Electrical Discharge Machining Tool Research Articles

Machining and wear rates in EDM of D2 steel: A comparative study of electrode designs and materials

Electrical discharge machining (EDM), especially the die-sinking variant, is a well-known slow machining process among non-conventional manufacturing processes. Different approaches are being researched to improve EDM performance characteristics especially increasing its material removal rate (MRR) and reducing the tool wear rate (TWR). This study aims to improve the EDM process performance through modifications in tool design and employing different tool materials. The performance of conventional EDM tool is compared with different tool designs while machining D2 steel. Moreover, tool designs are employed on different tool materials including copper (Cu), copper-tungsten alloy (CuW), and graphite (Gr) to investigate the combined effect of tool designs and materials on important performance indicators of EDM die-sinking. The machining time (MT), material removal rate (MRR), lateral tool wear (TWR_L), and diametric tool wear (TWR_D) are selected as the response measures. The modified tool designs reduce the machining time by 45%. Likewise, Cu and CuW remarkably improve the material removal rate by 80%. Similarly, the lateral and diametric tool wear of modified designs are less than the wear corresponding to conventional design. Microscopic analysis revealed two wear zones which are named as aggressive sparking zone and mild sparking zone. All materials (Cu, CuW, and Gr) with the modified tool designs show significantly less sparking zone compared with the conventional design. Moreover, the most appropriate combination of tool design and material is proposed to achieve better EDM performance.

Surface modification by electrical discharge machining: A systematic literature review and bibliometric analysis

In past few decades, the non-traditional machining techniques of electrical discharge machining (EDM) has been developed to machine materials that are difficult to cut. Additionally, the EDM method has also been employed to change the material's surface properties by applying a layer on the workpiece that is up to a few microns thick in order to improve the surface attributes. In past three decades, several numerous investigations on surface modification using EDM have been conducted globally. Present study provides a comprehensive review along with bibliometric investigation of the many approaches used to enhance the surface topology of the materials during the EDM process from 1993 to 2023. Firstly, a brief introduction to EDM-based different surface modification techniques such as electric discharge coating, surface texturing, surface alloying, and powder-mixed EDM has been given. All related documents were acquired from Scopus Core Collection and evaluated using a bibliometric analysis technique. The bibliometric analysis was examined based on the time distribution of articles, geography, top-cited documents, analysis of authors’ keywords, country-wise publications, etc. The result showed that India dominates this research area, followed by China, and there is a growing trend in the number of publications. Further, the influence of EDM parameters, dielectric fluid, tool, and work material etc. has also been discussed. The research work published related to topic has been summarized and resented in tabular format. This review offers interested scholars with a thorough overview of the significant achievements in the subject over the last few decades, including a description of the most relevant studies and their results. Moreover, potential areas for further investigation are emphasized with the goal of revitalize the interest of the worldwide scientific community in advancing this method.

CHARACTERIZATION AND PERFORMANCE IMPROVEMENT OF SiC-REINFORCED Cu-MATRIX-BASED COMPOSITES AS ELECTRODE FOR EDM MACHINING

Pure copper, copper-based alloys, brass, graphite and steel are the most common tool materials for the electrical discharge machining (EDM) process. The electrode material, which exhibits good conductivity to heat and electricity and possesses better mechanical and thermal properties, is preferred for EDM applications. The major problem with conventional electrodes like copper and graphite is their low wear resistance capacity. This study is on the fabrication of Cu–SiC composites as an electrode of EDM with improved wear characteristics for machining of hardened D2 steel which is widely used in die formation. Powder metallurgy route was used to fabricate the samples which was further followed by three-step sintering process. Copper metal was used as a matrix element which was reinforced with SiC in volume fractions of 10%, 15% and 20%. Based on the desirable properties for the EDM tool, the best composition of Cu–SiC composite tool tip was suggested and was further used for machining of D2 steel. The performance of newly developed Cu–SiC composite electrode in terms of surface roughness (SR), material removal rate (MRR) and tool wear rate (TWR) was explored, and it was compared with the pure copper electrode. Pulse on-time, pulse off-time and the input current were selected as the input process parameters. Result reveals that the TWR and SR were decreased by 12–18% and 10–12%, whereas the MRR was increased by 9–28% for Cu–SiC composite tool as compared to the pure Cu electrode. Adequacy of the results was checked by statistical analysis. The surface texture of tool and machined surface was analyzed using scanning electron microscopy (SEM). SEM micrograph revealed that surface cracks on composite tool tip were lesser than pure Cu tool tip, whereas the work surface was rough while machining with the copper tool surface. Therefore, the result indicates that the newly developed Cu–SiC composite tool can be used for machining of hard materials with EDM.

Surface integrity studies on ZrB2 and graphene reinforced ZrB2 ceramic matrix composite in EDM process

Zirconium diboride is a potential ceramic for high temperature applications because of its combination of properties, such as very high melting point, high hardness, elevated temperature strength, good thermal and electrical conductivity. Although the near net shape components are made from this material, machining is required to create additional features for the application requirements. This ceramic's high hardness and low fracture toughness make it very difficult to use the conventional processes for machining. The good electrical conductivity of this ceramic makes electrical discharge machining (EDM) the preferred machining process. This paper presents the surface and sub-surface modifications during Wire cut EDM (WEDM) and EDM of ZrB2 an ultra high temperature ceramic (UHTC) and ZrB2-GNP (ceramic matrix composite with 7 vol% Graphene Nano Platelets) along with the surface characterization of the copper electrode (EDM tool). Scanning Electron Microscope (SEM) with Energy Dispersive Spectroscopy (EDS) and Raman spectroscopy (for GNPs) were used to characterize the melt-solidified layer and the recrystallized region. The presence of micro cracks and pores was observed in the melt-solidified layer. Growing dendrites of ZrB2 were observed in the high magnification SEM images of the melt-solidified layer surface. Under the melt-solidified layer, a recrystallized fine grain structure was observed with reduced porosity compared to the rest of the bulk. After the WEDM of ZrB2-GNP (7 vol%), the stacks of cut GNP were retained, whereas GNPs were damaged after EDM The end surface of the copper electrode showed the partial deposition of ZrB2 and the formation of a micro scale pattern on it. The effect of peak current and pulse ON time on surface roughness (Sa), material removal rate (MRR) and relative tool wear (%) were studied for ZrB2-GNP (7 vol%) The results indicated that the surface roughness (Sa), MRR and the relative tool wear (%) increase with increasing peak current. The rise in pulse ON time also increases surface roughness (Sa) and MRR but reduces the relative tool wear rate (%)

Study of the performance of Cu-Gr composite tool during EDM of AISI 1020 mild steel

Copper and graphite are the commonly used tool materials in Electric Discharge Machining (EDM). The use of copper as tool material increases the material removal rate (MRR) of workpiece during EDM. However, the tool wear rate (TWR) of graphite electrode is less as compare to copper electrode. In the current work, an attempt has been made to find the performance of Cu-Gr composite material as EDM tool. Four EDM tools of different copper-graphite composition have been used to machine AISI 1020 mild steel. Both MRR and TWR have been considered to measure the performance of EDM. The results reveal that the increase of graphite percentage in Cu-Gr composite tool reduces TWR up to 83 % by reducing MRR 73%.

A decision-making model for tool material selection in electrical discharge machining

Electrical discharge machining (EDM) has emerged as an essential process for machining dies/moulds in electrically conductive materials. Apart from workpiece erosion, the inherent characteristic of the process leads to tool wear. Thus, selecting EDM tool material is critical for achieving higher efficiency and accuracy. The present study deals with framing a decision-making model to facilitate the selection of tool material for the EDM process. Key factors such as density, electrical resistivity, thermal conductivity, linear expansion coefficient, melting point, specific heat and cost are chosen as criteria. The concept of fuzzy logic has been applied to assign the weightage of each criterion by taking experts’ decisions in linguistic terms. Thereafter, the TOPSIS method is applied to rank the alternatives, wherein tungsten evolved as the best material, followed by copper graphite, copper, copper tungsten and tellurium copper. Further, sensitivity analysis is conducted to check the robustness of the developed model.

Validation of different tungsten carbide-cobalt grades as tool electrode material for sinking EDM

In sinking electrical discharge machining (EDM), tool electrode wear is crucial for an economical production. The tool electrode wear affects the process efficiency and determines the number of required tool electrodes for a specific machining process. Therefore, the relative tool wear, describing the relation of removed material volume between tool and workpiece electrode, needs to be minimised. The tool wear characteristics in sinking EDM depend strongly on EDM processing parameters and the applied electrode materials. Especially in micro-EDM, a significant increase of relative tool wear is representative. Because of its thermophysical properties tungsten carbide-cobalt (WC-Co) is a suitable material for the application as sinking EDM tool electrode. The economical production of WC-Co form electrodes for EDM sinking is enabled by recent advancements in precision milling of hard materials.Due to non-existent research on which composition of WC-Co is most advantageous for the application as sinking EDM tool electrode material, previous investigations have been intensified to describe correlations between material properties, EDM processing parameters and EDM processing results concerning material removal rate and relative tool wear. Therefore, various WC-Co grades with differing grain size and cobalt content were analysed in sinking EDM experimental studies. It was observed that the factor grain size showed an ambiguous effect concerning the process results. An increasing cobalt content led to a reduction of relative tool wear, which can be explained by the microstructure of the cobalt binder phase with its higher electrical conductivity. The WC-Co grades with beneficial EDM processing results have been further investigated in EDM parameter studies with differing tool electrode geometries. The experimental results concerning relative tool wear, with a minimum of 3 % for macro- and 5 % for micro-sized geometries, proved the suitability of specific WC-Co compositions as tool electrode material for sinking EDM.

Effects of primary and secondary metallization techniques on the performance of electric discharge machining (EDM) electrode produced by additive manufacturing and composite coating

In the present research study on electric discharge machining (EDM) tool is developed using additive manufacturing with different primary and secondary coatings. Often conductive silver painting or electroless nickel coating are used for primary metallization and copper electroplating as subsequent metallization for rapid EDM tool development. The use of composite electroless nickel coating and electroplating is frequently applied on steels for improving wear, corrosion, and hardness as well as thermal stabilities. However, the use of the composite coating misses in EDM tooling. The rationale behind this investigation is to explore the impact of primary and secondary metallization on EDM tool performance, particularly employing tungsten base composite coatings. Tungsten is used as an alloying element to get the composite coating of nickel tungsten and copper tungsten during primary and secondary metallization respectively. Square shaped tools are 3D printed with digital Acrylonitrile Butadiene Styrene (ABS) materials on polyjet printer employing a full factorial experimental plan. EDM machining is performed with standard settings for an hour, and the results of tool wear rate (TWR), material removal rate (MRR), and surface finish (Ra) are compared to identify the best combination of primary and secondary metallization for the optimum tool performance. The multi-objective optimization of the process is carried out by converting the output responses into a single performance index as a gray fuzzy reasoning grade (GFRG) using the fuzzy logic technique. The multi- objective optimization concludes that the electroless nickel tungsten composite coating with addition of tungsten micropowder as primary coating at a high level of primary coating thickness and copper as secondary coating forms the best combination of parameters for optimum tool performance.

Process parameters optimization of AISI M2 steel in EDM using Taguchi based TOPSIS and GRA

An attempt has been made to determine the suitable parameters that will give best quality product, on the basis of experimental data on the electric discharge machining (EDM) of AISI M2 steel with help of tungsten–thorium electrode as the EDM tool and compared the result based on different optimization techniques. In this study, Taguchi method along with TOPSIS & GRA has been applied to examine the capability of optimizing output performance characteristics for AISI M2 steel. The impact of input parameters (e.g. working current (IP), pulse on time (Ton) & spark gap (Sg)) on output parameters (e.g. MRR, EWR & SR) has been examined. To determine the most significant parameters analysis of variance (ANOVA) & F-test have been used at a 95% confidence interval by the application of MINITAB. Confirmatory tests validates the estimated results which show a correction of 0.037342 & 0.204935 in the preference values utilizing TOPSIS & GRA respectively.

Development and application of Cu-SWCNT nanocomposite–coated 6061Al electrode for EDM

Electric discharge machining (EDM), a popular non-traditional machining process, is applied for machining very hard conductive materials with desired shape, size, and dimensional accuracy. Generally, copper is used as EDM tool due to its excellent electrical and thermal conductivities. The scarcity and higher cost of copper is called for its replacement with aluminum and its alloys in the field of electrical, electronic, and mechanical industries. In this paper, a copper-single wall carbon nanotube (Cu-SWCNT) nanocomposite was deposited on 6061 aluminum and used as EDM electrode. Prior to deposition, the 6061aluminium surface was anodized to achieve a strong adhesive bond between coating and the substrate. A cationic dispersing agent (cetyl tri-methyl ammonium bromide) was mixed with electrolytic bath for getting a stable, colloidal, and uniform dispersed SWCNT copper sulfate solution. The surface of electrode and workpiece was characterized with SEM-EDX. The EDM operation was performed on AISI 304 SS workpiece using Cu-SWCNT nanocomposite–coated 6061Al electrode and compared the performances with uncoated and copper-coated 6061 aluminums. The experimental result showed that the MRR was increased by 3.13% and 14.52% and electrode wear rate was decreased by 21.04% and 29.6% for copper-coated and Cu-SWCNT composite–coated 6061Al electrodes, respectively, compared to uncoated or base 6061Al electrode.

Study of the Effect of Cryogenically treated tools during Rapid Drill Electro-discharge machining of Ti-6Al-4V alloy

Abstract Now-a-days, alloys and super alloys viz. Titanium and Inconel have abundant applications in manufacturing complex parts in aircraft, automotive, and other industrial usages. Machining of these materials becomes extremely difficult with conventional machining process at precision level. These materials can be machined with ease; with desired accuracy with non-conventional machining process like electrical discharge machining (EDM) process. However, the high erosion of EDM tool during machining has emerged as the major obstacle for tool engineers to achieve productivity of the process. In view of this, the present work proposes an experimental investigation on cryogenically treated brass and copper electrodes which were used for machining of Ti-6Al-4V alloy workpiece. The effect of cryogenic treatment of tools on different performance measures like material removal rate (MRR), tool wear rate (TWR) and radial overcut is investigated. Experiments were conducted by full factorial design to find the outcome of important process parameters viz. current (I), pulse on-time (Ton), voltage(V) and pulse-off time (Toff) on responses viz. MRR, TWR and radial overcut. It has been observed that owing cryogenic treatment tool wear and radial overcut reduces considerably where as MRR remains unaffected.

Improving EDM performance by adapting gap servo-voltage to machining state

Electrical discharge machining (EDM) has become popular after its development over 70 years, but its potentialities have still not yet been fully exploited. That is because EDM process is so complicated that it seemed impossible to form a closed-loop control of EDM process because of lack of an efficient quantitative description of the process. In this case, EDM performance which is composed of machining ability and machining rate has been stagnant for decades. In this paper, a close-loop control system for EDM was built to adapt an EDM crucial parameter, gap servo-voltage, to the timely varied machining states in machining for the purpose of improving EDM performance. To this end, the discharging pulses in the gap between electrode and work-piece were firstly discriminated from sampled signals of gap voltages and currents, and then arcing ratio was calculated to be a control index representing machining state. Gap servo-voltage was taken to be a control variable corresponding to the index since it is the sole parameter among process parameters that can immediately change machining situation by physically changing gap distance which is proportion to gap servo-voltage, and is thus the most efficient parameter to modify machining state. Through adjusting gap distance by adaptively regulating gap servo-voltage, arcing ratios were forced to follow an arcing ratio expectation closely with restricted variations around the expectation. Thus, both an efficient and stabilized machining can be achieved simultaneously. Comparable experiments demonstrated that the potentiality of the conventional EDM Tool assisted by the established adaptive gap servo-voltage control system has been exploited and EDM performance was enhanced greatly that machined depth had been improved nearly 3 times from the conventional EDM, and more than 2 times than the EDM assisted by another adaptive electrode-discharge-time control system; and the machining rate was also much faster than those of the other two.

Investigations of Effect of Rotary EDM Electrode on Machining Performance of Al6061 Alloy

Electric Discharge Machining is an essential process which is being used for machining desired shape using electrical discharges which creates sparks. There will be electrodes subjected to electric voltage and which are separated by a dielectric liquid. Removing of material will be due to the continuous and rapid current discharges between two electrodes.. The spark is very carefully controlled and localized so that it only affects the surface of the material. Usually in order to prevent the defects which are arising due to the conventional machining, the Electric Discharge Machining (EDM) machining is preferred. Also intricate and complicated shapes can be machined effectively by use of Electric Discharge Machining (EDM). The EDM process usually does not affect the heat treat below the surface. This research work focus on the design and fabrication of rotary EDM tool for machining Al6061alloy and investigation of effect of rotary tool on surface finish, material removal rate and tool wear rate. Also the effect of machining parameters of EDM such as pulse on & off time, current on material Removal Rate (MRR), Surface Roughness (SR) and Electrode wear rate (EWR) have studied. Al6061 alloy can be used for marine and offshore applications by reinforcing some other elements. The investigations have revealed that MRR (material removal rate), surface roughness (Ra) have been improved with the reduction in the tool wear rate (TWR) when the tool is rotating instead of stationary. It was clear that as rotary speed of the tool is increasing the material removal rate is increasing with the reduction of surface finish and tool wear rate.

Vibration-assisted electrical discharge machining of grooves in a titanium alloy (Ti-6A-4V)

In this paper, an inexpensive auxiliary tool vibration device is described that improves the efficiency of deep groove electrical discharge machining (EDM). Titanium alloy samples (Ti-6Al-4V) were machined using two different methods: unassisted normal EDM and vibration-assisted EDM, using copper, copper-tungsten, and graphite tool electrode materials. The vibration-assisted EDM machining was done at 40, 90, and 140 Hz, and the material removal rate, tool electrode wear rate, and surface roughness of the specimens were compared. Experimental results revealed that the material removal rate with vibration-assisted EDM was better than that obtained using unassisted EDM with copper and copper-tungsten electrodes. In this study, the vibration frequency was found to have an optimum value of 90 Hz with respect to surface roughness. It was found that the machining time for a groove 10 mm deep with vibration-assisted EDM was reduced by 200% compared to unassisted EDM. This new vibration device can help in the development of a more efficient deep groove EDM.

Effect of High Chromium Platinum steel with composite Copper-Tin material electrode on Electric Discharge Machining Performance

Electric discharge machining (EDM) is a non-traditional method in which thermoelectric energy helps to remove material from the work piece. EDM is widely used in machining material irrespective of its strength and any complex shape can be easily machined. EDM tool plays an important role in the effectiveness of the whole machining process. In this paper, sintered composite material tool electrodes have been prepared with Copper and Tin and have been used for the electric discharge machining of high chromium platinum steel. High chromium platinum steel has applications in the manufacturing of cardiovascular stents. The machining of high chromium platinum steel was accomplished using these electrodes on EDM. Taguchi method has been used to find the Material removal rate (MRR) and same has been compared between composite material electrode and reference copper electrode. The results were obtained using analysis of variance (ANOVA) and Taguchi’s approach. There was an increase of 96.31% of MRR when input current is increased from 5 A to 15 A while using Cu Electrode. In case of copper-tin composite material electrode, there was an increase of 99.73 % in MRR when input current was increased from 5A to 15A

Estimation of Recast Layer Thickness in Rotary Tool EDM Process for Machining AISI D3 Tool Steel

Out of the various non-traditional machining processes used these days, Electric Discharge Machining (EDM) has its own place for the machining of hard materials and creating intricate shapes in difficult-to-machine materials. The current research work focusses on the measurement of recast layer thickness of AISI-D3 tool steel using the rotary tool EDM process. The recast layer is an undesirable property of the material and a demerit of this process. The rotary tool EDM helps to reduce the thickness of this layer significantly.The average recast layer thickness (RLT) obtained with the rotary tool EDM process is 40.26 μm whereas it comes out to be 69.03 μm for the stationary tool EDM. The results show that the rotation of the tool reduces the recast layer thickness significantly.

Prediction of the heat-affected zone of tool steel EN X37CrMoV5-1 after die-sinking electrical discharge machining

This article describes the results of the experimental research on the heat-affected zone of the subsurface layers of eroded surface on medium-alloyed samples of steel EN X37CrMoV5-1 (W.-Nr. 1.2343) which occurs in die-sinking electrical discharge machining with Cu electrode. It assesses the direct effect and consequences of the heat-affected zone on the final quality of the machined surface. The aim of the experiments was to contribute to the knowledge database defining the influence of the main technological parameters of electrical discharge machining on the microhardness changes and the total depth of the heat-affected zone of the subsurface layers of experimental samples. The results of the experimental measurement were transformed into the mathematical models allowing simulation and prediction of the final quality of the machined surface after die-sinking electrical discharge machining tool steels with Cu electrode. The purpose of the mathematical models is to determine the optimal combination of process parameters and thereby achieve the desired quality of the products produced by this advanced technology.

Optimization of EDM process parameters in machining Si3N4–TiN conductive ceramic composites to improve form and orientation tolerances

Abstract In this research, investigational and experimental work was carried out on the electric discharge machining (EDM) of a Si 3 N 4 –TiN ceramic composite using a copper electrode as the EDM tool. These composites are used in high-temperature environments, such as in metal forming, extrusion dies, turbine blade and non-ferrous molten metal handling components. The Si 3 N 4 –TiN composite is difficult to machine using conventional machining techniques. However, it can be easily machined using a spark EDM process to obtain accurate dimensional and geometric tolerances. The machining parameters, such as the current ( I ), pulse on time ( T on ), pulse off time ( T off ), dielectric pressure (DP) and spark gap voltage (SV), were investigated using a Taguchi L 25 orthogonal array. The output characteristics, such as the material removal rate (MRR), tool wear rate (TWR), wear ratio (WR), surface roughness (Ra), top radial over cut (ROC Top ), bottom radial over cut (ROC Bottom ), taper angle ( θ ), circularity (CIR), cylindricity (CYL), perpendicularity (PER) and run out (RO), were examined during the sparking operation. The significance of the machining parameters was obtained using analysis of variance (ANOVA) based on grey relational analysis (GRA), which showed that the current, pulse on time and spark gap voltage were the most significant parameters. The results were further confirmed using an experiment that illustrated that the spark eroding process could effectively be improved.

Comparison on gas bubble and pulse trains of deep-cavity electrical discharge machining with/without rotary ultrasonic assistance

Fundamental observation of bubbles and debris in deep-cavity electrical discharge machining (EDM) with an ultrasonic spindle aimed at achieving higher machining efficiency is proposed and compared. Various discharge pulse trains for EDM, rotary EDM (R-EDM), ultrasonic vibration-assisted EDM (UA-EDM), and rotary ultrasonic EDM (RU-EDM) are investigated. Their effects on the removal efficiency, machining stability, and the tool wear rate are studied as well. It is found that EDM in deep cavity is actually discharged in the gas bubble most of the time except the short period at the very beginning stage. The main bubble at EDM tool jumping is maintained with a constant volume. And, the volume results in the boundary height of the bubble at the next EDM stroke. In which, ultrasonic vibration of sufficient strength was found to split main bubble quickly and improve the material removal rate at about 49 % through much higher frequency of pulse trains. Appended with rotation, the rotary ultrasonic vibration EDM can improve the tool wear rate but reduces the MRR in compared with conventional EDM.

Effect of Tool Rotation on MRR, TWR, and Surface Integrity of AISI-D3 Steel using the Rotary EDM Process

Electric discharge machining (EDM) is an acclaimed non-conventional machining process that is used for machining of hard or geometrically complex and electrically conductive materials which are extremely difficult to machine by conventional methods. One of the foremost demerits of this process is its very low material removal rate (MRR). For this, researchers have proposed some modifications like; providing rotational motion to the tool or workpiece, mixing of conducting fine powders (such as SiC, Cr, Al, graphite etc.) in the dielectric, providing vibrations to either the tool or the workpiece etc.The present research examines how the MRR and tool wear rates (TWR) vary with the variation in the tool rotation speed and their effects on the surface integrity of the workpiece. The results obtained clearly indicate that the tool rotation significantly improves the average MRR up to 49%. Moreover, the average surface finish also gets improved by around 9–10% while using the rotational tool EDM. Due to the tool rotation, the recast layer thickness is less for the rotary EDM as compared with the stationary tool EDM process. Furthermore, the micro-cracking on the recast surface of the workpiece is also less for the rotary tool EDM as compared with the stationary tool EDM.