Near-dry Electrical Discharge Machining Research Articles

Experimental Investigation of the Micro-hardness of EN-31 Die Steel in a Powder-Mixed Near-Dry Electric Discharge Machining Method

The Powder-Mixed Near-Dry Electric Discharge Machining (PMND-EDM) methodology has proven to be efficient in terms of machining rate, surface morphology, and environmental friendliness, unlike traditional EDM. In this study, the presence of a conductive metallic powder (zinc) in the dielectric medium was responsible for changing the topography of the workpiece (EN-31) and resulted in a higher micro-hardness value of the machined component. In this research, an approach has been made to optimize the significant process parameters by using a Taguchi L9 orthogonal array (OA) to obtain machined components with higher values of micro-hardness, which was measured in terms of Vickers hardness HV. The selected process parameters were tool diameter, mist flow rate, metallic powder concentration, and dielectric mist pressure. By introducing foreign particles (metallic powder), the topography of the machined products has been improved, and the micro-hardness value was found to be enhanced. The confirmation experiment was performed for optimal process parameter settings, and the enhanced microhardness value was found to be 506.63 HV in the machined EN-31 die steel.

A Review on Numerical Modeling of Electrical Discharge Machining

Electrical discharge machining is one of the important non-conventional machining operations in modern engineering field. Electrical discharge machined components are extensively used in various areas such as automobile, aerospace, medical, etc. The materials having high strength, hardness and wear resistance are effectively machined. The high accuracy and precision of electric discharge machines make it an important machining operation in the modern world. There are several modifications and process improvement techniques in this area to enhance the performance of electrical discharge machining. The process parameters, selection of dielectric medium and tool electrodes are important aspects of electrical discharge machining that determine the performance parameters such as MRR, TWR and surface integrity. There are various types of EDM based on the selection of dielectric medium. They are wet EDM, dry EDM, Powder mixed EDM and near-dry EDM. This literature review is classifying the EDM based on different dielectric medium and numerical modeling works on EDM are investigated. Numerical modeling using finite element method is focused in this paper. The process parameters which influence the modeling of EDM are also studied. It is found that near-dry EDM which use mixture of liquid and gas as the dielectric medium have superior performance characteristics compared with conventional EDM practices. There are few studies are carried out on the numerical modeling of near-dry EDM and further studies are to be carried out to optimize the performance of EDM. This paper aims to provide a review on different dielectric medium used in EDM and numerical modeling of electrical discharge machining by finite element method.

Near Dry and Powder Mixed Near Dry Electric Discharge Machining

Electric discharge machining (EDM) is a non conventional machining method to fabricate very tough and hard materials. Although EDM has played a vital role in machining industry but with advancement of technology, alternative advanced methods of machining have been evolved such as near dry EDM (ND-EDM) and powder mixed near dry EDM (PMND-EDM). These technologies have been proven more efficient than traditional EDM in terms of machining performance characteristics such as higher material removal rate (MRR), better surface finish (Ra) and low tool wear rate (TWR) with high tolerance quality products. In this study an approach has been made to draw experimental comparison between ND-EDM and PMND-EDM in terms of MRR, SR and TWR. The experimental result and analysis revealed that PMND-EDM was better machining method than ND-EDM as in the former technique, the M RR increased by 45.04 % while SR and TWR reduced by 45.33 % and 60.60% respectively.

Performance enhancement of rotary tool near-dry EDM of HSS by supplying oxygen gas in the dielectric medium

ABSTRACTThe present investigation was carried out with an objective to enhance the performance of the rotary tool near-dry EDM (RT-ND-EDM) process by adding oxygen gas in addition to the dielectric medium. The effects of the amount of oxygen, rotational speed of the tool, current, pulse on time, and liquid flow rate were investigated on the performance characteristics of RT-ND-EDM process using high-speed steel as work material. The material removal rate (MRR), hole overcut (HOC), and surface quality were chosen as performance characteristics to represent the viability of the process. Surface quality was measured and analyzed in terms of debris deposition, micro-globules on the surface, porosity, micro-cracks, blowholes, and flow marks. The analysis of experimental results of RT-ND-EDM process, when oxygen gas was used along with dielectric medium, revealed that the MRR was 203%, 110%, and 85% higher than that of MRR obtained by the dry EDM using air, dry-EDM using air-oxygen, and RT-ND-EDM process without oxygen, respectively. This can be attributed to the fact that the addition of oxygen in the water-air dielectric medium helped in more amount of melting due to the rapid oxidation of work material. The debris formed during the oxygen mixed RT-ND-EDM process, cross-sectional analysis of the machined surface and analysis of tool wear were also investigated.

An environment-friendly and sustainable machining method: near-dry EDM

ABSTRACTElectric discharge machining (EDM) is one of the unconventional machining methods used in machining difficult-to-cut materials. The EDM process uses hydrocarbons-based dielectrics during machining which produces hazardous gases and creates environmental as well as operator’s health and safety issues. Therefore, the present study explores the sustainable variant of EDM (Wet and near-dry EDM) along with the optimized process parameters (pulse-on-time and pulse-off-time) to achieve low gas emission concentration. Near-dry EDM was performed with two-phase dielectric medium (air and EDM oil) and only EDM oil used in wet EDM. The gas chromatography and mass spectrometry (GC-MS) were effectively employed for analyzing the components of gaseous emission. The investigation showed that near-dry EDM process has reduced 97% gaseous emission with higher MRR compare to wet EDM. This process may be termed as green machining process because of very less or negligible gas emission.

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

ABSTRACTRotary 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.

A Comparative Performance Study of Dry and Near Dry EDM Processes in Machining of Spring Steel Material

Abstract Near dry and dry electric discharge machining process are non-conventional machining processes which are considered as some of the best options for electric discharge machining (EDM) process by changing the dielectric fluid. These are used for machining of hard materials and intrinsic parts. In this paper comparison of near dry (NDEDM) and dry EDM processes are based on machining performance of spring steel material by drilling operation is shown by using Copper as an electrode. Machining performance is checked by measuring the material removal rate (MRR), Tool wear rate (TWR), and surface topography. Experimentation is performed by using the Taguchi method for Design of experiment (DOE) with the help of L9 array.SEM images are used to comment on surface topography of machined parts. Near dry EDM (NDEDM) machining method shows good performance in increasing MRR, lower TWR and better surface topography over dry EDM process.

Experimental Investigation of the Effect of Input Control Variables in Near Dry Electric Discharge Drilling Process

Abstract Electric Discharge Machining (EDM), in its dry state (also known as Dry-EDM), appears to be as one of the best non traditional machining processes in terms of its suitability with the environment but carrying a demerit of slower material removing rate along, though in case of Near Dry Electric Discharge Machining (N-D-EDM) more amount of discharge energy claims to overcome this demerit along with a significant reduction in the roughness of the surface and less deposition of debris. A N-D-EDM consists of the application of a mixture of liquid & gas which helps in acclimating the characteristics of liquid and di-electric as per the requirements of the research. The present research elucidates the investigation of the optimal levels of input control variables of Near Dry Electric Discharge Drilling (N-D-EDD) process in machining of blind holes of Al6063/10% SiC Metal Matrix Composites (MMCs). The input control variables of choice were discharge-current, pulse-on-time, duty-factor and tool-speed, while material removal rate (MRR) was chosen as the performance characteristic during the N-D-EDD. Design of Experiments and Response Surface Method (RSM) were implemented and tool-electrode with rotary motion was used to drill blind holes. The results of the experimental trial runs depicted that the selected input control variables of N-D-EDD had significant effects on MRR.

Multi Objective Optimization of Near-Dry EDM using MOORA-PCA based Taguchi Optimization Method

Multi Objective Optimization of Near-Dry EDM using MOORA-PCA based Taguchi Optimization Method

Genetic algorithm approach for optimizing surface roughness of Near dry EDM

In this paper, genetic algorithm (GA) approach is used in order to optimize the surface roughness (Ra) of near dry EDM (ND-EDM) surfaces. Taguchi orthogonal array of L27 is used as design of experiment for the five process parameters viz. pulse on time, duty factor, discharge current, gap voltage and tool rotating speed. ANOVA test was conducted and found that pulse on time was the most significant process parameters with 53.38% of contribution followed by duty factor and discharge current with 20.68% and 20.87% of contribution respectively. A regression mathematical model was developed and determined the relationship between the process parameters and surface roughness. GA approach was employed to optimize the process parameter. Then, a validation test was performed and confirmed the optimal process parameters values.

Grey-Taguchi Optimization of Near Dry EDM Process Parameters on the Surface Roughness

Near Dry Electrical Discharge Machining (ND-EDM) uses a minimum quantity lubrication (MQL) system to supply a little amount of controlled two phase dielectric fluid droplets between the gap of workpiece and electrode. In present study, Grey-Taguchi approach with L27 orthogonal array was considered to investigate and optimize the process parameters of ND-EDM viz. Pulse On Time, Pulse Off Time, Discharge Current, Gap Voltage and Tool Rotating Speed on the responses of surface roughness viz. Ra, Rt, Rsm, Rsk and Rku using the mixture of deionized water and air as the dielectric fluid for EN-8 material. Th0e five different response values of the surface roughness were converted into a single grey relational grade and determined the optimal machining parameters. Analysis of variance (ANOVA) was performed to find the significant process parameters on grey relational grade and found that discharge current and pulse-on time were the significant parameters in orders. Confirmation experiment was conducted and verified the optimal process parameters setting.

Influence of glycerin-air dielectric medium on near-dry EDM of titanium alloy

Ti-6Al-4V is one of the most commonly used titanium alloy. The applications involve in the area of aerospace, chemical engineering, biomedical implants, marine industries, etc. The electrical discharge machining (EDM) is an unconventional machining process. It is widely used to produce complex profiles on electrically conductive materials. Near-dry EDM is a process variant of the EDM process. Generally, it uses water-air mixture as a dielectric medium. Near-dry EDM is an environment friendly process. In this investigation near-dry EDM of Ti-6AL-4V was investigated with glycerin-air dielectric medium. The one-factor-at-a-time approach was used for experimentation. The process parameters selected for experimentation were current, duty factor, lift setting, sensitivity setting, flushing pressure, liquid flow rate and gap control. The responses measured were material removal rate (MRR) and surface roughness (SR). The experimental results revealed that glycerin-air dielectric medium produced higher MRR with fine surface finish even at higher current and wear ratio of the process was also less than 1%.

Experimental Investigation on Near-dry EDM using Glycerin-Air Mixture as Dielectric Medium

Near-dry electrical discharge machining (EDM) is an eco-friendly variant of conventional EDM. This article presents, an experimental investigation on near-dry EDM with high viscous liquid glycerin and air mixture as dielectric medium. In this study, face centered central composite design (CCD) had used to plan the experiments. Response surface methodology (RSM) was applied for proposing the mathematical model. The mathematical model was proposed to determine the significant effect of input parameters on response characteristic. In this investigation, input parameters used for experimentations were current, duty factor flushing pressure and lift. The response characteristic was measured in terms of material removal rate (MRR). Analysis of the results revealed that, all the input parameters were significant for MRR. It was observed that glycerin-air dielectric medium produced higher MRR than water-air dielectric medium at same parametric setting.

Influence of glycerin-air dielectric medium on near-dry EDM of titanium alloy

Ti-6Al-4V is one of the most commonly used titanium alloy. The applications involve in the area of aerospace, chemical engineering, biomedical implants, marine industries, etc. The electrical discharge machining (EDM) is an unconventional machining process. It is widely used to produce complex profiles on electrically conductive materials. Near-dry EDM is a process variant of the EDM process. Generally, it uses water-air mixture as a dielectric medium. Near-dry EDM is an environment friendly process. In this investigation near-dry EDM of Ti-6AL-4V was investigated with glycerin-air dielectric medium. The one-factor-at-a-time approach was used for experimentation. The process parameters selected for experimentation were current, duty factor, lift setting, sensitivity setting, flushing pressure, liquid flow rate and gap control. The responses measured were material removal rate (MRR) and surface roughness (SR). The experimental results revealed that glycerin-air dielectric medium produced higher MRR with fine surface finish even at higher current and wear ratio of the process was also less than 1%.

Steps towards green manufacturing through EDM process: A review

AbstractThis paper focuses on the current machining process initiatives, carried out by various researchers relevant to the environmental aspects, thereafter predicting EDM performances. electrical discharge machining (EDM) is widely used unconventional machining method, because of its ability to process very hard material with precision. In thermo-electric process, control spark generation between electrodes causes material removal; however, application of hydrocarbon oil based dielectric fluid is an issue of environmental disruption. Replacement of dielectric to rectify the problem is one of the main concerns in EDM research. This paper highlights dry-EDM, near-dry EDM and EDM in water, conceived as an environment friendly alteration in the oil EDM process referred as a green EDM process. The work provides a thorough review of dry, near-dry EDM and EDM in water as a process, where the target is to endeavor dielectric fluids which could be the alternative to replace hydrocarbon oil. It is perceived that ...

Experimental investigation on effects of dielectric mediums in near-dry electric discharge machining

A dielectric fluid plays a significant role on the machining efficiency of Electric discharge machining (EDM). Two phase (liquid-air) dielectric medium was utilized in near-dry (EDM). It is an environmentally friendly process. The present article reports the effect of different dielectric mediums on responses of near-dry EDM. Dielectric mediums used for experimentation were water-air, EDM oil-air and glycerin-air mixtures. The process parameters selected for experimentation were current, duty factor, flushing pressure and lift. Material removal mechanism of near-dry EDM is investigated using imaging techniques. Dielectric fluid with higher viscosity and higher Prandtl number provided better results than fluids with lower viscosity. The results reveal that the Material removal rate (MRR) with glycerin-air dielectric medium is about three-times higher than other dielectric medium used with negligible recast layer. The tool wear rate is negligible in near-dry EDM in relation to all the dielectric mediums.

Review on recent development in environmental-friendly EDM techniques

The electrical discharge machining (EDM) is unitary of the widely used unconventional machining because of its ability to cut very hard material engendering high dimensional accuracy as well. In thermo-electric process, control sparks generation between electrodes causes material removal; however, application of hydrocarbon oil based dielectric is an issuance of environmental disruption. To rectify this problem, replacement of dielectric is main concerns in EDM research. This paper highlights Dry-EDM, Near-Dry EDM and EDM in water, which is conceived as an environment amiable alteration in the oil EDM process. The work gives a thorough review of Dry, near-dry EDM and EDM in water as a process, where the target is to endeavor dielectric fluids that can be substituted bypassing hydrocarbon oil. It is perceived that water and gas based dielectrics could take over oil-based fluids in die sink applications. Novel technological advances in dry EDM machining processes, which deliberate the relatively advanced stage of a technology in to the area of academic and industrial research is briefly reviewed. An outline of the prospective trend of reviewing is intimate in the last fragment.

Review on Recent Development in Environmental-friendly EDM Techniques

The electrical discharge machining (EDM) is unitary of the widely used unconventional machining because of its ability to cut very hard material engendering high dimensional accuracy as well. In thermo-electric process, control sparks generation between electrodes causes material removal; however, application of hydrocarbon oil based dielectric is an issuance of environmental disruption. To rectify this problem, replacement of dielectric is main concerns in EDM research. This paper highlights Dry-EDM, Near-Dry EDM and EDM in water, which is conceived as an environment amiable alteration in the oil EDM process. The work gives a thorough review of Dry, near-dry EDM and EDM in water as a process, where the target is to endeavor dielectric fluids that can be substituted bypassing hydrocarbon oil. It is perceived that water and gas based dielectrics could take over oil-based fluids in die sink applications. Novel technological advances in dry EDM machining processes, which deliberate the relatively advanced stage of a technology in to the area of academic and industrial research is briefly reviewed. An outline of the prospective trend of reviewing is intimate in the last fragment.

Investigation of near dry EDM compared with wet and dry EDM processes

Material removal rate (MRR), tool wear ratio (TWR) and surface roughness (SR) obtained by near-dry EDM process were compared with wet and dry EDM at three levels of discharge energy in drilling of SPK steel. Surface integrity machined by this process was studied and compared with wet and dry EDM processes, by scanning electron microscopy (SEM). The results showed that at high level of discharge energy, wet EDM has the most MRR, TWR and SR, and dry EDM has the least MRR, TWR and SR, while at low discharge energy levels, near-dry EDM process has the most MRR and the least SR. SEM micrographs showed that the quality of surface obtained by near-dry EDM process is better than others and the machined surfaces by near-dry EDM process have lower micro-cracks and craters, relatively.

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.