Electrochemical Micromachining Research Articles

Electrochemical micromachining of magnesium AZ31 alloy using minimum quantity electrolyte

ABSTRACT Magnesium AZ31 alloy is endlessly receiving consideration as a light, bio-implant and biodegradable material. For enhancing the application of AZ31 alloy, machinability study is much needed. The galvanic corrosion while application of electrolytes over the magnesium alloy affects its surface, and this paper aims to overcome this issue with, a new electrolyte supply system. Here, the magnesium AZ31 alloy is processed for microhole generation by using the electrochemical micromachining technique. Sodium nitrate (NaNO3) and citric (C6H8O7) were preferred as the electrolyte and the process variables, namely machining voltage, duty cycle, and electrolyte concentration, were varied to analyze their effects on machining speed and overcut. The corrosion potentials for the AZ31 alloy after machining under the submerge condition and the minimum-quantity electrolyte condition were determined and compared. The study revealed that the minimum-quantity C6H8O7 electrolyte showed better hole geometry with high machining speed of 0.654 μm/s and minimum overcut of 82 μm, respectively.

Experimental investigation of electrochemical micromilling on titanium alloy (Ti6Al4V)

The demand for microscale components in Micro-Electromechanical Systems, the automobile industry, aerospace industry, and the medical field is rapidly increasing in the past few years. Titanium and titanium composite materials are the most appropriate material for all of these applications because of their high strength-to-weight ratio and high corrosion resistance. The machining of titanium at the microscale level has many challenges because of the mechanical and chemical qualities of titanium, it can be machined using both traditional and non-conventional methods. Electrochemical micromachining (EMM) is a noncontact, anodic dissolution of materials that are tough to fabricate, like in titanium alloy 'Ti6Al4V' can be achieved using a stress-free machining method. This research presents a thorough experimental analysis of electrochemical micro-milling on the titanium alloy Ti6Al4V. The impact of various treatment input variables like duty ratio, tool feed rate, machining voltage, and pulse frequency on geometrical accuracy of micro-features was investigated. The optimum parameters for microfeatures were identified as machining voltage of 12 V along with pulse frequency and micro tool feed rate of 180 KHz and 5 µ/sec respectively. The micro-features were generated by a layer-by-layer micro-milling technique with the help of a micro tool of 255-µm diameter.

Dynamic Electrolyte Spreading during Meniscus-Confined Electrodeposition and Electrodissolution of Copper for Surface Patterning.

Meniscus-confined electrodeposition and electrodissolution are a facile maskless approach to generate controlled surface patterns and 3D microstructures. In these processes, the solid-liquid interfacial area confined by the meniscus dictates the zone on which the electrodeposition or the electrodissolution occurs. In this work, we show that the process of electrodeposition or electrodissolution in a meniscus-confined droplet system can lead to dynamic spreading of the meniscus, thereby changing the solid-liquid interfacial area confined by the meniscus. Our results show that the wetting dynamics depends on the applied voltage and the type of interface underneath the droplet, specifically a smooth surface with a homogeneous solid-liquid interface or a superhydrophobic surface with a heterogeneous solid-liquid and liquid-vapor interface. It is found that both electrodissolution and electrodeposition processes induced droplet spreading in the case of a smooth surface with a homogeneous interface. However, a superhydrophobic surface with a heterogeneous interface under the droplet produced nonlinear spreading during electrodissolution and spreading inhibition during electrodeposition. The underlying mechanisms resulting in the observed behavior have been explicated. The dynamic droplet spreading could modify the dimensions of the patterns formed and hence is of immense importance to the meniscus-confined electrochemical micromachining. The findings also provide fundamental insights into the spreading behavior and wetting transitions induced by electrochemical reactions.

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.

Plasma-enabled electrochemical jet micromachining of chemically inert and passivating material

Electrochemical jet machining (EJM) encounters significant challenges in the microstructuring of chemically inert and passivating materials because an oxide layer is easily formed on the material surface, preventing the progress of electrochemical dissolution. This research demonstrates for the first time a jet-electrolytic plasma micromachining (Jet-EPM) method to overcome this problem. Specifically, an electrolytic plasma is intentionally induced at the jet-material contact area by applying a potential high enough to surmount the surface boundary layer (such as a passive film or gas bubble) and enable material removal. Compared to traditional EJM, introducing plasma in the electrochemical jet system leads to considerable differences in machining performance due to the inclusion of plasma reactions. In this work, the implementation of Jet-EPM for fabricating microstructures in the semiconductor material 4H-SiC is demonstrated, and the machining principle and characteristics of Jet-EPM, including critical parameters and process windows, are comprehensively investigated. Theoretical modeling and experiments have elucidated the mechanisms of plasma ignition/evolution and the corresponding material removal, showing the strong potential of Jet-EPM for micromachining chemically resistant materials. The present study considerably augments the range of materials available for processing by the electrochemical jet technique.

Experimental Investigation on Micro ECM Of Aluminium Metal Matrix Composite

Abstract: All engineering materials can be one or combination of processes in such a way that the material’s potential is fully exploited. This paper examines about the process parameters like electrolyte concentration, pulse on/off ratio, machining voltage, voltage frequency, tool vibration frequency on over cut and MRR (Material Removal Rate). Electrochemical machining is a method of removal of a metal by an electrochemical process. It is typically used for the mass manufacturing and is used for extremely working the hard materials or the materials that are difficult to machine using the conventional methods. In this project, we have chosen a composite (Al-6063) reinforced with MWCNT with various composition and found the optimization of parameters on machining rate, overcut, electrolytic concentration, machining voltage, voltage frequency, tool vibration frequency and pulse on/off ratio of a composite be achieved by using a method with EMM (Electrochemical Micro Machining). But before getting into the EMM, we had casted the composite using stir casting, then surface finishing and then we had sliced each composite for the EMM test. This project also attempts in establishing the comprehensive mathematical model for correlating the interactive and higher-order influences of various machining parameters. The MRR (Material Removal Rate) and radial overcut of the composite is achieved by using a method utilizing relevant experimental data as obtained through experimentation. Additionally, Scanning Electron Microscope (SEM) images are taken for the further understanding of microhole profile

Performance optimization of a PTFE-coated electrode in electrochemical micromachining

Performance optimization of a PTFE-coated electrode in electrochemical micromachining

Multiobjective Optimization of Heat-Treated Copper Tool Electrode on EMM Process Using Artificial Bee Colony (ABC) Algorithm.

Electrochemical micromachining (EMM) is a plausible method for manufacturing high accuracy and precision microscale components in a broad range of materials. EMM is commonly utilized to manufacture turbine blades for automobiles and aircrafts. In this present study, the EMM process was performed with a heat-treated copper tool electrode on aluminum 8011 alloy. The process parameters such as voltage, concentration of electrolyte, frequency, and duty factor were varied to analyze the effect of a heat-treated electrode on material removal rate (MRR), overcut, conicity, and circularity. It was observed that high MRR was obtained with lower overcut with an annealed electrode. The better conicity and circularity were obtained with a quenched electrode compared to other heat-treated and untreated tool electrodes. The artificial bee’s colony (ABC) algorithm was used to identify the optimum parameters and, finally, the confirmation test was carried out to evaluate the error difference on the machining process. The optimum combination of input process parameters found using TOPSIS and ABC algorithm for the EMM process are voltage (14 V), electrolyte concentration (30 g/L), frequency (60 Hz), and duty cycle (33%) for the annealed tool electrode and voltage (14 V), electrolyte concentration (20 g/L), frequency (70 Hz), and duty cycle (33%) for the quenched tool electrode. It was confirmed that 95% of accurate response values were proven under the optimum parameter combination.

Anodic Polarization Study of Step Pulse Waveform for Machining Accuracy in Electrochemical Micromachining

Electrochemical micromachining (EMM) shows promise as a versatile process for machining chemically resistant metallic materials in microsystems applications. A traditional rectangular pulse pattern has been modified into a step pulse waveform with a series of short rectangular pulses with different amplitudes. By establishing the experimental setup, anodic polarization behavior has been investigated throughout the dissolution process with 0.1 M H2SO4 electrolyte solution at different applied voltages under the application of rectangular and step pulse waveforms. Utilizing the step pulse waveform, oscillation of the anode potential and transpassive state have been obtained during machining. Thus, from polarization studies, it has been observed that at 13 V, the current density is accelerated in a moderate range, i.e., 0 to 33 A cm−2, which can reduce the anodic dissolution rate during the active state. Alternatively, the stray current effects and micro-sparks can be controlled because the duration of the passive state is very small and the RMS voltage can be reduced by 20.65% as compared to the rectangular pulse waveform. Further, overcut and tapering effects have been reduced by 83.99% to 51.39% and by 98.66% to 44.48% at the applied voltage of 13 to 17 V, respectively.

Neural Network (NN)-Based RSM-PSO Multiresponse Parametric Optimization of the Electro Chemical Discharge Micromachining Process During Microchannel Cutting on Silica Glass

The production of miniature parts by the electrochemical discharge micromachining process ([Formula: see text]-ECDM) draws the most of attractions into the industrial field. Parametric influences on machining depth (MD), material removal rate (MRR), and overcut (OC) have been propounded using a mixed electrolyte (NaOH:KOH- 1:1) varying concentrations (wt.%), applied voltage ([Formula: see text]), pulse on time ([Formula: see text]s), and stand-off distance (SOD) during microchannel cutting on silica glass (SiO[Formula: see text]). Analysis of variances has been analyzed to test the adequacy of the developed mathematical model and multiresponse optimization has been performed to find out maximum MD with higher material removal at lower OC using desirability function analysis as well as neural network (NN)-based Particle Swarm Optimization (PSO). The SEM analysis has been done to find unexpected debris. MD has been improved with better surface quality using a mixed electrolyte at straight polarity using a tungsten carbide (WC) cylindrical tool along with [Formula: see text], [Formula: see text], and [Formula: see text] axis movement by computer-aided subsystem and combining with the automated spring feed mechanism. PSO-ANN provides better parametric optimization results for micromachining by the ECDM process.

Assessment of Influence of the Process Parameters on Electrochemical Micromachining of 15-5 PH Stainless Steel

Assessment of Influence of the Process Parameters on Electrochemical Micromachining of 15-5 PH Stainless Steel

Processing and Profile Control of Microhole Array for PDMS Mask with Femtosecond Laser.

Polydimethylsiloxane (PDMS) is hailed as one of the foundational materials that have been applied to different products in various fields because of its chemical resistance, low cost, excellent flexibility, and high molding capability. With the aim to achieve surface texture with high efficiency by means of electrochemical micromachining with PDMS mask, a femtosecond laser is utilized to process a precision array of micro-through-holes on PDMS films as the molds. The ablation process of PDMS with a femtosecond laser was investigated via numerical simulation verified with experiments indicating a laser energy density of 4.865 mJ/mm2 as the ablation threshold of PDMS with the melting temperature of 930 K. The spiral scanning path with optimized radial offset was developed to ablate materials from the PDMS film to form the laminated profiles, and a tapered through hole was then formed with multilayer scanning. The profile dimension and accuracy were examined as control targets in terms of laser pulse energy and scanning speed, showing that a 12 μJ femtosecond laser pulse energy and 1000 mm/s scanning speed could bring about a nearly circular laminating profile with expected smaller exit diameter than the entry diameter. All the cross-section diameters of the microcone decreased with the increase of laser scanning speed, while the taper increased gradually and then saturated around a laser scanning speed of 800 mm/s due to the energy absorption resulting in smaller ablation in diameter and depth.

Desirability Function and GA-PSO Based Optimization of Electrochemical Discharge Micro-Machining Performances During Micro-channeling on Silicon-wafer Using Mixed Electrolyte

Desirability Function and GA-PSO Based Optimization of Electrochemical Discharge Micro-Machining Performances During Micro-channeling on Silicon-wafer Using Mixed Electrolyte

Fabrication of a Tool Electrode with Hydrophobic Features and Its Stray-Corrosion Suppression Performance for Micro-electrochemical Machining.

Micro-electrochemical machining (micro-ECM) can machine microstructures with excellent surface integrity on difficult-to-cut alloys. During micro-ECM, stray corrosion results in tapered sidewalls of machined structures. To suppress the stray corrosion, a novel tool electrode with the sidewall insulation of a gas film is proposed by fabricating the metal tool sidewall into a hydrophobic surface. The sidewall surface is designed to be characterized with spherical array cavities (radius of 500 nm) acting as the hydrophobic features, enhancing the gas-shielding effect of the gas film under electrolysis. The fabrication process of the hydrophobic sidewall is described in detail, including the self-assembly procedure of a monolayer template of Φ1μm polystyrene microspheres, the copper-electroforming procedure for filling the microspheres' gaps, and the removal procedure for forming spherical array cavities. The fabricated tool electrode (Φ500μm) obtains the hydrophobic features of a contact angle of up to 138°. As a result, bubbles generated on the tool surface can form an air-electrolyte interface instead of a dispersed bubble cluster. Micro-ECM experiments of microstructures verify that the novel tool electrode can improve machining accuracy by suppressing sidewall stray corrosion.

Development of a micro-electrochemical machining nanosecond pulse power supply.

Micro-electrochemical machining (micro-ECM) has been widely used for microscale and nanoscale processing of materials. The performance of the nanosecond pulse power supply is directly related to the precision of micro-ECM, which is one of the core technologies for micro-ECM. In this work, a nanosecond pulse power supply, with adjustable pulse frequency, duty cycle, and voltage, was designed with an STM32F103VET6 single-chip microcomputer as the control core and a metal-oxide-semiconductor field-effect transistor as the chopper switch component. The performance test has shown that the power supply can produce a continuous pulse with the highest frequency of 8MHz, the shortest pulse width of 50ns, the maximum peak current of 12A, and the maximum voltage of 10V. As compared with the power supply reported in the literature, the present power supply demonstrated the enhanced output current and improved waveform of the nanosecond pulse output, which could result in better machining accuracy and efficiency for micro-ECM.

Electrochemical Micromachining of Linear Micropattern on Stainless Steel Surface

Maskless electrochemical micromachining process with SU-8 2150 masked tool has been introduced containing microstructures with higherprofile accuracy that are generated on SS-304. In this research work, to make maskless EMM method with more cost-effective, substantial adaptations are provided to this technique and an advanced version of EMM process is applied for microtexturing. In this modified technique, a special microtextured cell unit including (micromachining cell, electrical connection, and electrolyte flow scheme) is assembled by the mechanical force and perpendicular cross flow system has been developed inside the cell. Experimentation is conducted to explore the machining influence of the advanced maskless EMM process for fabricating linear micropattern. The machining outcomes of voltage, frequency, and duty ratio on MRR, dimensional accuracy, textured depth, and surface roughness are investigated during microtexturing. The investigational research reveals that this advanced maskless EMM technique can generate highly identical micropatterns having MRR of 2.2 mg/min, width overcut of 19.76μm, textured depth of 14.4μm and surface roughness of 0.0307μm.

A performance study of electrochemical micro-machining on SS 316L using suspended copper metal powder along with stirring effect

ABSTRACT Electrochemical micro-machining (ECMM) is widely used for machining small-sized components, intricate shapes, and hard materials. Fabrication of micro-holes in stainless steel 316L (SS 316L) can be effortlessly achieved by the ECMM process rather than other machining methods, owing to its favorable machining characteristics and advantages. This paper tries to elucidate the performance of ECMM on the machining of SS 316L using an eco-friendly citric acid as an electrolyte medium, and the results are compared with copper metal powder suspended in a citric acid electrolyte (suspended electrolyte) and copper metal powder suspended in a citric acid electrolyte with the assistance of a mechanical overhead stirrer (suspended electrolyte with stirrer effect). The output performance parameters such as MRR and overcut are calculated by varying the input response parameters such as machining voltage, duty cycle, and electrolyte concentration. From the experimental results at higher parameter levels, the highest MRR and moderate overcut are obtained for suspended electrolyte with stirrer effect. For suspended electrolyte, moderate MRR and the highest overcut are detected. The least MRR and reduced overcut are found for citric acid electrolyte. SEM and EDAX analysis have been carried out to see the machined micro-hole and the composition present in the specimen.

Analysis of circuit current in electrochemical micromachining process under the application of different waveforms of pulsed voltage

Selection of optimal pulsed voltage parameters such as waveform, pulse rise and fall time, frequency, and duty ratio is very important to achieve the desired machining efficiency and accuracy in electrochemical machining (ECM). At present, this selection is done by conducting time-consuming and costly trial experiments. It is well understood that the volume and rate of material dissolution in ECM is dependent on the current flowing between the two electrodes. However, only a part of this current, called as Faradaic current, is responsible for the anodic dissolution and the rest of it, called as capacitive current, is consumed in charging the electrical double layer (EDL) capacitance which forms at the interface. Therefore, it is vital to understand the variation of Faradaic current in the system to arrive at optimal pulse parameters. An increase in the current flowing between the two electrodes does not ensures an increase in the Faradaic component of that current. To the best of authors' knowledge, there does not exists any method or device, to date, which can break the system current into its components and provide their variation explicitly. This research attempts to fill in this gap by provide a method of breaking the overall system current into its constituents by investigating the system under consideration using electrochemical impedance spectroscopy (EIS). The results of EIS are used to virtually construct an equivalent electrical circuit in MATLAB® Simscape and the current is simulated for different waveforms of pulsed voltage input. To access the correctness of the trends of Faradaic current obtained through simulations, an experimental study is conducted. Both simulation and experimental study is conducted for three waveforms of pulsed voltage namely: half wave rectified rectangular (RVW), sinusoidal (SVW), and triangular (TVW). For experimentation, these waveforms are obtained with the help of a rectification-cum-amplification circuit which is designed and developed in lab. Further optimization of triangular waveform is performed by varying its rise and fall time in five different cases. It is finally concluded that the trends of Faradaic current obtained from simulation study are in good agreement with the experimental results.

Performance study of electrochemical micromachining using square composite electrode for copper

The use of micro components is increasing day by day in the industries such as aviation, power circuit boards, inkjet nozzle, and biomedical. Among various non-traditional micromachining methods, electrochemical micromachining (EMM) shows unique characteristics, such as no tool wear, no residual stress, and high accuracy. In this research, EMM is considered to study the effect of square-shaped stainless steel (SS) and aluminum metal matrix composite (AMC) tools on square hole generation. The significant process parameters, such as machining voltage, duty cycle, and aqueous sodium nitrate (NaNO3) electrolyte of varying concentrations, are considered for the study. The performances of the EMM process are evaluated in terms of machining rate (MR) and Overcut (OC). The AMC tool shows 43.22% lesser OC than the SS tool at the parameter combinations of 8 V, 85%, and 23 g/L. Also, the same parameter combination MR for the SS tool is 71.6% higher than the AMC tool. Field emission scanning electron microscope image (FESEM) analysis shows that the micro square hole generated using composite electrode shows micro-pits on the circumference of the square hole. The energy-dispersive X-ray spectroscopy (EDAX) analysis is conducted to verify the presence and distributions of reinforcement in the AMC tool.

Effect of different electrolytes on electrochemical micro-machining of SS 316L

The use of stainless steel 316L (SS 316L) in the medical, marine, aerospace, bio-medical, and automobile sectors increases rapidly. Electrochemical micro-machining (ECMM) is the appropriate method for machining SS 316L due to its burr-free machining surface, no residual stress, and high precision. However, some limitations are found in using strong electrolytes, such as HCl, H2SO4, KOH, NaNO3, and NaCl, which reportedly face difficulties in disposing to the environment and handling issues. Hence, this paper addresses overcoming the disadvantages encountered in the ECMM process when using strong electrolytes to machine SS 316L. Therefore, different organic electrolytes such as tartaric acid (C4H6O6), citric acid (C6H8O7), and a combination of tartaric and citric acid (mixed electrolyte) are considered to select the best electrolyte. Process parameters like machining voltage, duty cycle, and electrolyte concentration are included in determining machining performance. The performance of ECMM is evaluated using material removal rate (MRR) and overcut. The overcut of tartaric acid electrolyte is 179% less than mixed electrolyte for the parameter combination of 12 g/l, 11 V, and 85%. On the other hand, the mixed electrolyte shows 114.2% higher MRR than the tartaric acid electrolyte for the parameter solutions of 25%, 11 V, and 20 g/l. Furthermore, the citric acid electrolyte shows the second-lowest overcut and higher MRR in all aspects of machining performance. Field emission scanning electron microscope (FESEM) studies are carried out to realize the effect of electrolytes on the machining surface.