Wire Electrochemical Micromachining Research Articles

Control of corner arc radius in wire electrochemical micromachining

Wire electrochemical micromachining (WECMM) technology is commonly used to process micro parts. Some thick parts contain many sharp structures, and have high machining accuracy requirements for the arc radius at the corner, such as jet sheet, micro gear, etc. However, when machining thick workpiece, it is easy to form a large arc radius at the corner due to stray corrosion and difficult discharge of electrolytic products. In order to solve this problem, this paper proposes a corner path optimization method, which reduces the arc radius of the sharp structure by adjusting the processing path of the wire electrode, thereby improving the machining accuracy of the sharp structures. The model of the relationship between the inclination of the machining path and the angle of the sharp structure is established. The inclination and offset distance of the processing path are obtained through theoretical calculation, and further optimized through experiments to avoid overcut or undercut at the corner. In the experiment, tungsten wires with different diameters were used as wire electrodes to process acute angle, right angle and obtuse angle structures on 510 μm thick 9Cr18Mo stainless steel. The influence of wire electrode processing path on the corner arc radius of different angle sharp structures was explored. The experimental results show that compared with the original path, the arc radius of the sharp structure could be reduced from tens of microns to <5 μm by using the optimized processing path.

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.

Micro-Shaping of Pure Aluminum in Long-Duration Wire Electrochemical Micromachining Using Bipolar Nanosecond Pulses.

With the increasing application of three-dimensional pure aluminum microstructures in micro-electromechanical systems (MEMS) and for fabricating terahertz components, high-quality micro-shaping of pure aluminum has gradually attracted attention. Recently, high-quality three-dimensional microstructures of pure aluminum with a short machining path have been obtained through wire electrochemical micromachining (WECMM), owing to its sub-micrometer-scale machining precision. However, machining accuracy and stability decrease owing to the adhesion of insoluble products on the surface of the wire electrode in long-duration WECMM, which limits the application of pure aluminum microstructures with a long machining path. In this study, the bipolar nanosecond pulses are used to improve the machining accuracy and stability in long-duration WECMM of pure aluminum. A negative voltage of -0.5 V was considered appropriate based on experimental results. Compared with the traditional WECMM using unipolar pulses, the machining accuracy of the machined micro-slit and the duration of stable machining were significantly improved in long-duration WECMM using bipolar nanosecond pulses.

Research on Integral Fabrication and Inner Surface Metallization of the High-Frequency Terahertz Hollow-Core Metal Rectangular Waveguide Cavity by a Combined Process Based on Wire Electrochemical Micromachining and Electrochemical Deposition

With the development of fabrication technology for terahertz rectangular cavity devices, the fabrication process of integral terahertz waveguide cavities has received much attention because of its beneficial effect on improving the transmission of terahertz signals. However, smaller feature sizes, higher dimensional accuracy, and more stringent requirements for cavity surface roughness and edge radius make it difficult to manufacture terahertz waveguide cavities with a high operating frequency by using existing micro-manufacturing technology. At the same time, the smaller feature size also makes it more difficult to realize uniform metallization on the inner surface of a terahertz waveguide cavity. In this paper, a new and improved combined manufacturing process based on wire electrochemical micromachining and electrochemical deposition is proposed to realize the integral fabrication and uniform metallization of the inner surface of a high-frequency terahertz metal rectangular waveguide cavity. A detailed description and analysis of this combined process are carried out, together with corresponding experimental investigations. An integral 1.7 THz hollow-core metal rectangular waveguide cavity with an end-face size of 165.9 μm × 88.3 μm, an edge radius of less than 10 μm, an internal bottom surface roughness of less than 0.10 μm, and an internal side surface roughness of less than 0.40 μm was manufactured, and high-quality metallization of its inner surface was also achieved.

Quasi-superhydrophobic microscale two-dimensional phononic crystals of stainless steel 304

Fabrication of metallic phononic and photonic crystals of characteristic size between 10 and 1000μm remains a challenge in precision using the conventional machining processes or too tedious for the cleanroom-based processes. We report the fabrication and elastodynamic bandgaps of two-dimensional phononic crystals (PhCs) machined on stainless steel 304 (SS304) substrates using the wire-electrochemical micromachining (wire-ECMM) process. Square arrays of pillars of length 400μm and cross section either 350×350μm2 or 250×250μm2 with periods 650 and 550μm, respectively, were micromachined on an SS304 homogeneous substrate. Based on these arrays, three types of PhCs were considered: air-SS304, water-SS304, and epoxy-SS304, where air, water, and epoxy are the hosts and SS304 pillars are the scatterers. We found that texturing the surface increased the contact angle of a 5-μl-water-droplet from 97.9° for an untextured SS304 substrate to a maximum of 145° for SS304 PhCs, making the latter quasi-superhydrophobic. Dispersion relations evaluated using the finite-element method revealed the presence of partial bandgaps in the 0.1–2.7 MHz for all PhCs and a complete bandgap for the epoxy-SS304 PhCs. Transmittance spectrums for incident plane waves also provided evidence for the occurrence of bandgaps. Furthermore, the buckling analysis indicated that these pillars do not undergo buckling until yield—making them mechanically robust.

Micro-Shaping of Pure Aluminum by Intermittent Ultrasonic Oscillation Assisted Wire Electrochemical Micromachining with an Ultra-Low-Concentration Mixed Electrolyte

Sacrificial mandrels and micro-components made from pure aluminum have considerable application potential for fabricating terahertz micro-cavity components and for MEMS. Although WECMM has significant advantages in micro-shaping micro-components from difficult-to-machine materials, high-quality micro-shaping of pure aluminum has always been very challenging due to its extremely high chemical activity in an aqueous solution. This study analyzes the electrochemical characteristics of pure aluminum and the corresponding machining experiments by traditional WECMM in various electrolytes, and manufactures a high-quality micro-slit with a short machining path in the obtained ultra-low-concentration mixed electrolyte. However, in a continuous long-term WECMM with a long machining path, poor mass transport leads to the accumulation of bubbles around the machining area and the deposition of insoluble products on the wire surface that reduce the machining stability and machining accuracy. Therefore, a mass transport method of using intermittent ultrasonic oscillation is proposed. The principle was expounded, systematic comparative experiments demonstrated the effectiveness of this method in continuous long-time WECMM in improving the machining stability and machining accuracy. Finally, a rectangular mandrel of pure aluminum with a path length greater than 10,000 μm was fabricated. After dissolving the rectangular mandrel, a terahertz hollow-core rectangular waveguide micro-cavity was produced.

Electrochemical Microslot Machining by Ultrasonic-Vibration-Aided Electrolyte on Nitinol Wire

In this research, the main purpose was to study the applicability of a machining method on microscale medical-equipment manufacturing. The characteristics of wire electrochemical micromachining (WECMM) against NiTi 50-50 wire was investigated. The study utilized a tungsten wire 0.03 mm in diameter as an electrode to cut a fine slot into the nickel–titanium wire. In order to reach a high-precision WECMM finish, an ultrashort pulse power generator was used as a power source to minimize the stray current effect, thus improving the machining accuracy. During the process, various machining parameters were tested for their effects on machining characteristics. In addition, ultrasonic-vibration-aided WECMM was investigated to determine whether it benefited the machining characteristics. The experiment’s results showed that under such an experiment setting, microslots can be successfully manufactured. Furthermore, with the advance adjustment of experimental parameters, the machining accuracy was improved. Finally, a fine slot was manufactured under the optimum experiment parameters and aided by ultrasonic vibration.

On altering the wetting behaviour and corrosion resistance of a large metallic surface area by wire electrochemical texturing

This paper presents a novel and practically applicable method for a quick fabrication of uniform surface patterns (periodic micro-pillars with rectangular and square cross-section) on a large surface area of any conducting or semi-conducting material using Wire Electrochemical Micromachining (Wire-ECMM). Micro pillars with a rectangular cross-section are generated by machining mutually perpendicular micro channels. The depth, spacing, and cross-sectional area of pillars are controlled by varying the process parameters and tool travel distance. Primary pillars (level-1 texture) are machined with a constant Direct Current (DC) voltage and secondary pillars (level-2 texture) are machined with a pulsed DC voltage using a tungsten wire of diameter 100 μm. An aqueous solution of sodium nitrate (NaNO 3 ) is selected as an electrolyte having a pH of about 7.01. A good repeatability in the geometrical parameters of a pillar profile is observed on analysing 3D profilometer micrographs of the textured surfaces. Wetting behaviour of textured surfaces with different geometrical parameters is observed using drop shape analyser. A surface with two levels of textures offers highest contact angle of 147.3° with deionized water. Corrosion current and resistance of the textured surfaces are obtained using Linear Sweep Voltammetry (LSV) and Electrochemical Impedance Spectroscopy (EIS), respectively. Results suggest that corrosion resistance depends upon the area of texture and is highest for the sample with the largest textured area. Also, a sample with the smallest value of area factor (ratio of total area of the top surface of all the pillars in a region to the total projected area of a region) offers highest resistance to corrosion. • A novel approach for large area texturing on any conducting and semi-conducting surface using Wire Electrochemical Micromachining (Wire-ECMM). • A study of the influence of different process parameters on various geometrical features of a textured surface. • A detailed characterization of different textured surfaces using SEM imaging and surface topography. • In depth analysis of the wetting and corrosion behaviour of the textured surfaces using drop shape analyser and Electrochemical Impedance Spectroscopy (EIS).

Electrodissolution Processes and Their Application in Manufacturing for Shaping and Finishing of Advanced Materials

Controlled material removal by anodic dissolution at high rates forms the basis of non-conventional metal shaping and finishing processes such as Electrochemical Machining (ECM), Electrochemical Micromachining (EMM), and Electropolishing (EP). These processes are employed in the manufacturing and processing industries for a variety of applications ranging from the machining of complex shaped components for heavy industries to the fabrication of microstructures in thin films and foils and microfinishing of superconducting radiofrequency cavities (1-3). Application of these processes for the production of reliable, reproducible, and high-yielding components require an understanding of the parameters that influence the anodic dissolution processes.ECM, EMM, and EP can be understood and theoretically modeled based on the same principles provided the scaling effects related to each process are considered (2). In the first part of this presentation, the high rate anodic dissolution behavior of different materials including refractory materials are described which helps in establishing the basic concepts that govern ECM/EMM/EP processes. Electrochemical reactions taking place at high anodic potentials depend on the metal-electrolyte combination and the operating conditions. These reactions include active metal dissolution, passivity, oxygen evolution, and the phenomena of passive film breakdown leading to the transpassive metal dissolution. In passivating electrolytes (containing oxidizing anions), oxygen evolution and metal dissolution take place simultaneously. The current density dependence of meat dissolution efficiency in such electrolytes provides minimized stray cutting in ECM. Mass-transport, current distribution, and surface film properties play a significant role in the metal removal rate and surface finish. Whereas the formation of a salt film on the dissolving anode in ECM electrolytes is well established, the identification of the rate-controlling species during electropolishing of metals in concentrated acid solutions remains a controversial issue.The second part of the presentation deals with the applications of these processes in the manufacturing of advanced products for the aerospace, biomedical, electronics, and photovoltaics industries. Different ECM techniques such as die-sinking, combined tool machining, EC drilling, and EC deburring are described that are used in the manufacturing of complicated shaped parts such as turbine blades. Maskless EMM methods such as Jet EMM, micro-drilling, and wire EMM are applied to fabricate precision microstructures. For process enhancement, assisted techniques such as laser, abrasive, vibration, and ultrasonic are incorporated with maskless EMM. For through mask electrochemical micromachining (TMEMM), an understanding of mass transport in a cavity and shape evolution modeling is critical. The use of laser patterned oxide film mask for Ti patterning is presented as an interesting application of TMEMM (4). A few case-studies on electropolishing are described which include the fabrication of STM probes and Nitinol stents, and microfinishing of print bands. In the microprocessor industry, a significant effort was invested in the development of EP and electrochemical mechanical planarization (ECMP) approaches as a no-contact or low-contact planarization processes for the integration of ULK/copper interconnects. The development work, including processing details and planarization efficiency of EP and ECMP, are reviewed. A critical evaluation of the current status of EP/ECMP vis a vis the chemical mechanical planarization (CMP) process is presented.References J. McGeough, Principles of Electrochemical Machining, Chapman and Hall, Wiley, London, 1974.M. Datta, Electrodissolution Processes: Fundamentals and Applications, CRC Press/Taylor and Francis, Boca Raton, 2020.E. J. Taylor and M. Inman, Electrochemical Surface Finishing, The Electrochemical Society Interface, Fall 2014, p47.P.-F. Chauvy, P. Hoffmann, D. Landolt, Electrochemical Micromachining of Titanium Through a Laser Patterned Oxide Film, Electrochem. Solid-State Lett., 4(5), C31 (2001).

Research on Machining Gap Distribution in Wire Electrochemical Micromachining

Wire electrochemical micromachining (WECMM) has become a research hotspot in recent years due to its advantages in machining metallic microstructures. Profiles of metallic microstructures fabricated by WECMM are determined by the machining gap distribution. This paper focuses on equilibrium machining gap distribution in WECMM. A two-dimensional electric field model of WECMM was established and the evolution process of slit profile was investigated. It was found that in machining equilibrium status, the machining gap gets the minimum value at the wire electrode feeding direction and exponentially increases with the increase of the induced angle between the wire electrode normal direction and its feeding direction. Furthermore, the effects of wire electrode diameter, machining voltage, and wire electrode feed rate on the equilibrium machining gap distribution were studied through machining simulation. The quantitative relationship among the machining gap at any wire electrode normal direction, the machining voltage, and the wire electrode feed rate was determined through function fitting. Finally, machining experiments were carried out to verify the regularity of the machining gap distribution. Experimental results are basically consistent with the simulation and function fitting results, with the ratio of the calculation error to the experimental value less than 12.78%.

Improving surface processing quality in wire electrochemical micromachining by gas bubble chain

Wire electrochemical micromachining (WEMM) is a promising method to fabricate microstructures, but the gas bubbles generated make it more difficult to discharge electrolytic products out of the tiny machining gap, posing a significant challenge in the fabrication of microstructures using WEMM. Hence, gas bubbles are generally considered to be removed from the machining region as soon as possible. Herein, gas bubbles are taken advantaged of as a positive role to get rid of electrolytic products from the machining region. In this paper, the ethylene glycol solution is employed as electrolyte in WEMM to generate a gas bubble chain. Simulation and experiments were carried out to verify the feasibility of the method. It is demonstrated that the electrolytic products can be removed by gas bubble chains, which makes a significant contribution to the dramatic improvement of surface processing quality. The surface roughness achieved using the method is Ra = 0.032 μm on 3J21 alloy sheet and Ra = 0.025 μm on 304 stainless steel sheet. Complex microstructures with smooth surfaces are successfully fabricated.

Electrochemical micromachining of ZrCu-based amorphous alloy in ethylene glycol solution

Their excellent physical, chemical, and mechanical properties give ZrCu-based amorphous alloys a wide range of application prospects as advanced functional and structural materials for military and aerospace uses and in precision devices. Micro-electrochemical technology has been used to process amorphous alloys, and this paper reports the wire electrochemical micro-machining (WECMM) of the Zr67Cu15Ni11Al4Ti3 amorphous alloy. The dissolution characteristics and processing of the alloy in aqueous solutions are analyzed to understand the WECMM of this ZrCu-based amorphous alloy. Unlike with Cu-free Zr-based amorphous alloys, the Cu in the present case is electrolyzed quickly and generates a large amount of product deposition on the surface of the cathode after it is ionized, thereby seriously hindering the processing. Unlike the pure charge-transfer control process in an aqueous solution, the polarization process of the alloy in a glycol solution is controlled by both charge transfer and diffusion. In a glycol solution, the two-phase electric double layer comprises a compact layer and a diffusion layer, ions move relatively slowly between the cathode and anode, and products form relatively slowly. This is effective in (i) strengthening the reverse electric field effect of the bipolar pulse, (ii) hindering the migration of cations to the cathode, and (iii) directly avoiding the formation of products, thereby allowing the formation of high-quality micro-structures of ZrCu-based amorphous alloy with a relatively large thickness of 550 μm.

Investigations into machining accuracy and quality in wire electrochemical micromachining under sinusoidal and triangular voltage pulse condition

• Application and optimization of novel pulsed voltage waveforms for improving the process accuracy in Wire-ECMM. • A mathematical analysis of the evolution of machining gap with time under the application of different voltage waveforms. • Finite element modelling for the visualization of current density distribution in the machining zone. • Evaluation of machining quality using three dimensional optical profilometer and SEM images of machined features. • Optimization of triangular pulsed voltage waveform by varying its rise and fall time for improving the process accuracy. Since the past two decades, improving machining accuracy, precision, and quality of machining in Wire-ECMM has been a prime focus of researchers across the globe. Application of high frequency pulse voltage for machining has served the purpose to a large extent. However, with high frequency pulse voltage, machining rate is compromised. Often, the use of very high frequency also necessitates the application of high voltage amplitude which consequently, leads to increased power consumption. To solve this problem, this research proposes the use of sinusoidal voltage waveform (SVW) and triangular voltage waveform (TVW) instead of a conventionally used rectangular voltage waveform (RVW) for machining. A mathematical analysis of the machining gap in the process using a mechanistic approach suggests that accuracy in terms of kerf width improves significantly when SVW and TVW are used for machining. Experiments are conducted to investigate the impact of pulse voltage waveform on different characteristic features of a kerf profile which are kerf width, edge fillet radius, corner radius, and taper angle. These waveforms are generated using a function generator with the help of a rectification cum amplification electronic circuit. Roughness of the surface machined using these three waveforms are also measured using optical profilometer. Experimental results suggest that the percent reduction in the kerf width for the three waveforms considered by changing the frequency of voltage pulse from 100 kHz to 200 kHz is significantly lower than that obtained by switching from RVW to TVW and keeping other pulse parameters such as frequency, amplitude, and duty ratio same. Using a wire (tool) made of tungsten and a diameter of 30 μm, minimum kerf width of 60 ± 2 μm, edge fillet radius of 11 ± 1 μm, and a negligible corner radius is obtained when TVW is used for machining. For the above stated parameters, profile roughness (R a ) & area surface roughness (S a ) of machined kerf are 1.43 μm and 1.55 μm respectively for RVW, which are reduced to 0.44 μm and 0.57 μm respectively, for TVW. To understand the reason behind the reduction of kerf width, corner radius, and edge fillet radius in case of TVW, as indicated by the experimental observations, numerical simulations are performed. For a comparative study, current density distribution pattern over the workpiece surface is plotted for the three waveforms. Later, TVW is further optimized by varying its ‘rise’ and ‘fall’ time. For this, a factor termed as Pulse Rise Factor (PRF) is defined and is varied in 5 steps. Experimental results suggest that kerf width is minimum 55.4 μm when PRF is zero and is maximum 71.8 μm when PRF is one. In the end, different micro features are machined using the optimal machining conditions.

Fabrication of microstructures with mirror surfaces by wire electrochemical micromachining of stainless steel 304 using NaNO3-ethylene glycol

Microstructures with superior surface quality have been becoming more and more important in many fields. Various methods have been exploited to fabricate high quality microstructures. Among those approaches, wire electrochemical micromachining (WEMM) is an effective and efficient way to manufacture micro components. Generating passive film on the workpiece is an alternative to improve surface quality in WEMM, which necessitates a delicate selection of electrolyte. NaNO3 solution as a passive electrolyte is beneficial to obtain good surface quality, but it barely takes effect in WEMM. Herein, an attempt is made to combine ethylene glycol (solvent) and NaNO3 (solute) to investigate its influences on surface quality in WEMM of stainless steel (304 SS). Electrochemical measurements reveal that 304 SS is subjected to secondary passivation in 1 mol/L NaNO3-ethylene glycol. X-ray photoelectron spectroscopy analysis indicates that the compositions of the passive films formed at various potentials are not exactly the same. Both the secondary passivation and the passive films make dramatic contributions to the improvement of the machined surface quality. Experimental results demonstrate that surface roughness achieved with ethylene glycol is Ra = 0.034 μm, noticeably smaller than that with traditional acid solutions. Finally, microstructures with ultra-smooth surfaces are fabricated on the 304 SS plate.

Revealing the Instantaneous Machining Gap Produced During wire Electrochemical Micromachining Using Electrochemical Deposition

Revealing the Instantaneous Machining Gap Produced During wire Electrochemical Micromachining Using Electrochemical Deposition

Generating micro grooves with a semicircular cross-section using wire electrochemical micromachining

Micro grooves with a semicircular cross-section of tens of microns in radius on metal foils have posed a challenge for machining. This paper proposed stepwise manipulating process parameters in wire electrochemical micromachining (WECMM) to improve the profile accuracy of micro grooves with a semicircular cross-section via evenly distributing the machining gap. Firstly, a two-dimensional model of the electric field was established to investigate the groove shaping process including the changes of machining gap distribution at all normal directions of a cylindrical wire electrode. It indicated that the groove machining process ended before it reached the equilibrium status of WECMM. The corresponding machining gap at the wire electrode feeding direction is much smaller than those at other normal directions. Thereafter, a non-uniform machining gap distribution brings the semicircular profile error when using a cylindrical wire electrode. In this study, stepwise manipulations of the applied voltage and electrode feed rate is proposed to apply at the moment when the machining allowances at all directions are at a comparative range. According to simulations, an optimized stepwise parametric manipulation of increasing the pulse voltage from 12.5 to 14 V and decreasing the wire electrode feed rate from 0.5 to 0.1 μm/s was activated at 113 s and proceeded till 145 s. In this way, the machining gap distribution uniformity is improved and the machining allowances at major normal directions of the cylindrical wire electrode are reduced to zero. Experiments verified that the groove profile error was reduced from $$ {3.39}_{-0.45}^{+0.22} $$ μm to $$ {3.38}_{-0.13}^{+0.16} $$ μm with optimized stepwise-manipulation. Finally, the feasibility of simultaneously machining 20 micro grooves with a semicircular cross-section of 50 μm in radius was verified in experiments.

The dissolution characteristics and wire electrochemical micromachining of metallic glass Ni82Cr7Si5Fe3B3

Abstract Wire electrochemical micromachining (WECMM) is a non-traditional technique that is suitable for micro-structures processing of metallic glass (MG). The composition of metallic glass is complex, and the electrochemical characteristics of metallic elements are different, which greatly increases the difficulty of high-quality electrochemical micromachining of MG. In this study, the electrochemical dissolution characteristics of the amorphous material, Ni82Cr7Si5Fe3B3, are analyzed in detail. The AC impedance spectrum and dissolution states of MG in 0.1 M NaCl, NaNO3, HCl, and H2SO4 solutions are explored, and the dissolution characteristics of metal elements in Ni82Cr7Si5Fe3B3 are also investigated to determine the electrolytic properties of MG. By comparing the results of WECMM experiments in different solutions, the appropriate solution was chosen as electrolyte, and the effects of different parameters on WECMM of Ni82Cr7Si5Fe3B3 were studied. Finally, the optimal processing parameters achieved by the experiments, 0.25 M dilute H2SO4 solution, ultrashort pulse voltage amplitude 7 V, pulse period 3 μs, a pulse duration of 90 ns and a feed rate of 0.2 μm/s were applied to complete the machining of the MG micro-slits. And several complex micro-structures with good surface morphology were thus obtained. For example, a gear with an index circle diameter of 1 mm, a curved cantilever beam with a width of 30.5 μm and a micro round wheel with the thickness of 100 μm.

Improving Machining Localization and Surface Roughness in Wire Electrochemical Micromachining Using a Rotating Ultrasonic Helix Electrode.

Wire electrochemical micromachining (WECMM) technology is regarded a promising method to fabricate high aspect ratio microstructures on hard-to-machining materials, however, the by-product accumulation in the machining gap limits its application. In this paper, a new method called ultrasonic-assisted wire electrochemical micromachining (UA-WECMM) is proposed to improve the machining performance of WECMM. Firstly, a flow-field simulation in the machining gap was carried out; the results showed that the ultrasonic vibration of electrode can remarkably enhance the mass transport in the machining gap and improve the machining condition. Secondly, experiments were performed to confirm the effect of ultrasonic vibration, which illustrated that the vibration with proper amplitude can reduce the slit width and improve the morphology of machined surface. Moreover, the influence of other machining parameters were also discussed. Finally, a T-type micro connector with good surface roughness (Ra 0.286 μm) was fabricated on a 300-μm-thick 304 stainless steel workpiece and a micro gear (diameter: 3.362 mm; Ra: 0.271 μm) with an aspect ratio of 7 was fabricated on a 2-mm-thick workpiece. It is proved that the proposed ultrasonic-assisted wire electrochemical micromachining method has considerable potential and broad application prospects.

Wire Electrochemical Micromachining of Aluminum Rings for the Fabrication of Short-Millimeter Corrugated Horns.

With the increase of working frequency, the feature size of a corrugated horn will be greatly reduced, causing challenges for fabrication. This paper investigated wire electrochemical micromachining (WECMM) of aluminum rings for assembly of a mandrel for electroforming, which has been a primary method for producing corrugated horns. By utilizing a rotary helical electrode and green additives, the removal efficiency of electrolytic products in WECMM was improved. It was found that the machined slits had good unilateral consistency on the left side of the electrode feeding direction when the electrode rotated clockwise. Complexing agent glutamic diacetic acid (GLDA) can compete with OH− for Al3+ and has an obvious effect in reducing insoluble electrolytic products. From experimental investigations on typical parameters, an optimal parameter combination considering slit homogeneity and machining efficiency was obtained. In an electrolyte solution containing 15 g/L sodium nitrate solution and 15 g/L GLDA, 100 μm-thick aluminum rings with good edge and surface qualities were fabricated at a rate of 1.2 μm/s using a helical electrode with a diameter of 0.3 mm. Finally, these aluminum rings were successfully applied to make an internal corrugated sample with a rib width of 100 μm and a groove depth of 500 μm.

Dynamic Liquid Membrane Electrochemical Modification of Carbon Nanotube Fiber for Electrochemical Microfabrication.

Carbon nanotube fibers (CNFs) are a promising material for use as lightweight, high-strength, electrically conducting tool cathodes in wire electrochemical micromachining (WECMM) in which a high-performance tool cathode is crucial for optimal processing performance. However, the outstanding advantages of pristine CNFs, such as fiber strength, electrical conductivity, and hydrophilic surface, have so far remained underutilized as tool cathodes in WECMM. Herein, electrochemical modification using a dynamic liquid membrane is proposed as an effective online method for functionalizing CNFs prior to WECMM. The proposed method not only improves the assembly accuracy and efficiency but also avoids unnecessary damage to the modified CNF during installation. The introduced functional groups (-OH and -COOH) effectively improved the electrical conductivity and hydrophilicity of CNFs. The influences of H2O2 concentration, applied voltage, and anodization time on the surface modification process were examined experimentally. The use of a pulsed voltage was further proposed to prevent the loss of fiber strength due to over-anodization. Finally, the use of modified CNF electrodes with good surface morphology, strength, and conductivity in WECMM was demonstrated to afford superior machining stability, efficiency, and accuracy as well as improved surface quality compared with the conventional tool cathodes.