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A film cooling hole is an efficient and reliable cooling method, which is widely used in aeroengine turbine blades to effectively improve the thrust–weight ratio of the engine. Electrical discharge machining is the most common manufacturing process for film cooling holes. Due to the rapid quenching after high-temperature melting, a certain thickness of the recast layer will be formed in the vicinity of the hole wall. The microstructure of the recast layer is considered to be an important factor affecting the performance of single-crystal blades. Generally, the recast layer has been thought of as one of the main reasons for the failure of turbine blades. Accordingly, the formation of the recast layer is an important and interesting issue to be revealed. In this work, the recast layer formed using electrical discharge machining on a single-crystal superalloy is studied with TEM. It is found that the recast layer is in the state of supersaturated solution with a single-crystal structure epitaxially grown from the matrix, and many dislocations were observed therein. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is a well-known manufacturing process that is reported for several times as an effective technique for cutting of nickel-based superalloy of Inconel 718 (IN718). A majority of existing researches in EDM of Inconel 718 are focused on machinability of material considering production rate, tool wear, surface roughness and dimensional tolerances. To the best of author's knowledge, corrosion resistance EDMed Inconel 718 has hardly been taken into consideration. In the present work, an experimental study was made to understand how the electrical discharge machining parameters, viz. pulse current, pulse on time and rotational motion of the tool electrode, influence the corrosion properties of IN718. Technique of potentiodynamic polarization curve was utilized to measure IC and EC of the samples. A number of seven samples were machined using single-factor experiments design, and the effect of EDM parameters on foresaid corrosion indices was studied. Surface roughness, surface morphology, hardness and residual stress distributions were taken into account for justification of the variations. It was obtained from the results that as a result of increase in current from 5 to 15A, the corrosion rate increases, where the current density increases from 0.15 to 0.28 μA/cm2, and corrosion potential decreases from 0.51 to − 2.49 VSCE. In addition, it was found that less value of pulse on time, i.e., 600 μs, results in best corrosion properties where increase up to 800 μs results in increase in corrosion density from 0.11 to 0.19 μA/cm2 and also reduction of corrosion potential from −0.34 to −1.13 VSCE. It was further found that increase in tool rotational speed from stationary condition up to 200RPM results in enhancement of corrosion resistance; here, the current density reduces from 0.4 to 0.088 μA/cm2 and increase in corrosion potential from − 1.89 to 0.11 VSCE. [ABSTRACT FROM AUTHOR]

AISI-D6 steel is widely used in the creation of dies and molds. In the present paper, first the electrical discharge machining (EDM) of the aforementioned material is performed with a testing plan of 32 trials. Then, artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) were applied to predict the outputs. The effects of some significant operational parameters—specifically pulse on-time (Ton), pulse current (I), and voltage (V)—on the performance measures of EDM processes such as the material removal rate (MRR), tool wear ratio (TWR), and average surface roughness (Ra) are extracted. To lead the process operators, process plans (i.e., parameter–effect correlations) are created. The outcomes exposed the upper values of pulse on-time caused by higher amounts of MRR and Ra, and likewise lower volumes of TWR. Furthermore, growing the pulse current resulted in upper volumes of the material removal rate, tool wear ratio, and surface roughness. Besides, the higher input voltage resulted in a lower amount of MRR, TWR, and Ra. The estimation models developed by using experimental data recounting MRR, TWR, and Ra. The root means the square error was used to determine the error of training models. Furthermore, the estimated outcomes based on the models have been proven with an unseen validation set of experiments. They are found to be in decent agreement with the experimental issues. The investigation shows the powerful learning capability of an ANFIS model and its advantage in terms of modeling complex linear machining processes. [ABSTRACT FROM AUTHOR]

The efficient removal of material debris by flushing is critical for the performance and the surface quality of the electrical discharge machining (EDM) manufacturing process. The particle concentration alters the thermal, mechanical, and electrical properties of the particle–dielectricum suspension and affects the manufacturing process and the surface quality by inducing high thermal loads. For the first time, we perform a direct particle–fluid simulation of the flushing cycle in a generic EDM cavity using a hierarchical Cartesian sharp-interface cut-cell method. The flow around each debris particle is completely resolved and the heat transfer between the particles and the fluid is taken into account. The rate of material removal and the cooling performance of the flushing mechanism are studied for three-volume loadings. The results show that the flow around the particles has a pronounced impact on the heat transfer between the dielectricum and the workpiece. A particle loading of 14% increases the mean heat transfer by approximately 16%. The particle loading also has a pronounced impact on the rate at which particles are flushed out of the cavity. Increasing the initial volume loading from 6% to 14% decreases the amount of particles that get flushed out of the cavity by 14%. [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]

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]

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]

Electrical discharge machining (EDM) researchers have explored a number of ways to improve the material removal rate (MRR) in order to meet the industrial need for fulfilling market demand. Tool wear rate (TWR) is also one of the important performance measures in EDM amongst other measures such as metal removal rate and surface roughness. In most EDM operations, the contribution of the tool cost to the operational costs is more than 70 %. As a consequence, the wear of the tool should be carefully taken into consideration when planning and designing EDM operations. Despite a range of different approaches, this new research shares the same objective of achieving more efficient material removal coupled with a simultaneous reduction in tool wear. This study reports on an investigation into the optimization of the die sink EDM process on EN31 die steel. Taguchi's method with multiple performance characteristics has been adopted to obtain an overall utility value that represents the overall performance of die sink EDM. The six input parameters are optimized by considering multi-performance characteristics including MRR and TWR. The predicted optimal values for MRR and TWR obtained for die sink EDM are 0.2421 g/min and 0.0087 g/min, respectively. The results were verified by conducting confirmation experiments. [ABSTRACT FROM AUTHOR]

Elman Networks is a one of the dynamic recurrent neural networks. In this research it is used for the prediction of surface roughness in Electrical Discharge Machining (EDM). Training of the models was performed with data from series of EDM experiments on SKD 11 (AISI D2) Tool steel; in the development of predictive models, machining parameters of discharge current, pulse duration and duty cycle were considered as model variables with a constant voltage 50 volt. For this reason, extensive experiments were carried out in order to collect surface roughness dataset. The developed model is validated with a new set of experimental data, and predictive behavior of models is analyzed. The reported results indicate that the proposed model can satisfactorily predict the surface roughness in EDM. And can be considered as valuable tools for the process planning for EDMachining. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is a manufacturing process whereby a desired shape is obtained through electrical discharges between an electrode and a work-piece, which are separated by a dielectric fluid. EDM produces a recast layer on the surface of the work-piece, which in carbon steels is typically harder and more brittle than the base metal, and is often characterized by microcracks. This type of damage, particularly in the notch region of a steel specimen, can adversely affect impact test results. The objective of this investigation is to assess the possible influence of EDM on miniaturized Charpy test results. We tested Kleinstprobe (KLST)-type Charpy specimens of two reactor pressure vessel (RPV) steels, machined with different combinations of two machining processes (EDM and milling). Comparison of the impact results, combined with metallographic observations and microhardness measurements on the recast layers and the base metals, indicated no detrimental effect of EDM on the impact toughness of the materials investigated. The maximum thickness of the recast layer was about 16 µm, and the magnitude of the EDM-induced hardening varied between 34 % and 84 % with respect to the hardness of the base material, depending on the carbon content of the steel. No microcracks were observed. [ABSTRACT FROM AUTHOR]

This paper aims to study the influence of process parameters on the breathing zone concentration of the aerosol generated from the electrical discharge machining process using Taguchi methodology. Peak current, pulse duration, dielectric level above the spark location and flushing pressure were the process parameters considered in this work. Characterization of the components present in the aerosol and its morphology are also presented. The metallic particles present in the aerosol were analyzed using Inductively Coupled Plasma (ICP). Gas Chromatography coupled with Mass Spectrometry (GC-MS) was used to analyze the hydrocarbon components attached to the aerosol. Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) techniques were applied to study the morphology of aerosol. Analysis of the results showed that the peak current and the pulse duration are the most significant parameters on the breathing zone concentration of aerosol. Investigation using ICP revealed that the major portion of aerosol (about 69%) constitutes metallic particulates. GC-MS analysis of the aerosol samples indicated the presence of about 20 different hydrocarbons. Morphology studies showed that the particulates are of spherical shape with average sizes ranging from 20 to 29 nm. The control measures to minimize the risk of exposure have also been discussed in this paper. [ABSTRACT FROM AUTHOR]

Machining fluid is a primary factor that affects the material removal rate, surface quality, and electrode wear of electrical discharge machining (EDM). Kerosene is the most commonly used working fluid in die sinking EDM, but it shows low ignition temperature and high volatility; if the improper operations are undertaken, it can cause conflagration. Using distilled water or pure water as the machining fluid in EDM, no fire hazard occurs, and the working environment is well; however, using distilled water or pure water as the machining fluid in EDM, the material removal rate of machining large surface is low, and the machine tool is easily eroded. Emulsion-1 and emulsion-2 used as working fluid in die sinking EDM are developed. The compositions of emulsion-1 and emulsion-2 are introduced. In comparison with kerosene, emulsion-1 and emulsion-2 used in EDM show high material removal rate, low surface roughness, high discharge gap, and good working environment. The electrode wear ratio in emulsion-1 is lower than that in kerosene. The electrode wear ratio in emulsion-2 is higher than that in kerosene. The effects of composition and concentration of emulsifier on the emulsion property and EDM performance have been investigated. The comparative tests of EDM performance with kerosene, emulsion-1, and emulsion-2 have been done. [ABSTRACT FROM AUTHOR]

Electrical discharge machining process is a potential method of shaping ({WC+TiC+TaC/NbC}–Co) cemented carbide known for its superior hardness and compressive strength at high temperature and resistance to diffusion wear. Yet, detailed study on electrical discharge machining of this material is lacking in the literature. In the present investigation, therefore, mathematical models are developed for material removal rate, wear ratio, and surface roughness in electrical discharge machining of this cemented carbide using the procedure of statistical design of experiments. Current setting, pulse on time, and pulse off time are chosen as input parameters. Based on available machine settings, a face-centered central composite design is selected for meaningful experimentations. The procedure may be extended to develop a data bank for such type of materials. Further, to reveal the attributes behind the removal of material from the work-piece surface, scanning electron micrographs are studied. It appears that sufficient superheating of work-piece material and subsurface boiling is essential for efficient material removal and that formation of pock marks due to burst of blisters and associated crack formation may be controlled by choosing a proper dielectric. [ABSTRACT FROM AUTHOR]

Studies the influence of electric parameters on machining targets in achieving parameter optimization, when electrical discharge machining oil supply tank with copper electrodes. Some parameters such as processing speed, electrode wear speed, machining gap and relative wear ratio are chosen as machining targets, applying grey theory to analyze the correlation degree between electric parameters and machining targets. Grey theory is put forward to optimize electric parameters, obtaining optimized parameters in single-object and multi-objects. Experimental results indicated that optimized parameters have a distinct effect on reducing electrode wearing speed and relative wear when adopting the optimized parameters. [ABSTRACT FROM AUTHOR]

The electrical discharge machining (EDM) process is optimum for accurate machining of complex geometries in hard materials, as those required in the tooling industry. It has become by far the most popular among the non-conventional machining processes. However, although a large number of EDM machines are sold every year, available knowledge of the process is still very empirical. Experimental trials are required in many cases to set up the optimum conditions for an EDM operation, resulting in increases in lead-time and cost for the final part. The reason for this is the complex nature of the process, highly stochastic, that involves simultaneous interaction of thermal, mechanical, chemical and electrical phenomena. Therefore, research efforts must be directed towards process modelling in order to reduce the experimental cost associated to the technology. In this work, an original computer simulation model of the EDM process is presented. The model is based on the numerical calculation of temperature fields within the workpiece, from which the amount of part material removed per discharge can be estimated. The objective is to theoretically predict material removal rate (MRR) and the final surface finish of the machined part using as input variables the EDM process parameters and the properties of the work material. The model has been validated by carrying out tests on an industrial EDM machine, showing that it can adequately predict MRR and surface roughness with errors below 9%. [ABSTRACT FROM AUTHOR]

Investigating machining performance of conductive ceramics (Al2O3 + 30 vol% TiC) using electrical discharge machining (EDM) is the aim of this work. The EDM machining parameters such as machining polarity, peak current, auxiliary current with high voltage, pulse duration, no load voltage, and servo reference voltage were chosen to explore the effects on material removal rate (MRR), electrode wear rate (EWR), and surface roughness (SR). The L18 orthogonal array based on the Taguchi experimental method was adopted to determine EDM machining characteristics systemically, and the experimental data were statistically analyzed by analysis of variance (ANOVA). Experimental results showed EDM is a feasible process to shape conductive ceramics, and relationships between machining characteristics and parameters were examined. Moreover, machining parameter optimal combination levels in machining conductive ceramics via EDM were also determined. [ABSTRACT FROM AUTHOR]

Abstract: Electrical discharge milling (ED-milling) is an emerging technology which entails a rotating cylindrical tool that is traversed along a predefined tool path to machine a cavity. This process configuration offers advantages such as minimal time/cost associated with tool manufacture and improved gap flushing, as compared to traditional die-sinking that involves complex three-dimensional tools. Rotating cylindrical tools, however, inherently preclude the machining of sharp features and correspond to increased relative electrode wear; the reduced machining engagement further restricts the machining power which in turn limits the removal rate. To this end, this paper presents a novel tooling concept that relates to a set of standard prismatic tools of an oblong section, which incorporate the favorable functional characteristics of both ED-milling and die-sinking technologies. Aspects of computer-aided manufacture referring to tool selection, sizing and path planning are discussed. The concepts developed are illustrated through the application of an oblong tool that rotates and translates to machine a sample two-dimensional cavity. [Copyright &y& Elsevier]

Abstract: A new mechanism of cutting pipe combined with electrical discharge machining (EDM) is designed. The mechanism is set up on the working table of electrical discharge machine and used to investigate the effects of machining parameters such as material removal rate (MRR), relative electrode wear rate (REWR) on machining characteristics. The machining variables including machining polarity, peak current, pulse duration and the rotary speed of electrode have been chosen to explore the machining efficiency. The purpose of this study is to confirm the mechanism could not only increase material removal rates but also decrease the electrode wear rates in the EDM process. [Copyright &y& Elsevier]

The addition of powder particles to the electrical discharge machining (EDM) dielectric fluid modifies some process variables and creates the conditions to achieve a higher surface quality in large machined areas. This paper presents a new research work that aims to study the improvement in the polishing performance of conventional EDM when used with a powder-mixed-dielectric (PMD-EDM). The analysis was carried out varying the silicon powder concentration and the flushing flow rate over a set of different processing areas and the effects in the final surface were evaluated. The evaluation was done by surface morphologic analysis and measured through some quality surface indicators. The results show the positive influence of the silicon powder in the reduction of crater dimensions, white-layer thickness and surface roughness. Moreover, it was demonstrated that an accurate control of the powder concentration and flushing flow is a requirement for achieving an improvement in the process polishing capability. [ABSTRACT FROM AUTHOR]

Abstract: Recently, a repeatable and scalable nanoscale electro-machining (nano-EM) process to produce sub-20nm scale features has been demonstrated. In the presented research, the behavior of the liquid dielectric (n-decane) machining medium in nano-confinement (<3nm) under physical boundary conditions is investigated using molecular dynamics (MD) simulation. Results show a four-fold increase in the density of n-decane indicating ‘quasi-solid’ behavior at the nano-EM interface, thereby acting as an effective charge transport medium between the nano-tool and the workpiece. The effect of such quasi-solid medium is demonstrated through the experimental observations of electrical breakdown (BD) at the sub-20nm scale interface. [Copyright &y& Elsevier]

This paper presents a virtual-instrumentation system (VIS) that aims at measuring the evolution of key magnitudes in a nonconventional machining process called wire electrical discharge machining (WEDM). The VIS consists of two well-different parts: the acquisition system that measures process signals (voltage and current) and the virtual measurement of relevant magnitudes (such as energy, peak-current distribution, and ignition delay time). The data-acquisition system provides flexibility and ease of storing tests under different machining conditions without extra hardware construction or adaptation. It is based on a commercial data-acquisition board that works at very high frequencies (up to 10 MSamples/s). The virtual measurement is carried out by modeling and processing the acquired signals. The VIS has been employed to monitor and detect low-quality cutting regimes in WEDM. [ABSTRACT FROM AUTHOR]

A new electrical discharge machining (EDM) system using a wire encased in a dielectric jacket is proposed as an alternative to conventional hole-fabrication EDM systems. The jacket suppresses secondary discharges occurring between the sidewalls of the wire and the fabricated hole, which allows fabrication of holes with higher aspect ratios compared to those formed by a conventional EDM system using naked pipe electrodes. In this new system, the tip of the wire electrode is stripped by displacing the jacket, which produces continuous sparks for workpiece erosion and keeps the bore and shape of the fabricated holes constant. In the present study, we developed a control system to maintain the exposed length of the tip without the need for visual observation and without the assumption that wear is constant over time. The exposed length of the tip of the wire electrode is related to the feed speed (toward the workpiece) of the electrode system. The jacket was displaced when the feed speed of the electrode system exceeded a threshold value, which resulted in slowing of the electrode system feed. The feed speed was kept within the specified range by determining a threshold value, which led to maintenance of a constant exposed length of the tip. This control system was validated in actual drilling tests. Optimizing the threshold feed speed contributed to a higher machining speed. [ABSTRACT FROM AUTHOR]

In order to achieve a mirror-like workpiece surface by EDM, a micro-energy EDM or a manual lapping is normally used. However, both methods are time consuming and economically unattractive. To have better performance, a sinking EDM machine was first used in this research on SKD 61 for a micro-energy discharge process followed by the electrophoretic deposition (EPD) process to coat Al2O3 particles uniformly on a rotation electrode. The precision polishing process was then applied on the discharged workpiece with suitable parameters including the voltage, electrode rotating speed, pH value of electrolyte, and abrasive concentration. After the EDM process, the surface roughness and the recast layer thickness of a workpiece could also be reduced. The experimental data showed that when 0.3 μm of Al2O3 particles was used for the EPD polishing process, the initial roughness of a discharge surface could be improved from 0.52 μm Ra (6.50 μm Rt) to a mirror-like surface of 0.068 μm Ra (0.742 μm Rt). Also, the total working time could be reduced significantly to within the range of 5 to 10 min. [ABSTRACT FROM AUTHOR]

This paper presents a residual modified grey dynamic model RGM(1,3) in order to fit and predict the performance characteristics of an electro-conductive ceramic (Al2O3+30%TiC) during electrical discharge machining (EDM). Grey system theory is suitable for the system in which some information is poor, incomplete and uncertain, so it is feasible to study the performance characteristics of EDM with this model. The RGM(1,3) model is modified to promote the forecasting accuracy of predicting values using the residual grey dynamic model GM(1,1). The fitted and predicted values of various performance characteristics, including the material removal rate (MRR), maximum surface roughness (Rmax), and electrode wear ratio (EWR) agreed sufficiently with the experimental data. It is proved that RGM(1,3) model fitted and predicted the above performance characteristics with a high predicting accuracy. Therefore this procedure of grey forecasting model is relatively simple and convenient, and it is greatly suited for the analysis of question which obtained a few experimental data, and acts an auxiliary to calculate the unfinished experimental data. [ABSTRACT FROM AUTHOR]

Abstract: An attempt was made to increase the machining speed of a new electrical discharge machining system for fabricating narrow, deep holes in metal. The method employs a wire encased in a dielectric jacket as the tool electrode, in contrast with the conventional pipe electrode. The role of the dielectric jacket is to completely suppress unnecessary secondary discharges occurring between the sidewalls of the wire and the fabricated hole. In the present study, the effectiveness of the combination of conductive working fluid and a capacitor connected to the work piece and the tool electrode was examined. Although electrode wear was severe, machining speed with this combination (saline water at 150–250μS/cm and capacitance at ∼8μF) was twice as fast compared with fabricating a hole (∅ 0.8–0.9mm) without a capacitor and saline water in a 20-mm thick carbon steel block. The mechanisms involved are discussed based on electrical circuit theory and electrochemical corrosion. [Copyright &y& Elsevier]

In this work we investigated the electrical discharge machining (EDM) of a Fe-Mn-Al alloy. The surface phenomena caused by EDM were studied in terms of machining parameters. An empirical model of the Fe-Mn-Al alloy was also proposed based on the experimental data. Experimental results indicate that the higher the discharge energy, the faster the machining time. This treatment introduces machining damage in the resolidified surface layer and worsens the surface roughness. The optimum pulse-on duration on the basis of the electrode wear ratio for the copper electrode was about 200 μs. The increase of crater depth with the applied pulsed current and pulse-on duration appears minimal under a small input energy. [ABSTRACT FROM AUTHOR]

As previously reported, several insulating ceramics such as Si3N4, SiC and ZrO2 have successfully been machined by sinking electrical discharge machining using the surface discharge modification phenomenon. As unstable discharges occur during the machining of Al2O3 ceramics, inferior machining properties have been obtained as compared to other ceramics. It seems that the formation process of the electrically conductive layer on the workpiece during discharge is much different compared with that of other dissociated ceramics at high temperature. In this study new methods are devised and the electrical discharge machining mechanism of insulating Al2O3 ceramics is researched using high purity alumina and single crystal Al2O3 of sapphire. Machining properties are dependent on the purity and structure of the workpiece, and correlated to its thermal properties. [Copyright &y& Elsevier]

Electrical discharge machining became a commercial process after the discovery of the importance of the dielectric fluid, which affects factors such as productivity and quality. Health, safety and environment are also important factors, particularly when oil-based fluids are used. This paper presents a literature survey on the use of dielectric fluids that provide an alternative to hydrocarbon oil. It has been reported that water-based dielectrics may replace oil-based fluids in die sink applications. Gaseous dielectrics such as oxygen may also be the alternative. Nonetheless, these need further research in order to be commercially viable. [Copyright &y& Elsevier]

In order to achieve high removal rate and low electrode wear in sinking electrical discharge machining (EDM) a stable machining process is required. The process stability is partly influenced by the contamination of the gap between the workpiece and the electrode. Additionally, it also depends on the size of the eroding surface at the given machining regime. When the eroding surface size varies with the depth of machining, the roughing regime has to be selected on-line. The work presented in this paper shows that the average discharge voltage depends on the eroding surface size. Through sets of experiments at constant machining parameters, varying size of the eroding surface and varying geometry of engaged surface were investigated. The average discharge voltages were calculated on the acquired electric voltage signals in the gap. The average discharge voltage is simple for on-line monitoring and it enables on-line detection of the eroding surface size as well as the on-line selection of the rough machining parameters. Thus the average discharge voltage depends on the geometry of the engaged surface, the prototype of the engaged surface has to be presented to the model for successful selection of the roughing regime as well. [Copyright &y& Elsevier]

In this paper, the machining phenomena in the electrical discharge machining (EDM) process are investigated through a new method of in-process measurement of gap distance. The aim of this study is to understand the cause of short-circuiting and to improve the machining rate. A pipe electrode is used and the working fluid is supplied to the gap space though a fixed restrictor and the pipe electrode. Since the pressure between the fixed restrictor and the tip of the pipe electrode (fluid pressure) depends on the gap distance, the absolute value of the gap distance can be determined in-process by measuring the fluid pressure. It is found that the gap distance at the moment when the short-circuiting occurs is more than several micrometers. This result indicates that the cause of the short-circuiting is the bridging of the gap space by collected debris. Based on these results, a new gap control method in which the gap distance is kept constant even when short-circuiting occurs is examined. [Copyright &y& Elsevier]

Electrical discharge machining (EDM) is widely used for manufacturing various kinds of dies and molds. However, EDM has numerous problems such as low material removal rate and generation of heat-affected zones, in which there are numerous cracks and microcraters. Recently, many new machining technologies utilizing EDM have been developed. However, the mechanism of material removal in EDM has not yet been sufficiently explained. In this study, to clarify the mechanism of material removal, first, the impulsive force transitions in an impulse discharge were measured. Second, how the mechanism by which the impulsive forces affect the crater formation by impulse discharge was examined. The following results were obtained: (1) a typical waveform obtained from an impulse discharge in kerosene consists of primary, secondary, tertiary and quaternary waves, and the intervals between the peaks of the waves gradually become smaller; (2) because the shape of the crater is strongly dependent on the polarities under the same conditions in EDM, the effect of the impulsive force acting between the workpiece and the electrode on the crater formation by impulse discharge may be insignificant. [Copyright &y& Elsevier]

In this paper, it is shown that dynamic optimization problems of first-order systems can be transformed into a static parametric programming problem, where the state plays the role of the parameter. Thus, an optimal feedback law is obtained. This concept is applied to the die-sinking electrical discharge machining, a highly time varying industrial process which necessitates adaptation of machining settings during operation. It is shown that the minimum-time operation of this process is equivalent to choosing the manipulated variables that maximizes the speed of machining at every position. [Copyright &y& Elsevier]

Electrical discharge machining (EDM) is used as a precision machining method for the electrically conductive hard materials with a soft electrode material. But recently we succeeded to machine on insulating material by EDM. The technology is named as an assisting electrode method. The EDMed surface is covered with the electrical conductive layer during discharge. The layer holds the electrical conductivity during discharge. For micro-EDM, the wear of tool electrode becomes lager ratio than the normal machining. So the micro-machining is extremely difficult to get the precision sample.In this paper to obtain a fine and precise ceramics sample, some trials were carried out considering the EDM conditions, tool electrodes material and assisting electrode materials. Insulating Si3N4 ceramics were used for workpiece. The machining properties were estimated by the removal rate and tool wear ratio. To confirm the change of micro-machining process, the discharge waveforms were observed. The micro-machining of the Ø0.05 mm hole could be machined with the commercial sinking electrical discharge machine. [Copyright &y& Elsevier]

Dielectric medium (kerosene) between the tool electrode and workpiece forms a reaction product, owing to thermal effect of discharge in the process of electrical discharge machining (EDM), which is emitted from the surface in the form of harmful gas and may get into the operator's body by breath system inhalation and contact with skin. Therefore, exhaust emissions should be considered as important performance indicators for the green machining in the process of EDM. Moreover, energy efficiency and machining productivity should be improved and the cut process must take ecological constraints into consideration. Thereafter, the definition of green manufacturing helps to evaluate different and sometimes conflicting aspects of the manufacturing process, such as machining productivity, surface quality, energy efficiency and exhaust emissions. But it is difficult to dynamically adjust the weights of different aspects according to the actual processing conditions. This paper proposes a framework for optimization of cutting parameters to minimize energy consumption and exhaust emissions during electrical discharge machining of Al 6061 and SKD 11. Three cutting process parameters (peak current, pulse period, and duty cycle) are tested against material remove rate (MRR), surface roughness (Ra), energy efficiency per volume (EEV), and exhaust emissions characteristics (EEC) for EDM of these two materials. First, the process energy and exhaust emissions are analyzed. The results show that EEV is negatively correlated with surface quality (Ra) for both Al 6061 and SKD 11 material. Second, two data analyses (Taguchi and adaptive-network-based fuzzy inference system (ANFIS) analyses) are utilized to obtain high MRR and best Ra, EEV and EEC for the desired machining performances and environmental sustainability. It is found that the relative errors between the predicted values and experimental results of MRR, Ra, EEV and EEC are all not more than 20%, and found that the maximum of mean relative errors of them is 13.04%. Finally, a framework implemented by an optimization system, based on ANFIS, enhanced cuckoo search (ECS) algorithm and desirability function, is built to obtain the desired cutting parameters. It is found that high peak current (8.94A) and pulse period (500 μ s) are recommended to obtain multi-objective optimization for machining Al 6061, and that the optimal solutions of the EEV and EEC are significantly decreased, by 87.13% and 37.09%, respectively. Similarly, high peak current (8.77A) and pulse period (261.5 μ s) are recommended to obtain multi-objective optimization for machining SKD 11, and the optimal solutions of the EEV and EEC are significantly decreased, by 93.73% and 46.85%, respectively. Thereafter, it can be concluded from the above research that the proposed technique offers significant advantages and potential for applications in the green manufacturing field. Image 1 • Energy efficiency per volume was negatively correlated with Ra. • Maximizing energy efficiency and minimizing exhaust emissions by empirical models were obtained. • Balancing the machining performances and environmental sustainability was considered. • An optimization system with manual multi-objective weights was build. • Green regions of exhaust-friendly and energy-friendly were acquired. [ABSTRACT FROM AUTHOR]