Study of the Effect of Machining Parameters on the Machining Characteristics in Electrical Discharge Machining of Fe-Mn-Al Alloy

In this work we investigated the electrical discharge machining (EDM) of a Fe-Mn-Al alloy. The surface phenomena caused by EDM were studied in terms of machining parameters. An empirical model of the Fe-Mn-Al alloy was also proposed based on the experimental data. Experimental results indicate that the higher the discharge energy, the faster the machining time. This treatment introduces machining damage in the resolidified surface layer and worsens the surface roughness. The optimum pulse-on duration on the basis of the electrode wear ratio for the copper electrode was about 200 μs. The increase of crater depth with the applied pulsed current and pulse-on duration appears minimal under a small input energy.     

Investigations on surface quality of WEDM-manufactured meso bevel and helical gears

This article presents investigations on and analysis of surface finish of meso bevel and helical gears made of stainless steel (SS 304) manufactured by wire electric discharge machining (WEDM) process using thin soft plain brass wire of 0.25?mm diameter. Effects of eight WEDM process parameters, namely, peak current, pulse-on time, pulse-off time, wire feed rate, wire tension, servo-gap voltage, dielectric pressure, and cutting speed on average and maximum surface roughness of the meso bevel and helical gears have been studied by conducting 31 experiments using one-factor-at-a-time approach to identify their optimum ranges/values for further experiments. Tooth profile, microstructure, microhardness, and topography of tooth flank surface have been studied for the best quality meso gears. Average and maximum surface roughness of tooth flank surfaces of meso bevel and helical gears increase with increase in peak current, servo-gap voltage, pulse-on time, wire feed rate, wire tension and cutting speed, and decrease with increase in pulse-off time while dielectric pressure does not significantly influence surface roughness. This work establishes that WEDM process can be an economic and sustainable manufacturing alternative for net-shaped meso-sized bevel and helical gears having better surface finish which will eliminate need of any subsequent finishing processes.     

Characteristic Analysis of EDMed Surfaces Using the Taguchi Approach

The electro-discharge machining (EDM) process plays an important role in manufacturing tools and dies. However, the performance and service life of an EDMed workpiece is greatly influenced by the surface characteristics developed during surface erosion. In this research, the Taguchi method was employed to evaluate the main factors influencing the characteristics of EDMed surface. With an aim to minimizing the formation of defects and obtaining optimum working conditions of EDM.

Analyzed results show that the main influencing factors for hole-enlargement are pulse current, pulse-on duration, and gap voltage. The main influencing factors for surface roughness are the pulse current, pulse-on duration, and specimen materials, while gap voltage is found to have only a negligible effect. Pulse current and pulse-on duration are the most important influencing factors affecting the thickness of the white layer. Estimations and confirmation experiments were performed, verifying the Taguchi predictions.     

Experimental Investigation and Optimization of Micro-EDMing Process for Silicon Substrates

Microelectrical discharge machining of n-type monocrystalline silicon is investigated in this study through a microgrooving process. The pulse duration, pulse frequency, spark current, and gap voltage are varied in the experiments. The groove geometries and roughness are measured together with the material removal rate and electrode wear ratio. The results have shown that a large and deep groove can be made at high machining rate when a high spark energy condition is applied. This can, however, increase the electrode wear ratio as a consequence, making the process inefficient. A multiresponse optimization, using Grey relational analysis, has been applied. The optimum cut result has shown that good cut quality, high material removal rate, and low electrode wear ratio are achievable from this study.     

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.     

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.     

EDM with an Air-Assisted Multi-Hole Rotating Tool

In the present research work, an extensive experimental study of air-assisted rotary electrical discharge machining (AAEDM) of high chromium, high carbon die steel has been made. Investigations have been performed to study the process factor effect namely pulse-on time, discharge current, duty cycle, tool rotation, and air pressure on material removal rate (MRR) and electrode wear ratio (EWR). A comparative analysis of solid rotary tool electrode electrical discharge machining (REDM) and AAEDM has been presented. It was found that a high MRR and low EWR occurred in AAEDM as compared to the REDM process, under the same processing conditions. Use of a multi-hole tool provided better circulation of dielectric in the discharge gap, thus it improved the flushing efficiency of the process. The results showed that the application of compressed air has a favorable influence on MRR and EWR.     

Machinability of titanium alloy through electric discharge machining

Titanium alloy (Ti-6Al-4V), being considered as hard-to-machine material, offers many challenges especially during conventional machining. Electric discharge machining could be a good option if it offers a good match between material removal rate and surface finish of the machined feature. The issue of appropriate selection of electrode material for good machining of Ti-6Al-4V is not yet comprehensively explored which is the core focus of this study. Moreover, the effect of pulse time ratio is thoroughly examined which is not specifically studied before. Discharge current and pulse time ratio are considered as the input variables, whereas the material removal rate and surface roughness are selected as performance measures of machinability. Copper, aluminum, brass and graphite are employed to evaluate the machining behavior. Experimental results revealed that aluminum electrode provides the lowest surface roughness, whereas the maximum material removal rate is achieved using graphite electrode. However, graphite electrode can offer high material removal rate with low surface roughness by initially employing negative tool polarity for rough machining and then positive tool polarity for fine machining.     

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.     

Investigation of the Tool Wear Rate in Tungsten Powder-Mixed Electric Discharge Machining of AA6061/10%SiCp Composite

This paper presents the experimental investigation on tool wear rate (TWR) in powder-mixed electrical discharge machining (PMEDM) of aluminum 6061 alloy reinforced with 10% silicon carbide particles (AA6061/10%SiC_p composite). Composite material is fabricated by mechanical stir casting process and further characterized by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Tungsten powder with concentration of 4 g/L is mixed in the dielectric fluid. To know the influence of powder suspension in dielectric fluid on TWR, comparative study is done on the basis of experiments performed using basic EDM and PMEDM process. Experiments have been designed as per central composite rotatable design (CCRD) using response surface methodology (RSM) approach. Four process parameters, namely, peak current, pulse-on time, pulse-off time, and gap voltage have been considered for TWR investigation. Individual and interactive influence of various parameters on TWR is explained with the help of analysis of variance and three-dimensional graphs. Using RSM approach, results have been further optimized. PMEDM approach provides 51.12% reduction in TWR for machining of AA6061/10%SiC_p composite.     

Experimental Analysis of Al–TiC Sintered Nanocomposite on EDM Process Parameters Using ANOVA

The size minimization of titanium carbide (TiC) particles was done by high-energy mechanical milling. Later Al and TiC powders were mixed to frame cylindrical preforms with 95% density using a die set. The cylindrical preform was sintered in a muffle furnace (575°C) and subsequently cooled. Characterization was done using scanning electron microscope (SEM), field emission scanning electron microscope, and energy-dispersive spectrum. An electrical discharge machining (EDM) and L9 orthogonal array was used to perform the experiments. The present investigation was carried out to optimize parameters such as current, pulse-on time, and gap voltage on metal removal rate (MRR) and tool wear rate (TWR) during EDM of as-sintered Al–5% reinforced with ≤200 nm and 2 µm TiC particle reinforcement. The rationality of the experimental plan and the effect of electrode wear ratio based on TiC particle addition were analyzed using analysis of variance (ANOVA) with consideration to MRR and TWR. The recast layer evolution during EDM process was assessed by SEM analysis.     

Optimization of cryo-treated EDM variables using TOPSIS-based TLBO algorithm

In order to machine hard and high-strength-to-weight ratio materials, electrical discharge machining (EDM) process is extensively used in aerospace, automobile and other industrial applications. However, high erosion of tool and improper selection of machining variables have emerged as a major obstruction to achieve productivity in this direction. High erosion of tool not only enhances the cost of machining but also increases the machining time by causing interruption during machining. Therefore, proper selection of machining variables and tool material life are the two vital aspects for the tool engineers working in EDM. In view of this, the present work proposes an extensive experimental investigation and optimization of machining variables of cryogenically treated brass tool materials on machining competences of Inconel 718 workpiece. The study primarily highlights the outcome of cryogenically treated soaking duration of tools along with other important process variables, viz. discharge current, open-circuit voltage, pulse-on time, duty factor and flushing pressure, on the performance measures such as electrode wear ratio (EWR), surface roughness and radial over-cut. The study revealed that soaking duration in deep cryo-treatment of the electrode is a significant variable to achieve improved machining characteristics. The performance measures are converted into equivalent single performance measure by calculating the relative closeness coefficient by the techniques for order preferences by similarity to ideal solution (TOPSIS) approach. Finally, a novel teaching–learning-based optimization (TLBO) algorithm has been proposed to find the optimal level of machining variables for the performance measures. The optimal levels of cutting variables obtained through the algorithm are validated through confirmation test, predicting an error of 2.171 percentages between the computational and experimental results. The predicted result suggests that the proposed model can be used to select the ideal process states to achieve productivity for the cryo-treated EDM.     

Examinations concerning the electric discharge machining of AZ91/5B4CP composites utilizing distinctive electrode materials

In this study, investigation has been conducted in the focus of obtaining better surface finish in the electro discharge machining (EDM) of AZ91/5B₄C_p magnesium composites using distinctive sort of anode viz. copper, tungsten–copper, brass, aluminum and 20Gr/AA6061 (GRAL-20) composites. The process parameters, pulse on time and current were performed to research the machining qualities through material removal rate (MRR) and tool wear rate (TWR). The machined composites were examined by optical microscopy (OM) and scanning electron microscopy (SEM). The formation of black spots was observed on machining with copper–tungsten and these black spots were not found when GRAL-20 was used as electrode. Machined with GRAL-20 electrode leads to the increase in spark gap, hence adequate flushing occurs; it eliminates re-melted layers on machined surface results in better surface roughness value. The results revealed that GRAL-20 electrodes posses better MRR followed by copper electrode whereas tungsten–copper exhibits better TWR followed by GRAL-20 electrode.     

Effect of Cryogenic Cooling of Tool Electrode on Machining Titanium Alloy (Ti–6Al–4V) during EDM

The discharge characteristics and discharge gap of machining Ti–6Al–4V titanium alloy by cryogenically cooled tool electrode electrical discharge machining (EDM) in distilled water were investigated in this study using the monopulse discharge method. The influence of the cryogenically cooled tool electrode on the discharge gap and the initial maintaining voltage between the electrode and workpiece were analyzed under various temperatures. Test results showed the initial maintaining voltage of the cryogenically cooled tool electrode EDM was lower than that of conventional EDM. The discharge gap of the cryogenically cooled tool electrode EDM was also smaller than that of conventional EDM, which improved the copying accuracy of die-sinking EDM. A comparative experiment of machining Ti–6Al–4V titanium alloy was carried out by using cryogenically cooled tool electrode EDM and conventional EDM, lower electrode wear, higher material removal ratio, and higher corner size machining accuracy was obtained by using cryogenically cooled tool electrode EDM.     

Application of multi-criteria decision making methods for selection of micro-EDM process parameters

Ti-6Al-4V super alloy is an important engineering material with good strength to weight ratio and a wide range of applications in a number of engineering fields because of its excellent physical and mechanical properties.This work determines optimum process parameters such as pulse on time,peak current,gap voltage and flushing pressure,which influence the micro-electro discharge machining(EDM) process during machining of Ti-6A1-4V using combined methods of response surface methodology(RSM) and fuzzy-technique for order preference by similarity to ideal solution(TOPSIS).Central composite design(CCD) is used in the experimental investigation.A decision making model is developed to identify the optimum process parameters in the microEDM process,which influences several machining criterions such as material removal rate(MRR),tool wear rate(TWR),overcut(OC) and taper.Triangular fuzzy numbers are used to determine the weighting factor for each process criterion.Further a fuzzy-TOPSIS method is used to select the most desirable factor level combinations.The proposed technique can be used to select optimal process parameters from various sets of combinations of process parameters in a micro-EDM process.     

Hole Quality and Damage in Drilling Carbon/Epoxy Composites by Electrical Discharge Machining

This study investigates the material removal mechanisms and machining damage in drilling of carbon fiber epoxy composite by electrical discharge machining (EDM). Detailed investigation of the morphology of the machined surfaces and elemental analysis were conducted inside a scanning electron microscope. Machining damage was characterized by the extent of delamination, hole taper, and the average width of the heat-affected zone (HAZ). The effect of pulse-on time and gap current on machining damage was also investigated. It was found that material removal occurred mainly in the form of decomposition of the polymer matrix and thermally induced fracture of the carbon fibers. Vaporization of the carbon fibers due to spark and Joule heating is also a possible mechanism. The width of HAZ was found to be influenced the most by pulse-on time where the minimum HAZ occurred for intermediate pulse-on time. Furthermore, the width of HAZ and hole taper in EDM were found to be comparable to or less than those obtained by laser cutting.     

Electrical Discharge Machining of Functionally Graded 15-35 Vol% SiCp/Al Composites

A functionally Graded 15-35 volume% silicon carbide particulate (SiC_p) reinforced Al359 metal matrix composite (SiC_p/Al MMC) was drilled by electrical discharge machining (EDM) to assess the machinability and workpiece quality. The machining conditions were identified for both the machining performance and workpiece quality of the EDM process, including some aspects of material removal mechanisms, material removal rate (MRR), electrode tool wear, and subsequent drilled hole quality including surface texture and roundness by using surface profilometry, coordinate measuring machine (CMM), and scanning electron microscopy (SEM). It was observed that the material removal rate increases with increasing peak current and pulse-on-time up to the optimal points and drops drastically thereafter. Higher peak current and/or pulse-on-time result in both the greater tool wear and the larger average diameter error. As the percentage of the SiC particles increases, MRR was increased and electrode wear was found to be decreased. At the EDM machined subsurface layer, the fragmented and melted SiC particles were observed under the SEM and EDX-ray examination.     

Experimental studies on electrical discharge wire cutting of Ni-rich NiTi shape memory alloy

The experimental investigation explores the effect of electrical discharge wire cutting (EDWC) variable parameters such as spark gap voltage, wire tension, pulse off time, wire feed rate, and pulse on time on the surface roughness, average cutting rate, and metallographic changes of Ni_55.95Ti_44.05 shape memory alloy (SMA). The spark gap voltage, pulse off time, and pulse on time have the significant effect on the surface roughness and average cutting rate, whereas wire tension and wire feed rate have the trifling effect. Ni_55.95Ti_44.05 SMA’s surface after EDWC is characterized by many discharge craters, microcracks, voids, and white layer of resolidified molten material. The elemental composition analysis of white layer using energy-dispersive spectroscopy divulges the deposition of the foreign element from the brass wire as well as the dielectric on the surface after EDWC. The machined surface as well as the wire electrode surface consists of various compounds of Ti, Ni, Zn, and Cu which have been identified by X-ray diffraction peak analysis.     

Powder Mixed Dielectric: An Approach for Improved Process Performance in EDM

The present study reports the outcome of experiments conducted to investigate the effect of parameters on improvement in the material removal rate (MRR), reduction in the tool wear rate (TWR), and overcut size for commonly used die steels. To overcome some of the shortcomings of electric discharge machining (EDM), an approach of powder mixing in dielectric fluids is adopted to investigate the influence of process parameters. The addition of powders in dielectric improves MRR and lowers TWR significantly. Powder concentration, current, and pulse-on time are three significant factors affecting MRR, TWR, and overcut size. An increase in powder concentration improves the process performance, but is limited by the possibility of arcing at higher concentration. Use of the powder resulted in increased effective spark length causing larger overcut. The problem is acute in trials conducted at high pulse-on duration with high powder concentration that leads to a ragged surface at cut edges. Furthermore, electrode tools with smaller tip included angle resulted in larger profile deviation at the machined surface as compared to trials conducted using tools with higher included angle. Surface morphological changes, grain size, microstrain, and material migration were investigated using SEM, XRD, and EDS analysis and a significant improvement in properties of the machined surface was observed.     

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.