Interelectrode Gap Research Articles

A novel maglev μ-EDM and its signal processing for machine condition monitoring on duplex stainless steel (DSS-2205)

This article introduces an innovative servo gap control mechanism for the micro-electrical discharge machining (µ-EDM) process. Magnetic levitation serves as the foundation for innovative gap control. Here, the magnetic force (Fem) is made balanced to gravitational force (Fg) and spring restoring force (Fs) to achieve a state of equilibrium. The equilibrium state of these forces provides the essential condition for the machine’s stability and fast positioning response. The system is empowered with a dedicated direct current power source and triggered with a spring-supported actuator arm. The oscillation of the actuator arm plays a crucial role in inducing dielectric straining within the narrow interelectrode gap. Later, the machining practicability and performance were tested by conducting preliminary experiments on duplex stainless steel (DSS-2205) in deionized water. The results indicate that the material ablation rate (MAR), tool ablation rate (TAR), average surface roughness (SR) and specific energy (SE) fall within the ranges of 117.6–223.8 μg/min, 10–29 μg/min, 1.614–2.370 µm, and 0.5396–0.9356 J/µg respectively. Furthermore, the system’s stability and health were evaluated through signal processing of the voltage-ampere (V-I) characteristic. It was found that the system maintains the proper gap efficiently and stably for the manifestation of regular discharge. The proposed solution may be a good alternative for servo gap control in μ-EDM.

INFLUENCE OF THE INTERELECTRODE GAP WIDTH ON THE QUALITY OF FOCUSING OF ELECTROSTATIC MIRRORS WITH ROTATIONAL SYMMETRY

The influence of the width of the interelectrode gap on the focusing quality of electrostatic mirrors with rotational symmetry, the electrodes of which are coaxial cylinders of equal diameter separated by gaps of finite width, has been studied. Formulas, convenient for the numerical calculation of the exact values ​​of the axial potential distribution in such mirrors, are proposed. Using the obtained formulas in numerical calculations and taking into account the width of the interelectrode gap, the geometric and electrical parameters of two- and three-electrode mirrors were determined, which provide spatial focusing of beams of charged particles simultaneously with the elimination of time-of-flight chromatic aberrations and spherical and axial chromatic spatial aberrations, the most important factors in terms of influence on the resolution of time-of-flight mass spectrometers and electron microscopes. It is shown that the width of the interelectrode gap has a significant effect on the quality of focusing of electrostatic mirrors with cylindrical electrodes.

Eco-Friendly Vibration-Assisted Electrochemical Polishing of Surfaces Generated by Wire Electrical Discharge Machining

The study demonstrates an in-house developed eco-friendly vibration-assisted electrochemical polishing (ECP) process, where the electrolyte flushing with the squeezing action of the vibrating tool eliminates the electrolytic by-products in the inter-electrode gap (IEG). A two-dimensional numerical model is developed to study the squeezing effect on changing bubble faction, anodic dissolution, and current density distribution. The effect of process parameters such as current density, electrolyte flow velocity, IEG, vibration amplitude of the tool, and vibration speed is analysed based on the experimental design matrix of response surface methodology (RSM) for minimising average surface roughness (Ra) of SS 304 component fabricated by electrical discharge machining. The numerical results indicated an increased flow velocity at IEG due to the vibration, resulting in an effective flushing of generated gasses. Current, IEG, vibration speed of the tool, vibration amplitude, and interaction between current-IEG, current-vibration speed, and IEG-vibration speed are identified as the most influential parameters by implementing the analysis of variance. The parameters are optimised using RSM, leading to a 96.71% reduction in Ra value and a 62.54% lower Ra value than the ECP without vibration, indicating the effectiveness of vibration-assisted ECP to achieve a high surface finish using eco-friendly electrolytes.

Mathematical modelling and experimental investigation of inter-electrode gap in vibration-assisted micro-EDM dressing

ABSTRACT Micro-electrical discharge machining (Micro-EDM) dressing with vibrating arrayed pre-drilled holes tool-plate can effectively improve the process stability and processing performance. But there is still a lack of systematic research on the specific effects of tool-plate vibration and ranges of amplitude and frequency. A mathematical approach is discussed along with experimental validation to explain the mechanism of contaminated dielectric fluid evacuation during tool-plate vibration-assisted and also how inter-electrode gap (IEG) is dynamically affected by vibration parameters. Tool-plate mostly allowed to vibrate axially (vertically) either to fabricate single or arrayed micro-rod(s), but most debris flush out radially. The proposed simplistic mathematical model quantitatively estimates the effect of axial vibration amplitude and frequency that are put by the tool-plate on the dielectric fluid, which is eventually flushing out from the IEG in radial direction. The amplitude and frequency of contaminated dielectric fluid carrying debris increase by 15 and 4.5 times, respectively, when moving radially, compared to when moving axially. The experimental study concludes that vibration amplitude from 0.65 µm to 4.41 µm improves normal pulse frequency by up to 52% and reduces spindle load by 50%. Additionally, performance measures such as mass of material removed exceed by 65% and area surface roughness enhanced by 60%.

Bottom-up designing nanostructured oxide libraries under a lab-on-chip paradigm towards a low-cost highly-selective E-nose

BackgroundThe multisensor concept has been developed as a powerful alternative to well-known gas-analytical instrumentation for applications where a fast but accurate and reliable assessment of the environment is required. The concept follows a biology-inspired approach where the selectivity towards various gases/odors is attained via pattern recognition of multisensory signal vectors. Herein, we discuss how to design a selective multisensor library based on various metal oxide nanostructures like a lab-on-chip using a simple but efficient bottom-up growth of materials over the multi-electrode chip under robust dc electrochemical protocols. ResultsIn addition to a conventional growth of oxide layers over the metal electrodes, we show that the fine nanowall-like oxide structures appear as a quasi-matrixed percolation film over the SiO2 substrate surface in the inter-electrode gaps to constitute a chemiresistive film. We have tested two directions while applying the technique to grow Co, Ni, Mn, and Zn oxides to develop on-chip sensor arrays of, (i) monoxide type employing the oxide films with gradual change of growth time, and (ii) multi-oxide type based on the four oxides. The materials were thoroughly characterized by electron microscopy, X-ray diffraction, thermogravimetric analysis, and X-ray photoelectron spectroscopy/mapping to prove the composition and structure. Among tested oxides, ZnO readily appears not only at the electric potential-targeted chip zone but also in other areas to dope the films for yielding heterojunctions with other oxides that enhances a variability of functional properties in the on-chip sensor array. The gas-sensing performance of the chips has been tested versus various chemically akin alcohol vapors at the sub- and low ppm range of concentrations in a mixture with air. SignificanceWe show that the grown oxide nanostructures exhibit a high-sensitive chemiresistive signal which allows one to build a multisensor vector signal, selective to the kind of alcohols, even at sub-ppm concentrations. Moreover, the multi-oxide library yields options for a superior selectivity under LDA metrics than the gradient-grown mono-oxide one due to the versatility of materials while the low-cost growth protocols remain to be the same in both cases. The delivered method to produce multisensor arrays allows one producing low-cost but efficient electronic nose units for numerous applications.

Fabrication of Die Sink Electrochemical Machining Tools Using Low Melting Fusible Alloy and Polymer Based Additive Manufacturing

The present work introduces a novel approach to fabricating die-sink tools for electrochemical machining (ECM) using low-melting fusible alloy and additive manufacturing. Three methods are proposed, each bettering the previous in manufacturing sustainability. The versatility of the process enables the fabrication of die-sink ECM tools that are hitherto considered challenging to fabricate. Finite element analysis was used to simulate the temperature rise of the low-melting (50 °C) tool due to Joule heating, accounting for electrolyte flow under various process parameters. A novel validation method employed a thermostat temperature probe as a cathode. Experiments based on the simulation data revealed that for a 4 mm tool diameter, the tool is unlikely to melt at 3 A current, 200 μm inter-electrode gap, 11.97 S m−1 electrolyte conductivity, and 1.7 m s−1 electrolyte velocity. A pulsed power supply was subsequently used to improve heat dissipation, and ECM was successfully carried out using tools of various shapes, demonstrating the effectiveness of the developed fabrication methods.

Increasing the Efficiency of Thermoelectric Conversion of Solar Energy

The article considers the latest achievements in the field of thermionic conversion of solar energy. The key aspects of thermionic emission, the problems of reducing the electrode work function and increasing the efficiency of devices are analyzed. It is shown that diamonds doped with phosphorus can be an attractive material for the purposes of thermionic emission. In this case, the presence of donor states can significantly narrow the space charge region, and at the same time reduce the potential barrier in the work function. The studies also found that the most successful and widely used method for overcoming the space charge effect is filling the interelectrode gap with cesium. The efficiency of thermionic conversion devices for solar energy increases by 1.6 times. Particular attention is paid to the use of new materials, such as nanostructures and carbon nanotubes, as well as promising technologies, such as photonic enhancement of thermionic processes. The analysis of the results showed that the photonic enhancement of the electron yield due to illumination is greater in p-type silicon, as predicted by theoretical models. The thermionic current increases by 1.7 times compared to silicon. The distance between the quasi-Fermi level and the Fermi level in n-type silicon is less than this distance in p-type silicon. As a consequence, the number of electrons in the conduction band is smaller. Methods for combating the space charge effect and optimizing the configuration of energy conversion systems are discussed.

Pulse dynamic regulation of electrochemical discharge milling by utilizing the slotted tube electrode

Electrochemical discharge machining (ECDM) has a splendid application potential for machining difficult-to-cut materials. It is a challenge to limit and control the discharge energy and area of DC power supply in ECDM. Owing to the uncertainty and randomness of the position and range of the single discharge, the unpredictable discharges deteriorate the surface quality of the workpiece, alter the size of the inter-electrode gap (IEG), and influence the distribution of the multi-physical fields. Therefore, to regulate the machining state and energy, the ideology of pulse dynamic machining is introduced, and a method of pulse dynamic ECDM utilizing the slotted electrodes is proposed. With the tool electrode rotating, the tube electrode transforms the pure electrochemical machining (pure-ECM) stage and the electrochemical discharge machining (ECDM) stage periodically through the slots at the bottom of it. The machining current waveform, surface roughness and sidewall taper of machined grooves, material removal rate (MRR), and relative tool wear rate (RTWR) are investigated. Additionally, the discharge types of the ECDM are explicitly defined and statistically classified. The experimental results show that the pulse dynamic regulation of hybrid machining using the slotted electrodes is beneficial to regularize the machining current waveform and optimize the machining quality.

An experimental study on heat transfer using electrohydrodynamics (EHD) over a heated vertical plate.

The Corona effect offers significant potential for improving heat transfer efficiency in air. This study thoroughly examined how a single corona discharge affects heat transfer on a heated vertical flat plate. Key parameters tested included corona voltage, the aspect ratio of the vertical plate (y/L), and the inter-electrode discharge gap ratio (x/d). The findings revealed that increasing the corona voltage and decreasing the discharge gap enhanced heat transfer efficiency along the vertical surface. A predictive formula for the local Nusselt number was developed to characterize heat transfer on the plate. Additionally, Particle Image Velocimetry (PIV) was used to analyze the corona wind generated by the discharge. The study observed that the corona wind formed a vortex in the upstream region, which resulted in lower heat transfer rates upstream compared to the downstream region.

Effect of Aqueous Electrolyte Composition on Efficiency of Electrochemical Post-Processing of Additive Manufacturing Products from Ti-6Al-4V Alloy Obtained by Selective Electron Beam Melting

The influence of the anionic composition of an aqueous electrolyte on the efficiency of the electrochemical leveling of the initial microgeometry of samples obtained by the selective electron beam melting (SEBM) at the following mode parameters was studied: current density – 20 A/cm2, initial interelectrode gap – 0.3 mm, average speed of electrolyte pumping – 12 m/c. Aqueous solutions of sodium chloride, nitrate, perchlorate and bisalt electrolytes based on them were studied. It was that aqueous solutions of sodium perchlorate have the best microleveling properties among the studied working media, which provides the ability to reduce the parameters Ra and Rz from values of 35 and 180 μm, respectively, to values of 3.2 and 20 μm during electrolysis of 30 s in a direct-flow electrolyzer. It was established that the microgeometry leveling corresponds to the model of the secondary distribution of dissolution rates; two main factors were identified that significantly influenced on the result: polarization of the electrodes and a decrease in the oxidation state of metal ions passing into the solution during electrochemical machining in the vicinity of the depression in relation to the protrusion due to changes in the local conditions of electrolysis. Microetching along grain boundaries in the studied electrolytes was not detected at the accepted parameters of the electrolysis mode.

Efficient evolution mechanism of electrolytic gas products from laser-assisted electrolyte jet machining

Efficient evolution of electrolytic gas products is one of the mechanisms for increased material removal rate in laser-assisted electrolyte jet machining. However, the evolution mechanism of electrolytic gas products with multiple energy fields in laser-assisted electrolyte jet machining is not clear. In order to quantitatively characterize the laser-assisted facilitation of the evolution of electrolytic gas products, a gas quantification and detection device was designed and built in this paper. Compared to traditional electrolyte jet machining, laser-assisted electrolyte jet machining of 2024-T3 aluminum alloy increased the gas production by 52 % in 180 s. For the anode, the surface modification induced by laser texturing reduces the oxygen evolution potential and surface free energy and promotes gas nucleation and detachment. In addition, laser-induced conductive plasma can enhance transient currents for electrolyte jet machining and cause machining vibrations. The cathodic gas discharge phenomenon was characterized in conjunction with interelectrode gap visualization experiments and cathodic nozzle damage. Experimental results show that cathodic gas discharge depends on strong electric field and high laser pulse fluence. In summary, laser temperature rise, anode surface modification, laser-induced plasma, plasma recoil and cathode gas discharge can all contribute to the evolution of electrolytic gas products.

Experimental Analysis and Hybrid-Optimization of Micro-ECDM Process Parameters to Enhance Micro-Machining Performances of Silica by Gaussian-Quantum-PSO

Nowadays, hybridization of different algorithms for the optimization of non-conventional machining processes tries to accomplish better results. The paper consists of experimental evolutionary-particle Swarm Optimization (PSO), Quantum-PSO and Gaussian Quantum Particle Swarm Optimization (G-QPSO)-based ANN modeling and comparative investigation on performances such as material removal rate (MRR), machining depth (MD), roughness of surface and overcut (OC) for machining of silica by ECDM process using mixed electrolyte. The paper also shows the co-efficient of NN models for different machining criteria and G-QPSO and also the comparative study of MD, roughness (SR), overcut (OC) as well as MRR using different algorithms and convergence test for fitness of experimental results also propounded to achieve cross-validation of models and multi-response optimal results for micro-machining of Silica by ECDM using PSO, QPSO and GQPSO. It is found that Gaussian Quantum Particle Swarm Optimization (G-QPSO)-ANN is more efficient for ECDM and achieves optimal results at 55-volt, pulse on time 52.3 s, inter-electrode gap (IEG) 30 mm, duty ratio 0.475 and electrolytic concentration 30 (wt.%).

Model modification and influence of edge effect on effective area of giant electro-rheological polishing using plate electrodes

Abstract Giant electro-rheological polishing (GPRP) is recognized as an innovative ultra-precision machining technology with significant potential. However, the pronounced edge effect within the GPRP's polishing gap can introduce errors in calculating the effective area and designing the electrode structure. This, in turn, may lead to under-polishing and an increased risk of insulation breakdown. In this study, COMSOL was employed to investigate the electric field distribution characteristics within the polishing gap. This exploration aimed to refine the calculation model of the effective area, optimize the plate electrodes' structure and size, and diminish the likelihood of insulation breakdown. Through systematic finite element simulations, the impact of polishing voltage, inter-electrode gap, and plate length on the edge effect was thoroughly analyzed to ascertain its influence range. The simulation findings revealed that, while maintaining a constant inter-electrode gap for the tool electrode, variations in the polishing gap, polishing voltage, and plate length within specific ranges resulted in an edge effect influence range of approximately 1 mm. Moreover, when the machining gap, polishing voltage, and plate length remained unchanged, the edge effect influence range increased proportionally with the electrode gap within a specific range, approximately equivalent to the size of the electrode gap. Experimental validation of the giant electro-rheological effect confirmed the existence and influence range of the edge effect, aligning with the finite element simulation results. Ultimately, modifications to the calculation model of the effective area were proposed, along with a solution to optimize the electrode size and structure, with the objective of reducing the probability of insulation breakdown. In practical applications, this work can provide a valuable reference for electrode structure design, insulation breakdown improvement and parameter selection.

Machining behaviour modulation of electrochemical milling via manipulation of inter-electrode gap: From electrochemical machining to electrochemical discharge machining

The inter-electrode gap (IEG) is a key factor in electrochemical machining (ECM), which directly governs the electric resistance of machining and affects the flow field. In conventional electrochemical milling, the actual IEG expands with the material removal of the workpiece, which increases the electric resistance and renders the electrolyte flow ineffective in transporting the electrolytic products. In this paper, a sinking push mode for electrochemical milling is proposed to minimise the IEG, thus improving material removal rate (MRR). Under a small IEG, electrochemical discharges are observed and damages the workpiece. Arising from this observation, electrochemical discharges are intentionally introduced to further improve MRR. And the material removal process is transformed from mere ECM to electrochemical discharge machining (ECDM). Furthermore, a novel ECDM-ECM mode is developed to eliminate the recast layer produced by discharge action. In this mode, the machining behaviour from ECM to ECDM can be altered by simply manipulating IEG distribution. Multiphysics simulations coupling electric field and flow field are conducted to better understand the mechanisms of the proposed modes. The IEG distribution, transient current behaviour, MRR, energy efficiency, surface integrity and tool wear are discussed by experiments. The ECDM-ECM mode successfully eliminates the recast layer with high MRR in a single controllable process, demonstrating its potential for producing high quality surfaces with high throughput.

Wire-to-two-drop plasma thruster: Experimental and numerical investigation of electroaerodynamic jet flow for micro aerial vehicle propulsion

Conventional micro aerial vehicles (MAVs) have primarily relied on complex, flapping-wing mechanisms for propulsion, often exhibiting limitations in terms of reliability and efficiency. To overcome these challenges, this study explores the potential of electroaerodynamic (EAD) thrusters as a novel propulsion system. By accelerating air molecules through ion collisions, EAD jet flow generates thrust, offering advantages such as noiseless operation and zero emissions due to its moving-part-free design. This research presents a comprehensive experimental and numerical investigation of a wire-to-two-drop thruster configuration to elucidate its electromechanical performance, plasma flow dynamics, and EAD jet characteristics. Experimental measurements of key parameters, including current, thrust, power, and effectiveness, were correlated with numerical simulations, demonstrating excellent agreement with a maximum error below 5%. These findings align strongly with established theoretical frameworks, revealing an inverse square root relationship between effectiveness and thrust. To optimize thruster performance, optimal operating voltages were identified at approximately 8.2, 9.4, and 11.6 kV for inter-electrode gap distances of 10, 15, and 20 mm, respectively, achieving a balanced trade-off between thrust and effectiveness. Detailed numerical visualizations of the plasma flow field, including velocity distribution, jet morphology, potential distribution, and electric field lines, provided valuable insights into the thruster's operation. Building upon these insights, a proof-of-concept EAD flier was constructed and tested, incorporating a serrated emitter electrode and lightweight materials. This flier achieved a mass of 0.5 g and generated a thrust of 0.77 g at 15 kV, resulting in a thrust-to-weight ratio of 1.54 and successful liftoff. This demonstration highlights the potential of EAD propulsion for practical MAV applications.

Electric-field assisted spatioselective deposition of MIL-101(Cr)PEDOT to enhance electrical conductivity and humidity sensing performance

Precise deposition of metal–organic framework (MOF) materials is important for fabricating high-performing MOF-based devices. Electric-field assisted drop-casting of poly(3,4-ethylenedioxythiophene)-functionalized (PEDOT) MIL-101(Cr) nanoparticles onto interdigitated electrodes allowed their precise spatioselective deposition as percolating nanoparticle chains in the interelectrode gaps. The resulting aligned materials were investigated for resistive and capacitive humidity sensing and compared with unaligned samples prepared via regular drop-casting. The spatioselective deposition of MOFs resulted in up to over 500 times improved conductivity and approximately 6 times increased responsivity during resistive humidity sensing. The aligned samples also showed good capacitive humidity sensing performance, with up to 310 times capacitance gain at 10 versus 90 % relative humidity. In contrast, the resistive behavior of the unaligned samples rendered them unsuitable for capacitive sensing. This work demonstrates that applying an alternating potential during drop-casting is a simple yet effective method to control MOF deposition for greater efficiency, conductivity, and enhanced humidity sensing performance.

Electric Discharge Between a Metal Cathode and a Liquid Non-Metal Anode

Gas-discharge plasma generated between a metal cathode and a liquid non-metallic anode at atmospheric pressure has been studied. The discharge is ignited by immersing the metal electrode in the electrolyte. The types and shapes of plasma structures generated in the interelectrode gap and their electrical parameters are considered. The results of thermographic analysis of the electrode surface under discharge conditions are presented. Using emission spectroscopy, the plasma composition, electron concentration and temperature of the heavy component were studied.

Advancing the process understanding and localization in jet electrochemical machining with electrolyte confinement through fluid dynamic simulations and experiments

Functionality-oriented micro-structures, such as micro-dimples and grooves, are widely used in tribology and heat transfer. Jet electrochemical machining (JEM) is effective to fabricate micro-structures on metallic surfaces. However, in traditional JEM, the unrestricted electrolyte flowing can induce stray corrosion on workpiece, and thus, both surface quality and machining localization are reduced. In this paper, a novel electrolyte-confinement technique is proposed for JEM, a high-density liquid (perfluorotripropylamine, FTPA) is used to confine the electrolyte flowing region on workpiece when electrolyte exits nozzle, facilitating reduction in stray corrosion on workpiece and overcut of micro-structures. A multi-physics model including two-phase flow field and electric field is developed to analyze the electrolyte confined by FTPA, and both simulation and observation results show that the area of electrolyte flowing on the workpiece is confined well by FTPA, and the current density distribution becomes concentrated, which enhances the machining localization. Compared to traditional JEM, the etch factor of micro-dimple is improved by 2.5 times and there is no stray corrosion. The material removal rate is increased due to the concentration of current distribution on the workpiece surface. Furthermore, profile evolution of micro-dimples revealed that with feed depth increased, FTPA could flow into the micro-dimple to protect the sidewall from continuous dissolution, thus forming vertical sidewall. Additionally, electrolyte flowing region is still confined during the scanning motion of nozzle, and the etch factor increases from 0.41 to 8.8 compared to traditional JEM. Moreover, increasing inter-electrode gap could reduce electrolyte flowing region on workpiece, further enhancing machining localization.

Characterization of 20 μm Dielectrophoretic Interelectrode Gap for Staphylococcus Aureus Rapid Detection Application

We propose an improvement of dielectrophoresis technique (DEP) by designing, simulating and experiment a 20 μm interelectrode gap for Staphylococcus aureus rapid detection application. In this paper, we use MyDEP simulation for DEP polarization Staphylococcus aureus on frequencies range. COMSOL simulation is utilized for comparison of 20 μm and 80 μm interelectrode gap based on trajectory and velocity of particles for Staphylococcus aureus application. We implied 20 μm interelectrode gap for Staphylococcus aureus application produced higher magnitude DEP force. Which gives accurate trajectory characterization and higher velocity of particle movement. DEP characterization using small interelectrode gap is capable of producing stable and optimum DEP value. It is demanding to distinguish the simulation Staphylococcus aureus using experimental method. DEP technique is important for analysis and characterization of the bacteria. The result show that 20 μm interelectrode gap has higher intensity of electric field which is 1.51 x 10^6 V/m in COMSOL simulation and produced 20.1 m/s for velocity of particle trajectories which is higher compared to 80 μm interelectrode gap. The DEP response was tested on 2.5 MHz, as crossover frequency response was observed on experimental and simulation. Thus, supportsthe capability of 20 μm interelectrode gap for Staphylococcus aureus rapid detection application. Furthermore, DEP characterization can be improvised by focusing on interelectrode gap for characterization among bacteria cells, critical for bacteria detection, manipulation, and isolation.

Analysis of charged particle flows in the interelectrode gap of an ion-optical system

Analysis of charged particle flows in the interelectrode gap of an ion-optical system