper electrode in kerosene mixed with boron oxide (B2O3) powders, the morphology of the machined specimens at different powder concentrations and pulse duration settings were observed and investigated. In addition, the micro hardness of the layers occurred as a result of EDM was measured and discussed. The highest surface hardness value of 941 HV is measured over machined specimen with B2O3 powder addition, whereas the lowest surface hardness value of 413 HV is measured. [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]

The possibility of using vibroacoustic signals for monitoring the efficiency of discharge pulses during electrical discharge machining is examined. Data on the effect of the variable dynamic characteristics of billets and background noise for electrical discharge machining in different frequency ranges on the parameters of vibroacoustic signals are presented. [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]

Investigations were conducted on the machining of AISI D2 tool steel via Conventional electrical discharge machining (CEDM) and Cryogenic cooled electrode in electrical discharge machining (CCEDM). Machining parameters, including discharge current, pulse on time, and gap voltage, were varied to investigate their effects on machining performance such as on Electrode wear ratio (EWR), surface roughness (Ra), microstructure, surface morphology, and elemental composition. Experimental results showed that EWR was reduced by 20% in CCEDM compared with in CEDM. Moreover, the Ra in CCEDM decreased by approximately 19% compared with that in CEDM. The results also indicated that the surface morphology of the workpiece machined via CCEDM was better than that of the workpiece machined via CEDM. Lastly, the damaged layer and microcracks were less in the workpiece machined via CCEDM than those in the workpiece machined via CEDM. [ABSTRACT FROM AUTHOR]

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

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

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

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

Pipe cutting technology plays an important role in the process of offshore platforms decommissioning, as many devices such as tubing, drill pipe, and casing need to be decommissioned. In this study, a novel cutting pipe technology based on electro-discharge machining (EDM) is proposed, and a cutting pipe mechanism is developed to cut the pipes for decommissioning offshore platforms. The machining principles and characteristics of the technique are described. The effects of machining parameters, including tool polarity, dielectric fluid, electrode material and width, pulse on-time, pulse off-time, peak voltage, and electrode rotation speed to machining performance, are investigated. The material removal rate (MRR) of the machined casing and tool electrode wear ratio (EWR) is obtained based on the calculation of the percentage of mass loss per machining time. The experimental results show that a better cutting performance can be obtained with negative tool polarity at the conditions of dielectric fluid of emulsion, pulse on-time of 500 μs, pulse off-time of 200 μs, peak voltage of 70 V, copper electrode width of 28 mm, and electrode rotation speed of 250 rpm is a better choice. Additionally, the cutting slots surface has been investigated by the means of SEM. The cutting slots machined by the rotary EDM are clean and smooth. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is capable of fabricating thin wall structures due to the absence of physical contact between the tool and workpiece. However, the presence of impulsive force does exist during the sparking process, which could give rise to limitations in fabricating small features. The L9 Taguchi method together with the analysis of variance was used to determine the significance of various machining parameters on the specific impulsive force. Through the statistical analysis, it was observed that discharge energy was the most significant factor that influenced the specific impulsive force. Hence, it is important to understand the effects of specific impulsive force in EDM and to investigate its influence that limits the fabrication of thin wall structures. The limit in which the machined part is able to maintain its geometrical integrity is described as the critical wall thickness. The effects of specific impulsive force on thin wall structure were studied through determining the critical wall thickness for various discharge energies. The experimental work showed that both electrothermal erosion and brink erosion, which is attributed by the specific impulsive force was responsible for the loss of geometrical integrity of the wall structure. As the wall thickness falls below a critical value in a given discharge energy setting, the brink erosion was observed. The limit that established the critical wall thickness was elucidated by conflating the thermal erosion and brink erosion. [ABSTRACT FROM AUTHOR]

In most of the commercially available EDM systems, the control parameters such as the electrode jump height and the discharge machining time between two consecutive electrode jump actions are set manually to constant values which can ensure stable machining even under the worst machining conditions. It is beneficial to keep the machining process stable, but much time is consumed in the electrode jump process. In order to improve the EDM efficiency, a new adaptive control strategy which directly and automatically regulates the electrode jump height and discharge machining time has been developed in this paper. Experimental results show that the adaptive control system can obviously improve the machining efficiency regardless of the surface area, shape, and depth of the machined dies. Meanwhile, the accuracy and surface roughness of the fabricated dies can be well retained. [ABSTRACT FROM AUTHOR]

In this paper, the effect of the shapes of the tool and the workpiece on the dynamic behavior of an electrical discharge generated vapor bubble in the process of EDM (Electrical Discharge Machining) is investigated. The boundary integral equation method is employed for numerical simulation of the problem. Results show that in the case of the concave tool and workpiece the lifetime of the electrical discharge generated vapor bubble is longer than the case of the flat tool and workpiece. By increasing the concavity of the shapes of the tool and the workpiece, the lifetime of the bubble increases. Results also show that in the case of the convex tool and workpiece, the lifetime of the electrical discharge generated vapor bubble is shorter than the lifetime of the bubble in the case of the flat tool and workpiece. In this case also, by increasing the convexity of the shapes of the tool and the workpiece, the lifetime of the bubble decreases. Numerical results show that in the case of the concave tool and workpiece the rate of pressure drop on the surface of the workpiece is higher than the rate of pressure drop on the workpiece in the cases of the flat and convex tool and workpiece. The high rate of pressure drop on the surface of the workpiece leads to the ejection of more molten material from the crater and consequently leads to more material removal rate. [ABSTRACT FROM AUTHOR]

This study investigates how machining characteristics and surface modifications affect low-carbon steel (S15C) during electrical discharge machining (EDM) processes with semi-sintered electrodes. Among the machining characteristics determined, the material removal rate (MRR), surface deposit rate (SDR), and electrode wear rate (EWR) are included. Additionally, exactly how semi-sintered electrodes affect the surface modifications is also evaluated by electron probe microanalyzer (EPMA), micro hardness, and corrosion resistance tests. The experimental results confirmed that the composition of the semi-sintered electrodes is transferred onto the machined surface efficiently and effectively during the EDM process, and that the process is feasible and can easily form a modified layer on the machined surface. [ABSTRACT FROM AUTHOR]

In this paper the effect of ultrasonic vibration of the tool in the process of electrical discharge machining is investigated. The ultrasonic vibration of the tool has significant effect on the dynamic behaviour of the vapour bubble generated between the tool and the workpiece due to the electrical discharge. The computational simulation of the bubble behaviour is carried out by employing the boundary integral equation method. Results show that when the electrical discharge occurs in the closest position of the tool to the workpiece, the vapour bubble expands to the largest maximum volume of the bubble and the lifetime of the bubble is the longest. This in turn makes the pressure inside the bubble decrease rapidly to the lowest magnitude and causes melted material at the sparked point vaporize and leave the crater on the surface of the workpiece. [ABSTRACT FROM AUTHOR]

This research uses data mining to effectively analyze and confirm that the factors affecting discharge for electrical discharge machining (EDM) are, pulse-on time, pulse-off time, open discharge voltage, or interval voltage. The Taguchi method is used to experiment with electrodes of the same size and different shapes, based on key factors acquired under the consideration of the interaction between factors, and analyze the experimental results respectively with average values and S/N ratio. Eventually, the research will determine and calculate the best combination of factors of each quality property (machining and reaming amount, surface roughness, electrode corner loss, and material removal rate (MRR)) by analyzing predicated values and prove it with experimental data. The experiment proves that the interaction between factors really exists and that the best combination of factors acquired has favorable effects and credibility. [ABSTRACT FROM AUTHOR]

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