Electrode Rotation Speed Research Articles

High-speed dry electrical discharge machining

A novel high-speed dry electrical discharge machining (EDM) method was proposed in this study. Using this method, the material can be rapidly melted by extremely high discharge energy and flushed out of the discharge gap by high-pressure and high-speed air flow. The material removal rate (MRR) of dry EDM was significantly improved by the proposed method. The MRR of dry EDM is usually in tens mm3/min, whereas the MRR of the proposed method can be as high as 5162mm3/min, which improves the MRR by 2nd to 3rd order of magnitude. Investigation was conducted systemically. The influences of work piece polarity, discharge current, pulse duration time, gas pressure, and electrode rotation speed on machining performance were studied. The machining mechanism of this method was thoroughly analyzed. Moreover, the re-solidified layer, surface morphology, elementary composition, and phase of AISI 304 stainless steel for high-speed dry EDM were also investigated. Theoretical and technical foundations were laid for the industry application of dry EDM.

Optimization of Electric Discharge Machining of M2 Tool Steel Using Grey Relational Analysis

Tool steels are very difficult to machine by conventional machining processes owing to their high hardness value. Electric discharge machining (EDM) provides an easy method of machining such materials even by using a softer tool material. The present work aims to optimize the output parameters like metal removal rate (MRR), electrode wear ratio (EWR) and over cut (OC) with respect to the input parameters like tool rotation speed, voltage and spark time during electric discharge machining of tool steel M2 using Grey relational analysis with a L9 orthogonal array. The electric discharge machining was done by a rotary brass electrode of 18.8mm diameter to make 4mm deep blind holes on tool steel M2 work-piece using EZNC EDM machine. The analysis of variance (ANOVA) of the gray value was also performed. The electrode rotation speed was found to affects the output parameters most followed by voltage and the spark time.

Nicotine as Corrosion Inhibitor for 1018 Steel in 1M HCl under Turbulent Conditions

An electrochemical impedance technique for determining corrosion inhibition of nicotine in HCl on AISI 1018 steel under concentrations from 0 to 50 ppm found that the organic compound is a better corrosion inhibitor under static conditions. The inhibition efficiency (IE) increased with inhibitor concentration reaching an IE>90%, at 10 ppm. For [nicotine] ≤ 50 ppm, the IE value reached 71%, at 40 rpm, but diminished then to 33% upon changing the working electrode rotation speed to 500 rpm. The thermodynamic analysis showed a process ruled by physisorption according to the Langmuir adsorption model mechanism. Furthermore, the inhibition kinetics study showed that nicotine gave good protection against corrosion up to 72 hours of immersion with IE ≤ 87%. Finally, with increased temperature the IE values diminished from 90% at 25°C to 57% at 70°C, concluding that at high temperatures nicotine is ineffective at inhibition, because the temperature decrease, persistence layer easily desorbs.

An experimental investigation into the micro-electro-discharge machining behaviour of aluminium alloy (AA 2024)

Aluminium (Al) alloys are extensively used in all areas of manufacturing including automotive and aerospace industries due to its lightweight, excellent machinability, good surface finish at high cutting speed, low cutting forces and outstanding tool life. Although Al alloys have excellent machinability with conventional machining processes, electric discharge machining (EDM) and micro-EDM are often used to machine intricate features in Al alloys for plastic injection moulds and electronic applications. Present study aims to investigate the influence of various operating parameters on the micro-EDM behaviour of an important Al alloy AA 2024, commonly known as ‘Duralumin’. The machining behaviour has been investigated by engraving micro grooves on the surface of the AA 2024 using different parameters settings from a resistance-capacitor (RC) type pulse generator. The operating parameters studied were capacitance, resistance, supply voltage, electrode rotational speed and gap control parameters. The micro-EDM machinability of the AA 2024 alloy was evaluated in terms of the material removal rate (MRR), tool wear ratio (TWR), surface roughness (SR) and machining depth of the micro grooves. It has been found that the increase of capacitance and voltage results in increase of discharge energy, causing higher MRR at the expense of higher tool wear and rougher machined surface. On the other hand, too low capacitance and gap voltage result in unstable machining by creating arcing and short-circuiting, which again makes the surface defective in addition to reducing the machining speed. The careful selection of gap control parameters improves the machining stability by reducing the arcing and short-circuiting as well as improves the overall machining performance. For stable micro-EDM with higher machining speed and improved surface finish, the identification of optimum parameters is needed. With this said, the recommended settings of parameters for micro-EDM of AA 2024 were found to be the voltage of 160 V, capacitance of 10,000 pF and resistance of 470 Ω, spindle speed of 720 rpm, gap feed rate of 0.01 mm/s, gap control factor of 50 and gap threshold voltage of 80 %.

A Novel Compound Machining of AISI 321 Stainless Steel Using Small Diameter Electrodes

Experiments of high-efficiently compound machining (CM) combined by EDM and arc machining of AISI 321 stainless steel at 658mm3/min material removal rate (MRR) using solid electrodes of different materials and different diameters of less than 5mm were conducted. The CM process parameters, including electrode rotation speed, peak current, electrode materials and electrode diameter, were studied to evaluate the effect on MRR, relative electrode wear rate (REWR) and width of overcut (WOC). The re-solidified layer of 321 for CM was also investigated. Faster electrode rotation speed, higher peak current, larger electrode diameter and pure tungsten electrode material are essential to achieve lower REWR and higher MRR. The processing conditions were bad using electrode diameter of 2mm. The re-solidified materials are significantly more densely than base materials.

Experimental Investigations into the Effects of Microelectric-Discharge Milling Process Parameters on Processing Ti–6Al–4V

Microelectric-discharge milling is acquiring more importance in micromanufacturing because of its unique ability to produce three-dimensional microcavities with high aspect ratio in electrically conductive advanced materials regardless of its mechanical properties. The present study investigates the effects of major microelectric-discharge milling process variables [voltage (V), capacitance (C), electrode rotational speed (ERS), and feed rate (FR)] on Ti–6Al–4V. The output performance measures were identified as material removal rate (MRR) and tool wear rate (TWR) to assess the machinability of Ti–6Al–4V. Experiments were designed and carried out based on response surface methodology-Box-Behnken statistical design. The most influencing parameters for responses (MRR, TWR) were found to be capacitance and FR. At a capacitance of 0.4 µF and FR of 18 mm/min, maximum MRR of 0.9756 mg/h, and TWR of 0.6342 mg/h were observed. Similarly at 0.01 µF and 6 mm/min, minimum MRR of 0.2308 mg/h, and TWR of 0.1259 mg/h were obtained.

RDE study of thiosulfate oxidation on gold

Gold rotation disk electrode was used to study thiosulfate oxidation processes. The values of current in anode voltammograms measured on the fresh electrode surface are independent of the electrode rotation speed. This means that the rate of the process under study is limited by slow (in comparison with diffusion) heterogeneous reactions. The probable mechanisms of these reactions were analyzed. Voltammograms have a maximum of current and depend on the voltammetric scan rate. The reason of these effects is connected with electrode passivation.

Kinetics Study on O2 Adsorption and OHad Desorption at Pt(111), Its Implication to Oxygen Reduction Reaction Kinetics

Kinetics of dissociative O2 adsorption, OHad desorption, and oxygen reduction reaction (ORR) at Pt(111) electrode in 0.1 mol/L HClO4 has been investigated. Reversible OHad adsorption/desorption occurs at potentials from 0.6 V to 1.0 V (vs. RHE) with the exchange current density of ca. 50 mA/cm2 at 0.8 V, the fast kinetics of OHad desorption indicates that it should not be the rate determining step for ORR. In the kinetic- or kinetic-mass transport mix controlled potential region, ORR current at constant potential displays slight decrease with reaction time. ORR current in the positive-going potential scan is slightly larger than that in the subsequent negative-going scan with electrode rotation speed (>800 r/min) and slow potential scan rate (<100 mV/s). The open circuit potential of Pt/0.1 mol/L HClO4 interface increases promptly from 0.9 V to 1.0 V after switch from O2 free- to O2-saturated solution. The increase of open circuit potential as well as ORR current decays under potential control due to the accumulation of OHad from dissociative adsorption of O2. It indicates that at Pt(111) the net rate for O2 decomposition to OHad is slightly faster than that for OHad removal, one cannot simply use the assumption of rate determining step to discuss ORR kinetics. Instead, the ORR kinetics is determined by both the kinetics for O2 decomposition to OHad as well as the thermo-equilibrium of OHad+H++e ⇌H2O.

EIS Evaluation of Cefalotine as Corrosion Inhibitor for API 5L X52 Steel Immersed in Acid Medium. Effect of [Cefalotine], Hydrodynamic Conditions, Temperature and Immersion Times

The corrosion behavior of pipeline steel grade API 5L X52 immersed in 1M HCl aqueous solution in the presence and absence of cefalotine, was evaluated using EIS and a rotating disk electrode. The effect of different experimental conditions namely: Cefalotine concentration, electrode rotation speed, temperature and immersion times on the corrosion inhibition efficiency (IE) of Cefalotine, were evaluated. It is shown that at stagnant conditions (0 rpm), the IE increased with inhibitor concentration, Fig. 1, reaching a value of ca. 87% at 25 ppm and 89% at 200 ppm. When the steel working electrode rotation speed was varied, it was found that for [Cefalotine] ≥ 25 ppm, the IE reached a maximum value, ca. 85%, at 40 rpm, however, it diminished to ca. 75% when the electrode rotation speed reached 1000 rpm. Furthermore, when the temperature of the corrosive media was increased from 25 to 45 °C, at stagnant conditions with 200 ppm cefalotine, the IE values remain to ca. ~80%. For stagnant conditions, 50 ppm cefalotine and 25 °C, an IE greater that 94% was found for the inhibitor even after 336 exposure hours to the corrosive media.

Modeling of Material Removal Mechanism in Micro Electric Discharge Milling of Ti-6Al-4V

Micro EDM milling process is accruing a lot of importance in micro fabrication of difficult to machine materials. Any complex shape can be generated with the help of the controlled cylindrical tool in the pre determined path. Due to the complex material removal mechanism on the tool and the work piece, a detailed parametric study is required. In this study, the influence of various process parameters on material removal mechanism is investigated. Experiments were planned as per Response Surface Methodology (RSM) – Box Behnken design and performed under different cutting conditions of gap voltage, capacitance, electrode rotation speed and feed rate. Analysis of variance (ANOVA) was employed to identify the level of importance of machining parameters on the material removal rate. Maximum material removal rate was obtained at Voltage (115V), Capacitance (0.4μF), Electrode rotational Speed (1000rpm), and Feed rate (18mm/min). In addition, a mathematical model is created to predict the material removal

Micro-electro discharge machining of non-conductive zirconia ceramic: investigation of MRR and recast layer hardness

Increasing material removal rate (MRR) and minimizing recast layer hardness are critical issues in machining non-conductive ceramic using micro-electro discharge machining (micro-EDM). This paper presents the analysis of MRR and recast layer hardness of zirconium oxide (ZrO2) due to micro-EDM using EDM-3 dielectric fluid and tungsten tool electrodes. The two main parts of this research are process development and the analysis of MRR and recast layer hardness. In process development, the appropriate use of assisting electrode (AE), polarity, flushing, feed rate, gap voltage, and tool electrode rotational speed are identified. The better machinability of ZrO2 was found to be with copper adhesive as AE, positive workpiece polarity, 3-μm/s feed rate, and workpiece submerged in dielectric fluid with one-way circulation. Empirical models are developed for the estimation of MRR and recast layer hardness. The optimum parameters for maximum MRR and minimum recast layer hardness are found to be at a 370-rpm rotational speed and at 80-V gap voltage.

Mass-Transport Characteristics of Oxygen at Pt/Anion Exchange Ionomer Interface

This work quantifies the mass-transport characteristics of O2 at Pt/anion exchange ionomer by determining the solubility and diffusion coefficient of O2 in Tokuyama AS-4 anion exchange ionomer film. Electrochemical methods such as linear sweep voltammetry and chronoamperometry are performed on rotating disk electrode to determine these parameters. The diffusion process in AS-4 ionomer film is found to be Fickian in nature; that is, it is shown that the diffusion coefficient is independent of concentration and film thickness by calculating the diffusion coefficient at various film thicknesses and rotation speed of electrode. In comparison with Nafion ionomer, the magnitude of diffusion coefficient in anion exchange ionomer is found to be one order higher, and solubility is found to be one order lower. However, the overall permeability, defined by product of diffusion coefficient and solubility is similar to Nafion ionomer film. In addition, durability studies of anion exchange ionomer-coated Pt disk shows electrochemical stability of anion ionomer in alkaline media. With these studies, it is shown that O2 transport at the Pt/anion exchange ionomer interface is not expected to limit alkaline membrane fuel-cell cathode performance.

Numerical simulation of the primary, secondary and tertiary current distributions on the cathode of a rotating cylinder electrode cell. Influence of using plates and a concentric cylinder as counter electrodes

Numerical simulations of primary, secondary and tertiary current distributions on the cathode of a rotating cylinder electrode (RCE) cell, using four-plate, six-plate, and a concentric cylinder as counter electrodes, were calculated using the finite element method. Copper electrodeposition from an acidic sulfate electrolyte is used as a test system. Charge transfer kinetics is described by a Tafel approximation while mass transport is considered using a Nernstian diffusion layer expression. The importance of using plates and concentric counter electrodes on RCE cathode is demonstrated. The effects of applied current density and electrode rotation speed on the distribution of current on RCE cathode are analyzed. Electrodeposition experiments with copper enable comparisons with the simulations.

Surface roughness analysis and magnetic property studies of nickel thin films electrodeposited onto rotating disc electrodes

Ni films were electrodeposited onto polycrystalline gold substrates mounted on a rotating disc electrode. The effects of rotation speed, film thickness and current density on the kinetic roughening and magnetic properties of the films were investigated. The film surface roughness was imaged using an atomic force microscope (AFM). The results indicate that the film roughness increases as the film thickness or deposition current density increases. We found that the electrodeposited Ni films exhibit anomalous scaling since both local and large-scale roughnesses show a power-law dependence on the film thickness. The effect of electrode rotation speed on the film surface roughness was also investigated. Scanning electron microscopy studies (SEM) had a good agreement with the AFM results. The average crystalline size of the film surfaces is also calculated from X-ray line broadening using (220) peak and Debye–Scherrer formula. The obtained results agree with that of AFM and SEM. The Ni thin films which are grown at different deposition current densities and rotation speeds exhibit in-plane magnetization with coercivities less than 110 Oe.

Rapid Regeneration of Chelated Iron Desulfurization Solution Using Electrochemical Reactor with Rotating Cylindrical Electrodes

A new electrochemical reactor with rotating cylindrical electrodes was designed and used to increase the regeneration efficiency of chelated iron desulfurization solution. The influence of operating parameters, such as the rotation speed of electrode, voltage, and inlet air and liquid flow rates, on the regeneration rate was investigated. Compared with the traditional tank-type reactor, the regeneration rate with the new electrochemical reactor was increased significantly. Under the optimum conditions, the regeneration rate was increased from 45.3% to 84.8%. Experimental results of continuous operation indicated that the new electrochemical regeneration method had some merits including higher regeneration efficiency, smaller equipment size and good stability in operation.

Influence of the Hydrophobic Groups on Quaternary Ammonium Additives for Copper Electrodeposition

A series of quaternary ammonium compounds with different hydrophobic groups as spacers were synthesized. The influence of the hydrophobic groups on the additives for copper electrodeposition was investigated using a galvanostatic measurement on a RDE electrode. The increase of the length of the alkyl chain within the compounds enhances the suppressing capability. The introduction of a hydroxyl group or a phenyl ring into the hydrophobic groups in the molecular structures reduces the suppressing capacity. The results obtained from SEM measurements indicate that the presence of the quaternary ammonium compounds in the electrolytes may produce regular and relative leveling morphologies of copper deposits. The via-filling experiments without SPS exhibit that an almost complete filling was achieved for compound 1d (C6 alkyl chain as a hydrophobic group), whereas a bad filling was obtained for compound 1a (C3-OH chain as a hydrophobic group). With SPS, the vias were perfectly filled both for compound 1a and 1d. However, the initial increment of growth was still conformal for the compound 1a. These results indicate the influence of the hydrophobic groups of the quaternary ammonium compounds on the filling behaviors and they are in agreement with the galvanostatic measurements at different electrode rotation speeds.

Electrochemical Investigation of the Corrosion Behavior of API 5L-X65 Carbon Steel in Carbon Dioxide Medium

The corrosion behavior of API 5L-X65 carbon steel in a carbon dioxide (CO2)-saturated solution was investigated by electrochemical measurements (polarization curves, Levich plots, and electrochemical impedance spectroscopy) with a rotating disk electrode. Different experimental conditions such as hydrodynamics, immersion time, and temperature were considered. From the polarization curves, it was shown that both the anodic and cathodic current densities decreased as the electrode rotation speed, the immersion time, and the temperature increased. This behavior was in agreement with the impedance results obtained at the corrosion potential. It was shown that the corrosion processes were initially controlled by mass transport but they became under activation control for longer immersion times. Scanning electron microscopy was used to characterize the corrosion products. For short immersion times (2 h and 6 h), the corrosion products mainly deposited on the cathodic sites (pearlitic zones) of the carbon steel surface forming a heterogeneous layer, whereas they covered the whole electrode surface after longer periods (>15 h). At a microscale, localized corrosion, as a result of galvanic coupling between pearlite and ferrite, was also observed.

Modeling and Optimization of a Roll-Type Electrostatic Separation Process Using Artificial Neural Networks

The aim of this paper is the development of a procedure for the optimization of electrostatic separation processes using artificial neural networks (ANNs) in association with genetic algorithms. The objective was to maximize the insulation product, the control variables being the high voltage that supplies the electrode system and the rotation speed of the roll electrode. The ANN model is compared with that obtained using the classical experimental design methodology. The predicted optimum is confirmed by experiment.

An Effective MECE Module as a Recycling Process for PET Diaphragm of Digital Paper

A newly devised process using micro-electrochemical machining (MECE) is described as a recycling module in the current study. The purpose is the precise removal of In2O3SnO2 thin-film nanostructures from optical PET diaphragm surfaces for digital-paper surface. In the current experiment it was found that a large rotational diameter (Dc) for the cathode with a small gap width between the anode and the PET diaphragm surfaces was found to remove the In2O3SnO2 rapidly. A small edge radius of the cathode, or a short arc length of the anode, reduces the time taken for In2O3SnO2 removal. A high feed rate of the PET and adequate electrical power results in fast machining. Pulsed direct current improves dregs discharge and this is an advantage with a fast feed. A high electrode rotational speed also corresponds to faster removal of the In2O3SnO2 nanostructures. The development of the proposed precision production design is based on both technical and economic considerations.

고분자 전해질 연료전지 캐소드용 코발트-폴리아닐린-탄소로 구성된 비귀금속 촉매의 제조 및 특성 평가

고분자 전해질 연료전지(Polymer Electrolyte Membrane Fuel Cell, PEMFC) 상용화를 위해 해결해야 할 과제 중의 하나인 가격 저감을 이루기 위한 방법으로 백금 촉매를 대신할 비귀금속(non-precious metal) 촉매 제조에 관한 연구를 수행하였다. 비귀금속 촉매의 합성은 산소환원반응(oxygen reduction reaction, ORR)의 활성점으로 알려져 있는 코발트-질소(Co-N) 결합을 형성하기 위해 질소를 포함하는 폴리아닐린(PANI)과 코발트염(Co precursor), 그리고 카본 블랙(C)을 일정한 비율대로 혼합한 후 특별한 열처리 과정 없이 단순한 화학적 환원법에 제조되었다. 제조된 Co-PANI-C 복합 촉매의 구조 분석을 위해 X-선 회절분석(X-ray diffraction, XRD)과 열중량분석(thermogravimetric analysis, TGA)을 실시하였고, ORR에 대한 활성을 평가하기 위해 rotating disk electrode(RDE) 및 rotating ring disk electrode(RRDE) 측정을 수행하였다. 그 결과 Co-PANI-C 복합 촉매는 ORR반응에 대한 개시 전압은 백금 촉매보다 60 mV 밖에 낮지 않은 값을 보였지만, 반응에 의해 발생되는 환원 전류는 여전히 백금 촉매보다 낮은 값을 보였다. 이 밖에도 전극 회전 속도에 따른 ORR 특성 변화, 전압 사이클 회수에 따른 내구성 변화, 연료전지 적용 시 성능 변화에 대해 논의할 것이다. In order to overcome the cost issue for commercialization of polymer electrolyte membrane fuel cell (PEMFC), this research was conducted for replacing platinum cathode catalyst with non-precious metal catalyst. The non-precious metal catalyst (Co-PANI-C) was synthesized by the simple reduction method with polyaniline (PANI), carbon black, and cobalt precursor without any heat treatment. Characterization of new Co-PANI-C composite catalysts was done by the measurement of X-ray diffraction (XRD) and thermogravimetric analysis (TGA) for structure analysis and performed by rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) for electrochemical analysis. As a result, Co-PANI-C catalyst showed 60 mV lower on-set potential for oxygen reduction reaction (ORR) than Pt/C catalyst, but the overall reduction current of Co-PANI-C catalysts by ORR was still smaller than that of Pt/C. In addition, the ORR behavior of Co-PANI-C catalysts depending on the rotation speed of electrode and the stability of Co-PANI-C catalyst under potential cycling and the performance of fuel cell conditions are also discussed.