Near-dry Electrical Discharge Research Articles

Machining characteristics and optimization of TC4 alloy by mixed gas atomization discharge ablation milling (MA-DAM)

A method using mixed gas atomization discharge ablation milling (MA-DAM) for machining titanium alloys was proposed to address the processing efficiency and quality issues in conventional near-dry electrical discharge milling (N-EDM). By analyzing the discharge waveform, a pulse discharge physical model was established to reveal the machining mechanisms of N-EDM and MA-DAM. It was found that the latter had a unique ablation process compared to the former, resulting in better machining performance. The results of oxygen concentration experiments showed that compared to N-EDM, MA-DAM improved the material removal rate by 55.6 % and reduced the relative electrode wear rate by 50 %, but increased the width of the overcut by approximately 10 % and the average roughness by approximately 17 %. Orthogonal experiments and variance analysis were conducted to study the effects of the current, duty cycle, gas pressure, and atomization rate on the machining performance indicators. Finally, grey relational analysis was used for the multi-objective optimization of machining parameters to obtain the optimal process configuration for MA-DAM, which was validated through experiments.

Multi-axis near-dry Electrical Discharge machining using inconel 718 alloy

ABSTRACT In the current research work, in-house developed and fabricated multi-axis near-dry Electrical Discharge Machine (near-dry EDM) has been used having different tool positions, i.e. tool electrodes in horizontal position (Case-I) and vertical positions (Case-II) as a novel machining techniques in hard-to-reach places and also to improve the process performance. Design of Experiment tool has been used with three process parameters: voltage, discharge current, and pulse-on-time for experimentation purposes. In order to maximize Material Removal Rate (MRR), it was necessary to compare and enhance these parameters in both cases, i.e. Case-I, and Case-II. The machining process is significantly influenced by the vertical tool positions, as indicated by the largest percentage contribution in the Analysis of Variance results. The voltage has the least influence, while the pulse-on time is relatively less. In contrast, for the horizontal tool position, the voltage proved the most prominent factor in terms of influence, while the current ranked second in significance. Conversely, the pulse-on time exhibited the least impact among the three factors. The highest MRR 2.45 mm3/min was achieved in the vertical tool position while in horizontal machining, the highest MRR 0.144 mm3/min was observed. These findings provide valuable insights into the multi-axis near-dry EDM with proposed methodology.

Study on the effect of different electrode forms on the surface modification of Ti–6Al–4V alloy by near-dry electrical discharge machining

The surface modification of Ti–6Al–4V alloy was achieved by using an electrical discharge machining (EDM) surface modification technology under the action of pulsed discharge to induce an in-situ synthesis reaction between the molten metallic material and the ionized elements in the atomized medium. In this study, nitrogen and urea solutions are used as the gas-liquid phases of the atomization medium. ANSYS simulation software was used to simulate and analyze the interpolar pressure and flow field of the different electrodes. The effect of different electrode forms on the EDM surface modification layer was investigated by designing comparative trials. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and other detection methods were used to characterize the process indicators, such as surface morphology, roughness, hardness, and wear resistance of the reinforced layer. It was found that a thick and uniform continuous layer can be obtained on the Ti–6Al–4V alloy substrate using multi-channel electrode machining, and the thickness is about 65 μm. XRD analysis indicates that the reinforced layer mainly contains TiN, Ti2N, Ti2AlN, Ti2O, and CuO phases. The samples with reinforced layers were shown to have higher hardness (1578 HV) and better wear resistance than the titanium substrates. The main wear mechanism is spalling wear and light oxidation wear.

Sustainable developments in near-dry electrical discharge machining process using sunflower oil-mist dielectric fluid.

In this study, a near-dry electrical discharge machining (NDEDM) process has been conducted using compressed air mixed with a low quantity of biodegradable refined sunflower oil (called oil-mist) to investigate the machining characteristics. The Box-Behnken method looks at how oil flow rate (OR), air pressure (AR), spark current (SC), and pulse width (PW) affect gas emission concentration (GEC), material removal rate (MRR), and surface roughness (SR). The TOPSIS (The Technique for Order of Preference by Similarity to the Ideal Solution) technique estimates the parameter optimal set for the best machining characteristics. The optimal machining parameters have been used to examine the microstructure of the machined surfaces using a scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis. The 0.981mg/min of GEC, 55.145mg/min of MRR, and 2.43µm of surface roughness have been attained by the 14ml/min flow rate, 7bar of air pressure, 10 A spark current, and 48µs pulse duration of the sun-flower oil-mist NDEDM process.

Experimental investigation and multi-objective optimization of eco-friendly near-dry electrical discharge machining of shape memory alloy using Cu/SiC/Gr composite electrode.

The near-dry electrical discharge machining processes have been conducted using air-mist or gas mist as a dielectric fluid to minimize the environmental impacts. In this article, near-dry electrical discharge machining (NDEDM) experiments have been performed to improve machining performance using an oxygen-mist dielectric fluid, a copper composite electrode, and Cu-Al-Be polycrystalline shape memory alloy (SMA) work materials. The copper composite electrode is made up of 12 wt% silicon carbide and 9 wt% graphite particles. The oxygen-mist pressure (Op), pulse on time (Ton), spark current (Ip), gap voltage (Gv), and flow rate of mixed water (Fr) were used as process parameters, and the material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR) were used as performance characteristics. The global optimal alternative solution has been predicted by the PROMETHEE-II (Preference Ranking Organization METhod for Enrichment Evaluations-II) optimization technique. The best combinations of process parameters have been used to examine the microstructure of composite tools and SMA-machined surfaces by scanning electron microscopy (SEM) analysis. The best global optimum settings (oP: 9bar, Ip: 60µs, Ip: 12 A, Gv: 40V, and Fr: 12ml/min) are predicted to attain optimum machining performance (MRR: 39.049g/min, TWR: 1.586g/min, and SR: 1.78µm). The tool wear rate of the NDEDM process has been significantly reduced by the copper composite electrode due to increasing microhardness, wear resistance, and melting point. When compared to the pure copper electrode tool, the MRR of NDEDM is improved to 21.91%, while the TWR and SR are reduced to 46.66% and 35.02%, respectively.

Experimental investigation on the effects of green dielectric medium air and argon on the near-dry electrical discharge machining of titanium alloy

Experimental investigation on the effects of green dielectric medium air and argon on the near-dry electrical discharge machining of titanium alloy

Investigating the Performance of the Rotary Tool Near-Dry Electrical Discharge Machining Process through Debris Analysis

Investigating the Performance of the Rotary Tool Near-Dry Electrical Discharge Machining Process through Debris Analysis

Study on parameter’s optimization for the minimizing of the residual stress in powder mixed near-dry electric discharge machining

There are some undesired effects left in the machined products by electric discharge machining (EDM) and the most prominent among those is the residual stress. These induced residual stresses influence fatigue behavior, dimensional stability, and stress corrosion which is responsible for the failure of the machined product. It was observed that the products obtained by powder mixed near dry- EDM or (PMND-EDM) have a considerably low value of residual stress (RS). The objective of this research is to minimize the residual stresses induced in the machined workpiece (EN-31) by optimizing the process parameters which affects the machining characteristics significantly. Selected parameters were tool diameter, mist flow rate, metallic powder concentration, and mist pressure while the workpiece selected was EN-31 due to its desirable mechanical properties and immense applications in the manufacturing industry. The minimum value of residual stress at optimized values of process parameters was found to be 106.32 MPa.

An extensive review on sustainable developments of dry and near-dry electrical discharge machining processes

Abstract Electrical discharge machining (EDM) is very essential unconventional electro-thermal machining process to machine the contour profile of hard materials in modern production industries. The liquid dielectric fluid has been replaced by the gas and minimum quantity of liquid mixed with gas (gas-mist) to encourage the green machining processes. The various gases and gas-mist have been used as the working fluid in dry and near-dry EDM respectively. The research-contextual, various dielectric fluids, sustainable and innovative developments, process parameters, machining characteristics, and optimization techniques applied in various dry and near-dry EDM have been illustrated through an extensive literature survey. Future research opportunities in both dry and near-dry EDM have been summarized to promote eco-friendly EDM research activities.

Performance enhancement of rotary tool near-dry EDM process through tool modification

The performance enhancement of the rotary tool near-dry electrical discharge machining (RT-ND-EDM) process by modifying the tool electrode geometry was explored in the present work. The experiments were performed using the tubular tool, slotted tools, and helical tools. The number of slots in slotted tool electrodes and the number of starts in the helical tool electrodes were selected based on the experimental results. Also, the performance of the selected tool electrodes was compared with that of the basic tubular tool electrode. The effects of input parameters (tool rotation speed, current, pulse on time, gas pressure, and the LFR) on the performance of the RT-ND-EDM process are assessed for selected tool electrodes. This research established the efficacy of introducing slotted and helical features into rotating cylindrical tools to enhance the performance of the RT-ND-EDM process. The flushing of the inter-electrode gap is of decisive importance with respect to material removal rate, geometric accuracy, and surface quality of work material during the RT-ND-EDM process. The results revealed that a double-start helical-shaped tool electrode resulted in better process performance among all the selected shape electrodes.

Performance enhancements in powder-mixed near-dry electric discharge machining

Powder-mixed near-dry electric discharge machining (PMND-EDM) process have been attracting attention in the manufacturing community because of its capability to produce the end products with better surface quality characteristics and improved machining rate. Present work is an effort to understand the influence of process variables like tool diameter, flow rate of dielectric mist, concentration of metallic powder and mist pressure of dielectric medium. Taguchi method orthogonal array L9 was used for the conduction of experiments. Analysis of variance (ANOVA) was employed to find out the significance of process parameters. The results reveal that the optimum process parameters for the experimental condition for maximum MRR (0.11 mg s-1)was at tool diameter at A1 (2mm), flow rate of mist at B3 (15 ml min -1 ), concentration of metallic powder at C3 (25 gm l -1 ) and mist pressure of dielectric at D3 (0.6 MPa). It has been also concluded that metallic powder was responsible for surface modification to achieve higher micro-hardness value up to 530.10 Vickers hardness number along with refined surface characteristics.

Thermophysical-Based Modeling of Material Removal in Powder Mixed Near-Dry Electric Discharge Machining

Electrical discharge machining (EDM) is a non-conventional method of machining hard materials with intricate shapes. Near-dry electric discharge machining (ND-EDM) is an advanced method of EDM which is eco-friendly and is more efficient in terms of material removal rate (MRR) than traditional EDM. In this research, an approach has been made to perform a new electrical discharge machining operation on EN-31 steel which utilizes metallic powder as an additive along with a gaseous dielectric (for example air) in ND-EDM. This advanced method of machining is known as powder mixed near-dry EDM. This study involves modeling for output process parameter—Material Removal Rate. The mathematical model was developed using the approach of Gaussian heat distribution. FEM modeling was done on ANSYS WORKBENCH 16.0 module. The experiments were performed and comparative study was done between the results obtained by modeling and experiments. The maximum experimental MRR was 7.68 mm3/min, and the error percentage between experimental, mathematical and FEM was under 30%. It was concluded that the modeling was done successfully and results obtained do comply with the methodology of the research.

Study on the Influence of Metallic Powder in Near-Dry Electric Discharge Machining

Near-dry electrical discharge machining (ND-EDM) is an eco-friendly process. In this study, an approach has been made to make the machining process more efficient than ND-EDM with the addition of metallic powder with the dielectric medium to machine EN-31 die steel. Powdermixed near-dry EDM (PMND-EDM) has several advantages over the ND-EDM or conventional electrical discharge machining (EDM) process, such as a higher material removal rate (MRR), fine surface finish (Ra), sharp cutting edge, lesser recast layer, and lower deposition of debris. The output response variables are MRR, Ra, residual stress (RS) and micro-hardness (MH) of the machined surfaces. Further study of the workpiece was performed, and a comparative study was conducted between ND-EDM and PMND-EDM. In this proposed method of machining, the MRR, Ra, and MH increased by 17.85 %, 16.36 %, and 62.69 % while RS was reduced by 56.09 %.

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.

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.

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.

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.

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.

Near-dry electrical discharge machining of stainless steel

Near-dry electrical discharge machining (NDEDM) has characteristics of high material removal rate (MRR) and low tool wear rate (TWR). NDEDM uses the mixture of air and water as a two-phase dielectric fluid, so it does not produce toxic fumes like conventional EDM which uses hydrocarbon-based oils as the dielectric fluid. Realising all these advantages of NDEDM, it was selected to machine stainless steel. The effect of pulse current (IP), pulse-on time (Ton) and lift setting on NDEDM of stainless steel was investigated. Taguchi's technique was applied to obtain an optimal setting of the process parameters. 'The higher the better' approach was used for MRR as higher MRR is desired. The measured results and subsequent analysis revealed that IP was the only significant parameter. MRR increases with an increase in IP. Also, TWR was found to be negligible in comparison of MRR.

Investigation of the effects of magnetic field on near-dry electrical discharge machining performance

The stability of electrical discharge machining process would be improved by better expelling debris from machining gap. In this investigation, a rotational external magnetic field was applied around machining gap of near-dry electrical discharge machining process to make a new hybrid method for machining of stiff and high-strength parts. The Taguchi method of design of experiments was employed to study the effects of applying magnetic field in near-dry electrical discharge machining process. The experimental results showed that in magnetic field–assisted near-dry electrical discharge machining, material removal rate is more and surface roughness is less than in near-dry electrical discharge machining process without magnetic field, but tool wear rate is a little more. Also, the optical micrographs of the surfaces machined indicated better surface integrity resulted by magnetic field–assisted near-dry electrical discharge machining as compared to near-dry electrical discharge machining process without magnetic field.