Parametric optimization of multiwalled carbon nanotube-assisted electric discharge machining of Al-10%SiCp metal matrix composite by response surface methodology

The demand for miniaturized products having a glossy surface or nano-level surface is increasing exponentially in automobile, aerospace, biomedical, and semiconductor industries. The mirror-like surface finish has generated a need to develop advanced machining processes. The addition of powder particle into electric discharge machining (EDM) oil is considered a promising technique to achieve surface integrity at the miniaturization level. In this research, the Al–10%SiC_p metal matrix composite (MMC) has been machined after mixing the appropriate amount of multiwalled carbon nanotubes (MWCNTs) into the EDM dielectric fluid. An advanced experimental setup has been designed and fabricated in the laboratory for conducting the experiments. This proposed technology is called nano powder mixed electric discharge machining (NPMEDM). The input parameters of NPMEDM are also optimized using central composite rotatable design (CCRD) based on response surface methodology (RSM) in order to obtain the best surface finish and material removal rate (MRR). The MRR has been increased by 38.22% and surface finish has been improved by 46.06% after mixing the MWCNTs into the EDM dielectric fluid. The results indicate that the combination of parameters A5, B5, C5, and D5 might have produced maximum MRR, whereas A1, B1, C1, and D3 have produced minimum surface roughness (SR).     

An Experimental Study on Electrical Discharge Machining of Manganese-Zinc Ferrite Magnetic Material

The objective of this research is to investigate the machining characteristics of manganese-zinc (Mn-Zn) ferrite magnetic material using electrical-discharge machining (EDM). The material removal rate, the surface topography, the surface roughness, the recast layer, and the chemical composition of the machined surface were studied in terms of EDM processing variables. Experimental results indicate that the morphology of debris revealed the mechanism of material removal. The surface microgeometry characteristics are not always uniform and homogenous and the EDM process produces much damage on the machined surface. The material removal rate, the surface roughness, and the recast layer are proportional to the applied discharge energy.     

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.     

Performance analysis of magnetorheological fluid-assisted electrical discharge machining

In this study, a newly developed method of electric discharge machining has been proposed, which uses magnetorheological (MR) fluid instead of conventional oil like kerosene. The paper aims to reveal the process parameters that affect the material removal rate (MRR) during newly developed EDM process. This hybrid machining process showed dual advantage of high-quality machined surface with improved cutting efficiency. The viscoelastic nature of MR fluid is found to give polishing effect as well as high material removal resulting in more stable processing and improved EDM performance. The experimentation has been performed to determine effect of duty cycle, discharge current, pulse on time, percentage concentration of alumina particles surface roughness, and MRR. It has been found that MRR and surface finish improved significantly. The experimental results demonstrated that the EDM process combined with MR fluid resulted in an increase in MRR and surface finish significantly under a certain limit of carbonyl iron percentage (CIPs) in MR fluid.     

Influence of graphite powder mixed EDM on the surface integrity characteristics of Inconel 625

Surface integrity in electric discharge machining (EDM) has always been a major concern in the manufacturing industry. Although, EDM with a powder suspended dielectric has shown good potential in enhancing the material removal rate and improving surface finish, influence of the same on the overall surface integrity is not very clear. The current work utilized the graphite powder and evaluated its role in combination with concentration and machining parameters, on surface roughness (Ra), surface crack density (SCD), white layer thickness, microhardness depth profile, possible phase changes, and residual stress during powder-mixed EDM (PMEDM) of Inconel 625 (a nickel-based super alloy), that is now-a-days regularly used in aerospace, chemical and marine industries. The results showed that significant reduction in surface roughness, crack density, and white layer thickness is possible with the PMEDM process. It also promoted formation of carbides and other alloy compounds which is responsible for augmentation of hardness in surface and subsurface region. The added particles also caused a decline in tensile residual stress of the machined samples.     

Investigation of magnetic field-assisted EDM of composites

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

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

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

Effect of Crystallographic Anisotropy on Micro EDM Process

In this paper, experiments are conducted by machining from different crystallographic orientations of monocrystalline silicon, and the effects of crystallographic orientation on the micro electrical discharge machining (EDM) process are discussed. The results demonstrate that the machining speed and surface roughness are varied when crystallographic orientation changes. The surface roughness is seen to vary by as much as twofold with crystallographic orientation, while the ratio between the maximum and minimum values of material removal rate is 1.76. The unique material removal mechanism of micro EDM enhances the effects of crystal anisotropy on micro electrical discharge machining process.     

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

Abstract

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

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

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

Performance of Additive Mixed Kerosene–Servotherm in Electrical Discharge Machining of Monel 400™

In general, kerosene and commercial grade EDM oils are conventional dielectric fluids in electrical discharge machining (EDM), despite their poor performance measures being major drawbacks. The aim of this study was to develop a dielectric fluid offering good performance measures in the EDM process, by determining the appropriate proportion of kerosene–servotherm and analyzing its performance with and without the additive concentration in EDM of monel 400?. Sixteen samples of kerosene–servotherm of varying proportions were used in this study. The optimum proportion of kerosene–servotherm was found to be 75:25, which resulted in the highest material removal rate (MRR) as compared with tool wear rate (TWR), and surface finish was found to be poorer than when using kerosene alone. In addition, 1 l of kerosene–servotherm concentrated with 6 g of graphite powder (one micron) exhibited substantial improvement in MRR, surface finish, and TWR compared with conventional dielectric fluids. Therefore kerosene–servotherm (75:25) concentrated with 6 g/l of graphite powder can be accepted as a potential dielectric fluid offering high MRR along with enhanced surface finish in EDM.     

The Feasibility Analysis of Electrical-Discharge Machining of Carbon-Carbon Composites

The objective of this research is to investigate the feasibility of using Electrical-Discharge Machining (EDM) for carbon-carbon composite materials as well as the effects of major machining parameters. The material was machined by electrical-discharge sinker using copper electrode. The mechanism of material removal has been revealed by the morphology of debris. The material removal rate, the surface topography and the recast layer that remains on the workpiece surface were studied in terms of EDM processing variables (e.g., pulse current and pulse duration time). The machined surface showing resolidification was examined by Scanning Electron Microscopy (SEM). A qualitative energy dispersive spectroscopic analyzer was used to measure the amount of migrated alloy in the workpiece and the chemical composition of recast layer. The machining damage, the recast layer, and the mass transfer was proportional to the power input. The EDM process is a feasible method for machining of carbon-carbon composites.     

Electrical discharge machining studies on reactive sintered FeAl

bdElectrical discharge machining (EDM) studies on reactive sintered FeAl were carried out with different process parameters. The metal removal rate and tool removal rate were found to increase with the applied pulse on-time. The surface roughness of machined surface also changed with the applied pulse on-time. XRD analysis of machined surface of sintered FeAl showed the formation of Fe₃C phase during the EDM process. The debris analysis was used to identify the material removal mechanism occurring during the EDM of sintered FeAl.     

Optimization of material removal rate and surface roughness during electric discharge machining of ultra-fine grained Al6082 using Taguchi technique

In the current work, the statistical analysis of various electric discharge machining parameters on Al6082 ultra-fine grained aluminium alloy using Taguchi method has been presented. Repetitive corrugation and straightening (RCS) method was employed to obtain ultra-fine grained aluminium alloy. The electric discharge machining studies were carried out for test variables – pulse off time, pulse on time and current (I). The specimens were machined in dielectric medium with current range of 3 A to 9 A in step of 3 A. Machining features of the samples analysed statistically by adopting the Taguchi's - design of experiments (DOE) methodology. Impact of parameters on material removal rate (MRR) and surface roughness (SR) were examined via signal-to-noise ratio (S/N ratio, expressed in decibel, dB) as well as analysis-of-variance (ANOVA). Outcomes disclose that every selected response explicitly surface roughness (SR) and material removal rate was significantly influenced by parameters. The material removal rate was found to rise with discharge current and decrease with the duration of pulse on time and the duration of pulse off time. On the other hand, the surface roughness increased with increase in peak current and decreased with pulse on time and pulse off time especially. The machining mechanisms were examined by scanning electron microscopy.     

Machining Characteristics of Inconel 718 by Sinking-EDM and Wire-EDM

Inconel 718 superalloy has wide applications in several industries due to its excellent mechanical properties. However, it is very difficult to machine using conventional cutting and grinding because of its high strength at elevated temperatures. Electrical discharge machining (EDM) is an alternative competitive process to machine Inconel alloys by electrical erosion. However, machinability and surface characteristics of EDMed Inconel surfaces are poorly understood. This study focuses on the machining characteristics of Inconel 718 by Wire-EDM and Sinking-EDM with a new Cu-SiC electrode, respectively. Material removal efficiency, surface roughness, surface topography, surface alloying, and electrode wear have been characterized. It is found that the high toughness of Inconel 718 would be the major contributing factor to the absence of microcracks on the EDMed surface. The new fabricated Cu-SiC electrode for Sinking-EDM has better performance in terms of material removal rate (MRR), surface roughness, and electrode wear. The higher melting temperature and fine microstructure of SiC contribute to the lower electrode wear of the new Cu-SiC electrode than the traditional Cu electrode.     

Constrained multi-objective optimization of EDM process parameters using kriging model and particle swarm algorithm

This paper investigates the highly nonlinear relationship between process parameters and machining responses, including material removal rate (MRR), surface roughness (SR), and electrode wear rate (EWR) of electric discharge machining (EDM) using Kriging model. Subsequently, an emerging multi-objective optimization algorithm called particle swarm is used to determine the best machining conditions that not only maximize the machining speed but also minimize the EWR with a constraint of the SR. The experiment was carried out with P20 steel on a CNC EDM machine using copper electrode. The research result shows that the MRR increases sharply when increasing the discharge current just like other researches pointed out. However, the relationship between EWR and current is complicated. EWR appears the minimum value when the current is around 30?A. The speed of change of MRR per unit of EWR is the highest when the SR is around 14.5?µm. The combination of Kriging regression model and particle swarm optimization is considered as an intelligent process modeling and optimization of EDM machining. The proper selection of process parameters helps the EDM operator to reduce the machining time and cost.     

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

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

Slotted electrodes for the improvement of machining performances in EDM drilling

In electrical discharge machining (EDM), poor debris removal may occur under certain conditions. This leads to debris accumulation and degrades machining efficiency. In this study, the rotation and retracting movements of slotted electrodes were coordinated during EDM to realize a pumping effect for expelling debris in the gap between the electrodes and workpieces. The study compared the performance of different slotted electrodes with that of a regular cylindrical (RC) electrode. Moreover, a computational fluid dynamics module was adopted to simulate the effects of the RC and slotted electrodes on debris removal capability in EDM under different conditions. The experimental results demonstrated that among all slotted electrodes, the deep slotted electrode engendered the most-favorable debris removal capability. The deep slotted electrode saved machining time by shortening the electrode jump time or even obviating electrode jumping. This increased the material removal rates by 120%–153% during EDM drilling.     

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

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

Machining of Engineering Ceramics by Ultrasonic Vibration Assisted EDM Method

Ultrasonic vibration assisted EDM was performed by using an ultrasonic machine tool with a d.c. power supply, with its positive and negative poles connected to the workpiece and the tool electrode, respectively. The pulse discharge is produced by the relative motion between the tool electrode and the workpiece. In the working process of this combined technology, ultrasonic machining and EDM are complementary techniques. Experimental results show that the material removal rate is a little more than just the sum of ultrasonic machining and EDM, while surface roughness is about the same as that for ultrasonic machining.