Electrical Discharge Machining Technology Research Articles

A comprehensive review of parametric optimization of electrical discharge machining processes using multi-criteria decision-making techniques

Optimization of electrical discharge machining (EDM) processes is a critical issue due to complex material removal mechanism, presence of multiple input parameters and responses (outputs) and interactions among them and varying interest of different stakeholders with respect to relative importance assigned to the considered responses. Multi-criteria decision making (MCDM) techniques have become potent tools in solving parametric optimization problems of the EDM processes. In this paper, more than 130 research articles from SCOPUS database published during 2013–22 are reviewed extracting information with respect to experimental design plans employed, materials machined, dielectrics used, process parameters and responses considered and MCDM tools applied along with their integration with other mathematical techniques. A detailed analysis of those reviewed articles reveals that the past researchers have mostly preferred Taguchi’s L9 orthogonal array as the experimental design plan; EDM oil as the dielectric fluid; medium and high carbon steels as the work materials; peak current and pulse-on time as the input parameters; material removal rate, tool wear rate and surface roughness as the responses; and grey relational analysis as the MCDM tool during conducting and optimizing EDM operations. This review paper would act as a data repository to the future researchers in understanding the stochastic behaviour of EDM processes and providing guidance in setting the tentative operating levels of varying input parameters along with achievable response values. The extracted dataset can be treated as an input to any of the machine learning algorithms for subsequent development of appropriate prediction models. This review also outlines potential future research avenues, emphasizing advancements in EDM technology and the integration of innovative multi-criteria decision-making tools.

Fabrication of robust superhydrophobic surface on TC4 alloy by wire electrical discharge machining

Superhydrophobic metal surfaces have significant applications in various areas such as surface self-cleaning, resistance reduction, anti-corrosion, etc. However, inexpensive preparation methods for superhydrophobic surfaces with a good mechanical stability are still to be developed. In this study, microarray structures on TC4 alloy were readily fabricated using a wire electrical discharge machining technology. Following the treatment with a fluorinating reagent, the microarray surface exhibited excellent superhydrophobic properties, where the largest contact angle and the smallest sliding angle reached 159° and 3°, respectively. Influences of the dimensions of microarray structure on the TC4 alloy surface wettability were also investigated in this study. Experiments show that this superhydrophobic surface possesses favorable self-cleaning, good mechanical stability, and promising anti-corrosion properties. In addition, by controlling the dimensions of the microstructure a superhydrophobic surface with a gradient wettability was also fabricated, which exhibits the property of doing nondestructive transportation of liquids.

Thermal model of crater formation process in electrical discharge machining

The formation mechanism of the discharge crater in electrical discharge machining process is not fully understood, which affects the application of electrical discharge machining technology. In this paper, a thermal-fluid coupling model was proposed by COMSOL Multiphysics software, and the influence of discharge parameters, including peak current, pulse on-time, and the material of tool electrode and workpiece, on crater formation process was analyzed. The temperature distribution, the flow field velocity, heating region, and morphological changes of the discharge crater were analyzed to illustrate the formation mechanism of the discharge crater. By comparing the experimental results with the numerical simulation results, it was found that under the same discharge energy, the peak current has a greater influence on the discharge crater size than the pulse on-time. Moreover, through analysis of the influence of tool electrode materials and workpiece materials, it was found that the crater size is influenced by the boiling point of tool electrode material and the melting point of workpiece material. The experimental and numerical simulation results showed that the simulation results are consistent with the experimental results, which verifies the applicability of the thermal-fluid coupling model in studying the crater formation mechanism in electrical discharge machining.

Machining characteristics in ultrasonic vibration-assisted powder-mixed electrical discharge machining of TiN ceramics

This study aims to investigate the application and machining characteristics of brittle conductive ceramics using ultrasonic vibration-assisted powder-mixed electrical discharge machining (UV-PMEDM) technology. Titanium nitride (TiN) ceramics are widely used in aerospace, biomedicine, and electronics due to their excellent properties. However, the conventional mechanical machining methods of these materials result in severe tool wear, high costs, and low efficiency. Although electrical discharge machining (EDM) can overcome some limitations, it typically exhibits a low material removal rate and poor surface quality. This study utilizes the UV-PMEDM technology to process TiN ceramics. Single-factor experiments are conducted to analyze the effects of processing parameters, including ultrasonic amplitude, powder concentration, pulse-on time, and pulse-off time, on the material removal rate, surface roughness, and relative electrode wear rate, which indicate the EDM processing performance. With the assistance of ultrasonic vibration and mixed powders, the material removal rate of TiN ceramics using UV-PMEDM reaches 0.50 mm3/min, while maintaining a relative electrode wear rate below 1 % and surface roughness lower than 4.2 μm. The synergistic combination of ultrasonic vibration and mixed powders significantly enhances the processing efficiency and reduces surface roughness of TiN ceramics. These findings contribute to a better understanding of machining strategies for brittle conductive ceramics.

Numerical simulation and experimental study of micro-structured surface of sapphire ground by structured grinding wheel

The efficiency and form accuracy of micro-structured surface preparation can be greatly improved by using structured wheels to grind micro-structured surfaces. In this study, the structural design of the grinding wheel surface was first carried out. Then, the geometric analysis of the designed structured 3D model of the grinding wheel is carried out to establish a numerical model for grinding micro-structured surfaces with structured grinding wheels and to investigate the effects of different velocity ratio, grinding depth and dressing angle on the size and distribution of surface microstructures. Finally, the surface of the grinding wheel is structured using wire electrical discharge machining (WEDM) technology, and the microgroove grinding experiment on the sapphire surface is carried out. The research results show that the established numerical simulation can accurately describe the formation mechanism of micro-structured surfaces ground by structured grinding wheels. At the same time, it is found that the shape of micro-grooves on the sapphire surface ground by the structured grinding wheel is basically complete. This further shows that the technology developed in this research can produce the micro-structured surfaces with good quality.

Investigation of Machining Characteristics in Electrical Discharge Machining Using a Slotted Electrode with Internal Flushing.

In die-sinking electrical discharge machining (EDM), it is challenging to implement internal flushing, mainly because it is easy to produce residual material columns on the workpiece cavity's bottom surface, affecting the processing quality and efficiency. In order to solve this problem, the internal flushing slotted electrode EDM technology was proposed. The slotted electrode was designed, and its preparation method was described. The influence of pulse width, pulse interval, and flushing pressure on the performance of the internal flushing slotted electrode EDM was studied using single-factor experiments. The experimental results indicate that, with the increase in pulse width, the material removal rate (MRR) increases first and then decreases, while the electrode wear rate (EWR) and the relative electrode wear rate (REWR) decrease gradually; with the increase in pulse interval, the MRR decreases, while the EWR and the REWR increase gradually; with the increase in flushing pressure, the MRR increases first and then decreases, while the EWR and the REWR increase gradually. When the slotted electrode is used for continuous internal flushing EDM, the appropriate pulse width, flushing pressure, and smaller pulse interval can improve the MRR and reduce the EWR and the REWR.

Formability improvement of hot embossing for functional micro-array structures with a novel exhaust punch

Surface microstructures can endow materials with excellent functions such as enhanced heat transfer. However, with the continuous improvement of function enhancement, it is urgent to develop the manufacturing technology of more complex multiscale functional microstructures. Herein, an exhaust hot embossing based on a novel multi-block assembled punch is developed to fabricate micro-array structures, and the microformability of conventional process and exhaust process is compared. The combined processing technology of slow-feeding wire cut electrical discharge machining and micro electrical discharge machining is adopted to manufacturing the assembled exhaust punch with numerous micro-holes and complex multiscale features. The processing quality of the assembled punch is better than the integrated punch, and the surface roughness of each position of the assembled punch is Ra ＜ 0.2 μm. During hot embossing experiments, it is found that the exhaust process could significantly improve the filling performance. At 300 °C, the exhaust process realizes complete filling of the microstructures under the maximum load of 25 kN, whereas the conventional process requires 50 kN. Meanwhile, it is also found that the exhaust process can significantly improve warping and surface coarsening defects compared to the conventional process. The pool boiling test was carried out on the fabricated micro-array structures, and it was found that its heat transfer performance is significantly enhanced compared with other tested surfaces, which will be applied in enhanced heat transfer.

Ways to improve the efficiency of cooled radiators of electronic equipment manufactured using deep drilling technology

This article discusses the option of increasing the thermal efficiency of cooling radiators for electronic equipment manufactured using deep drilling technology. It is proposed to use electrical discharge machining technology to increase the efficiency of deep drilling channels. In a plate made of aluminum alloy, round holes are drilled along the entire length of the workpiece. Then wire for electrical erosion processing is fed into the round hole, which makes it possible to obtain a cross-section with a larger heat transfer area. The article discusses five options for sections of increased area. The heat removal efficiency for each of the cooling channel cross-section options was considered by modeling in the Solid Works Flow Simulation software environment. Distilled water was used as a coolant. The volumetric coolant flow rate is 0.8 liters per minute. The coolant temperature and the ambient temperature are equal to 25 degrees Celsius. The study considers a 30-watt thermal equivalent. The simulation results show that an increase in the heat exchange area in cooled radiators makes it possible to reduce the thermal equivalent temperature in a steady state, which indicates an increase in the thermal efficiency of the radiator. To confirm the modeling results, test the manufacturing technology and use of radiators with deep drilling, a thermal mock-up was made. Tests of the thermal model were carried out under conditions that best corresponded to the modeling conditions. A comparison of the results of modeling and experiment shows that the values obtained as a result of the experiment exceed the values obtained from modeling in all cases. The excess value ranges from 4.7 degrees to 7.4 degrees and is associated with the presence of an air gap between the copper plate and the radiator plate, the actual value of which exceeds the value of the calculation model. Analysis of the research results shows that the considered method of refining cooling channels obtained by deep drilling does not allow obtaining a qualitative increase in efficiency; the difference between the best and worst results does not exceed 3°C. The benefits obtained by this modification amount to a few degrees, which indicates the limited use of this method.

Effect of Wire Electric Discharge Machining Parameters on Material Removal Rate in Machining of Titanium Grade 7 Alloy

Titanium alloys are widely used in various fields, including the medical field, the automotive and manufacturing sectors. Traditional machining processes are only useful for a limited number of tasks due to the detrimental effects they have on the strength and stiffness of the machined alloys. However, one of the most favoured post-processing equipment used to obtain a high-quality surface is the wire electrical discharge machining (WEDM) technology. The most crucial aspects of WEDM are the rates of the electrical current and voltage, in addition to the pulse-on and pulse-off durations. As a form of wire, WEDM makes use of brass wire that has been zinc-coated. The WEDM method is utilised in the machining of titanium alloy of grade 7 for this project. The surface of titanium grade 7 that had been processed using WEDM was analysed with a scanning electron microscope. The pictures revealed that the material exhibits homogenous solidification and a columnar grain structure along the build direction. As the pulse-on time gets longer, the Material Removal Rate (MRR) also gets higher. When the pulse-on time is set to 60 µs, the greatest MRR that can be achieved is 7.357 mm3/min. As the pulse-off duration gets longer, the MRR is getting lower. At a pulse-off time of 20 µs, the minimal MRR is reached, and it is equivalent to 5.935 mm3/min. At a peak current 6A, the highest MRR is measured is equivalent to 7.795 mm3/min.

Multimethod analysis of three rotary instruments produced by electric discharge machining technology.

This study aimed to compare three rotary instruments produced by the EDM process with the heat-treated ProTaper Gold system regarding design, metallurgy, mechanical properties and shaping ability. HyFlex EDM (25/~), Neoniti (25/.06), EDMax (25/.06) and ProTaper Gold (25/.08v) instruments (n = 58 per group) were compared regarding design, metallurgy and mechanical performance. Unprepared canal areas were calculated for each system after preparation of mesiobuccal, mesiolingual and distal canals of mandibular molars (15 canals per group) using micro-CT technology. Statistical analyses were performed using One-way anova post-hoc Tukey and Kruskal-Wallis post-hoc Dunn's tests (α = 5%). All instruments had asymmetrical blades, no radial lands, no major defects and almost equiatomic nickel/titanium ratios, but different cross-section designs, tip geometries and surface appearances. Although instruments had distinct transformation temperature curves, they showed crystallographic martensitic arrangement at 21°C and mixed austenite plus R-phase at body temperature. Neoniti and HyFlex EDM showed similar results in all mechanical tests (p > .05), while EDMax and ProTaper Gold had similar time to fracture (p = .841), maximum bending load (p = .729), and cutting ability (p = .985). ProTaper Gold showed the highest torque to failure (p < .001) and HyFlex EDM had the lowest buckling resistance (p < .001). Mean percentages of unprepared canal areas ranged from 20.4% to 25.7% in the mesial canals, and from 20.8% to 26.2% in the distal canal, with no statistical differences among systems (p > .05). Instruments' geometry and phase transformation temperatures influenced the results of the mechanical tests, but not their shaping ability.

GEOMETRIC PRECISION OF THE CYLINDERS SURFACES MACHINED WITH WEDM TECHNOLOGY

One of the progressive production technologies through which it is possible to machine complicated shapes in materials characterized by high hardness is electrical discharge machining with a wire electrode. However, as with other progressive technologies, in the case of electrical discharge machining technology, demanding customer requirements for the geometric accuracy of the machined surface are not always met. These errors occur for various reasons. These are, for example, the vibrations of the wire tool electrode, its destruction during the machining process, the setting of technological and process parameters, but also errors in the design of the machine and the software control of the tool path. These and other errors have a primary role in the emergence of geometric inaccuracy of the machined surface after electrical discharge machining with a wire tool electrode. A special problem in the case of electrical discharge technology is the machining of internal and external cylindrical surfaces. As a result of the mentioned causes, deviations occur during their machining, which subsequently cause problems for the manufactured products during their assembly as well as the operation itself. Therefore, the objective of the experimental research was to identify the extent of these geometric deviations on the inner and outer cylindrical surfaces during electrical discharge machining with a wire tool electrode.

Examining the surface roughness and kerf quality of micro-slots cut on the surfaces of Ti-B4C nanocomposites by WEDM: a desirability approach

Micro slots and textures are created on Titanium (Ti) composites to improve its surface characteristics. Micro-textured Ti composites are generally recommended for bio implants, automobile, and aerospace components. In the current research, Ti-B4C nanocomposites were prepared by powder metallurgical route. Micro slots were cut on the Ti-B4C surfaces by Wire Electrical Discharge Machining (WEDM) Technology by varying the current, pulse-ON time, and pulse-OFF time. Scanning electron microscopy and XRD analysis validates the uniform distribution and inclusion of B4C nanoparticles in Ti matrix. Response surface methodology was used to plan the experimental runs. Analysis of variance and desirability analysis were employed to identify the most suitable machining factors for obtaining the minimum surface roughness, lower kerf width and higher material removal rate (MRR). Increase in applied current and pulse-ON time, increases the MRR. Increase of pulse-OFF time from 50 μs to 60 μs gradually reduces the MRR and reduce the surface roughness of the cut slots. Contrastingly an increase in pulse-ON time increases the roughness due to an extensive melting and resolidification of Ti nanocomposites. The morphology of the WEDMed surface reveals the recast layer and localized melting zones on the cut surfaces.

Construction of Multiphase Mixing Interface for Delay Icing Based on Microarray Surface

Slippery liquid‐infused porous surface (SLIPS) is an emerging anti‐icing method. The anti‐icing mechanism of SLIPS is to prevent the heat transfer from liquid droplets to the surface by forming an oil film on the solid surface. However, the contact area between the droplet and the surface of the specimen increases due to the existence of the oil film, which accelerates the heat transfer and emergence of ice. Herein, in order to further improve the anti‐icing performance of SLIPS, a microscale square column array is fabricated by wire cut electrical discharge machining (WEDM) technology, on which a circular hole structure is constructed by nanosecond laser. Lubricating oil is then injected into the fluorinated surface to produce SLIPS. The maximum contact angle (CA) of the surface is 150° ± 1.2° and the contact angle hysteresis (CHA) is 1.2°. The contact mode of droplets on the surface is liquid–oil and liquid–gas, which is a multiphase mixing interface. The icing test shows that the icing time of the droplet is 4785 s at a surface temperature of −10 °C, exhibiting a good icing‐delay performance.

Short communication: Experiment study on micro-textured tool with internal cooling

Abstract. Higher cutting force and its temperature with faster tool wear are the causes of higher production costs and lower machining efficiency. In this paper, with the help of electrical discharge machining (EDM) and laser technology, texture holes are implemented on the rake face and the principal flank face of the tool. The cutting force, friction characteristics of rake face and surface roughness of rake face are compared with the micro-textured cutting tool and the processing technology system of non-textured inner cooling hole. The results show that the coolant can be effectively sent to the interface surfaces due to the internal cooling texture cutter.

Multi-Scale Structure and Directional Hydrophobicity of Titanium Alloy Surface Using Electrical Discharge.

Titanium alloys with special macro-micro composite structures of directional hydrophobicity are difficult to prepare due to poor thermal conductivity and good corrosion resistance, inhibiting the wide engineering applications for aerospace, marine engineering, and biomedicine. To prepare macro-micro composite structures on the surface of titanium alloys and achieve directional hydrophobicity, the sub-millimeter structures with an edge width of 150 μm, a groove width of 250 μm, and a depth of 250 μm were fabricated on the titanium alloy by wire electrical discharge machining (WEDM) technology, and high voltage-induced weak electric arc machining (HV-μEAM) was used to fabricate micro-scale feature size micro-structures on the processed macro-structure edges. The influence of process parameters on the morphology of microstructures was studied experimentally. The smooth surface of the titanium alloy is isotropically hydrophilic, and its contact angle is 68°. After processing the macrostructure on the titanium alloy surface, it shows directional hydrophobicity after being modified by low surface energy materials. The macro-micro composite structure formed by HV-μEAM realizes a directional hydrophobic surface with contact angles (CA) of 140° (parallel direction) and 130° (perpendicular direction), respectively. This surface has been modified with low surface energy to achieve contact angles of 154° and 143°. The results of the abrasion resistance test show that under the load of 100 g, it retains directional hydrophobicity at a friction distance of 700 mm with 600# sandpaper. The existence of the sub-millimeter macrostructure is the reason for the directionality of surface hydrophobicity. The microstructure can realize the transformation of the titanium alloy surface from hydrophilic to hydrophobic. Under the combined effects of the macro and micro composite structure, the surface of the titanium alloy shows obvious directional hydrophobicity.

Approaching ideal energy absorption through the multicellular structure with gradient material distribution

Energy absorption of traditional tubular energy absorbers is restricted by the low structure efficiency, which makes the mean crushing force of the structure usually much lower than its yield strength. The combination of a multicellular design and a gradient-thickness strategy significantly improves the energy-absorption ability of thin-walled energy absorbers while reducing weight. Gradient-thickness multicellular tubes (GTMT) were studied in this paper to demonstrate this advantage. Mechanical performances of GTMT with two material-distribution principles, sample gradient thickness (SGT) and modified gradient thickness (MGT), were investigated experimentally and numerically, primarily in terms of folding behaviors, energy-absorption ability, and load-carrying capacity undulation. Wire-cut electrical discharge machining technology was used to create a series of aluminum alloy specimens that were then compressed under quasistatic loading conditions.Following that, finite element method was used to run detailed numerical simulations. The effect of geometric configuration was determined after conducting parametric studies with different cell density and thickness gradient coefficients. The results showed that, compared to a traditional multicellular tube, a gradient-thickness one with MGT material distribution can improve structural efficiency with a stable loading history. Increases in cell density and thickness gradient coefficient have positive effects on energy-absorption ability; however, excessively high parameter values will lead to global bending deformation and weaken the mean crushing force. Therefore, reasonable parameter matching is vital. The result shows that when the cell density reached 9 × 9 and the thickness gradient coefficient reached 1.4, the mean crushing force was 98.16% of the full-plastic strength of the matrix, and there was no irregular deformation, indicating that ideal energy absorption is almost achieved. These achievements pave a way for achieving ideal energy absorption.

Experimental study on forming consistent accuracy and tool electrode wear involved in fabricating array microelectrodes and array micro holes using electrical discharge machining

Despite the non-contact nature of electrical discharge machining (EDM) process makes it become one of most promising methods to fabricate array micro structures, the low consistent accuracy, serious tool wear and low prepared efficiency has hindered the development and applications of EDM technology in fabricating array micro structures. To fill this gap, the mixture feeding model was firstly introduced to fabricate array microelectrodes by low speed wire electrical discharge machining (LS- WEDM) to balance the contradiction between consistent accuracy and prepared efficiency. Firstly, the contrast experiments of preparing array microelectrodes with various feeding models were conducted, and results indicated that the processing efficiency of square array microelectrodes obtained by mixture model was increased by 36.4% compared to constant velocity model. Besides, the consistent accuracy, corner radius and taper accuracy of square array micro holes were investigated in detail. The effects of lifting model and lifting speed on surface roughness parameters of inner wall of square array micro holes were disclosed. Moreover, the transverse and longitudinal tool electrode wear of square array microelectrodes were qualitatively measured and analyzed, and the mechanism for tool electrode loss involved in preparation of array micro holes in Ni-base single crystal superalloy was revealed. The research results are of great significance for improving the prepared accuracy of array microelectrodes and promoting engineering application of EDM technology in preparing array micro structures.

Prediction and analysis of EDM performances considering random multiple-pulse discharges based on geometric optimization modeling

Continuous electrical discharge machining (EDM) is characterized by random discharge positions, uncertain discharge energy, extremely short discharge time, extremely narrow tool-workpiece gaps, etc. Theoretical research into the mechanisms leading to thermal erosion of material and the associated surface morphology has become urgent to allow the continued development and application of EDM technology. Firstly, multi-pulse theory and geometric optimization are utilized to derive an expression for the material removal rate and surface roughness in multi-pulse EDM. Secondly, based on the characteristics of multi-pulse discharge, a multi-pulse numerical simulation model was established to predict the material removal volume, surface roughness, and thickness of the recast layer. Finally, the results predicted by the geometric and numerical models are compared with the experimental results. Experimentally, 0.176 mg of material is removed in the multi-pulse EDM; the theoretical calculation and numerical simulation of the same produce errors of 5.11% and 11.36%, respectively. The analogous results for the surface roughness are 1.623 μm, 8.93%, and 1.23%. The experimentally determined thickness of the recast layer was 5.31 μm, which corresponds to an error in the simulation error of 7.53%.

Design of a Noncircular Gear Mechanism With Twice Unequal Amplitude Transmission Ratio

Abstract This article proposes a new noncircular gear transmission mechanism with an involute–cycloid composite tooth profile to obtain the twice unequal amplitude transmission of noncircular gears. That is, the instantaneous transmission ratio has twice obvious fluctuations with unequal amplitude in a complete rotation cycle of gear transmission. The twice unequal amplitude transmission ratio curve was designed based on Fourier and polynomial functions, the change law of the Fourier coefficient on the instantaneous transmission ratio was analyzed, and the pressure angle and contact ratio of the involute–cycloid composite tooth profile was calculated. The involute–cycloid composite tooth profile noncircular gear was machined by wire cut electrical discharge machining technology, while its meshing experiment was performed using high-speed camera technology. The results demonstrate that the instantaneous transmission ratio curve value obtained via the high-speed camera experiment was consistent with the simulation value of virtual software. Furthermore, the involute–cycloid composite tooth profile was applied in the seedling pickup mechanism of noncircular gear planetary gear train. The possibility of the application of the involute–cycloid composite tooth profile in the seedling pickup mechanism was verified by comparing the consistency of the theoretical and simulated seedling picking trajectory.

Study of the EDM Process of Bimetallic Materials Using a Composite Electrode Tool.

New types of profile products make complex use of bimetals. These materials possess a set of properties such as strength, corrosion resistance, thermal conductivity, heat resistance, wear resistance. For the processing of such products, it is advisable to use electrophysical processing methods, one of which is the technology of copy-piercing electrical discharge machining (EDM). Currently, EDM is one of the most common methods for processing products from modern bimetal materials. An urgent task is to study the EDM process of bimetallic materials. The aim of the work was to increase the efficiency and accuracy of the EDM process of bimetallic products using electrode-tools with different physical and mechanical properties. Bimetal—weld coated steel backing, base material—09G2S steel, surfacing material—M1 copper were used. The processing of the bimetallic workpiece was carried out on an Electronica Smart CNC copy-piercing EDM machine. EI used graphite, copper, and composite. A theoretical model was developed that allows calculation of the amount of removal of bimetallic material of steel–copper depending on the EDM modes and the ET (electrode tool) material. During the processing of the steel layer, regardless of the EI material, microcracks were formed along the grain boundaries, and during the processing of the copper layer, enlarged holes resulted.