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Roundness error plays an important role of rotating parts in engineering fields and it has a significant influence on the machining quality and accuracy during electrochemical machining (ECM) process. The precision ECM could be processed only if the initial roundness error is decreased or eliminated and the inter-electrode gap (IEG) becomes steady after reaching an equilibrium state. However, a constant voltage is generally used in ECM process. And a long time and a large allowance are required to level the profile error of workblank if the initial profile error is large. In this study, the focus herein is on the acceleration of the leveling process of the rotary workpiece. A counter-rotating electrochemical machining (CRECM) process method with a variable voltage is proposed to improve the leveling ability. For a rotary workpiece with elliptical contours, the machining voltage can be dynamically adjusted based on the IEG through the approximate regulation of sine waves according to modeling-based analysis. The method aims to improve the leveling ability by expanding the difference in the magnitude of electric current between the high and low points on the profile of the anode workpiece under different voltages. The results of experiments confirmed that the proposed method significantly reduced the leveling time from 36 to 7 min (by 81%), and the depth of dissolution of the highest point on the profile from 1.68 to 0.45 mm while reducing the roundness error from 0.5 to 0.05 mm. The leveling ratio increased from 0.26 to 0.99. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Modern high-performance photodetector research is driven by the need to simultaneously improve multiple parameters, but also fit the decreasing size of electronics and maintain low production price. Here, we demonstrated how our synthesized ZnO tetrapod (ZnO-T) nanostructure was deposited on electrodes with variating gap by four coating methods including drop casting, microdrop casting, spray coating and slot-die coating with the same thickness. Optimizing the inter-electrode gap and coating method the record IUV/IDark ratio per unit area value of 8.73 × 106 was obtained. The fastest rise time 0.78 s and fastest decay time 0.94 s were obtained by slot-die coated sensors. High photoresponse of ZnO-Ts, the inter-electrode gap size influences formation of ZnO-T microstructure during coating process and morphology influence on photoresponse was explained. We demonstrate that even with the same optimized ZnO-T nanostructures photoresponse can be improved by 2 orders of magnitude. Our work shows the importance of coating morphology and inter-electrode gap optimization.

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. [Display omitted] • A sinking push mode is proposed to minimise the IEG in electrochemical milling. • Fast electrolyte flow is employed to break potential electrochemical arcs. • Stray corrosion is avoided by achieving a high ending current density. • Machining behaviour from ECM to ECDM can be adjusted by controlling IEG. • A novel hybrid ECDM-ECM mode is proposed to effectively remove the recast layer. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is a non-conventional method of machining hard materials with intricate shapes. Near-dry electric discharge machining (ND-EDM) is an advanced method of EDM which is eco-friendly and is more efficient in terms of material removal rate (MRR) than traditional EDM. In this research, an approach has been made to perform a new electrical discharge machining operation on EN-31 steel which utilizes metallic powder as an additive along with a gaseous dielectric (for example air) in ND-EDM. This advanced method of machining is known as powder mixed near-dry EDM. This study involves modeling for output process parameter—Material Removal Rate. The mathematical model was developed using the approach of Gaussian heat distribution. FEM modeling was done on ANSYS WORKBENCH 16.0 module. The experiments were performed and comparative study was done between the results obtained by modeling and experiments. The maximum experimental MRR was 7.68 mm3/min, and the error percentage between experimental, mathematical and FEM was under 30%. It was concluded that the modeling was done successfully and results obtained do comply with the methodology of the research. [ABSTRACT FROM AUTHOR]

The micro-electric discharge machining (micro-EDM) process had been studied by a number of researchers incorporating the single-spark numerical simulation technique. However, due to the stochastic nature of spark generation, complexities arise in determining the precise location of sparks and exact crater overlapping. Owing to this randomness, modelling of the micro-EDM process using the multi-spark approach has not been attempted hitherto. In this research work, an endeavour has been made to propose an improved concept of occurrence of sparks based on a minimum inter-electrode gap presented by the randomly assigned surface roughness to the tool and workpiece electrodes. The inadequacies associated with the single-spark modelling of the micro-EDM process can be overcome to a larger extent by deterministic estimation of the distinct spark location. The essential crater dimensions are inferred from single-spark simulation to estimate the exact number of sparks essential for the removal of a single layer in the multi-spark simulation. Numerically simulated single-crater dimensions are validated with the experimentally determined crater. Further, multi-spark simulation is performed, and successive layers are removed from the workpiece to generate a feature with a certain depth. The effect of the thermophysical properties of workpiece materials (copper, SS-EN 24, and Ti-6Al-4V) on the linear material removal rate (MRRl) is analysed. Simulation results illustrate that among the three materials, Ti-6Al-4V and SS-EN 24 result in the highest and lowest MRRl, respectively. The multi-spark approach presented in this work essentially differs from the occurrence of multiple sparks from a single-pulse input. [ABSTRACT FROM AUTHOR]

Day-to-day interest is growing in the drilling of high aspect-ratio deep microholes in various hard-to-machine and newer materials. Besides cost-effectiveness in the manufacturing process, an accurate dimension with the good surface finish is essential for microhole drilling. The conventional methods encounter various problems such as residue stresses, heat generation near cutting zone, high tool-wear, etc. Electrochemical microdrilling (ECMD) is one of the cost-effective techniques, provide a better alternative in drilling microholes with reasonably accurate dimensions and good surface finish in various industrial applications especially in computer, electronic, and aerospace industries. This article reviews current researches and developments of electrochemical processes for circular microholes drilling. It highlights the effects of various key factors (such as the development of microtools, electrolyte, inter-electrode-gap monitoring and control, etc.) on the aspect-ratio and accuracy of circular microholes, produced by ECMD. For further research, it will open up various challenging opportunities, especially in the field of (i) development and handling of microtool electrodes, (ii) development and handling of electrolytes medium, (iii) development in monitoring and controlling techniques of inter-electrode-gap, and (iv) development in strategies for process control for drilling high quality, deep and high aspect-ratio circular microholes into hard-to-machine materials using ECMD. [ABSTRACT FROM AUTHOR]

Abstract: Electrochemical Additive Manufacturing—a novel non-thermal metal additive manufacturing process offers some advantages over traditional energy beam-based layered manufacturing processes, which have several inherent limitations such as thermal damages, residual stress, and part size restrictions. In this process, the principle of localized electrochemical deposition of metals is combined with the additive manufacturing procedure to manufacture metal parts at room temperature directly from computer-aided design files. The focus of research work presented in this paper is on the modeling of the current density produced in the electrochemical deposition system based on the Fick’s law of diffusion and electrode kinetics using the Butler-Volmer equation. The current densities involved in the micro-electrochemical additive manufacturing on nickel have been found to be several orders of magnitude higher than the standard electroplating studies, making it a very high overpotential deposition. The model developed in this work was used to study the effects of applied potential, pulse duty cycle, inter-electrode gap, and concentration on the current density and the transient diffusion layer thickness. The model predicted that lower inter-electrode gaps facilitated higher current density leading to faster deposition rates. The pulse voltage was found to produce higher current densities during the pulse-on time. The modeled current density values were validated with experimental results using the in-house-built electrochemical additive manufacturing setup.Graphical Abstract: [ABSTRACT FROM AUTHOR]

A new copper electrolytic cell with two different inlet/outlet configurations was designed and modeled to study the effects of direct side inflows on electroplating and fluid flow field. Unlike electrolyte inflows in conventional electrolytic cells that have an inlet and an outlet far from electrodes, direct side inflows go directly to the inter-electrode gap from inlets on the side walls and have direct impact on the fluid flow field between electrodes. Copper electrorefining was simulated in the new electrolytic cell for both inlet/outlet configurations. The results show that direct side inflows can lead to more uniform species distribution and more efficient mass transfer, which can allow electroplating at higher current densities and lower electrolyte copper concentrations. Also, direct side inflows intensify electrolyte flows and convection in the inter-electrode gap, which is the underlying reason for the improved mass transfer in the new electrolytic cell. The upper-inlet/lower-outlet configuration has advantages over the lower-inlet/upper-outlet configuration in electrolyte flow field and mass transfer, as well as slime particle movement and collection. [ABSTRACT FROM AUTHOR]

Equations are provided for calculating and establishing a relationship in the form of an integral curve between emissions the probability of their occurrence. Regularities are revealed for the effect on emissions: number of fields and the number inter-electrode gaps (IEG) in a field, number of faulty gaps between electrodes, field electrode shaking regimes, and inter-electrode distance. Recommendations are formulated for electrostatic precipitator construction for effective cleaning conditions with prolonged operation. [ABSTRACT FROM AUTHOR]

Abstract: Pulsed electrochemical micromachining is a metal dissolution process where the capacitive behaviour of the double layer enhances the confinement of the machining profile, when very short voltage pulses are applied. During the pulses, the dissolution is confined to electrode regions where the tool–workpiece gap is the smallest. The model used combines the potential distribution in the electrolyte with the load–unload behaviour of the double layer. The model is solved using the Finite Element Method. The pulse and double layer charging are the main focus and therefore no shape change is included in the model at this point. The influence of the double layer, pulse signal parameters and inter-electrode gap size on the dissolution current density (material removal depth), as a function of time, is investigated. An estimation of the double layer loading time is presented, as well as a quantification method for the metal removal confinement, by comparing the calculated error against an ideal removal profile. The influence of pulse characteristics on the dissolution process has also been studied. It was found that a strongly non-linear polarization in combination with nano-second pulses and a small gap size increases the confinement. All the simulation results were obtained on an axisymmetric case by considering several geometrical set-ups. [Copyright &y& Elsevier]

At 38th Symposium, Shy and co-workers investigated a turbulence-facilitated-ignition (TFI) phenomenon via both conventional-single-spark-discharge (CSSD) and nanosecond-repetitively-pulsed-discharge (NRPD) at various pulsed-repetitive-frequency (PRF=5–70 kHz) using a fixed inter-electrode gap (d gap =0.8 mm) in a randomly-stirred lean n-butane/air mixture with Lewis number Le ≈2.2 ≫ 1 over a range of r.m.s. turbulent fluctuating velocity (u ′=0–2.1 m/s). It was found that the ignition probability (P ig) decreases significantly with increasing u ′ for most PRFs, except at PRF=60 kHz having turbulent P ig, T = 37% at u ′=0.5 m/s > laminar P ig, L = 34%, showing possible TFI. Using the same methodology, this paper presents two new P ig datasets at d gap =0.6 mm and 2.0 mm over wider ranges of PRF=1–90 kHz and u ′=0–2.8 m/s. All NRPD experiments apply the same total ignition energy E tot ≈23 mJ via a train of 11 pulses, each pulse having about 2.2 mJ except for the first pulse having about 1 mJ when using sufficiently high open-circuit-voltage of 28 kV. Note that E tot ≈MIE L ≈23 mJ at d gap =0.8 mm as a baseline for comparison; MIE L is the laminar minimum ignition energy measured by CSSD at 50% ignitability and MIE L =26.3 mJ/3.4 mJ at d gap =0.6 mm/2.0 mm. While TFI is noticeably observed at d gap =0.6 mm when PRF=60 kHz with P ig, T = 92% at u ′=0.5 m/s > P ig, L = 78%, turbulence reclaims its dominating role when u ′ > 1.4 m/s with P ig, T << P ig,L. At d gap =2.0 mm, there is no TFI ; a P ig,T transition is found where the decrease of P ig,T with u ′ changes from gradually to rapidly when u ′ > u ′ c (critical u ′ depending on PRF). We also discover that the curves of P ig,T versus PRF are highly non-monotonic with peaks around PRF=40 kHz for u ′ > 1.4 m/s; too high PRFs are detrimental for spherical flame ignition. These results are explained by coupling effects of d gap , PRF, u ′, and differential diffusion. [ABSTRACT FROM AUTHOR]

Jet electrochemical machining (JEM) is a promising way to generate grooves in difficult-to-machine materials. The electrolyte flow distribution in multi-grooves machining is quite different from that of a single groove. If the tubes are too close together, the reflected electrolyte jets interfere with each other, which will seriously affect the multi-grooves critical performances such as machining accuracy and stray corrosion upon the non-processing areas. This paper proposes using tube electrodes in a row (TER) with reasonable tube interval to lessen undesirable machining affects from the electrolyte flow interference and insulation coatings to reduce stray corrosion in the non-processing regions. It was observed that in multi-grooves machining, electrolyte baffles and plenty of droplets generate due to intensive electrolyte flow interference, and the electrolyte droplets gradually slid toward the tube tip and eventually fall onto the anodic surface as intermittent stray current passages when TER without coatings was used in JEM, which lead to stray corrosion in the non-machining zones. Simulations and experiments showed that when the tube sides were insulated, the current density distribution on the surfaces between adjacent grooves declined drastically, and stray corrosion reduced in the undesirable areas. Moreover, it was found that when the tubes were too close to each other, the electrolyte droplets from flow interference drop faster, thereby deteriorating the current stability and multi-grooves edges. Thus, a tube interval exceeding 3.00 mm was found to be acceptable for JEM with TER. Based on these findings, by using TER with a tube interval of 4.00 mm, both denser crisscross and parallel grooves with groove interval of 2.00 mm and rare stray corrosion were fabricated in a large-area surface (28 mm × 45 mm) by planning the tool path properly. Also, multi-grooves with different groove depths were produced simultaneously at one time on the workpiece merely by setting different inter-electrode gaps for each component tube in the TER. [ABSTRACT FROM AUTHOR]