Electrical Discharge Machining Research Articles

Research on the key techniques of composite processing of EDM and vibration ultrasonic drilling

PurposeUtilizing electrical discharge machining (EDM) to process micro-holes in superalloys may lead to the formation of remelting layers and micro-cracks on the machined surface. This work proposes a method of composite processing of EDM and ultrasonic vibration drilling for machining precision micro-holes in complex positions of superalloys.Design/methodology/approachA six-axis computer numerical control (CNC) machine tool was developed, whose software control system adopted a real-time control architecture that integrates electrical discharge and ultrasonic vibration drilling. Among them, the CNC system software was developed based on Windows + RTX architecture, which could process the real-time processing state received by the hardware terminal and adjust the processing state. Based on the SoC (System on Chip) technology, an architecture for a pulse generator was developed. The circuit of the pulse generator was designed and implemented. Additionally, a composite mechanical system was engineered for both drilling and EDM. Two sets of control boards were designed for the hardware terminal. One set was the EDM discharge control board, which detected the discharge state and provided the pulse waveform for turning on the transistor. The other was a relay control card based on STM32, which could meet the switch between EDM and ultrasonic vibration, and used the Modbus protocol to communicate with the machining control software. FindingsThe mechanical structure of the designed composite machine tool can effectively avoid interference between the EDM spindle and the drilling spindle. The removal rate of the remelting layer on 1.5 mm single crystal superalloys after composite processing can reach over 90%. The average processing time per millimeter was 55 s, and the measured inner surface roughness of the hole was less than 1.6 µm, which realized the micro-hole machining without remelting layer, heat affected zone and micro-cracks in the single crystal superalloy.Originality/valueThe test results proved that the key techniques developed in this paper were suite for micro-hole machining of special materials.

Dielectric Fluids for the Electrical Discharge Machining: A Review

An extensive examination of the effect of dielectric properties of the Electrical Discharge Machining (EDM) operation machining variables is being done in the present study. Irrespective of the material's hardness, an EDM is an unconventional thermo-erosion machining procedure. It gave the workpiece a better and more detailed surface topography. Dielectric is an essential EDM component that typically affects the operation's high material removal rate and surface integrity. The dielectric fluid acts as a medium that modulates electrical sparks and traps energy due to the operation. It cleans up the trash and cools the workpiece. Whenever powders like Ti, Si, graphite, Cu, Al2O3, and others are added to the dielectric fluid, the fluid's conductivity increases the micro-hardness of the substance. For executing studies in EDM, choosing a proper dielectric from the number of fluids now offered is crucial. Adopting different additives in the dielectric fluid impacts the optimization of machining parameters and related characteristics are addressed in this study in light of existing research. The studies show the effect on various output parameters.

Growth of α-Al2O3 layer involving abnormal oxides in FeCrAl alloy tube fabricated by WEDM process and electrical insulating performance in fusion reactor blanket

The tubular specimens of FeCrAl alloy APMT (Fe-22Cr-5Al-3Mo) were fabricated by a wire electrical discharge machining (WEDM) process. The oxidation characteristics of the machined surface were investigated by means of the oxidation tests performed in air atmosphere at the temperatures of 1273 K and 1373 K up to 100 h. The abnormal oxides such as CuAl2O4 and ZnAl2O4 were grew on the recast layer which was locally remained on the machined surface even after the mechanical polishing procedure. The α-Al2O3 layer involving the abnormal oxides was formed on the machined surface in the oxidation treatment at 1273 K for 10 h. The apparent electrical conductivity of the layer involving the abnormal oxides was larger than that without the abnormal oxides. Thick Al-rich oxide layer was formed under the abnormal oxides when the oxidation treatment was performed at 1373 K. The apparent electrical conductivity of the oxide layer became lower due to the presence of the thick Al-rich oxide. This oxide layer formed at 1373 K could function as an electrical insulating layer to reduce the magnetohydrodynamic pressure drop in liquid breeder blanket systems of magnetic confinement fusion reactors.

Evaluating the bio-functionalities of Ti-6Al-7Nb alloy after surface modification using electrical discharge machining

The present work evaluates the influence of surface modification on the bio-functionalities of Ti-6Al-7Nb alloy in terms of apatite formation, metal ion release rate and anti-bacterial activities. The surface modification in the form of change in surface integrity, and increases in the exposed surface area, has been achieved using wire-electrical discharge machining (WEDM) and electrical discharge μ-drilling(EDD). Due to high discharge energies, molten material will deposit on the parent material (recast layer), which increases the surface roughness (parent surface 0.5 μm to 2.34 μm) and hardness (patent material 304VH to 385VH) after subsequent re-solidification and quenching. Surface roughness and hardness near the micro-drilled hole are observed to increase. After surface modification, the apatite formation is increased on Ti-6Al-7Nb alloy with increasing immersion time and the ion released rate was found lowest on the WEDMed surface as compared to micro drilled and polished surface. Field-emission electron scanning microscopy (FESEM) and energy dispersive x-ray spectroscopy (EDAX) observations confirmed the presence of phosphate and calcium ions on the WEDMed surface and nearby the micro-drilled surface. The variation in colour of the simulated body fluid (SBF) after the immersion of WEDMed, EDD, and polished samples indicates the variable effecton pH levels of the SBF solution for three types of samples.The anti-bacterial bioactivity of Ti-6Al-7Nb was found to be better on the WEDMed surface as compared to polished surfaces, which is due to the formation of a rutile-TiO2 layer on WEDMed surface.

An investigation on wire-EDM of a biodegradable ZE41A magnesium alloy

ABSTRACT The ZE41A magnesium alloy is a propitious material for biomedical applications since it offers a concoction of good biocompatible and biodegradable properties. The wire cut electrical discharge machining (WEDM) is used for machining magnesium alloys primarily because it can produce products with good dimensional accurateness when compared one-on-one with the traditional machining methods. The kerf width and surface roughness are pivotal response factors heavily impacted by WEDM machining parameters. The current research uses WEDM to machine the biodegradable magnesium alloy ZE41A. The preliminary studies were conducted to identify the range of machining parameters by carefully considering kerf width and surface roughness as the responses. The central composite rotatable design determines the optimal experiments to evaluate the response parameters. Based on a comparative analysis, it is clinched that the flushing pressure is a dominant parameter on both kerf width and surface roughness. The experimental data is further processed to develop an empirical or experimental model for both responses as a function of machining parameters. The corroboration experiments were conducted to test the predictability of the experimental model. The accurateness of the empirical model was examined with the experimental results, and the outcomes were found to be satisfactory.

Influences of single-pulse energy distribution on WEDM cutting efficiency

ABSTRACT In wire electrical discharge machining (WEDM), cutting efficiency is a significant process index whose improvement has always been the research focus. Among the many factors affecting cutting efficiency, discharge energy is the most important factor. Different energy distribution form pulses were obtained by changing the peak currents at single-pulse different discharge stages. Through single-pulse discharge experiments, pulse energy distribution how to impact discharge channel motion characteristics was studied. When the energy distribution is changed through gradually increasing the peak current, an outward-pointing pressure difference will be formed inside the channel, which provides a driving force for the channel to move faster, accelerating the material erosion rate and increasing the discharge crater surface size. The cutting results reveal consistent variations in the cutting efficiency and surface size of individual discharge crater with the pulse energy distribution form. Through changing single-pulse energy distribution, the cutting efficiency can be improved by about 21%.

Application of integrated entropy-COPRAS and ANN approaches for maximizing wire EDM machinability attributes of Al6082-T6/GNP/TiB2 composites

Wire Electrical Discharge Machining (WEDM) utilizes electrical sparks to cut conductive materials precisely. It employs a thin, electrically charged wire to erode the material, creating complex shapes with high accuracy, tight tolerance, and minimal material waste. The current study investigates the effect of WEDM process parameters on the various output properties of machining a hybrid Aluminium metal matrix nanocomposite (HAMMNC). A series of experiments were conducted on a composite constructed using Taguchi’s standard L18 Orthogonal Array (OA) design. The acquired responses of Material-Removal-Rate (MRR), Surface-Roughness (SR), and Kerf-Width (KfW) were optimized using integrated Entropy-COPRAS and artificial neural network (ANN) algorithms respectively. The relative significance ( Qi )values obtained for the alternatives are analyzed with the Taguchi method. The outcomes showed that the optimal setting of WEDM process variables is achieved at Servo Voltage: high volts; Pulse-on-time: 60 μs; Pulse-off-time: 16 μs; Peak Current: 6 Amp; Variable frequency: 18 Hz; Speed: 50 RPM; Sim Speed: 30 RPM respectively. The models developed from ANN were adequate and accurate from the results of error histogram and regression plots and they are best suited for the prophecy of future responses. The surface morphology studies confirmed the appearance of pockmarks, voids, and globules of debris on the Wire EDMed surfaces.

Demonstration of an integrated-heating load frame for quantitatively assessing microscale tensile properties of copper and Zircaloy-2

Small-scale mechanical testing (SSMT) is of great interest in the nuclear materials community as it permits the use of surrogate irradiation techniques, such as ion beam irradiation when investigating the impact of irradiation damage on mechanical properties. The design of a micro-electro-mechanical-system (MEMS) micro-tensile stage is demonstrated to enable micron-sized specimen testing up to failure under ambient and reactor-relevant temperatures. Copper and Zircaloy-2 microscale specimens, having gauge lengths of 200 μm, gauge widths of 48 μm, and specimen-dependent constant gauge thicknesses of 10 μm to 26 μm, are fabricated using micro-wire electrical discharge machining and focused ion beam milling. From each gauge section, microstructure data is captured prior to testing using electron backscatter diffraction analysis, and an optimized digital image correlation speckle pattern is deposited on the specimen surface. The speckle pattern is tracked during deformation and post-processed to obtain strain-field evolution maps throughout deformation. Strain maps provide a means to account for and explain microstructure-dependent features observed in the captured stress-strain curves. The combination of using micro-wire electrical discharge machining, focused ion beam cleaning, and ion beam induced platinum deposition for micron-sized specimen preparation as well as utilizing microfabrication techniques to fabricate an integrated heating microtensile load frame reported herein serve as a demonstration of SSMT approaches that can be adopted to tackle challenging problems in nuclear materials research, including but not limited to the effects of ion beam irradiation on mechanical performance and providing experimental data to support small-scale modeling efforts of embrittling precipitates or radiation-induced segregation.

Artificial neural networks-based modelling of effects of cryogenic electrode treatment, nano-powder, and surfactant-mixed dielectrics on wear performance and dimensional errors on superalloy machining

In the present era dominated by Industry 4.0, the digital transformation and intelligent management of industrial systems is significantly important to enhance efficiency, quality, and the effective use of resources. This underscores the need for a framework that goes beyond merely boosting productivity and work quality, aiming for a net-zero impact from industrial activities. This research introduces a comprehensive and adaptable analytical framework intended to bridge existing gaps in research and technology within the manufacturing sector. It encompasses the essential stages of using artificial intelligence (AI) for modelling and optimizing manufacturing systems. The effectiveness of the proposed AI framework is evaluated through a case study on electric discharge machining (EDM), concentrating on optimizing the electrode wear rate (EWR) and overcut (OC) for aerospace alloy Inconel 617. Utilizing a comprehensive design of experiments, the process modelling through an artificial neural network (ANN) is carried out, accompanied by careful fine-tuning of hyperparameters throughout the training process. The trained models are further assessed using an external validation (Valext) dataset. The results of the sensitivity analysis indicated that the surfactant concentration (Sc) has the highest level of influence, accounting for 52.41% of the observed influence on the EWR, followed by the powder concentration (Cp) with a contribution of 33.14%, and the treatment variable with a contribution of 14.43%. Regarding OC, Sc holds the highest percentage significance at 72.67%, followed by Cp at 21.25%, and treatment at 6.06%. Additionally, parametric optimization (PO) shows that EWR and OC overcome experimental data by 47.05% and 85.00%, respectively, showcasing successful performance optimization with potential applications across diverse manufacturing systems.

Effects of current intensities on material removal rate, electrode wear rate, and surface roughness of machining high carbon high chromium steel

AbstractThe electrical discharge machining is very successful and generally recognized for producing complicated shapes and small openings with exceptional precision. The objective of this study is to assess the impact of different electrical discharge machining parameters on the attributes of the machining process. The evaluation of the machining process was conducted based on the workpiece‘s material removal rate, the rate at which the electrodes wear, and the level of surface roughness. Simultaneously achieving a high material removal rate, low electrode wear rate, and high surface roughness is not possible with a specific combination of approaches due to their contradicting nature. Frequently, it is necessary to independently apply many measures instantaneously in order to assess their impact on various responses. This research investigates the machining of high carbon high chromium steel making use of electrical discharge machining with aluminum, copper, and graphite electrodes. The study focuses on the impact of different current intensities on the rate of material removal, electrode wear, and surface roughness. The experimental results demonstrate that the highest material removal rate (mmcubicmin−1) is achieved at a current density of 12 A when using a copper electrode (54.67), as opposed to aluminum electrode (22.91) and graphite electrode (29.43).

Criticality of volumetric defect structure on fatigue properties of stainless steel 316L fabricated by laser powder direct energy deposition

As one of the significant metal additive manufacturing (AM) processes, laser powder direct energy deposition (LP-DED) has established its role in specific applications, including component repair, coatings, and multi-material structure. However, one of the limiting factors for the wide adoption of LP-DED is the formation of volumetric defects during the printing process. These defects are one of the crucial causes of poor and scattered mechanical properties, especially fatigue performance, by accelerating fatigue crack initiation, growth, and final failure. Unraveling defect structure-fatigue correlations can help understand how defects are affecting fatigue properties, how critical they are, and, finally, what solutions can be utilized to diminish their harmful effects. In this research study, novel defect features, including size features, shape descriptors, and location features, were proposed and investigated regarding fatigue properties in LP-DED. Accordingly, stainless steel 316L (SS 316L) blocks were fabricated by LP-DED. After cutting out the dog-bone samples by wire electric discharge machining (EDM), X-ray Computed Tomography (XCT) and subsequent fatigue tests were conducted. The defect features and their statistical descriptors were extracted from XCT data. By statistical analysis of the features, valuable insights regarding their correlations with fatigue life were realized.

Predicting energy transfer to the workpiece in wire electrical discharge machining using inverse heat transfer technique

Predicting energy transfer to the workpiece in wire electrical discharge machining using inverse heat transfer technique

Exploring the machined surface characteristics of Haynes 25 superalloy: Cost mitigation and quality enhancement perspective

The current study investigates the surface characteristics and machining cost of electrical discharge machining (EDM) of Haynes 25 superalloy using tools made by additively manufactured CuCr1Zr, pure copper and graphite. Before assessing machinability, the workpiece and tool materials were characterized using Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD) and evaluations of tensile strength, micro-hardness, density and thermal conductivity. The effects of current (I), voltage (V), pulse duration (Ton), duty cycle (τ) and flushing pressure (Fp) is analyzed on surface characteristics viz. surface roughness (SR), surface crack density (SCD), recast layer thickness (RCT), heat-affected zone (HAZ), micro-hardness (MH) and machining cost (MC). Post machining XRD analysis revealed the formation of cobalt oxides like (CoO and Co3O4) affecting the micro-hardness of the machined surface. Alongside, a field emission scanning electron microscopy (FESEM) is carried out which confirms, the deposition of metal carbides and oxides on the EDMed surface. Current and pulse-on-time significantly influenced performance, with optimal EDM parameters identified and validated through confirmative experiments, resulting in a mean error of ∼2.84 %. It is seen that the use of additively manufactured CuCr1Zr tools resulted in improved machined surface characteristics and a more cost-effective approach for producing intricate profiles with minimal surface defects.

Application of ANFIS approach for prediction of performance measures in wire electric discharge machining of SAE 1010

Application of ANFIS approach for prediction of performance measures in wire electric discharge machining of SAE 1010

Surface characteristics and machining rate of SS 316L coating developed using hydroxyapatite-mixed EDM process

Hydroxyapatite (HA) or bioceramic-based coatings on stainless steel (SS) 316L significantly enhance the biofunctionality of the base material's surface. However, HA's low thermal conductivity and brittleness limit its effectiveness as a coating material. This study investigates HA coating on SS 316L using electric discharge machining (EDM) with varying discharge energies and powder concentrations. Surface morphology, elemental composition, and phase analysis of untreated and coated samples were characterised using field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD). The results demonstrate that the HA-assisted EDM process creates a coating comprising biocompatible oxides, phosphates, carbides, and intermetallic compounds. The coating exhibits a thin resolidified layer of 10.74 μm, characterised by redeposited spherical debris, shallow cavities, and a surface texture of 2.688 μm. The layer's hydrophilic nature is confirmed by a minimum contact angle of 47.68°. Taguchi analysis indicates that the machining rate is optimised at an HA powder concentration of 16 g/l, with peak current and HA powder concentration being the most influential parameters affecting resolidified layer thickness, surface texture, and wetting angle. The research intends to motivate SS 316L medical device manufacturers to implement the HA-assisted EDM process for bioimplant's dual machining and coating.

Process parameters optimization of EDM for hybrid aluminum MMC using hybrid optimization technique

This study explores how machining parameters affect Surface Roughness (SR), Tool Wear Rate (TWR), and Material Removal Rate (MRR) during Electrical Discharge Machining (EDM) of a hybrid aluminum metal matrix composite (AMMC). The composite includes 6 % Silicon carbide (SiC) and 6 % Boron carbide (B4C) in an Aluminum 7075 (Al7075) matrix. A combined optimization approach was used to balance these factors, evaluating Pulse ON time, Current, Voltage, and Pulse OFF time. Response Surface Methodology (RSM) optimized single responses, while multi-response optimization employed a hybrid method combining the Entropy Weight Method (EWM), Taguchi approach, TOPSIS, and GRA. Analysis of Variance (ANOVA) assessed parameter significance, revealing substantial impacts on SR, MRR, and EWR. Based on TOPSIS and GRA, optimized parameters achieved a desirable balance: high MRR (0.4172, 0.5240 mm³/min), minimal EWR (0.0068, 0.0103 mm³/min), and acceptable SR (10.3877, 9.1924 μm) based on EWM-weighted priorities. Confirmation experiments validated a 15 % improvement in the closeness coefficient, and a 16 % improvement in the Grey relational grade, which considers combined SR, MRR, and EWR performance. Scanning Electron Microscope (SEM) analysis of surfaces machined with optimal parameters showed minimal debris, cracks, and no recast layer, indicating high surface integrity. This research enhances EDM optimization for AMMC, achieving efficiency in machining, minimizing tool wear, and meeting surface quality requirements.

Investigating micro drilling with electrical discharge machining on nickel-based superalloy: effects of electrode material and diameter

Investigating micro drilling with electrical discharge machining on nickel-based superalloy: effects of electrode material and diameter

Investigation on materials removal rate and surface roughness of temperature resisted Waspaloy during electric spark machining utilizing gray relational analysis

Investigation on materials removal rate and surface roughness of temperature resisted Waspaloy during electric spark machining utilizing gray relational analysis

Machinability of gas metal arc based 3D printed Al-Mg 5356 alloy using wire-EDM

Wire-Arc Additive Manufactured (WAAM) is relatively new method of metal 3D printing in which the raw material is heated by the gas metal arc and the molten metal pool is deposited layer-by-layer using a computer numerically controlled axis drive system. Since WAAM needs a finishing process for attaining the final dimensions of the components, there is a need to investigate the machinability aspects of WAAM fabricated materials. This work investigates the machinability of Al-Mg 5356 alloy test samples fabricated by WAAM process using wire-electric discharge machining (Wire-EDM). The test samples were subjected to Wire-EDM and the obtained material removal rate (MRR), kerf width (KW) and surface roughness (Ra) were investigated at different Wire-EDM process settings of voltage, current, pulse-on time (Ton), pulse-off time (Toff) and wire speed (Ws). Statistical analysis revealed that current had a significant influence on MRR. Ton had a strong influence on KW and Ra, whereas Toff exhibited a considerable impact on all these responses. Notably, Ws demonstrated a significant impact on Ra. However, voltage was found to have statistically negligible impact on all the machining responses. Microstructural investigations and compositional analysis were conducted providing valuable information on the cut surfaces. The results derived from the present investigation are useful for predicting the optimum process parameter settings for machining of WAAM-based 3D printed Al-Mg alloy in various manufacturing industries.

Bubble behavior of single-pulse discharge in EDM

The removal of machining debris in the narrow discharge gap primarily relies on high pressure bubble expansion and fluid agitation induced by the bubble pulsation in electrical discharge machining (EDM). Observing bubble behavior and elucidating the mechanism of bubble behavior is an increasing concern in EDM. The purpose of this study is to investigate the bubble behavior of single pulse discharge in EDM. Using a high-speed camera, this study observed the bubble evolution and measured the discharge duration dependent bubble characteristics. The results show that the bubble experiences rapid expansion, contraction, primary pulsation, intense pulsation in the post-discharge process, and subsequent bubble energy dissipation behavior. Furthermore, the arc plasma persists for a duration even after the discharge ends in positive polarity machining. The findings suggest that bubble behavior in single-pulse discharges is primarily dominated by the discharge energy, with the bubble behavior during the discharge significantly influenced by the jumping and oscillation of the arc plasma. Our research may introduce new ideas for improving the depth-to-diameter ratio of deep micro-holes in EDM and provide fresh perspectives on the mechanism analysis of how machining parameters affect machining performance. For instance, by synchronizing the pulse intervals with the bubble stabilization time, bubble coalescence can be reduced, thus increasing bubble removal in the small machining gap. The stability of deep micro-hole EDM may depend on bubble behavior, which is determined by the electrical parameters.