Spark EDM Research Articles

FEM modeling for predicting temperature profile of heat affected zone in single spark EDM process

FEM modeling for predicting temperature profile of heat affected zone in single spark EDM process

Numerical Simulation of Melt-Pool Hydrodynamics in μ-EDM Process

The machining efficiency and productivity of the micro-electrical discharge machining (μ-EDM) process can be enhanced by the fundamental insights on the plasma-material interaction, which can be appraised via experimental and numerical analysis of discharge crater formation. The high-power density with low pulse-duration results in the transformation of the solid workpiece into liquid and even vaporisation phase to generate a crater. The crater dimension largely depends on the extent of vaporization induced recoil pressure as well as the pressure exerted by the expanding plasma channel. Efforts have been made by the researchers to analyse the plasma characteristics viz. its temperature, pressure and the role of plasma pressure on the material removal. However, there is a scarcity of the realistic data pertaining to precise plasma pressure which consequences in less accurate estimation of the numerically simulated crater. Moreover, the extent of evaporation is delayed due to activation of plasma pressure. Therefore, it is imperative to conduct a sensitivity analysis of variation of plasma pressure to improve the predictive nature of three-phase multi-physics numerical modelling of the μ-EDM.In the present paper, an endeavour has been made to consider the multi-phase transformation corresponding to the high-power density applied to the workpiece. Further, the effect of parameters such as Marangoni convection, Young Laplace surface tension pressure, vapour induced recoil pressure and a time-varying plasma pressure on the melt-pool hydrodynamics are considered. A 2D phase-field numerical model for the machining of Ti-6Al-4V has been formulated considering the aforementioned parameters. The numerical model is implemented in the commercial finite element method (FEM) software COMSOL Multiphysics. The simulation results reveal that the material removal in the initial phase of pulse-duration is dominated by vaporisation along with the melt expulsion due to recoil pressure which governs the crater size. The vaporisation of the Ti-6Al-4V is delayed to 4250 K due to active plasma pressure in the melt-pool. In the remaining pulse period, the surface tension induced backflow of molten metal along with Marangoni convection result in non-uniform perturbation at the bottom of the crater. Finally, the simulated crater is validated with the experimentally determined one-off crater using a dedicated single spark EDM circuit.

Investigation on spark electrical discharge machining of Si3N4 based advanced conductive ceramic composites

Ceramics are increasingly being used in aerospace, and have been used in the engineering industry for many years. Because ceramic is generally lighter than metal alloys, EDM has long been used for conductive ceramic materials for their forming complex shaped holes and design of all kinds of industrial applications. Furthermore, a considerable number of engineering challenges can be expected regarding the processing of ceramic materials on a percentage of composition level. In order to examine the investigation of the material removal mechanism and surface topography at a different processing temperature in the limit of high-temperature 1200–1600 °C of silicon nitride (Si3N4) based advanced ceramic composites (ACC) and analyzing various process parameters of spark EDM. Establish the relationship between the geometrical tolerances, crack behavior, Thermal spalling, pores and craters were investigated. Furthermore, the advantage, disadvantage, application, and productivity introduced conductive ceramic composites has been explored. In this work we reviewed the EDM characteristics of Si3N4-TiN and Nickel-Titanium alloys and also comparative analyses of the microstructure; hardness and composition of Electrical discharge machined surfaces were discussed.

Fatigue life and Fracture Morphology of Inconel 718 machined by spark EDM process

Abstract Fatigue life of electric discharge machined and end milled samples of Inconel 718 alloy at high cycle fatigue mode was investigated. The objective of this work is to determine the influence of recast layer formed during the electric discharge machining on the fatigue life of Inconel 718. Data were generated in the fully reversed fatigue mode at ambient temperature using samples fabricated by following ASTM E606 standard. The specimens were machined on a spark electric discharge die sink machine. The specimens were subjected to fatigue, and the resulting fatigue lives and fracture morphology were compared with that of the end milled specimen. The surfaces of the specimens were examined under optical and scanning electron microscopes, and the roughness of the surfaces was measured using a standard surface profilometer. From the results of the investigation, it was concluded that the fatigue life of the samples fabricated by Spark Electric Discharge Machining decreased slightly when compared with that of the end milled sample. The results are explained using the data recorded on recast layer thickness, fracture mechanism observed because of the EDM process, and optical and scanning microscopy.

Effect of recast layer thickness on the mechanical characteristics of INCONEL 718 machined by spark EDM process

An experimental investigation was conducted to determine the effects of the recast layer, formed after the spark EDM, on the strength characteristics of the inconel 718 alloy. The parameters such as peak discharge current, current pulse duration, gap voltage and pulse off time were chosen to study the influence of machining characteristics on the mechanical properties of the material. SEM and EDS studies were used to understand the impact of the recast layer thickness on the mechanical properties of the machined samples.

A Review on Less Tool Wear Rate and Improving Surface Quality of Conductive Ceramic Composites by Spark EDM

Electrical discharge machining is a process for shaping hard metals and forming deep complex shaped holes by spark erosion in all kinds of electro-conductive materials. A study was carried out on the influence of the parameters such peak current, voltage, pulse on time and pulse off time, electrode diameter, emulsion concentration, electrode vibration. EDM researchers are reported for improving the machining characteristics have been categorized as process parameters optimization, multi spark technique, powder mixed EDM.In this paper authors have reviewed the research work carried out in the development of EDM within the past decades for the improvement of machining characteristics such as Surface Roughness and Tool Wear Ratio. The final part of the paper discusses these developments and outlines the trends for future research work.

Numerical simulation of multi-spark electric discharge machining analysis for Ti6Al4V alloy drilling

In this paper a thermal model has been developed for numerically analyzing the multi spark EDM drilling mechanism using finite element methods. The sequential multi electric sparks for drilling process provides heat flux for simulation model. The thermal model also envelopes realistic considerations like effective latent heat of melting, Gaussian heat distribution of heat source, spark radius equation encompassing discharge current and pulse on time, etc for predicting the rate of metal removal and shape of the drilled hole cavity. This developed model has been used to determine the effect of parameters used as input for EDM process like discharge current, voltage, pulse duration and duty cycle on MRR and crater cavity. The impact of discharge energy on MRR is studied and behaviors of crater depth on variance in input operation parameters are examined. The results obtained could be used to carry out experiments and develop an empirical model which could predict results for operation output parameters like MRR, TWR and surface roughness in advance.

Effect of recast layer on the low cycle fatigue life of electric discharge machined inconel 718

The effect of the recast layer formed during electric discharge machining of Inconel 718 on the fatigue life at room temperature was investigated. Data were generated in the uniaxial tension low cycle fatigue (LCF) mode at ambient temperature using flat 5 mm thick tensile specimen prepared as per ASTM E08. Taguchi's L9 orthogonal array is used to derive the experimentation outcomes for 4 different parameters with three levels. The parameters varied are peak discharge current (Ip), current pulse duration (Ton), gap voltage (V) and pulse off time (Toff). Thus machined samples were subjected to fatigue at a selected stress, and the resulting fatigue lives were compared with that of the parent end milled material. The surfaces of the fatigued specimens were examined under optical and scanning electron microscopes, and the roughness of the surfaces was measured using a standard profilometer. Analysis of the results obtained was correlated with the machining parameters and the surface quality obtained from the spark EDM process and the thickness of the recast layer formed during the process. The results obtained from micro hardness measurements, profilometry, optical and scanning microscopy were illustrated.

Optimization of EDM Parameters on Machining Si3N4–TiN Composite for Improving Circularity, Cylindricity, and Perpendicularity

The dominance of the spark eroding process in complex ceramic components has promoted a significant growth analysis in the ceramic composites domain in modern manufacturing industries. The latest developments in ceramic components are concentrated on both the enhancement of the mechanical properties and the machinability of complex 3D parts while using spark EDM. The current (I), pulse on time (Ton), pulse off time (Toff), and dielectric flushing pressure (DP) are considered sparking parameters for the machining of a Si3N4–TiN ceramic composite. These composites find their application in high-temperature environments, viz. metal forming, extrusion dies, turbine blade, and non-ferrous molten metal handling components. Taguchi's orthogonal array (OA), L18, has been used to design the experiments. The optimal machining inputs are determined by the grey relational grade (GRG), which is attained from the grey relation analysis (GRA) for various response characteristics, such as the material removal rate (MRR), tool wear rate (TWR), circularity (CIR), cylindricity (CYL), and perpendicularity (PER). The significant parameters are identified via an analysis of variance (ANOVA). Finally, the optimized process parameters resulting in a higher MRR, lower TWR, lower form tolerance, and decreased orientation tolerance are verified through a confirmation test demonstrating that sparking process responses can be effectively improved.

Optimization of Machining Characteristics in EDM of Si<sub>3</sub>N<sub>4</sub>-TiN Composites by Taguchi Grey Relational Analysis

In this study, Sparking parameters specifically Current (I), pulse on time (ton), pulse off time (toff), spark gap and dielectric flushing pressure (P) are optimized with the consideration of multi responses such as Material Removal Rate (MRR) and Electrode wear Rate (EWR). The characteristic features of the Spark EDM process are explored through Taguchi L18 orthogonal array design of experimental studies with various process parametric combinations. To optimize the above machining parameter, grey relation techniques are used. Based on the grey relation grade, optimum levels of parameters have been identified and major contribution of parameters is determined by ANOVA. Verification test is conducted to validate the test result.

Development of parallel spark electrical discharge machining

This paper describes the development of parallel spark EDM method. In the discharge circuit, the electrode is divided into multiple electrodes, each of which is electrically insulated and connected to the pulse generator through a diode. A capacitor is inserted parallel to each discharge gap between each electrode and workpiece (here workpiece is common for each electrode). Compared with conventional EDM in which only a singular discharge can be generated for each pulse, multiple discharges can dispersively be generated for each pulse in parallel spark EDM. Results of experiments on parallel spark EDM and conventional EDM show that not only is the machining process more stable, but the machining speed and surface roughness can also be improved with parallel spark EDM.