Micro-electrical Discharge Machining Research Articles

Mechanism Analysis of Discharge Energy in the Electrostatic-Field-Induced Electrolyte Jet Micro-EDM.

The discharge energy determines the machining resolution, minimum processable feature size, and surface roughness, which makes it a hot research topic in the microelectrical discharge machining (EDM) field. In this paper, a kind of novel discharge-energy-generation method in micro-EDM is investigated. In this method, the opposite induced charges on the electrolyte jet and workpiece serve as the source of the discharge energy. The operating mechanism of this discharge energy is revealed by analyzing the equivalent discharge circuit. The unique discharge current and voltage between the electrolyte jet and the workpiece are sampled and investigated. In contrast with the pulsating energy in conventional EDM, this study shows that the direct current (DC) voltage source can automatically generate a continuously periodical pulsating discharge in the electrostatic-field-induced electrolyte jet (E-Jet) EDM process. After further analyzing the electric signals in a single discharge process, it can be found that the interelectrode voltage experienced a continuous sharp electric breakdown, a nearly unchanging process, and a fast exponential recharging process. The discharge frequency increases as the electrolyte concentration and interelectrode voltage increase but decreases as the interelectrode distance increases. The discharge energy per pulse increases with the increasing interelectrode distance and electrolyte concentration but with the decreasing interelectrode voltage. Finally, the electrostatic-field-induced discharge-energy generation and change mechanisms are revealed, which provides a feasible method for micro-EDM with continuous tiny pulsed energy only using the DC power supply.

Study on the Electrical and Geometrical Parameters of Micro Electrical Discharge Machining

Introduction: Micro-Electrical Discharge Machining (μEDM) is a technique for noncontact machining of conductive or semiconductor materials. It is mainly adapted to machining hard materials. Its principle is based on the creation of electrical discharges between the micro tool and the workpiece, which are immersed in a dielectric. Methods: Methods: It is a complementary process to mechanical or laser micromachining techniques or microelectronics (RIE, DRIE, LIGA). These methods can reach a resolution of 50 nm, but their main drawback is that they are mainly dedicated to silicon. The µEDM process depends on several physical, geometrical, and/or electrical parameters that need to be optimized in order to achieve a resolution lower than 5 µm in a reproducible way. The objective of this paper is to study the effect of the applied voltage VEE and the micro-tool diameter on the machining performances (removed volume, lateral gap, machining depth, and crater shape). Result: Result: The optimal parameters were used during drilling holes. An applied voltage of VEE = 50V was used as an optimal parameter. Conclusion: Concerning the diameter of the micro tool, we propose to use large diameter wires (Φ=250μm; Φ=125μm) during the roughing phase for machining complex structures and small diameter micro tools (Φ=80μm; Φ=40μm; Φ=20μm) during the finishing phase.

Comparative study of micro-die sink and micro-EDM drilled holes for electrode wear and surface roughness

Electrical Discharge Machining (EDM) is one of the most widely used non-traditional machining processes due to its numerous advantages. Since there is a continuous demand for miniaturized components, micro-EDM became a very popular process. The high temperature of melting and vaporization in the machining zone causes uncontrollable electrode wear to occur in the micro-Electrical discharge machining (micro-EDM) process. In the micro-EDM process, it will make a great impact on dimensional accuracy. In this study, a comparison of micro die sinking and micro Electric Discharge drilling processes has been conducted for the three varying levels of parameters for Voltage, Capacitance, and their effect on the Electrode Wear Rate (EWR) and Surface Roughness (Sa) were studied. Then the parameter that is more strongly influencing the unwanted EWR and Surface Roughness was identified and discussed. The maximum percentage change in surface roughness while micro-EDM die sinking and micro-EDM drilling was found to be 66% and 50%. for the given capacitance also 68% and 49% for the given voltage. Similarly, the highest percentage of EWR occurred while micro-EDM die sinking and micro-EDM drilling has been found at 67% and 65% for the given capacitance also 78% and 52% for the given voltage. The erosion of electrode at the bottom surface has been observed before and after the micro-EDM die-sinking and drilling processes.

Investigation on Wire Electrochemical Discharge Micro-Machining.

With the development of MEMS, the machining demand and requirements for difficult-to-machine metal micro parts are getting higher. Microelectric discharge machining is an effective method to process difficult-to-machine metals. However, the recast layer caused by high temperatures in microelectric discharge machining affects the properties of machined materials. Here, we propose the wire electrochemical discharge micro-machining (WECDMM) and develop a new electrolyte system, which removes the recast layer. In this study, the mechanism of WECDMM was elucidated. The electrolyte was optimized through a comparison experiment, and NaNO3-glycol solution was determined as the best electrolyte. The influences of key process parameters including the conductivity of the electrolyte, pulse voltage, pulse-on time and wire feed rate were analyzed on the slit width, standard deviation, the radius of fillet at the entrance of the slit and roughness. Typical microstructures were machined, which verified the machining ability of WECDMM.

Mathematical modeling for radial overcut on powder mixed micro-electrical discharge machining (μ-EDM) of TZM-molybdenum superalloy by response surface methodology

Mathematical modeling for radial overcut on powder mixed micro-electrical discharge machining (μ-EDM) of TZM-molybdenum superalloy by response surface methodology

Sensors-based discharge data acquisition and response measurement in ultrasonic assisted micro-EDM drilling

Micro-electrical discharge machining (μEDM) suffers from the problem of low material removal rate (MRR) and poor surface finish, especially when there are recurring abnormal sparks. Such sparks are mainly due to the accumulation of unflushed debris in the discharge zone resulting in a frequent arcing phenomenon. Vibration assistance to μEDM has proven contributions to the MRR and surface finish enhancement, but the intrinsic information on discharge pulse modification due to the vibration is unclear. The present work proposes a pulse categorization strategy to understand the nature of discharge pulses during the conventional and ultrasonic vibration assisted μEDM. The discharge pulses were acquired at a sufficiently high sampling rate using NI LABVIEW-based data acquisition through an in-house developed pulse discrimination system (PDS). The developed PDS is simultaneously used to estimate the real-time discharge energies of individual pulses and their histograms with the machining progress. The acquired information from the developed PDS is used to justify the variations in discharge energy, discharge frequency, surface roughness and accuracy with increasing machining depth. Vibration assistance to the μEDM process was found beneficial, with an 18% increase in the discharge energy, and a 7.14% reduction in the percentage error in depth. The surface roughness at high-energy settings reduces from 3.2 μm to 0.45 μm because of ultrasonic vibration assistance.

Synergic effect of TMD coating on textured steel using micro-EDM

Modifying the surface of materials through texturing and coating can have a significant impact on their tribological properties. In the present study, a hybrid surface modification process, texturing combined with coating, has been applied to a steel surface and the tribological behavior in lubricated conditions was studied. The surface of the steel was textured using micro-electric discharge machining (micro-EDM) to create two distinct patterns (rectangular and circular). Following this, transition metal dichalcogenides (TMD); tungsten-sulphur‑carbon (WSC) coating was applied to the surface using magnetron sputtering. To evaluate the specimens, they were subjected to tribological testing in various lubrication conditions using a block-on-ring configuration. The results were corroborated using a reciprocating sliding test and compared to those of a smooth uncoated specimen. The findings revealed that the tribological properties of the textured and coated specimens were enhanced, particularly in specimens with circular dimple patterns. The WSC coated circular dimple specimens showed a reduction of the COF by 7–12 %, in the boundary lubrication regime and by 9–25 %, in the mixed and hydrodynamic lubrication regimes as compared to the untreated specimen.

A High Energy Density Pulsed Power Supply for Micro Electrical Discharge Machining of High Aspect Ratio Holes

Abstract In micro-electrical discharge machining (EDM), it is difficult to guarantee machining efficiency and accuracy when further increasing the aspect ratio of microholes due to poor circulation of working fluid and removal of debris. In order to increase the ratio of material vaporization erosion and reduce the ejection of large debris caused by material melting, this study proposes a high energy density pulsed power supply that increases the peak discharge current by adding energy-storage inductors with designed charging and discharging control. Machining microholes of diameters from 100 μm to 200 μm with aspect ratios of 10:1, 20:1, and 30:1 show that when the inductance increases from 4.7 μH to 20 μH, the peak current increases by more than two times and the machining efficiency improves by approximately 30%, and the accuracy of the aperture consistency is enhanced, while the occurrence of microcracks on the machined surface is significantly reduced.

Multi-objective parameter optimization of ultrasonic vibration–assisted micro-EDM of Ti-6Al-4V alloys

Regarding the low machining efficiency and poor surface quality in micro-electrical discharge machining (μ-EDM) of large depth-to-diameter ratio micro-holes, this paper focuses on ultrasonic vibration–assisted multi-objective optimization in μ-EDM to achieve high material removal rate (MRR) and low tool wear rate (TWR). In this work, second-order quadratic models were developed for MRR and TWR, considering the peak voltage (Up), peak current (Ip), pulse width (Width), frequency (Freq.), ultrasonic amplitude (UA), and rotation speed (Rot.) as the machining parameters, using the Plackett–Burman design and Box–Behnken design. The developed models were used for multi-objective optimization by desirability function approach to determine the optimum machining parameters. The optimized parameters were processed for micro-holes, and it was found that the surface quality of the micro-holes was significantly improved.

Surface modification of biodegradable Mg alloy by adapting µEDM capabilities with cryogenically-treated tool electrodes.

Biomaterials are engineered to develop an interaction with living cells for therapeutic and diagnostic purposes. The last decade reported a tremendously rising shift in the requirement for miniaturized biomedical implants exhibiting high precision and comprising various biomaterials such as non-biodegradable titanium (Ti) alloys and biodegradable magnesium (Mg) alloys. The excellent mechanical properties and lightweight characteristics of Mg AZ91D alloy make it an emerging material for biomedical applications. In this regard, micro-electric discharge machining (µEDM) is an excellent method that can be used to make micro-components with high dimensional accuracy. In the present research, attempts were made to improve the µEDM capabilities by using cryogenically-treated copper (CTCTE) and brass tool electrodes (CTBTE) amid machining of biodegradable Mg AZ91D alloy, followed by their comparison with a pair of untreated copper (UCTE) and brass tool electrodes (UBTE) in terms of minimum machining-time and dimensional-irregularity. To investigate the possible modification on the surfaces achieved with minimum machining-time and dimensional-irregularity, the morphology, chemistry, micro-hardness, corrosion resistance, topography, and wettability of these surfaces were further examined. The surface produced by CTCTE exhibited the minimum surface micro-cracks and craters, acceptable recast layer thickness (2.6µm), 17.45% improved micro-hardness, satisfactory corrosion resistance, adequate surface roughness (Ra: 1.08µm), and suitable hydrophobic behavior (contact angle: 119°), confirming improved biodegradation rate. Additionally, a comparative analysis among the tool electrodes revealed that cryogenically-treated tool electrodes outperformed the untreated ones. CTCTE-induced modification on the Mg AZ91D alloy surface suggests its suitability in biodegradable medical implant applications.

Development of AHP-embedded Deng’s hybrid MCDM model in micro-EDM using carbon-coated electrode

Abstract The use of thin film-coated micro-tool electrode introduced a new technical solution to bring the best technical–economic efficiency in the field of non-conventional machining processes. Multi-objective optimization of process parameters in micro-electrical discharge machining (EDM) is very limited with the help of thin film-coated micro-tool, which brought benefits for the industry. In this research work, the technological parameters such as voltage (V), spindle rotation, and capacitance (C) in micro-EDM using carbon-coated electrode were optimized, and Z-coordinate depth of cut and tool wear rate were selected as response variables. Taguchi is combined with Deng’s method to solve this multi-objective decision problem. The results showed that Taguchi–Deng’s method is the right solution for multi-target decision in micro-EDM using the coated electrode. C is the strongest influence on optimal efficiency, and it is the smallest with V. The machining quality under optimal conditions is improved.

Study on surface fabrication and drag reduction performances of gradient hydrophobic aluminum alloy

An underwater superhydrophobic (SH) surface drag reduction is an effective drag reduction method. However, drag reduction failure is likely to occur on the SH surface at high water velocity. To solve this problem, we designed an SH and hydrophilic interphase (SH-H) and gradient SH-H (GSH-H) structure on the surface of aluminum alloy by laser etching and micro-electric discharge machining (EDM) methods. The laser scanning interval of the SH segment was 10 μm while that of the hydrophobic segment was 250 μm. The hydrophilic segment was cut by micro-EDM without laser processing. The SH and hydrophobic segments were treated with fluor silane to obtain surfaces with low surface energy. In this work, the flow field characteristics of the SH-H and GSH-H model with different Re were simulated by setting a sliding wall for numerical calculation. the drag reduction ability of samples for varying Reynold number (Re) were studied in pressure difference drag-reduction channel. The simulation results show that the SH-H structure can still seal a thin gas film at Re = 4000, and has a good drag reduction effect. The experiment results show that the drag reduction on the SH-H surface was up to about 45.45%. Moreover, when soaking in water for 30 min and Re = 3500, the sample surface still had the drag reduction effect, and the prepared SH surface had good mechanical stability. It is expected that this research can provide reference and ideas for solving the problem of gas film loss on the SH surface.

Simultaneous improvement of Z-coordinate and overcut in EDM of titanium grade 5 alloy using a carbon-coated micro-tool electrode

Depth of machining and dimensional accuracy are important parameters in assessing the quality of microelectrical discharge machining (EDM); therefore, enhancement of these two entities is highly essential. The optimal process parameters in microEDM are significantly influenced by the electrode material, which directly affects the machining quality. In this study, depth of machining ([Formula: see text] co-ordinate) and overcut (OVC) in microEDM with carbon-coated electrode were selected; and capacitance ([Formula: see text]), voltage ([Formula: see text]), and rotary tool (RT) were the process parameters. The experimental work was performed on a titanium alloy (Ti-6 Al-4 V) with a thin film-coated microtool electrode. The surface of the tungsten carbide microtool electrode was coated with carbon and the thickness of the coating was approximately five microns. The results show that the Taguchi–multi-objective optimization based on ratioanalysis (MOORA) — analytic hierarchy process (AHP) is the best combination for performing a simple and concise calculation in the machining process; and [Formula: see text] V results in higher machining efficiency with [Formula: see text] pF and [Formula: see text] rpm. Our results show that the quality of the machined surface and machining accuracy in microEDM using coated electrode at optimal parameters are good.

Numerical simulation and experimentation to investigate the performance of powder mixed dielectric in electrical discharge micromachining

In the current work, numerical simulation and experimentation are carried out to investigate the performance of powder mixed dielectric in the electrical discharge micromachining process. Three distinct powders, namely aluminum (electrically conductive), silicon (semi-conductive), and aluminum oxide/alumina (electrically non-conductive) dispersed in the kerosene dielectric, are considered. For a constant applied voltage, a silicon powder particle inserted in the gap immersed with liquid dielectric shows an enlargement in the inter-electrode gap (∼38% and 63% with circular and elliptical powder) compared to the pure dielectric. The enlarged inter-electrode gap increases the machining yield due to improved flushing efficiency. The intensification of the electric field near the particles’ surface lowers the breakdown voltage and charging time of the capacitor for the constant inter-electrode gap, resulting in a decrease in discharge energy per pulse and increased spark frequency. The influence of powder material properties and their sizes on breakdown strength is analyzed. Further, the discharge parameters acquired from the electric field numerical simulation of powder mixed dielectric have been utilized to conduct the numerical simulation of single crater formation with pure dielectric and powder mixed dielectric. The simulated single carters’ dimensions are validated with the experimentally machined single craters. Numerical simulation and experimentation of powder mixed dielectric depict the effectiveness of aluminum oxide powders in addition to silicon and aluminum powders when dispersed in kerosene host dielectric.

Characterization of process parameters in micro EDM on stainless steel

A versatile operational technique called Micro-Electrical Discharge Machining (Micro-EDM) is employed to initiate miniature holes in hard materials to enable efficient conduction in the applications of micro machining. Short-term discharge of electric pulses of a high discharge current between the tool used and the work piece eliminate material on the surface. A study was performed to evaluate the impact of Micro-EDM process characteristics on Stainless Steel 304 with the help of a brass electrode the high utility levels of the metal in several industries. The current study undertakes to experiment with pulse durations of 3 μs, 4 μs, and 5 μs at a current intensity range of 20A with an emphasis on performance measurements including Metal Removal Rate (MRR) and Tool Wear Rate (TWR).This is achieved by drilling 1.0 mm and 1.5 mm micro holes on SS 304. The Taguchi approach uses a mixed 2–3 design to assess the findings. Subsequently, the outcomes of the study of tiny holes related to both diameters are contrasted to determine the significance of factor variables.

Fabrication of Micro-Ball Sockets in C17200 Beryllium Copper Alloy by Micro-Electrical Discharge Machining Milling.

Micro-liquid floated gyroscopes are widely used in nuclear submarines, intercontinental missiles, and strategic bombers. The machining accuracy of micro-ball sockets determined the motion accuracy of the rotor. However, it was not easily fabricated by micro-cutting because of the excellent physical and chemical properties of beryllium copper alloy. Here, we presented a linear compensation of tool electrode and a proportional variable thickness method for milling micro-ball sockets in C17200 beryllium copper alloy by micro-electrical discharge machining. The machining parameters were systematically investigated and optimized to achieve high-precision micro-ball sockets when the k value was 0.98 and the initial layer thickness was 0.024 mm. Our method provided a new way to fabricate micro-ball sockets in C17200 with high efficiency for micro-liquid floated gyroscopes.

Multi-objective optimization in micro-electrical discharge machining using titanium nitride coated WC electrode

Multi-objective optimization in micro-electrical discharge machining using titanium nitride coated WC electrode

Measurement and Metrology in Advanced Manufacturing Processes

New and improved measurement methods are paramount to ensure in-process monitoring of advanced manufacturing processes and quality products. This editorial discusses the outline of the special issue consisting of 15 peer-reviewed manuscripts in the domain of "Measurement and Metrology in Advanced Manufacturing Processes." These research and review articles discuss the relevance, state-of-the-art methods, and ongoing research on the advancement of manufacturing processes with measurements and metrology perspectives by different research groups globally. The significance of measurement and metrology is recognized in various applications such as additive manufacturing, photopolymer jetting, submerged arc welding, micro-electrical discharge machining, and reverse manufacturing.

A Study of Nano-Tungsten Colloid Preparing by the Electrical Spark Discharge Method.

This study developed an energy-enhanced (ee)-micro-electric discharge machining (EDM) system for preparing nano-tungsten (nano-W) colloids. This system enables spark discharge using tungsten wires immersed in deionized water, to produce nano-W colloids. Compared with the chemical preparation method, the processing environment for preparing colloids in this study prevented nanoparticle escape. Among the nano-W colloids prepared using the ee-micro-EDM system and an industrial EDM system, the colloid prepared by the ee-micro-EDM system exhibited a more favorable absorbance, suspensibility, and particle size. The colloid prepared by the ee-micro-EDM system with a pulse on time and off time of 10-10 μs had an absorbance of 0.277 at a wavelength of 315 nm, ζ potential of -64.9 mV, and an average particle size of 164.9 nm. Transmission electron microscope imaging revealed a minimum particle size of approximately 11 nm, and the X-ray diffractometer spectrum verified that the colloid contained only W2.00 and W nanoparticles. Relative to industrial EDM applications for nano-W colloid preparation, the ee-micro-EDM system boasts a lower cost and smaller size, and produces nano-W colloids with superior performance. These advantages contribute to the competitiveness of the electrical spark discharge method in the preparation of high-quality nano-W colloids.

Evaluating the Feasibility of Using Biodegradable Castor Oil as a Dielectric Medium during Micro-Electrical Discharge Machining of Inconel 718

Evaluating the Feasibility of Using Biodegradable Castor Oil as a Dielectric Medium during Micro-Electrical Discharge Machining of Inconel 718