Conventional EDM Process Research Articles

Investigation of process parameters for modeling of ceramic composite SiSiC IN dry EDM (DEDM) cutting

The manufacturing industry is currently grappling with issues related to energy dissipation and product quality, both of which significantly impact productivity. In addressing this pertinent concern, this study endeavours to identify the key indicators that contribute a crucial role in machining process. The Dry EDM (DEDM) emerges as a novel technology, wherein environmentally friendly gases serve as an alternative dielectric medium instead of liquid EDM approaches. In conventional EDM process, hydrocarbon oils release toxic emissions while the gases used in Dry EDM process don’t produce harmful emissions and hence make the DEDM process sustainable.An investigation has been carried out to observe the influence of different gases like O2, N2 and Air on Siliconized Silicon-Carbide plate (SiSiC) of ø50mm*2 mm under Dry Electrical Discharge Machining. Effect of different tools is also observed using varying shapes of electrodes like plane Cu electrode of ø6 mm diameter with 60 mm length and tubular shape with outer diameter ø6mm and inner diameter ø5.1 mm with a length of 60 mm. The three gases are one by one supplied through a nozzle in the presence of plane Cu electrode to make the holes in SiSiC plate. The same process is executed with tubular Cu electrode. Modified Taguchi Orthogonal Array is applied to analyze the effect of control factors such as gap voltage, discharge current and pulse on-time through a series of experiments. Effect of different shape of tools and different gases is observed for the material removal rate (MRR) and surface roughness (SR) of specimen.In this paper, a latest DEDM process of swirl assisted flushing is proposed which provides a new technique to solve the problems of low MRR and poor surface integrity. Swirl assisted flushing works on Decay Law and also microscopic investigation justifies its validity. It is concluded by this research that current and Pulse on time are more contributing factors about 53.3 % and 27 % respectively. Furthermore, it is noted that DEDM increases MRR 19.5 % and lowers Ra approximately 2/3 than traditional machining. The MRR of O2 is about 3.1 times more than Air and N2 comes at least position while N2 creates better quality of surface due to formation of an inert nitride layer. Empirical relations are established for SR and MRR using Minitab 18 Software to develop a robust model. Confirmation test is performed to check the validity of developed mathematical model. The Novelty of this research is also extended by introducing a new method SAF. The results are finally evaluated by ANOVA.

Study the effect of EDM parameters on surface roughness of cryogenically treated AISI 304 steel

Powder mixed electric discharge machining (PMEDM) has an edge over the conventional EDM process owing to the presence of electrically conductive powder nixed in the dielectric fluid to achieve improved surface integrity of machined components. Cryogenic treatment of work material and tool material has the potential to yield better machining performance in the EDM process. This paper presents the findings of the experimental investigation subjected to the application of PMEDM to machine cryogenically treated AISI 304 using the cryogenically treated electrode made of Copper. The RSM-based approach was deployed to design the experiments to study the influence of parameters viz. powder concentration, current, pulse-on time, and duty cycle on surface roughness. A regression analysis was carried out to establish a relationship between surface roughness and given machining parameters which were also validated through residual plots.

Multi-response optimization of magnetic field assisted EDM through desirability function using response surface methodology

Abstract Magnetic field assisted electrical discharge machining (MFAEDM) is the modification of in conventional EDM process by use of magnetic field on EN-31. This article explain the application of response surface methodology to analyzes the effect of various process parameters such as Ton, Toff and Ip on performance measures such as material removal rate (MRR), electrode wear rate (EWR) and overcut (OC). Analysis of variance was used to check the adequacy of response surface model and significance of process parameters on performance measures. Multi-objective desirability function has been applied to obtain the optimal process parameter settings. Thereafter, machined surface of EN-31 characterized through SEM and EDX. The novelty of this paper is to improve the strategies for flushing the debris which remain clogged in standard EDM in-between machining gap that will interrupts the regular discharge conditions and reduces cutting rate as well as deteriorate the surface characteristics.

A semi-empirical model to predict material removal rate during air-assisted electrical discharge machining

The present study is focused on exploring the use of air-assisted electrical discharge machining (AAEDM) of high carbon high chromium die steel. One of the notable drawbacks of conventional EDM machining is low material removal rate (MRR). So, there is a critical need to evolve a method that can increase the MRR of conventional EDM process. This experimental study is focused on the use of compressed air in die sinking EDM, under controlled machining conditions to evaluate MRR. The influence of process parameters, viz., discharge current, pulse on time, duty cycle, tool rotation and discharge air pressure, on MRR has been investigated. ANOVA has been performed to select the significant factors affecting MRR. An effort has been done to establish a semi-empirical model to predict MRR in AAEDM process of high carbon high chromium die steel using dimensional analysis. The experimental and predicted values through semi-empirical model are found to be in accord with each other. The surface morphology analysis has been performed by using scanning electron microscope for machined specimens. The energy-dispersive X-ray spectrometer analysis has been used to investigate the material removal mechanism in AAEDM process.

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

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 (Ra), 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 Ra decreased by 12%, 24% and 13.3%, respectively and when SiC powder used MRR increased by 23.2%, TWR and Ra decreased by about 25% and 14.2%, respectively.

On the design and application of hybrid electrical discharge and arc machining process for enhancing drilling performance in Inconel 718

In recent years, Inconel 718 is widely used in industries like aerospace, oil and gas, and automobile due to their unique combination of hardness, strength, temperature, and corrosion resistance properties. However, these materials pose challenges during conventional machining due to their high work hardening tendency, poor thermal conductivity, and chemical affinity towards the tool material. Consequently, rapid tool wear during the machining of Inconel 718 results in poor productivity. To overcome these issues, a non-contact hybrid electrical discharge and arc machining (HEDAM) process has been developed to machine such difficult-to-cut materials. Firstly, the design and development of the HEDAM circuit has been discussed. Subsequently, the working principle of the newly developed process has been studied followed by its performance comparison with the conventional EDM process. In addition, the material removal mechanism has also been discussed in detail. Finally, experimental results were reported, where holes were drilled using the developed HEDAM process. The HEDAM process has exhibited significant improvements in terms of material removal rate (MRR) which is around 12 times higher and electrode wear ratio (EWR) that is half when compared to conventional EDM. This high performance HEDAM process resulted in successful and efficient drilling of Inconel 718.

On sustainable manufacturing titanium alloy by high-speed EDM milling with moving electric arcs while using water-based dielectric

Abstract In order to solve the environmental pollution and low machining efficiency of conventional EDM process, a sustainable manufacturing method of high-speed EDM milling while using water-based dielectric is proposed. Firstly, the machining principle of moving electric arcs was investigated. Then, models were established and utilized to explain the characteristics of high-speed EDM milling with moving electric arcs. Experiments on machining titanium alloy with this method were carried out to analyze the machining characteristics. The experimental results showed that the material removal rate (MRR) was significantly improved. The maximum MRR was almost five times greater than that of conventional EDM. Moreover, the lower tool-electrode wear in high-speed EDM milling was obtained, which can be attributed to the high-speed rotation of tool-electrode and protective layer formation on the tool-electrode surface caused by sputtering and deposition of Ti-6Al-4V.

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

ABSTRACTElectrical 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.

Electrical Discharge Machining of Metal Matrix Composites with a High Speed Non-Round Electrode

An electrical discharge machining process with a high electrode rotation speed (EDM-HS) has been developed to solve the problems of the conventional EDM process in machining metal matrix composites (MMCs). The EDM-HS process employs a non-round tool electrode. The experiment results showed that the materials removal rate (MRR) of the workpiece can be improved significantly by employing a non-round tool electrode. The relationship between the pulse duration, machining current, duty cycle, the rotation speed of the tool electrode and the MRR has been studied respectively. And the machining mechanism of this EDM-HS process has been analyzed both theoretically and experimentally. The results showed that the non-round electrode can enlarge the machining gap and with a high electrode rotation speed, the machined debris can be discharge out of the machining area effectively and hence a stable machining condition can be obtained. As a result, a higher MRR can be achieved. Moreover, an orthogonal analysis has been utilized to study the relative importance of the machining parameters on MRR. It was found that to obtain the highest MRR, the electrode rotation speed was the most influential factor among the duty cycle, machining current, pulse duration and electrode rotation speed. This outcome supports that it is feasible to use this novel method to machining particulate reinforced MMCs, where a higher MRR can be achieved.

Experimental Investigations during Dry EDM of Inconel - 718

Dry EDM is a modification of the conventional EDM process in which the liquid dielectric is replaced by a gaseous medium. Tubular tool electrodes are used and as the tool rotates, high velocity gas is supplied through it into the discharge gap. The flow of high velocity gas into the gap facilitates removal of debris and prevents excessive heating of the tool and work piece at the discharge spots. It is now known that apart from being an environment- friendly process, other advantages of the dry EDM process are low tool wear, lower discharge gap, lower residual stresses, smaller white layer and smaller heat affected zone. Keeping literature review into consideration, in this paper, an attempt has been made by selecting compressed air as a dielectric medium, with Inconel - 718 as a work piece material and copper as a tool electrode. Experiments are performed using Taguchi DoE orthogonal array to observe and analyze the effects of different process parameters to optimize the response variables such as material removal rate (MRR), surface roughness (Ra) and tool wear rate (TWR). In the current work, a unit has been developed to implement dry EDM process on existing oil based EDM machine.

Surface Characterization, Material Removal Mechanism and Material Migration Study of Micro EDM Process on Conductive SiC

SiC is an important industrial ceramic and also the fourth hardest ceramic after diamond, boron nitride and boron carbide. Due to very low fracture toughness, it is very difficult to machine SiC using conventional machining methods. EDM can machine such materials irrespective of their hardness. Micro electrical discharge machining (micro-EDM) is an adaptation of conventional EDM process that has similar electro-thermal methods of material removal for manufacturing miniature or micro parts. Micro EDM is used for obtaining burr-free micro dimensional apertures in difficult-to-cut materials. For improved understanding of the micro EDM process and achieve high quality machining on conductive SiC, it is necessary to characterize the machined surface and understand the material removal and material migration mechanism. In this work, micro depth holes were machined in SiC workpiece. The experimentation was planned using Taguchi's L9 theory. A combination of scanning electron microscopy (SEM), white light interferometry (WLI), energy dispersive x-ray spectroscopy (EDX), atomic force microscopy (AFM) and X-ray diffraction (XRD) was used to characterize the machined surface and study the material removal and material migration mechanism. It was found that improved characterization and understanding of μEDM can lead to better micro-machining of conductive SiC.

High speed abrasive electrical discharge machining of particulate reinforced metal matrix composites

A high speed abrasive electrical discharge machining (AEDM-HS) process has been developed to improve the performance and save the machining energy of the conventional EDM process in machining particulate reinforced metal matrix composites (MMCs). The AEDM-HS process functions under a combined action of spark erosion and direct mechanical grinding. A set of experiments was conducted and the results showed that the material removal rate (MRR) of AEDM-HS was much higher than that of EDM under the experimental conditions of this study. Moreover, the surface roughness value (Ra) measured for the AEDM-HS specimen was about six times smaller than that of the specimen machined without high speed abrasive action (i.e., EDM alone). The material removal mechanism of this novel process has been analyzed by means of single-pulse experimentation. And the relative importance of the various processing parameters on MRR was established using orthogonal analysis. The results showed that the MRR is influenced by the machining factors in the order of duty cycle > current > pulse duration. This study showed that the AEDM-HS process is superior to the EDM process for machining particulate reinforced MMCs, where a higher machining efficiency and a better surface quality can be obtained.

Predictor Equations for Estimating Crater Dimensions in PMEDM Process Using Fem Simulation and Experimental Validation

In the present study, the powder mixed EDM (PMEDM) process was simulated using FE approach to obtain simulated temperature profiles for estimating the crater dimensions and volume removed during formation of each crater. The craters formed in PMEDM process had higher diameter and shallow depth resulting in improved MRR and better surface finish. The addition of powder increased the amount of heat available at the workpiece between 20-25% as compared to conventional EDM process. The results were subsequently validated experimentally to compare the actual measurements with the simulation output. Predictor equations for crater radius and depth incorporating the significant factors were developed and also validated with the experimental results.

A Novel High Efficiency Electrical Erosion Process – Blasting Erosion Arc Machining

A novel low cost, high efficiency material removal process namely the Blasting Erosion Arc Machining (BEAM) is proposed and implemented to perform bulk removing of alloys including the difficult-to-cut materials. Compared with conventional EDM process, the BEAM process erodes the work piece materials with electrical arcing instead of sparking.The most critical enabling mechanism of BEAM is how to make the arcing plasma column break off, and resulting in a consequent blast effect, by which the molten material is blown off from the molten pool efficiently. In order to avoid continuous and steady arcing, a strong multi-hole inner flushing is a prerequisite for the BEAM process. During BEAM, the high velocity flushing induces a strong hydrodynamic force into the gap, which distorts, elongates or even breaks the arcing plasma column. During the arc breaking process, an extremely strong blasting will blow off the molten material explosively. This arc breaking mechanism is named hydrodynamic arc breaking mechanism and it is the principle of BEAM process.The preliminary experiments demonstrated the material removal rate of the BEAM process is extremely higher than that of traditional EDM or even the milling process. For example, the MRR of BEAM of Inconel718 exceeds 11,300/min as well as the tool wear ratio is lower than 1%. Obviously, BEAM is a promising process in the high efficiency machining of the difficult-to-cut materials. Besides, it is also an environmentally friendly machining process because the working fluid is water-based dielectric rather than hydrocarbon dielectric oil.

Electric Discharge Grinding of Polycrystalline Diamond Materials

The poor electric conductivity of polycrystalline diamond (PCD) makes it difficult to machine with the conventional EDM process. Inappropriate selection of parameters of the power generator and the servo system leads to unstable working condition and low material removal rate. This paper introduces a method to find optimal parameters in the Electrical Discharge Grinding (EDG) of PCD materials with Taguchi method. The theory and detailed procedures are presented, experimental results are analyzed. The optimized configuration was validated through confirmation tests.

Effect of process parameters on the performance of EDM process with ultrasonic assisted cryogenically cooled electrode

In this work the parametric study on EDM process using ultrasonic assisted cryogenically cooled copper electrode (UACEDM) during machining of M2 grade high speed steel has been performed. Electrode wear ratio (EWR), material removal rate (MRR) and surface roughness (SR) was the three parameters observed. Discharge current, pulse on time, duty cycle and gap voltage were the controllable process variables. The effect of process variables on EWR, MRR and SR has been analyzed. The MRR, EWR and SR obtained in EDM process with normal electrode, cryogenically cooled electrode and ultrasonic assisted cryogenically cooled electrode have been compared. EWR and SR were found to be lower in UACEDM process as compared to conventional EDM for the same set of process parameters, while MRR was at par with conventional EDM process. The surface integrity of work piece machined by UACEDM process has been found to be better as compared to conventional EDM process. The shape of the electrode has also been measured and it was found that the shape retention was better in UACEDM process as compared to conventional EDM process. Thus in the present work UACEDM process has been established to be better than conventional EDM process due to better tool life, tool shape retention ability and better surface integrity.

PARAMETRIC INFLUENCE AND OPTIMIZATION OF WIRE EDM OF HOT DIE STEEL

Wire-cut Electro Discharge Machining (WEDM) is a special form of conventional EDM process in which the electrode is a continuously moving conductive wire. The present study aims at determining parametric influence and optimum process parameters of Wire-EDM using Taguchi's technique and a Genetic algorithm. The variation of the performance parameters with machining parameters was mathematically modeled by Regression analysis method. The objective functions are defined as Dimensional Error (DE), Surface Roughness (SR) and Volumetric Material Removal Rate (VMRR). Experiments were designed as per Taguchi's L16 Orthogonal Array (OA) wherein Pulse-on duration, Current, Pulse-off duration, Bed-speed and Flushing rate have been considered as the important input parameters. The matrix experiments were conducted for the material Hot Die Steel (HDS) having the thickness of 40 mm. The Heat Affected Zone (HAZ) characteristics of the eroded materials were assessed by Scanning Electron Microscope (SEM) and the microhardness of the material was tested using Vickers microhardness tester. The results of the study reveal that among the machining parameters, it is preferable to go for smaller pulse-off duration for achieving overall good performance. Regarding pulse-on duration, higher values are recommended for error constrained machining with higher MRR and constrained/limited values for attaining good surface texture. Smaller current is suggested for better surface finish/texture control, medium range for error control and high value for MRR. Finally, the validation exercise was performed with the optimum levels of the process parameters. The results confirm the efficiency of the approach employed for optimization of process parameters in this study.

Geometry and surface damage in micro electrical discharge machining of micro-holes

Geometry and subsurface damage of blind micro-holes produced by micro electrical discharge machining (micro-EDM) is investigated experimentally to explore the relational dependence with respect to pulse energy. For this purpose, micro-holes are machined with various pulse energies on plastic mold steel samples using a tungsten carbide tool electrode and a hydrocarbon-based dielectric liquid. Variations in the micro-hole geometry, micro-hole depth and over-cut in micro-hole diameter are measured. Then, unconventional etching agents are applied on the cross sections to examine micro structural alterations within the substrate. It is observed that the heat-damaged segment is composed of three distinctive layers, which have relatively high thicknesses and vary noticeably with respect to the drilling depth. Crack formation is identified on some sections of the micro-holes even by utilizing low pulse energies during machining. It is concluded that the cracking mechanism is different from cracks encountered on the surfaces when machining is performed by using the conventional EDM process. Moreover, an electrically conductive bridge between work material and debris particles is possible at the end tip during machining which leads to electric discharges between the piled segments of debris particles and the tool electrode during discharging.

Characterization of plasma in micro-EDM discharge using optical spectroscopy

This paper presents the spectroscopic measurement of temperature and electron density in the micro-EDM (micro electric discharge machining: μ -EDM) process. A systematic study using L-18 orthogonal array experiments based on the Taguchi method is conducted to understand the effect of varying process parameters including voltage, current, spark gap and electrode size on the plasma characteristics. The line pair method and the Stark broadening of the H β spectral line are used to compute plasma temperature and electron density, respectively. The spark gap and electrode size are found to have a significant influence on the plasma characteristics. The plasma produced by low-energy discharge in μ -EDM is more non-ideal, denser, and colder than the high-energy discharge plasma produced in the conventional EDM process. The interparticle distance is roughly equal to the Debye length ( λ D ), resulting in more electrostatic interactions between ions.

Magnetic field assisted micro electro-discharge machining

This paper studies the feasibility of application of a magnetic field to obtain higher aspect ratio micro holes on hardened tool steel using the micro electro-discharge machining (micro EDM) process. The magnetic field has been introduced to improve debris circulation. Implementing magnetic force perpendicular to the electrode's rotational force produces a resultant force that is efficient in transporting debris out of the hole during machining. With the magnetic field assisted micro EDM process a hole depth of 1177 µm is achieved in 360 min in tool steel. This is 26% higher when compared with the conventional micro EDM process under similar working conditions. No significant difference is noticed in the side wall surface roughness values in the two cases.