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

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]

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]

With the development of micro electro mechanical system (MEMS), the application of micro components is becoming increasingly wide. Micro electrical discharge machining (micro EDM) is one of the most effective manufacturing processes for micro components. During past few decades, some innovative methods for improving micro EDM performance have been proposed. Using special-shaped electrode is just one of them. Although micro EDM with helical electrode has been proposed and the availability has been proved for several years, relatively little is known about the precise effect of helical electrode rotation on micro EDM performance. In this study, micro through-holes were machined on Ti6Al4V sample with a cylindrical electrode and helical electrode. The helical electrode achieves better machining performance overall compared to the cylindrical electrode due to its favorable debris removal ability. The higher the rotational speed of helical electrode, the higher the material removal rate (MRR). When using the cylindrical electrode, the MRR first increases and then decreases after reaching a peak at 3000 rpm. Higher MRR is obtainable with the helical electrode with reverse rotation; with forward rotation, it yields higher machining precision (lower overcut and taper rate). [ABSTRACT FROM AUTHOR]

Limited efforts have been made to transform electrical discharge machining to a green and sustainable machining process. Current electric discharge machining (EDM) processes use hydrocarbon or synthetic-based dielectric fluids. These fluids emit harmful vapors when they break down, raising concerns for machine operators and for the environment. Biodiesel (BD) has similar properties as conventional dielectric and it can be used in place of conventional dielectric fluids. This research aims to study the effects of biodiesel dielectric in EDM process, especially in micromachining. Experiments are carried out in both low and high energy settings, on bulk metallic glass (BMG) and titanium alloy (Ti-6Al-4 V) using 200-μm-diameter electrodes. Canola BD and sunflower BD are compared against conventional dielectric in terms of material removal rate and tool wear ratio. The experimental evidence showed that both canola and sunflower BD are able to outperform conventional dielectric, and thus suggesting that BD has the potential to replace conventional dielectric as to provide a more sustainable machining process in the future. [ABSTRACT FROM AUTHOR]

In the electrical discharge machining (EDM) of deep holes, electrode wear may cause the dimensions of the finished holes to deviate from their design values. In practice, the extent of the electrode wear and the surface roughness of the machined holes depend not only on the EDM machining parameters (e.g., the pulse duration, the pulse current, and so on), but also on the electrode route motion. Accordingly, the present study performs an experimental investigation into the effects of three different electrode routes (straight dip, spiral attack hole, and awl free expand hole) on the electrode wear and surface roughness of the machined holes in the EDM machining of PDS5A and PDS-1 mold steel, respectively. Overall, the experimental results show that of the three electrode route motions, the awl free expand hole motion results in a more uniform wear of the electrode and a lower surface roughness of the machined hole. [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]

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]

The die sinking version of electrical discharge machining (EDM) is a current manufacturing technology widely disseminated in several industrial sectors. In the recent past, developments in the high-speed milling (HSM) have narrowed the EDMs’ traditional application domains. As a result, a strong research effort has been focused on EDM leading to the reduction of the operation time and cost and to the increase of final surfaces quality. To identify future trends and perspectives of development within the industrial application of EDM technology, a survey was conducted among mould-making industrial companies and EDM equipment manufactures. The survey was designed to allow the exposure of the most relevant weaknesses and strengths of the technology and the identification of short-term threats and opportunities. In parallel, the expected impacts of the most recent developments of conventional EDM were assessed. To structure and systematize the overall analysis and quantify the total impact of each technologic innovation, a criteria matrix evaluation method was used. The results show that EDM technology will be kept as a reference manufacturing process in the mould-making industry. The maximization of EDM advantages in domains that no other technology can effectively achieve (complex geometries and hard materials processing) is one of the main reasons pointed out for the sustainability of EDM future competitiveness. The other reasons are the reduction of operative and set-up time, the reduction of operator intervention, and the extension toward surface-polishing operations. [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]

This paper deals with the effect of copper tool vibration with ultrasonic (US) frequency on the electrical discharge machining (EDM) characteristics of cemented tungsten carbide (WC-Co). It was found that ultrasonic vibration of the tool (USVT) was more effective in attaining a high material removal rate (MRR) when working under low discharge currents and low pulse times (finishing regimes). In general, the surface roughness and the tool wear ratio (TWR) were increased when ultrasonic vibration was employed. It was observed that application of ultrasonic vibration significantly reduced arcing and open circuit pulses, and the stability of the process had a remarkable improvement. This study showed that, there were optimum conditions for ultrasonic assisted machining of cemented tungsten carbide, although the conditions may vary by giving other input parameters for those which had been set constant in the present work. [ABSTRACT FROM AUTHOR]

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]

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]

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]