Showing papers on "Electrical discharge machining published in 2016"

Fabrication and Machining of Metal Matrix Composites: A Review

Abstract: Intrinsically smart, metal matrix composites (MMCs) are lightweight and high-performance materials having ever expanding industrial applications. The structural and the functional properties of these materials can be altered as per the industrial demands. The process technologies indulged in fabrication and machining of these materials attract the researchers and industrial community. Hybrid electric discharge machining is a promising and the most reliable nonconventional machining process for MMCs. It exhibits higher competence for machining complex shapes with greater accuracy. This paper presents an up-to-date review of progress and benefits of different routes for fabrication and machining of composites. It reports certain practical analysis and research findings including various issues on fabrication and machining of MMCs. It is concluded that polycrystalline tools and diamond-coated tools are best suitable for various conventional machining operations. High speed, small depth of cut and low feed ra...

A review on material removal mechanism in electrochemical discharge machining (ECDM) and possibilities to enhance the material removal rate

Abstract: The concept of electrochemical discharge machining (ECDM), also known as electrochemical spark machining (ECSM), was presented for the first time in 1968. Since then, this technology remains as research topic and was never explained seriously for industrial applications. The ECDM is a non-traditional machining technology used for machining of electrically non-conducting materials like glass, ceramics, quartz, etc. The literature reveals that the concept of mechanism of material removal in this machining process is not yet understood well. However, phenomena involved in the material removal needs to be investigated well in order to improve the process. In this paper, the concept of mechanism of material removal in ECDM is reviewed till date; scopes for further research have been identified. Possible future efforts to enhance the material removal rate in ECDM are also discussed.

Micro-electro discharge machining drilling of stainless steel with copper electrode: the influence of process parameters and electrode size

Abstract: This article is about the implementation of an acquisition system for the measurement of micro-electro discharge machining process parameters and the statistical analysis of their influence on the process performance. The micro-electro discharge machining drilling of 316L stainless steel with copper tubular electrodes was studied and the exchanged power was taken into account as a comprehensive variable able to represent the effect of the peak current and voltage on the final result. The direct proportionality between the exchanged power and the nominal process parameters was verified. A linear and non-linear regression approach was used in order to obtain predictive equations for the most important aspects of micro-electro discharge machining process, such as the machining time and the electrode wear.

Multi-objective optimization of powder mixed electric discharge machining parameters for fabrication of biocompatible layer on β -Ti alloy using NSGA-II coupled with Taguchi based response surface methodology

Abstract: The success of an implant depends upon surface characteristics like roughness, topography, chemistry and hardness. The fabrication of a hard surface in combination with micron-, submicron- and nano-scale surface roughness is a great challenge for biomanufacturing industries. The surface microhardness (MH) needs to be maximized while controlling the Surface roughness (SR). The present research is the first study in which the application of Non-dominated sorting genetic algorithm (NSGA)-II coupled with Taguchi based Response surface methodology (RSM) is used to predict the optimal conditions of Powder mixed electric discharge machining (PMEDM) parameters to fabricate the biocompatible surface on β-phase Ti alloy. Batch vial tests were first carried out in accordance with the L25 orthogonal array. ANOVA analysis gave the significant influencing factors and then mathematical models were developed between input parameters and output responses like SR and MH using Taguchi based RSM technique. These models were then optimized using NSGA-II to obtain a set of Pareto-optimal solutions. From the series of multiple solutions, the best optimal condition to achieve required low SR and high MH was determined, which are 13 A peak current, 5 μs pulse duration, 8% duty cycle (longer pulse-interval) and 8 g/l silicon powder concentration for achieving a required low SR and high MH. The MH considerably increased about 184% compared to the base material, and about 1.02 μm SR can be achieved in combination with micron-, submicron- and nano-scale surface features.

Assessment of operational feasibility of waste vegetable oil based bio-dielectric fluid for sustainable electric discharge machining (EDM)

Abstract: Since the first application of electric sparks for the material removal was demonstrated, the electric discharge machining (EDM) process has gone through considerable changes in terms of technology and application. The process has surpassed the technological barriers by overcoming its then thought limitations like processing speed, material conductivity, dimensional and geometrical accuracies, and surface finish. However, environmental impact due to release of toxic emission products, operator health concerns due to release of toxic fumes, vapours and aerosols during the process, poor operational safety due to fire hazards and electromagnetic radiation, and toxic and non-biodegradable dielectric waste generated are some of the concerns still prevailing in EDM process. Authors, in this paper, have assessed the operational feasibility of waste vegetable oil (WVO) as possible alternative dielectric fluid and compared the response patterns of WVO with hydrocarbon oil, kerosene. Experiments were performed using spark current, gap voltage, pulse on time (pulse duration) and pulse off time (pulse interval) as control parameters to study the response behaviour for material removal rate (MRR), electrode wear rate (EWR) and tool wear ratio (TWR). The results obtained reveal that WVO-based bio-dielectric fluid can be used as an alternate to hydrocarbon-, water- and synthetic-based dielectric fluids for EDM. Besides the successful trials for operational feasibility assessment, application of bio-fluids offers a cleaner, greener and safer solution for dielectric to improve sustainability of EDM process by improving environmental friendliness, operational safety and personnel health issues of the process. Based on the experimental results and observations, the authors have suggested further scope of works to improve sustainability of the EDM process.

State of the art in powder mixed dielectric for EDM applications

Abstract: Electrical discharge machining (EDM) is a non-conventional machining technique for removing material based on the thermal impact of a series of repetitive sparks occurring between the tool and workpiece in the presence of dielectric fluid. Since the machining characteristics are highly dependent on the dielectric’s performance, significant attention has been directed to modifying the hydrocarbon oil properties or introducing alternative dielectrics to achieve higher productivity. This article provides a review of dielectric modifications through adding powder to dielectric. Utilizing powder mixed dielectric in the process is called powder mixed EDM (PMEDM). In order to select an appropriate host dielectric for enhancing machining characteristics by adding powder, a brief background is initially provided on the performance of pure dielectrics and their selection criteria for PMEDM application follow by powder mixed dielectric thoroughly review. Research shows that PMEDM facilitates producing parts with predominantly high surface quality. Additionally, some studies indicate that appropriate powder selection increases machining efficiency in terms of material removal rate. Therefore, the role of powder addition in the discharge characteristics and its influence on machining output parameters are explained in detail. Furthermore, by considering the influence of the main thermo-physical properties and concentration of powder particles, the performance of various powder materials is discussed extensively. Since suitable powder selection depends on many factors, such as variations in EDM, machining scale and electrical and non-electrical parameter settings, a thorough comparative review of powder materials is presented to facilitate a deeper insight into powder selection parameters for future studies. Finally, PMEDM research trends, findings, gaps and industrialization difficulties are discussed extensively.

Parametric Optimization for Selective Surface Modification in EDM Using Taguchi Analysis

Abstract: This paper introduces selective modification of surface by electric discharge machining process and its parametric optimization A hard layer of tungsten and copper mixture is created at selected area of aluminum surface The process is done using W–Cu powder metallurgical green compact tool and masking technique in die-sinking electric discharge machining (EDM) The modified surface is evaluated by the performance measures such as tool wear rate, material transfer rate, surface roughness, and edge deviation from the pre-defined boundary line of deposited layer by analysis of variance using Taguchi design of experiment Minimum surface roughness of 45 µm and minimum edge deviation of 3729 µm is achieved The hardness of the surface layer is increased more than three times of base metal Overall effects of parameters are also analyzed considering multiple performance criteria using overall evaluation criteria The modified surface is characterized using scanning electron microscopy and energy dispersive

Deposition and Analysis of Composite Coating on Aluminum Using Ti–B4C Powder Metallurgy Tools in EDM

Abstract: The present work investigates the method of depositing a ceramic coating on the surface of aluminum by means of electrical discharge coating (EDC) in electrical discharge machining (EDM). The present study makes use of powder metallurgy (P/M) green compacts made of titanium, boron carbide, and aluminum (Ti + B4C + Al) powder as the EDM tool for surface modification of aluminum workpieces. EDM process was carried out with different tool parameters like composition of the electrode material, compaction pressure of the green compacts, and different settings of the process variables like peak current and pulse duration setting. Responses observed were material deposition rate (MDR), tool wear rate (TWR), and average layer thickness (LT). Experiments were designed and carried out using Taguchi L18 orthogonal array. The most influential parameter for responses MDR, TWR, and LT was found to be peak current (Ip) with a percentage contribution of 60.72%, 59.52%, and 42.09%, respectively. In addition, various other...

Electrical Discharge Machining of Ti6Al4V in Hydroxyapatite Powder Mixed Dielectric Liquid

Abstract: Hydroxyapatite (HA) powder suspension in deionized water was used as a dielectric liquid during electrical discharge machining (EDM) of Ti6Al4V work material. The machined surfaces were evaluated by scanning electron microscopy (SEM), energy dispersive spectroscopy, and optical microscopy. The powder particles in the dielectric liquid extensively migrated and formed an HA-rich layer on the work material surface under specific machining conditions. The result was attributed to the generation of secondary discharges due to altered discharge conditions. The particles divided the primary discharge channel into several secondary ones. When the main discharge channel subdivided into several sub-discharges with comparable energy densities, the particles in the discharge region got stuck among them. Then, they moved toward the melted cavities and penetrated the surface at the end of the discharge duration. The results suggest the process as a practical alternative for producing biocompatible interfaces or coating...

Optimization of process parameters of green electrical discharge machining using principal component analysis (PCA)

Abstract: The objective of this research is to solve the multi-response parameter optimization problems of green manufacturing. A combination of gray relational analysis (GRA) associated with principal component analysis (PCA) method has been developed and has optimized the process parameters of green electrical discharge machining (EDM). The major performance characteristics selected are process time, relative tool wear ratio, process energy, concentration of aerosol, and dielectric consumption. The corresponding machining parameters are peak current, pulse duration, dielectric level, and flushing pressure. Initially, Taguchi (L9) orthogonal array has been used to perform the experimental runs and the optimal process parameters using the GRA approach. The weighting values corresponding to various performance characteristics are determined using PCA. Thereafter, analysis of variance (ANOVA) is applied to determine the relative significant parameter and percentage of contribution of machining parameters; the peak current is the most influencing parameter having 52.87 % of contribution followed by flushing pressure, dielectric level, and pulse duration with 22.00, 21.52, and 3.55 %, respectively. Finally, multiple regression analysis is performed to determine the relationship between machining parameters and performance characteristics. The Fuzzy-TOPSIS and VIKOR methodologies have been used to compare the results of the proposed methodology, and the optimum process parameters obtained are peak current (4.5 A), pulse duration (261 μs), dielectric level (80 mm), and flushing pressure (0.3 kg/cm2).

Surface Roughness and Microhardness Evaluation for EDM with Cu–Mn Powder Metallurgy Tool

Abstract: In the present research, composite electrode (Cu–Mn) manufactured through powder metallurgy has been used to machine hot die steel (H11) by electrical discharge machining (EDM) process with the aim of inducing manganese and carbon into the machined surface. Such alloying is expected to improve the microhardness and other surface characteristics. Best level of process parameters for better surface finish and high microhardness are found using Taguchi method. Six processing parameters are considered and their significance is investigated by analysis of variance. Techniques like energy dispersive spectroscopy, scanning electron microscopy, and X-ray diffraction are used to ascertain the surface characteristics. Surface machined at optimum process conditions for microhardness shows 93.7% improvement due to formation of cementite, ferrite and manganese carbide phases. Surface roughness having Ra value of 3.11 µm has been achieved.

A particle swarm approach for multi-objective optimization of electrical discharge machining process

Abstract: This paper proposes an experimental investigation and optimization of various machining parameters for the die-sinking electrical discharge machining (EDM) process using a multi-objective particle swarm (MOPSO) algorithm. A Box---Behnken design of response surface methodology has been adopted to estimate the effect of machining parameters on the responses. The responses used in the analysis are material removal rate, electrode wear ratio, surface roughness and radial overcut. The machining parameters considered in the study are open circuit voltage, discharge current, pulse-on-time, duty factor, flushing pressure and tool material. Fifty four experimental runs are conducted using Inconel 718 super alloy as work piece material and the influence of parameters on each response is analysed. It is observed that tool material, discharge current and pulse-on-time have significant effect on machinability characteristics of Inconel 718. Finally, a novel MOPSO algorithm has been proposed for simultaneous optimization of multiple responses. Mutation operator, predominantly used in genetic algorithm, has been introduced in the MOPSO algorithm to avoid premature convergence. The Pareto-optimal solutions obtained through MOPSO have been ranked by the composite scores obtained through maximum deviation theory to avoid subjectiveness and impreciseness in the decision making. The analysis offers useful information for controlling the machining parameters to improve the accuracy of the EDMed components.

Investigation of material removal rate and surface roughness in wire electrical discharge machining process for cementation alloy steel using artificial neural network

Abstract: Investigating the effect of process parameters on material removal rate and surface roughness is very important for process planing in wire electro-discharge machining. In this study, wire electro-discharge machining of cementation alloy steel 1.7131 is experimentally studied, then linear regression model and feedforward backpropagation neural network were established to predict surface roughness and material removal rate for effective machining. The full factorial experiment was chosen for experiments. Experiments were performed under different cutting conditions of pulse current, frequency of pulse, wire speed, and servo speed. The optimized neural network with the best performance for prediction had eight neurons in the hidden layer, capability with 0.773 % overall mean prediction error, while 2.547 % errors was revealed by regression model. Totally, the comparison of the results showed that the neural network is more robust with better accuracy.

Effect of Tool Rotation on MRR, TWR, and Surface Integrity of AISI-D3 Steel using the Rotary EDM Process

Abstract: Electric discharge machining (EDM) is an acclaimed non-conventional machining process that is used for machining of hard or geometrically complex and electrically conductive materials which are extremely difficult to machine by conventional methods. One of the foremost demerits of this process is its very low material removal rate (MRR). For this, researchers have proposed some modifications like; providing rotational motion to the tool or workpiece, mixing of conducting fine powders (such as SiC, Cr, Al, graphite etc.) in the dielectric, providing vibrations to either the tool or the workpiece etc.The present research examines how the MRR and tool wear rates (TWR) vary with the variation in the tool rotation speed and their effects on the surface integrity of the workpiece. The results obtained clearly indicate that the tool rotation significantly improves the average MRR up to 49%. Moreover, the average surface finish also gets improved by around 9–10% while using the rotational tool EDM. Due to the too...

Steps towards green manufacturing through EDM process: A review

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

Parametric optimization of electrical discharge machining process on α–β brass using grey relational analysis

Abstract: In the present work, a multi response optimization technique based on Taguchi method coupled with grey relational analysis is used for electrical discharge machining operations on duplex (α–β) brass. Stir casting technique was used to fabricate the duplex brass plates. The mechanical properties of the material are reported. Experiments were conducted with three machining variables such as current, pulse-on time and spark voltage and planned as per Taguchi technique. Material removal rate (MRR), electrode wear rate (EWR), and surface roughness (SR) are chosen as output parameters for this study. Results showed that, peak current and spark voltage were the significant parameters to affect MRR, EWR, and SR as per grey relational grade. The optimal combination parameters were identified as A3B3C2 i.e., pulse current at 14 A, pulse on-time at 200 µs, and voltage at 50 V. Analysis of variance was used for analyzing the results. The confirmation tests were performed to validate the results obtained by grey relational analysis and the improvement was achieved.

Surface crack density and recast layer thickness analysis in WEDM process through response surface methodology

Abstract: In this work, quantitative assessment of surface damage in terms of parameters like surface crack density and recast layer thickness in wire electrical discharge machining (WEDM) process has been u...

Ultrasonic vibration–assisted electric discharge machining: A research review:

Abstract: Ultrasound waves are directly being used in many of the industrial applications including material removal for generating profiles on material surfaces. Trend has been shifted to use ultrasonic sou...

Parametric optimization of EDM process on α–β brass using Taguchi approach

Abstract: In the present work, stir casting route is used to fabricate the duplex (α–β) brass plate. The machineabilty behavior of the (α–β) brass is analyzed during Electrical Discharge Machining (EDM) using Taguchi method. Experiments were conducted with three machining variables such as current, pulse-on time and voltage. Material removal rates (MRR), Electrode wear rate (EWR) and surface roughness (SR) are chosen as the output parameters. Results of SN ratio analysis showed that peak current was significant factor to affect the all the responses. Analysis of variance (ANOVA) was used to identify the contribution of each parameter.

Parametric optimization of MRR and surface roughness in wire electro discharge machining (WEDM) of D2 steel using Taguchi-based utility approach

Abstract: This paper reports the effect of process parameters on material removal rate (MRR) and surface roughness (Ra) in wire electro discharge machining of AISI D2 steel. The wire electro discharge machining characteristics of AISI D2 steel have been investigated using an orthogonal array of design. The pulse on time and servo voltage are the most significant parameter affecting MRR and surface roughness during WEDM process. The simultaneous performance characteristics MRR and surface roughness was optimized by Taguchi based utility approach. The machined surface hardness is higher than the bulk material hardness due to the repetitive quenching effect and contained various oxides in the surface recast layer. The experiments were performed by different cutting conditions of pulse on time (T on ), pulse off time (T off ), servo voltage (SV) and wire feed (WF) by keeping work piece thickness constant. Taguchi L27 orthogonal array of experimental design is employed to conduct the experiments. Multi-objective optimization was performed using Taguchi based utility approach to optimize MRR and Ra. Analysis of means and variance on to signal to noise ratio was performed for determining the optimal parameters. It reveals that the combination of Ton3, Toff1, SV1, WF2 parameter levels is beneficial for maximizing the MRR and minimizing the Ra simultaneously. The results indicated that the pulse on time is the most significant parameter affects the MRR and Ra. The melted droplets, solidified debris around the craters, cracks and blow holes were observed on the machined surface for a higher pulse on time and lower servo voltage. Recast layer thickness increased with an increase in pulse on time duration. The machined surface hardness of D2 steel is increased due to the repetitive quenching effect and formation oxides on the machined surface.