Fluid Of Electrical Discharge Machining Research Articles

MULTI-RESPONSE OPTIMIZATION OF DIELECTRIC FLUID MIXTURE IN EDM USING GREY RELATIONAL ANALYSIS (GRA) IN TAGUCHI METHOD

In the current study, combining the powder with dielectric fluid in electrical discharge machining (PMEDM) is a very fascinating technological approach. This approach is the most effective at increasing both productivity and the quality of a machined surface at the same time. The Taguchi–GRA approach was used to optimize the surface roughness (SR), material removal rate (MRR), and micro-hardness of a machined surface (HV) in electrical discharge machining of die steels in dielectric fluid with mixed powder. Workpiece materials (with 3 levels such as SKD61, SKD11, and SKT4), electrode materials (with 2 levels such as copper, and graphite), pulse-on time, electrode polarity, current, pulse-off time, and titanium powder concentration were all used in the study. The effect on the ideal results was also evaluated using some interaction pairings among the process parameters. Powder concentration, electrode material, electrode polarity, current, pulse-on time, pulse-off time, and Interaction between workpiece material and powder concentration were obtained to be significant in the ideal condition, where larger MRR and HV are wanted (as per the HB criterion), but lower values are desired for the remaining responses, such as surface roughness (SR). Powder concentration was also discovered to be a major component, however, it only accounts for 8.35 percent of the ideal condition. MRR = 54.36 mm3/min, SR = 5.65 m, and HV =832.66 HV were the best quality attributes based on the grey grade.

Feasibility of Jatropha and Rice bran vegetable oils as sustainable EDM dielectrics

ABSTRACT Electrical discharge machining (EDM) is a nontraditional machining process used for machining hard conductive materials by employing an electrically conductive tool and dielectric. In present days, biodielectric fluids are being used as substitutes with some exceptional attributes in EDM. In that context, the objective of the current work is to study the effectiveness of vegetable oil as dielectric fluid in EDM. In this article, experiment has been conducted using Jatropha biodiesel (Jatropha BD), Rice bran biodiesel (Rice bran BD) and EDM oil as dielectric fluid. The experimental results have reported that the material removal rate (MRR) patterns of Jatropha BD and Rice bran BD oil are almost similar to those of EDM oil, whereas in most of the cases, Jatropha BD displays better surface quality than the Rice bran BD oil. However, both the vegetable oils show superior surface quality compared to EDM oil. Evolvements of unhygienic and toxic gases and generation of nonbiodegradable wastes are few of the critical issues for inferior sustainability and biodegradability of dielectrics. Based on the test results of dissolved gas analysis, transesterified Jatropha oil and Rice Bran oil have been introduced as sustainable and biodegradable dielectrics in EDM.

Analysis of kerf accuracy in dry micro-wire EDM

Mineral oil–based liquids are normally used as the dielectric fluid in electrical discharge machining (EDM) where it has the ability in improving the efficiency of the machining process. Nevertheless, these dielectric fluids have the tendency to cause environmental problems. Therefore, as an alternative, gas has been introduced as the dielectric fluid also known as dry EDM (DEDM) process. However, kerf variation in dry micro-wire EDM (DμWEDM) process remains a critical issue. Thus, the objective of this research is to investigate kerf accuracy in DμWEDM. Experimental investigation was carried out on a stainless steel (SS304) with a tungsten wire as the electrode and compressed air as the dielectric fluid using integrated multi-process machine tool, DT 110 (Mikrotools Inc., Singapore). Central composite design (CCD) was used to design the experiment using two controlled parameters: capacitance and gap voltage. Analysis of variance (ANOVA) was used to analyse the results and to evaluate the adequacy of the developed model. The results were obtained by measuring the kerf using a scanning electron microscope (SEM) (JEOL JSM-5600, Japan). The investigation of kerf was divided into two responses which were upper kerf and bottom kerf. Empirical models were developed, and it was found that both parameters (capacitance and gap voltage) have high influence on both responses. The optimum parameters for both minimum upper and bottom kerf were found to be 0.1 nF capacitance and 91 V gap voltage. The developed models were found to be adequate since the percentage error is relatively small (< 3%).

Recent Advances and Perceptive Insights into Powder-Mixed Dielectric Fluid of EDM.

Electrical discharge machining (EDM) is an advanced machining method which removes metal by a series of recurring electrical discharges between an electrode and a conductive workpiece, submerged in a dielectric fluid. Even though EDM techniques are widely used to cut hard materials, low efficiency and high tool wear remain remarkable challenges in this process. Various studies, such as mixing different powders to dielectric fluids, are progressing to improve their efficiency. This paper reviews advances in the powder-mixed EDM process. Furthermore, studies about various powders used for the process and its comparison are carried out. This review looks at the objectives of achieving a more efficient metal removal rate, reduction in tool wear, and improved surface quality of the powder-mixed EDM process. Moreover, this paper helps researchers select suitable powders which are exhibiting better results and identifying different aspects of powder-mixed dielectric fluid of EDM.

Application of TOPSIS to Taguchi method for multi-characteristic optimization of electrical discharge machining with titanium powder mixed into dielectric fluid

Mixing powder into dielectric fluid in electrical discharge machining (PMEDM) is a very interesting technological solution in current research. This method has the highest efficiency in simultaneously improving the productivity and quality of a machined surface. In this study, material removal rate (MRR), surface roughness (SR), and the micro-hardness of a machined surface (HV) in electrical discharge machining of die steels in dielectric fluid with mixed powder were optimized simultaneously using the Taguchi–TOPSIS method. The process parameters used in the study included workpiece materials (SKD61, SKD11, SKT4), electrode materials (copper, graphite), electrode polarity, pulse-on time, pulse-off time, current, and titanium powder concentration. Some interaction pairs among the process parameters were also used to evaluate the effect on the optimal results. The results showed that MRR and HV increased and SR decreased when Ti powder was mixed into the dielectric fluid in EDM. Factors such as powder concentration, electrode material, electrode polarity, and pulse-off time were found to be significant in the optimal indicator (C*) and the S/N ratio of C*. Powder concentration was also found to be the most significant factor; its contribution to C* was 50.90%, and S/N ratio of C* was 51.46%. The interactions of the powder concentration and certain process parameters for C* were found to be largest. The optimum quality characteristics were MRR = 38.79 mm3/min, SR = 2.71 μm, and HV = 771 HV. The optimal parameters were verified by experiment, and its accuracy was good (max error ≈13.38%). The finished machined surface under optimum conditions was also analyzed. The machined surface quality under optimum conditions was good. In addition, the results of the study showed the TOPSIS limitations of TOPSIS in a multi-criteria optimization problem.

Machining characteristics of a hybrid process of EDM in gas combined with ultrasonic vibration

This study integrated the removal mechanisms of electrical discharge machining (EDM) in gas and ultrasonic vibration to explore the benefits of the developed hybrid process in improving the machining characteristics. The developed hybrid process was adopted to determine the machining performances for SKD 61 steel through the experimental investigation. It is well known that using kerosene as a dielectric fluid in EDM would evoke the undesirable problems like fire hazard, air pollution, and environmental damage. In this study, the air, oxygen, and argon gas media were employed in the experiments to investigate the effects on material removal efficiency, surface integrity, and thickness of recast layer. The experimental results show that the hybrid process obtained higher material removal rate (MRR), lower electrode wear rate (EWR), and finer surface roughness (SR). In addition, the oxygen medium could facilitate the reaction within the machining gap to increase the exploding and melting effects. Thus, the MRR obtained by oxygen has the highest values. The argon was an inert gas that could prevent the oxidation during the process, and the lower EWR could be obtained using argon as a medium in the EDM process. The ultrasonic vibration incorporated in the process could effectively reduce the surface defects that were generated on the machined surface. Generally, the different gas media supplied into the machining area could create various mechanisms. The ultrasonic vibration incorporated into the process could also promote the machining performances of the developed hybrid process.

Study of Electrical Discharge Machining Performance in Water-Based Working Fluid

In this study, the role of working fluid in electrical discharge machining (EDM) was investigated based on its electrical conductivity. The function of gas bubble in material removal process was studied by comparing the crater that formed in water discharge with that formed in air discharge. The mechanism of material removal for EDM in water-based working fluid was proposed by analyzing the discharge voltage. Experiments were conducted to learn the influence of discharge parameters and working fluid conductivity on the crater forming process. The detected discharge waveform demonstrated that the effect of electrolytic reaction in the discharge process could be controlled by changing the conductivity of the working fluid. This study shows that water-based working fluid has good application prospects in EDM machining.

Effect of Powder Concentration in EDM Process with Powder-Mixed Dielectric (PMD-EDM)

Ti–6Al–4V is widely used in the aerospace, automobile, and biomedical fields, but is a difficult to machine material. Electrical discharge machining (EDM) is regarded as one of the most effective approaches to machining Ti–6Al–4V alloy, since it is a noncontact electro-thermal machining method, and it is independent from the mechanical properties of the processed material. In electro discharge machining (EDM), dielectric plays an important role during machining operation. The machining characteristics are greatly influenced by the nature of dielectric used during EDM machining. In present paper silicon powder suspended kerosene as dielectric is used to explore the influence of these dielectrics on the performance criteria such as material removal rate (MRR), tool wear rate (TWR) and surface roughness (Ra) during machining of titanium alloy (Ti-6Al-4V). Peak current, pulse on time, pulse off time and concentration of powders added into dielectric fluid of EDM were chosen as process parameters to study the PMEDM performance in terms of MRR, TWR and Ra. The experiments were carried out in planning mode on a specially designed experimental set up developed in laboratory. Response surface methodology, employing a face-centered central composite design scheme has been used to plan and analyze the experiments.

Investigation into effects/Investigating the effects of titanium powder concentrations mixed in dielectric fluid on material machining removal and surface roughness of SKD61 steel after electrical discharge machining by reverse electrode polarity

Electrical discharge machining (EDM) has found widespread applications in tool , mold and aerospace industries. Therefore, enhancement of the quality of the EDM process has become a major research concern. In this paper, the effect of various titanium powder concentrations on the Material Removal Rate (MRR), tool wear rate (TWR), surface roughness (Ra) in powder mixed electrical discharge machining (PMEDM) have been studied. The workpiece is SKD61steel and electrode made from copper with reverse polarity were used in experimental study. The results showed that titanium powder mixed into the dielectric fluid of EDM can enhance MRR without increasing TWR and Ra.

Modeling and analysis of machining parameters for surface roughness in powder mixed EDM using RSM approach

Electrical discharge machining (EDM) is one of the most successful and widely accepted non-conventional machining processes for production of complex shapes with high accuracy irrespective to its hardness by removing material through electrically discharges in the presence of dielectric fluid. The paper presents the state of the art technology of high-performance machining of advanced materials i.e. Powder mixed EDM. In this article, parametric optimization of Surface Roughness (SR) study on the powder mixed electrical discharge machining (PMEDM) of H11 steel has been carried out. Response surface methodology (RSM) has been used for developing, improving and optimizing the experiments. Central composite experimental design was used to estimate the model coefficients of the process parameters. Pulse time on, discharge current and concentration of Aluminum powder added into dielectric fluid of EDM were chosen as process parameters to study the PMEDM performance. Experiments have been performed on newly designed experimental setup and the analysis of variance revealed that the factors peak current and concentration are most influential parameters affecting SR. Keywords: Powder EDM, H11 steel, Modeling, Surface roughness, Response Surface Methodology (RSM).

Machining Efficiency Evaluation of Cryogenically Treated Copper Electrode in Additive Mixed EDM

The present experimental investigations have been carried to evaluate machining efficiency with additive powder mixed in dielectric fluid of electrical discharge machining on Inconel 718 with copper and cryogenically treated copper electrodes. Experiments have been conducted to study the effect of input parameters viz. polarity, type of electrode, peak current, pulse on time, duty cycle, gap voltage, retract distance, and concentration of fine graphite powder on machining efficiency. Machining efficiency is evaluated in terms of tool wear rate (TWR) and wear ratio (WR). The optimum factor/level combination of process parameters has been determined by Taguchi's approach treating performance measure as single objective response. Analysis of variance (ANOVA) is employed to indicate the level of significance of machining parameters for TWR and WR. The recommended optimal process input conditions have been verified by conducting confirmation experiments and significant improvement in TWR and WR is observed.

Effect of chromium powder suspended dielectric on surface roughness in PMEDM process

In this paper, a surface roughness (SR) study on the powder mixed electrical discharge machining of EN8 steel has been carried out. Response surface methodology has been used to plan and analyse the experiments. Average current, pulse on time, diameter of electrode and concentration of chromium powder added into the dielectric fluid of electrical discharge machining were chosen as process parameters to study the powder mixed electrical discharge machining performance in terms of SR. Experiments have been performed on a newly designed experimental set-up developed in the laboratory. An empirical model has been developed for SR. In addition, the recommended model has been verified by conducting confirmation experiments.

Current Research Trends on Dry, Near-Dry and Powder Mixed Electrical Discharge Machining

Electrical discharge machining (EDM) technique has been widely used in modern metal working industry for producing complex cavities in dies and moulds, which are otherwise difficult to create by conventional machining. The process has the advantage of being able to machine hardened tool steels. However, its low machining efficiency and poor surface finish restricted its further applications. To address these problems, one relatively new technique used to improve the efficiency and surface finish is EDM in the presence of powder suspended in the dielectric fluid. Powder mixed electric discharge machining (PMEDM) is one of the recent innovations for the enhancement of capabilities of EDM process. In PMEDM, the electrically conductive powder is mixed in the dielectric fluid of EDM, which reduces the insulating strength of the dielectric fluid and increases the spark gap between the tool and workpiece. As a result, the process becomes more stable, thereby, improving the material removal rate (MRR) and surface finish. Moreover, the surface develops high resistance to corrosion and abrasion. This paper presents the current research trends on dry, near dry EDM and review on research carried out in the area of PMEDM.

Effects of Polymer Particles Suspending in Dielectric Fluid on Surface Roughness of EDM

Suspending powder in dielectric fluid of EDM (electrical discharge machining) has been developed to improve the quality of machined surface recently. The used powders are usually Al, Cu, Cr and so on metal powder because conductive particle can increase the spark gap and improve surface roughness of machined surface. Semi-conductive powder, Si is also utilized for the sake of increasing machining speed. This paper presents a new tryout to suspend polymer particles in the dielectric fluid of EDM. Experimental results show that the EDM process with suspending polymer particles still can be carried out but its surface roughness is not so good in conventional EDM oil. However the conventional EDM oil was taken the replace of silicone oil, suspending polyaniline (PANI-emer) of high molecular weight (Mw~65000) has finer improvement even better than using Si powder. Its surface roughness achieves less than Ra 0.2μm at low concentration and will be decreased gradually with increasing the concentration of PANI-emer (Mw~65000). The surface roughness is Ra 0.14μm when the powders concentration is 10g/l. Even for different type of polyaniline shows different machining characteristics. The surfaces roughness becomes worse when the concentration of low molecular weight PANI-emer (Mw~20000) is higher. An electric-conductive PANI-salt powder has a rapid decrease of surface roughness with increasing its concentration than other materials.

Investigation of emulsion for die sinking EDM

Machining fluid is a primary factor that affects the material removal rate, surface quality, and electrode wear of electrical discharge machining (EDM). Kerosene is the most commonly used working fluid in die sinking EDM, but it shows low ignition temperature and high volatility; if the improper operations are undertaken, it can cause conflagration. Using distilled water or pure water as the machining fluid in EDM, no fire hazard occurs, and the working environment is well; however, using distilled water or pure water as the machining fluid in EDM, the material removal rate of machining large surface is low, and the machine tool is easily eroded. Emulsion-1 and emulsion-2 used as working fluid in die sinking EDM are developed. The compositions of emulsion-1 and emulsion-2 are introduced. In comparison with kerosene, emulsion-1 and emulsion-2 used in EDM show high material removal rate, low surface roughness, high discharge gap, and good working environment. The electrode wear ratio in emulsion-1 is lower than that in kerosene. The electrode wear ratio in emulsion-2 is higher than that in kerosene. The effects of composition and concentration of emulsifier on the emulsion property and EDM performance have been investigated. The comparative tests of EDM performance with kerosene, emulsion-1, and emulsion-2 have been done.

Electrical discharge machining in distilled water

The performances of kerosene and distilled water as the dielectric fluid in electrical discharge machining (EDM) were compared over the pulse energy range 0.72 – 288 mJ. Machining in distilled water resulted in a higher metal removal rate and a lower wear ratio than in kerosene when a high pulse energy range (72 – 288 mJ) was used. With distilled water, the machining accuracy was poor but the surface finish was better. Electron microprobe analysis revealed that the deposition of tool material (copper) on the work surface (high carbon steel) was low when machining took place in distilled water at a high pulse energy (288 mJ) and in kerosene at a low pulse energy (72 mJ). It is concluded that distilled water may be used as a dielectric fluid in EDM at a high pulse energy range.

Effect of the addition of graphite powder to kerosene used as the dielectric fluid in electrical discharge machining

Experimental results reveal that the addition of about 4 g of fine graphite powder (10 μm in average size) per litre of kerosene increases the metal removal rate (MRR) by 60% and the tool wear rate (TWR) by 15% in electrical discharge machining. The wear ratio TWR/MRR is reduced by about 28%. This effect may be attributed to the reduction in the breakdown voltage of the kerosene dielectric caused by the addition of the graphite powder. A scheme of in-process measurement of graphite contamination, based on measuring the clarity of the kerosene with a photodiode, is proposed.

放電加工における加工液の電気濾過

To remove sludge produced in a dielectric fluid during electrical discharge machining, it is a usual practice to use a mechanical filter. The mechanical filter, however, is poor in filtering capacity and tends to be clogged.This paper is concerned with performance of an electrostatic filter utilizing electrophoretic phenomena, illustration of which is made by YASPARK FILTER F-60. This filter, (tank capacity of 60 l and filtering capacity of 20 l/min), removes sludge completely from the fluid in electrical discharge machining on 1.5 kW power supply, making possible continuation of machining with the fluid free from sludge.