Experimental investigations into the performance of EDM using argon gas-assisted perforated electrodes

In the present work, a parametric study of EDM process using Argon-Gas-Assisted EDM (AGAEDM) with rotary tool during machining of high chromium high carbon diesteel has been performed. The pulse on time, tool rotation, discharge current, duty cycle, and gas pressure were selected as process factors. The effects of process factors were investigated on responses viz. surface roughness (SR), material removal rate (MRR), and electrode wear ratio (EWR). A comparison between solid tool, air-assisted tool, and argon-assisted tool has also been presented. It was found that EWR and SR were less during AGAEDM process as compared to rotary EDM(REDM) with solid tool and air-assisted EDM (AAEDM) with rotary tool under same process parameters. However, MRR was found to be higher in AAEDM process. The regression analysis and analysis of variance have been done to develop and find the adequacy of the developed models of MRR, EWR, and SR. It was observed that surface integrity of workpiece machined by AGAEDM was better than workpiece machined by AAEDM and conventional REDM process.     

Electrical Discharge Machining (EDM) Characteristics Associated with Electrical Discharge Energy on Machining of Cemented Tungsten Carbide

In this investigation, cemented tungsten carbides graded K10 and P10 were machined by electrical discharge machining (EDM) using an electrolytic copper electrode. The machining parameters of EDM were varied to explore the effects of electrical discharge energy on the machining characteristics, such as material removal rate (MRR), electrode wear rate (EWR), and surface roughness. Moreover, the effects of the electrical discharge energy on heat-affected layers, surface cracks and machining debris were also determined. The experimental results show that the MRR increased with the density of the electrical discharge energy; the EWR and diameter of the machining debris were also related to the density of the electrical discharge energy. When the amount of electrical discharge energy was set to a high level, serious surface cracks on the machined surface of the cemented tungsten carbides caused by EDM were evident.     

EDM with an Air-Assisted Multi-Hole Rotating Tool

In the present research work, an extensive experimental study of air-assisted rotary electrical discharge machining (AAEDM) of high chromium, high carbon die steel has been made. Investigations have been performed to study the process factor effect namely pulse-on time, discharge current, duty cycle, tool rotation, and air pressure on material removal rate (MRR) and electrode wear ratio (EWR). A comparative analysis of solid rotary tool electrode electrical discharge machining (REDM) and AAEDM has been presented. It was found that a high MRR and low EWR occurred in AAEDM as compared to the REDM process, under the same processing conditions. Use of a multi-hole tool provided better circulation of dielectric in the discharge gap, thus it improved the flushing efficiency of the process. The results showed that the application of compressed air has a favorable influence on MRR and EWR.     

Investigation of magnetic field-assisted EDM of composites

The Electrical Discharge Machining (EDM) technique was performed under the magnetic field influence to determine the material removal mechanism as well as surface roughness (SR) of nonmagnetic material. This study presents an exploration of the hybrid EDM technique assisted by magnetic field, with an aim to improve process performance. Herein, magnetic field intensity, peak current, duration of pulse-on/off, tool electrode material, and SiC percentage distribution were opted as the machining parameters. The chosen parameters were analyzed for their effects on the material removal rate (MRR) and SR while machining of SiC-reinforced aluminum-based metal matrix composites. Taguchi methodology was adopted for optimization of process parameters to achieve better MRR and lower SR. The experimental results witnessed improved surface finish and enhanced material removal ability of the process and also inferred that the magnetic field-assisted EDM facilitated the process stability.     

Investigation into the Effect of Voltage Excitation of Pre-Ignition Spark Pulse on the Electro-Discharge Machining (EDM) Process

Studying the variation of the electro-discharge machining (EDM) process outputs due to the change in shape of the generated pulse is one research aspect in the EDM process. In this study, the effects of voltage excitation of the pre-ignition spark pulse on the process outputs material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (Ra) have been investigated. Experiments were designed using design of experiments (DOE), and the results were analyzed using analysis of variance (ANOVA). Based on the results, it has become clear that applying voltage excitation of the pulse produces effective pulses, which in turn lessens EWR, increases MRR, and improves surface quality. Hence, the suitability of this method has been verified for EDM.     

Parametric Evaluation on Near-Dry Electric Discharge Machining

Near-dry electric discharge machining (EDM) is an eco-friendly process. It does not produce toxic fumes and consequent health hazards. The near-dry EDM generally utilizes a mixture of two phase (liquid and air) dielectric for machining. This investigation reports the influence of four processing parameters, viz. current, flushing pressure, duty factor, and lift on three responses. The responses measured were material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR). The work material chosen was high speed steel (HSS). Mathematical models have been proposed herein for evaluation of the effect of processing parameters in near-dry EDM. These models were developed using response surface methodology (RSM). The experimental results reveal that the process parameters taken into consideration were significant for MRR. The TWR was negligible in near-dry EDM. This process gives a finer surface finish with thinner recast layer even at higher discharge energies as compared to conventional EDM.     

Multiobjective optimization and analysis of copper–titanium diboride electrode in EDM of monel 400™ alloy

Electrical discharge machining (EDM) is one of the most accepted machining processes in the precision manufacturing industry. In EDM process, finding an alternative tool material is the demand in modern manufacturing industry. Therefore, an attempt had been made to fabricate copper–titanium diboride powder metallurgy electrode to test in EDM on monel 400? material. The experiments are planned using center composite second-order rotatable design and the model is developed by response surface methodology. The machining characteristics have analyzed using the developed model. In this study, four input parameters such as titanium diboride percentage, pulse current, pulse on time, and flushing pressure are selected to evaluate the material removal rate (MRR) and tool wear rate (TWR). The adequacy of the developed regression model has tested through analysis of variance test. The desirability-based multiobjective optimization is used to find the optimal process parameter which has given maximum MRR and minimum TWR. The optimum process parameters obtained were titanium diboride of 16%, pulse current of 6 A, flushing pressure of 1 Mpa, and pulse on time of 35?µs. The validity of the response surface model is further verified by conducting confirmation experiments.     

Performance evaluation of Al2O3 nano powder mixed dielectric for electric discharge machining of Inconel 825

Electrical discharge machining (EDM) process is popular for machining conductive and difficult-to-cut materials, but low material removal rate (MRR) and poor surface quality are major limitations of the process. These limitations can be overcome by adding the suitable powder in the dielectric. The powder particles influence electric field intensity during the EDM process which in turn improve its performance. The size (micro to nano) and properties of the mixed powder also influence the machining efficiency. In this regard, the objective of the present work is to study the performance of EDM process for machining Inconel 825 alloy by mixing Al₂O₃ nanopowder in deionized water. The experimental investigation revealed that maximum MRR of 47?mg/min and minimum SR of 1.487?µm, which are 44 and 51% higher in comparison to conventional EDM process, respectively, can be achieved by setting optimal combinations of process parameters. To analyze these observed process behavior, pulse-train data of the spark gap were acquired. The discharge waveform identifies the less arcing phenomenon in the modified EDM process compared to conventional EDM. Further, surface-topography of the machined surface was critically examined by capturing field emission scanning electron microscopy and atomic force microscopy images.     

Effect of tool rotation in near-dry EDM process on machining characteristics of HSS

Rotary tool near-dry electrical discharge machining (RT-ND-EDM) is a process variant of EDM, which utilizes two phase dielectric medium instead of a conventional liquid or gaseous dielectric medium. The present work, RT-ND-EDM was investigated while machining of high speed steel (AISI M2 grade) using glycerin-air dielectric medium. The effect of various input process parameters was investigated on material removal rate (MRR), surface roughness (SR), and hole overcut (HOC). The input parameters considered were tool rotation speed, current, pulse on time, liquid flow rate, and gas pressure. Experiments were designed and conducted using response surface methodology. Regression models were also developed. The results revealed that the tool rotation speed has a significant effect on MRR, SR, and HOC. FE-SEM micrographs showed that the machined surfaces obtained by RT-ND-EDM have relatively lower micro-cracks, debris accumulation and craters. Also, deep through holes were successfully drilled in 24 mm plate using RT-ND-EDM process.     

Multi-objective parametric optimization of powder mixed electro-discharge machining using response surface methodology and non-dominated sorting genetic algorithm

Powder mixed electro-discharge machining (EDM) is being widely used in modern metal working industry for producing complex cavities in dies and moulds which are otherwise difficult to create by conventional machining route. It has been experimentally demonstrated that the presence of suspended particle in dielectric fluid significantly increases the surface finish and machining efficiency of EDM process. Concentration of powder (silicon) in the dielectric fluid, pulse on time, duty cycle, and peak current are taken as independent variables on which the machining performance was analysed in terms of material removal rate (MRR) and surface roughness (SR). Experiments have been conducted on an EZNC fuzzy logic Die Sinking EDM machine manufactured by Electronica Machine Tools Ltd. India. A copper electrode having diameter of 25?mm is used to cut EN 31 steel for one hour in each trial. Response surface methodology (RSM) is adopted to study the effect of independent variables on responses and develop predictive models. It is desired to obtain optimal parameter setting that aims at decreasing surface roughness along with larger material removal rate. Since the responses are conflicting in nature, it is difficult to obtain a single combination of cutting parameters satisfying both the objectives in any one solution. Therefore, it is essential to explore the optimization landscape to generate the set of dominant solutions. Non-sorted genetic algorithm (NSGA) has been adopted to optimize the responses such that a set of mutually dominant solutions are found over a wide range of machining parameters.     

Effect of deep cryotreated tungsten carbide electrode and SiC powder on EDM performance of AISI 304

Abstract

Powder mixed electric discharge machining (PMEDM) is a further advancement of conventional EDM process in which electrically conductive powder is suspended in the dielectric fluid to enhance the material removal rate (MRR) along with the surface quality. Cryotreatment is introduced in this process for improving the cutting tool properties as well as tool life. In this investigation, EDM is performed for the machining of AISI 304 stainless steel using cryotreated double tempered tungsten carbide electrode when SiC powder is suspended in the kerosene dielectric. The influence of process parameters viz. pulse on time, peak current, duty cycle, gap voltage and powder concentration on tool wear rate (TWR), surface roughness (R_a), and MRR has been studied. Metallographic analysis was carried out for the machined surfaces. By the addition of powder concentration and cryotreated double tempered electrode, significant improvement in the machining efficiency has been found out. When cryotreated electrode used MRR, TWR and R_a decreased by 12%, 24% and 13.3%, respectively and when SiC powder used MRR increased by 23.2%, TWR and R_a decreased by about 25% and 14.2%, respectively.     

Experimental investigation of water-in-oil nanoemulsion in sinking electrical discharge machining

The most common dielectric in sinking electrical discharge machining (EDM) is kerosene. However, kerosene is inflammable; besides, it can be decomposed and release harmful gases during machining process. And, owing to its low viscosity, using kerosene in sinking EDM has low machining efficiency. Accordingly, conventional sinking EDM using kerosene as dielectric has poor safety, unfriendly environment impact, and low machining efficiency. A new water-in-oil (W/O) nanoemulsion is presented in this paper. This W/O nanoemulsion not only can eliminate the hazards from kerosene to operator and environment but also improve the machining performance of conventional sinking EDM. This research aims to experimentally investigate the machining performance of W/O nanoemulsion in comparison with kerosene in sinking EDM at relatively low discharge energy. The effects of electrode material, electrode polarity, peak current, and pulse duration on machining performance are studied. The machined surface and recast layer of workpiece are characterized as well. The experimental results demonstrate that compared with kerosene, using W/O nanoemulsion in sinking EDM can obtain a higher material removal rate (MRR), a lower relative electrode wear rate (REWR), and a machined workpiece with fewer defects and thinner recast layer.     

Influences of Process Parameters on MRR Improvement in Simple and Powder-Mixed EDM of AA6061/10%SiC Composite

In the present work, aluminum alloy 6061/10%SiC composite is machined using numerical controlled Z-axis (ZNC) electrical discharge machining (EDM) process. Improvement in material removal rate (MRR) is explored using tungsten powder suspended dielectric fluid in EDM process (powder-mixed electrical discharge machining (PMEDM)). Peak current, pulse on time, pulse off time, and gap voltage are studied as process parameters. Mathematical relation between process parameters and MRR is established on basis of response surface methodology. The results obtained are further compared with MRR achieved from machining using simple EDM. The existence of tungsten particles in kerosene resulted in 48.43% improvement in MRR. The influence of tungsten powder-mixed dielectric fluid on machined surface is analyzed using scanning electron microscope and energy dispersive spectroscopy (EDS). The results revealed improvement in surface finish and reduction in recast layer thickness with PMEDM. EDS analysis reported presence of tungsten and carbon in recast layer deposited on machined surface.     

Optimization of cryo-treated EDM variables using TOPSIS-based TLBO algorithm

In order to machine hard and high-strength-to-weight ratio materials, electrical discharge machining (EDM) process is extensively used in aerospace, automobile and other industrial applications. However, high erosion of tool and improper selection of machining variables have emerged as a major obstruction to achieve productivity in this direction. High erosion of tool not only enhances the cost of machining but also increases the machining time by causing interruption during machining. Therefore, proper selection of machining variables and tool material life are the two vital aspects for the tool engineers working in EDM. In view of this, the present work proposes an extensive experimental investigation and optimization of machining variables of cryogenically treated brass tool materials on machining competences of Inconel 718 workpiece. The study primarily highlights the outcome of cryogenically treated soaking duration of tools along with other important process variables, viz. discharge current, open-circuit voltage, pulse-on time, duty factor and flushing pressure, on the performance measures such as electrode wear ratio (EWR), surface roughness and radial over-cut. The study revealed that soaking duration in deep cryo-treatment of the electrode is a significant variable to achieve improved machining characteristics. The performance measures are converted into equivalent single performance measure by calculating the relative closeness coefficient by the techniques for order preferences by similarity to ideal solution (TOPSIS) approach. Finally, a novel teaching–learning-based optimization (TLBO) algorithm has been proposed to find the optimal level of machining variables for the performance measures. The optimal levels of cutting variables obtained through the algorithm are validated through confirmation test, predicting an error of 2.171 percentages between the computational and experimental results. The predicted result suggests that the proposed model can be used to select the ideal process states to achieve productivity for the cryo-treated EDM.     

Optimization of Process Parameters to Improve Form and Orientation Tolerances in EDM of MoSi2-SiC Composites

In this research, an investigation and experimental work were carried out on electric discharge machining (EDM) of intermetallic base MoSi₂-SiC ceramic composite with copper electrode. It is extremely difficult to machine MoSi₂-SiC composite using conventional machining techniques. However, it can be easily machined by executing spark EDM parameters to induce the correct optimum result. These composites find their application in high-temperature environments, viz. fuel turbo pump rotors, inlet nozzles, combustion chambers, injectors, nozzle throats, and nozzle extensions. The sparking parameters, namely current (I), pulse on time (T_on), pulse off time (T_off), spark gap (SG), and dielectric pressure (DP), were investigated by L₁₈ orthogonal array. The optimal process parameters were determined by the grey relational grade (GRG) obtained through the grey relational analysis (GRA) for multiple performance characteristics, viz. material removal rate (MRR), electrode wear rate (EWR), circularity (CIR), cylindricity (CYL), and perpendicularity (PER). The significant process parameters were obtained by analysis of variance (ANOVA) based on GRG, which showed current, pulse on time, and DP. The results were finally established using a confirmatory experiment, which showed the spark eroding process could effectively be improved.     

Improving the machining performance characteristics of the µEDM drilling process by the online cryogenic cooling approach

Productivity and surface quality would significantly affect the performance of the micro electrical discharge machining process (µEDM). Thus, the machining performance would be enhanced by improving the material removal rate (MRR) and surface quality. In this investigation, cryogenic LN₂ cooling was introduced to the conventional µEDM setup for developing an innovative process of cryogenically cooled µEDM process (CµEDM). The favorable outcomes of this process were estimated by selecting discharge current (I_p) and pulse on duration (T_on) for determining the effects of the machining performance including MRR and surface integrity. Surface quality was also analyzed by microstructural analysis and a scanning electron microscope (SEM) for evaluating the effects of the cryogenically cooled µEDM process. The experimental result shows 54–62% improvement in MRR and 22–36% improvement in average roughness values. Hence, it is suggested that cryogenically cooled µEDM facilitates improvement in productivity and surface quality.     

Electrical Discharge Machining of Functionally Graded 15-35 Vol% SiCp/Al Composites

A functionally Graded 15-35 volume% silicon carbide particulate (SiC_p) reinforced Al359 metal matrix composite (SiC_p/Al MMC) was drilled by electrical discharge machining (EDM) to assess the machinability and workpiece quality. The machining conditions were identified for both the machining performance and workpiece quality of the EDM process, including some aspects of material removal mechanisms, material removal rate (MRR), electrode tool wear, and subsequent drilled hole quality including surface texture and roundness by using surface profilometry, coordinate measuring machine (CMM), and scanning electron microscopy (SEM). It was observed that the material removal rate increases with increasing peak current and pulse-on-time up to the optimal points and drops drastically thereafter. Higher peak current and/or pulse-on-time result in both the greater tool wear and the larger average diameter error. As the percentage of the SiC particles increases, MRR was increased and electrode wear was found to be decreased. At the EDM machined subsurface layer, the fragmented and melted SiC particles were observed under the SEM and EDX-ray examination.     

Surface and porous recast layer analysis in µ-EDM of MWCNT-Al2O3 composites

Machining of ceramic materials has been a major challenge owing to high hardness and brittleness. The reinforcement of a conducting filler allows permissible machining in electrical discharge machining (EDM) process. The current effort analyses the impact of multi-walled carbon nanotubes (MWCNT) of concentrations of 2.5 and 5 vol. %, as conducting filler towards machinability of alumina composites in µ-EDM process. The influence of tool materials and its rotation are closely analyzed. A successful machining process is observed in both the two composites, with a higher material removal rate (MRR) in 5 vol. % MWCNTs. When the tool starts to rotate at 750 rpm, an increment of around 60–65% is observed in MRR for both the two composites. Similarly, the surface roughness (R_a) decreases by a factor of 20?25%. The brass tool is observed to yield better machining capabilities due to the frequent initiation of sparks. A highly porous machined surface is observed in both the two composites. This scenario depicts the spalling effect as more dominant than melting-evaporation effect. The extent of porous recast layer on the drilled edges is found to reduce with increasing the speed of tool rotation.     

Investigating Feasibility Through Performance Analysis of Green Dielectrics for Sustainable Electric Discharge Machining

This work represents a feasibility study for the newly proposed vegetable oil-based green dielectric fluids, biodielectric1 (BD1) and biodielectric2 (BD2) for electric discharge machining (EDM). Comparative analyses for BD1, BD2, and kerosene have been studied to assess the performance in terms of material removal rate (MRR), electrode wear rate (EWR), and relative wear ratio (RWR) for P20 + cold-worked plastic injection mold steel using electrolytic grade copper electrode. Current, gap voltage, pulse on time (T_on), and pulse off time (T_off) have been chosen as input parameters, and one variable at a time approach has been used for designing experimental plan for investigating the feasibility of the newly suggested fluids. The results obtained show that the performance of the newly suggested biodielectrics BD1 and BD2 is better than commercially used hydrocarbon-based dielectric, i.e., kerosene, for MRR and RWR. Analysis of variance results indicated that current is the most influencing parameter for MRR and EWR, while T_on is the most significant parameter for RWR. Under the influence of current, BD1 and BD2 produced 38% and 165% improvement in MRR, respectively. Moreover, BD1 and BD2 resulted 30% higher and 7% lower RWR, respectively, under the influence of T_on.     

Performance evaluation of cryogenically assisted electric discharge machining (CEDM) process

The performance of cryogenically assisted electric discharge machining (CEDM) process has been evaluated in the presented research paper. The machining of cryogenically treated (CT) and cryogenically untreated (CUT) AISI D2 tool steel work specimens using cryogenically cooled (CC), CT, and CUT copper electrodes have been performed. The effects of various parameters, namely, workpiece condition, tool condition, nozzle flushing, peak current, duty cycle, pulse duration, and gap voltage, have been studied on the performance indicators, viz. the material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR). The best parametric combinations have been suggested to obtain the desired quality characteristics. The interaction effects among various parameters have also been presented. An increase of approximately 18% in MRR and a reduction of 26% and 11% in TWR and SR, respectively, were observed, during the machining through CEDM in contrast to EDM. The confirmatory experiments suggested that experimental values were in permissible agreement with the predicted values for all the performance measures. Finally, the comparison of the CEDM with that of EDM process, in the light of SEM graphs, has been presented.