Electrochemical Micromachining Process Research Articles

Optimization of Electrochemical Micromachining Process Parameters for Machining of AMCs with Different % Compositions of GGBS Using Taguchi and TOPSIS Methods

In recent years, the application of aluminum metal matrix composites is expanding to various fields like aerospace, automobile and other industrial machineries. This paper presents the machinability of ground-granulated blast furnace slag (GGBS)-reinforced aluminum 6061 metal matrix composites using electrochemical micromachining for material removal rate (MRR) and radial overcut (ROC). Input voltage, duty cycle, electrolyte concentration and % of composition are selected as the input process parameters. Experiments have been investigated using the L18 mixed-level orthogonal array, and process parameters are optimized using Taguchi technique. The model equation for MRR and ROC is developed using regression analysis. Analysis of variance is performed, and the most significant factor is found to be percentage (%) composition of GGBS. Additionally, the multi-criteria decision-making technique has been used to find optimal machining parameters for higher MRR and lower ROC. The optimal combination for higher MRR and lower ROC is 10 V, 50%, 35 g/l and 12% of GGBS composition. The confirmation test has been carried out to validate the results, and the obtained optimal parameter levels are very close to an ideal solution.

Influence of Process Parameters on Machinability of Inconel 718 by Electrochemical Micromachining Process using TOPSIS Technique

Accurate and precise micromachining with intricate features is an essential requirement for various applications of engineering materials in the present scenario. This is effectively achieved by the enhancing the electrochemical machining process, since it is a new and promising technique offering distinct advantages in overall machining quality. The turbine performance depends on a turbine blade and many small apertures with varying diameters of 0.5–4 mm for reducing the heat produced during its operation for improving efficiency. The present study was carried out for investigating the effects of diverse input process factors on the machining accuracies in the electrochemical micromachining process under two different electrolytes such as sodium chloride and sodium nitrate. The sodium chloride was found to have a higher material removal rate compared to sodium nitrate as electrolyte. A better surface finish and radial overcut were achieved with sodium nitrate compared to sodium chloride electrolyte. The optimum combination of ECMM process parameters was determined using TOPSIS method and verified with a confirmation test.

Investigation into fabrication of microslot arrays by electrochemical micromachining

Maskless electrochemical micromachining (EMM) is a prominent and unique surface texturing method to fabricate the arrays of microslots. This article investigates the generation of microslot arrays using maskless EMM method. The developed prototype maskless EMM setup consists of EMM cell, power supply connections, electrode holding devices and constricted vertical cross flow electrolyte system for the fabrication of microslot arrays economically. One textured cathode tool with SU-8 2150 mask is used to produce 22 microslot arrays. Influences of EMM process parameters including voltage, electrolyte concentration, inter electrode gap, flow rate and machining time on the machining performance that is, width overcut, depth and surface roughness (Ra) of microslot arrays are investigated. For lower width overcut, controlled depth, and lower surface roughness, machining with lower voltage, lower electrolyte concentration, lower inter electrode gap, higher flow rate and lower machining time are recommended. From the analysis, it is observed that the best machining conditions including inter electrode gap of 50 μm, applied voltage of 6 V, electrolyte concentration of 20 g L−1, flow rate of 5.35 m3 hr−1 and machining time of 1 min fabricate regular microslot array with mean width overcut of 24.321 μm, mean machining depth of 10.7 μm and mean surface roughness of 0.0101 μm.

Parametric analysis of fabrication of through micro holes on titanium by maskless electrochemical micromachining

Machining of micro features on titanium is a complex task due to its natural physical and chemical properties. Electrochemical micromachining (EMM) presents several advantages, such as minimum or no tool wear, stress-free machining with greater surface finish. This paper demonstrated successful fabrication of micro feature, i.e., through micro holes on pure commercial titanium with the help of maskless electrochemical micromachining process. Influence of various EMM process parameters, i.e., machining voltage, pulse frequency, duty ratio, and micro tool feed rate on machining accuracy in terms of radial overcut and conicity of micro hole as well as material removal rate (MRR), has been investigated to establish suitable process parameters for through micro hole generation. Surface quality of machined micro holes with respect to EMM process parameters was also investigated. Outcomes of this experimental investigation ensure fabrication of through micro holes with minimum overcut and taper angle. Machining voltage of 8 V, pulse frequency of 200 kHz, and micro tool feed rate of 0.6 μm/s with lower duty ratio are proved to be major influencing parameters. Surface roughness of 0.09 μm has been achieved with most suitable process parameters. In situ fabricated disk micro tool has been utilized to enhance machining accuracy. The study presented in this article can be a potential application for generation of various other micro features on pure commercial titanium which will find potential applications in microneedles, drug delivery systems, and features for various BioMEMS and engineering applications.

(Invited) Electrochemical Micromachining Based on Confined Etching

Micromachining is becoming the cutting-edge of high-tech manufacturing because of the increasing industrial demand for supersmooth surfaces and functional three-dimensional micro/nano-structures in microelectromechanical systems, ultra-large scale integrated circuits, miniaturized total analysis systems, precision optics and so on. Taking advantage of no tool wear, no surface stress, environmental friendliness, simple operation, and low cost, electrochemical micromachining (ECM) has an irreplaceable role in micromachining. We present here our perseverant research in the last two decades on how to “confine” the ECM processes to occur at micrometer or even nanometer scale, that is, to ensure ECM with nanoscale accuracy. We have been developing the confined etchant layer technique (CELT) to fabricate three-dimensional micro- and nanostructures (3D-MNS) on different metals and semiconductor materials since 1992. In general, there are three procedures in CELT: (1) generating the etchant on the surface of the tool electrode by electrochemical or photoelectrochemical reactions; (2) confining the etchant in a depleted layer with a thickness of micro- or nanometer scale; (3) feeding the tool electrode to etch the workpiece. Scavengers, which can react with the etchant, are usually adopted to form a confined etchant layer. Through the subsequent homogeneous reaction between the scavenger and the photo or electrogenerated etchant in the electrolyte solution, the diffusion distance of the etchant is confined to micro- or nanometer scale, which ensures the nanoscale accuracy of electrochemical machining. However, because the thickness of the electrolyte solution between the tool electrode and the workpiece are usually at micro/nano-meter scale, it is a challenge to solve the problems of potential distribution and mass transfer in the ultra-thin layer electrolyte cell. In this presentation, we will introduce our recent work on the external physical field induced electrochemical reactions in which there is no need of 2-electrode or 3-electrode system in the conventional electrochemical system.

Electrochemical Micro-Machining Process Parameter Optimization Using a Neural Network-Genetic Algorithm Based Approach

Electrochemical Micro-Machining Process Parameter Optimization Using a Neural Network-Genetic Algorithm Based Approach

전기화학 미세가공기술의 현황

Electrochemical micromachining (ECM) processes use anodic dissolution of metals to remove workpiece materials. ECM processes including electrochemical milling and drilling, wire electrochemical machining and electrochemical etching offer a better alternative in manufacturing complex features and nano-pattern surface. Electrochemical discharge machining (ECDM) uses high temperature of electrochemical spark, which is suitable process for micro machining of hard brittle and non-conductive materials such as glass and ceramic. In this paper, the state of the art in electrochemical micro machining technologies was reviewed. Also, some hybrid machining methods are introduced.

Performance optimisation of electrochemical micromachining of micro-holes on Inconel 625 alloy

This work involves producing micro holes on Inconel 625 alloy through Electrochemical micromachining (EMM) process. The input parameters investigated are supply voltage, electrolyte concentration and duty ratio. The cathode tool used is a conical tipped stainless steel needle and the electrolyte is acidified sodium nitrate solution. Taguchi design of L9 Orthogonal Array is followed for experimental work. The performance analysis is done through process responses such as machining rate and overcut. The experimental results have given the optimum parameter combination for higher machining rate as 16 V supply voltage, 35 g/lit electrolyte concentration and 45% duty ratio and for lesser overcut as 12V, 35 g/lit and 45% duty ratio. The influence of input parameters on the process is also studied. The multi-objective optimisation technique used has produced 12 V, 30 g/lit and 45% duty ratio as the ideal combination for achieving higher machining rate and lower overcut.

Performance optimisation of electrochemical micromachining of micro-holes on Inconel 625 alloy

This work involves producing micro holes on Inconel 625 alloy through Electrochemical micromachining (EMM) process. The input parameters investigated are supply voltage, electrolyte concentration and duty ratio. The cathode tool used is a conical tipped stainless steel needle and the electrolyte is acidified sodium nitrate solution. Taguchi design of L9 Orthogonal Array is followed for experimental work. The performance analysis is done through process responses such as machining rate and overcut. The experimental results have given the optimum parameter combination for higher machining rate as 16 V supply voltage, 35 g/lit electrolyte concentration and 45% duty ratio and for lesser overcut as 12V, 35 g/lit and 45% duty ratio. The influence of input parameters on the process is also studied. The multi-objective optimisation technique used has produced 12 V, 30 g/lit and 45% duty ratio as the ideal combination for achieving higher machining rate and lower overcut.

Investigations into insertion force of electrochemically micro-textured hypodermic needles

Electrochemical micro-machining (ECMM) is being a widely used process for replicating multiple micro-structures for micro-texturing due to its heat-free and zero tool wear processing. This paper outlines an experimental study of the tribological behavior of medical hypodermic needles. The real surface contact area of textured needles is calculated and related to insertion force. Insertion force of textured needles is investigated by puncturing and inserting in a hydrogel sample with and without castor oil. An electrochemical micro-machining process is extended for machining of micro-dimples, circular micro-grooves, and linear micro-channels on curved metallic surfaces for creating micro-textures. Insertion force of micro-textured needle is recorded using a load cell, and comparison of it with untextured needles shows the significance of micro-textures. From the experimental study, it is witnessed that micro-textures developed on the needle decreased the insertion force and changed the behavior of fracturing of the hydrogel as compared to the needle without textures. The needle with circular micro-channels (grooves) confirmed the minimum insertion force compared to other micro-textured needles. Reduction in insertion force with respect to micro-dimples, parallel micro-channels, and circular micro-channels are 5.6, 25.5, and 37.8%, respectively. Calculation and analysis of surface area in all the three micro-textured needles support the reason of reducing the force in the case of circular micro-channels. In the case of circular micro-channels, contact area decreases more and fracture in the lateral direction is minimal; hence, insertion force recorded is minimum.

Investigation of the influence of ultrasonic stirring on mass transfer in the through-mask electrochemical micromachining process

Surface texturing is a widely accepted approach for friction reduction between mechanical components. Through-mask electrochemical micromachining is a simple and reliable process for metal surface texturing in which mass transport conditions have profound influence on final machined quality. An ultrasonic stirrer is usually adopted for mass transfer enhancement. However, understanding of the effects of ultrasonic stirring on mass transfer is limited, and is far from sufficient for developing guidelines for its practical application. In this work, the influences of ultrasonic stirring parameters on mass transfer have been investigated numerically and experimentally. With the numerical method, periodic pressure change in the electrolyte over time has been obtained, showing that ultrasonic stirring results in drastic transient pressure change in electrolyte fluid fields. Parameters related to ultrasonic frequency, vibration amplitude, and the depth of anode surface immersed in the electrolyte solution influence pressure amplitude. Validation experiments have been conducted and etched surface profile and morphology characterized, which show that the experimental observations are in agreement with numerical predictions. With the optimized mass transfer, well-defined micro-pits array of 30 μm and a smooth etched surface on tin-bronze substrate in large scale have been demonstrated.

Impact of the shape of electrode-tool on radical overcut of micro-hole in electrochemical micromachining

To make use of the full capability of electrochemical micro-machining (EMM), a meticulous research is needed to improve the material removal, surface quality and accuracy by optimizing various EMM process parameters. Keeping this in view, an indigenous development of an EMM machine set-up has been considered to carry out a systematic research for achieving a satisfactory control on the EMM process parameters to meet the micromachining requirements. In this study an EMM machine has been developed and experiments were conducted to study the influence of some of the major process parameters such as the machining voltage, electrolyte concentrations, the pulse-on-time and the machining current on the machining rate and accuracy. The effect of the shape of the tool electrode tips on EMM has been investigated experimentally with 304 stainless steel sheets. The machining rate and the overcut are significantly influenced by the shape of the tool electrode tip.

Development of a modified through-mask electrochemical micromachining for micropatterning nonplanar surface

To achieve cost-effective patterning of microfeatures on the nonplanar surfaces, a modified through-mask electrochemical micromachining process (TMEMM) was developed in which a layer of flexible insulating media with interconnected micropores is filled in the interelectrode gap and presses the through mask, considerably facilitating the mechanically attachment of the reusable through mask to the complex workpieces during EMM. A uniquely special tool cathode with a variety of outlet passages was correspondingly designed to significantly alleviate mass transfer limitation because of introduction of the flexible media. Some numerical and experimental investigations were then carried out to evaluate this proposed TMEMM process, with the focus on analyzing the dimension distribution uniformity of the machined microdimples. It is showed that the modified active TMEMM process exhibits favorable machinability and applicability to produce microdimples with significantly uniform geometric profiles on the planar and nonplanar surfaces.

Experimental investigation into micromilling of microgrooves on titanium by electrochemical micromachining

Titanium possesses excellent physical and chemical properties such as higher strength to weight ratio, greater biocompatibility and outstanding corrosion resistance. Therefore, titanium is highly demanding material in aerospace to biomedical applications from macro to micro scale levels. However, machining of titanium in macroscopic or microscopic domain is a complex task either by conventional or nonconventional machining processes. Electrochemical micromachining (EMM) could be one of the alternatives for machining of titanium in microscopic area. The study elaborated in this paper demonstrates successful micromilling of through microgrooves on pure commercial titanium utilizing maskless electrochemical micromachining. Layer-by-layer micromilling strategy has been successfully employed with the help of in-situ fabricated disc shape microtool for micromilling of through microgrooves. Influence of various EMM process parameters such as machining voltage, pulse frequency and microtool feedrate on machining accuracy of through microgrooves were also investigated and established most suitable EMM process parameters for successful micromilling of through microgrooves on pure titanium. This paper also demonstrated successful fabrication of few complex geometry microgrooves by electrochemical micromilling for practical applications. Micromilling of microgrooves on pure titanium by EMM may find vital applications for MEMS, micro fluidics, microsensors, micro engineering and biomedical systems.

Fabrication of microgrooves with varied cross-sections by electrochemical micromachining

Microgrooves are one of the important micro-features machined on various microproducts. The demand of complex microgrooves with varied cross section has increased in various fields, since specific cross-sectional shape of microgroove improves the product performance, due to increased inner surface area. Machining of simple microgroove is relatively easy, but when the cross section of the microgroove is varying along its depth, it becomes difficult from microtool fabrication point, as well as from the process point of view. The purpose of this study is to verify the possibilities of machining varied cross-sectional microgrooves on metallic surfaces by electrochemical micro-machining (EMM). Different cross sections of the microgrooves have been machined by regulating the important EMM process parameters such as applied voltage, duty ratio, and machining time, along the depth during machining of microgrooves, utilizing developed experimental setup. This technique enables the machining of various cross sections of the microgrooves by EMM utilizing the single-disk shape microtool. Finally, machining of different cross-sectional microgrooves like reverse tapered, barrel shaped, double stepped, spherical based microgrooves, and microgroove with internal pocket has been demonstrated successfully. The experimental findings may be useful for machining of complex microgrooves suitable for micro-coolers, micro-reactors, and micro-mixers etc. which needs specific geometry for product functioning.

Analysis on electrochemical discharge machining during micro-channel cutting on glass

Modern industrial field of micro-machining has an attractive attention to increase the machinability of electrically non-conducting materials. Electrochemical discharge micro-machining process has the ability to machine high strength non-conducting brittle materials like glass. This paper shows a development of second-order correlation between the various machining criteria and different process parameters such as applied voltage, electrolyte concentration and inter-electrode gap (IEG). The analysis of variance (ANOVA) has been performed to find out the adequacy of the developed models. The research paper includes the effects of various process parameters on material removal rate (MRR), overcut (OC), heat affected zone (HAZ) and machining depth (MD) during micro-channel generation on glass. This paper also represents the single as well as multi-objective optimised results to determine the suitable parametric combination for maximum MRR and machining depth and minimum overcut and HAZ area using response surface methodology (RSM) and genetic algorithm (GA).

Optimizing electrochemical micromachining parameters for Zr-based bulk metallic glass

Bulk metallic glasses (BMGs) contain a unique combination of enhanced mechanical and chemical properties due to the absence of crystalline features, but their machining processes are still being developed. Electrochemical micromachining (ECMM) with microtool electrodes is a promising technique for microshaping BMGs without the use of elevated temperatures or deformation – both of which can induce crystallization. This work systematically studied the mechanisms and processing parameters responsible for degradation of the material surface allowing the development of a novel protocol for utilizing the ECCM technique for Zr based BMGs. Anodic polarization of Zr57Ni20Al15Cu5.5Nb2.5 BMGs in 2.94M NaNO3 and subsequent microscopy revealed that the primary corrosion mechanism during electrochemical micromachining is pitting. Through chronoamperometry the repassivation potential was determined to be 2.235V. This voltage was used to prevent spontaneous repassivation during electrochemical micromachining. The Taguchi method was used to assess the effect of electrolyte flow rate, duty cycle and pulsed voltage range. Signal-noise ratios and analysis of variance were used to optimize ECMM parameters of the electrochemical micromachining process. Through this method, an electrolyte flow rate of 0.4L/min with a duty cycle of 1:10 and a voltage range of 2.235–3V was determined to yield the optimal holes with respect to the aspect ratio, surface roughness and the rate of electrochemical micromachining of Zr-based BMGs.

Performance analysis of process parameters on machining α–β titanium alloy in electrochemical micromachining process

Due to inherent properties of Ti-6Al-4V alloy, it is being used in the application of fuel injector nozzle for diesel engine, aerospace and marine industries. Since the electrochemical micromachining process involves the no heat-affected zone, no tool wear, stress- and burr-free process compared to other micromachining processes, it is widely used in the manufacturing field to fabricate complex shape and die. Hence, it is highly important to compute the optimum input parameters for enhancing the machining characteristics in such machining process. In this study, an attempt has been made to find the influence of the process parameters and optimize the parameters on machining α–β titanium alloy using Taguchi-grey relational analysis. Since applied voltage, micro-tool feed rate, electrolyte concentration and duty cycle have vital role in the process, these parameters have been chosen as the input parameters to evaluate the performance measures such as material removal rate, surface roughness and overcut in this study. From the experimental results, it has been found that micro-tool feed rate has more influence due to its importance in maintaining inter electrode gap to avoid micro-spark generation. It has also been found that lower electrolyte concentration with lower duty cycle produces lower surface roughness with better circularity on machining α–β titanium alloy. The optimum combination has been found using Taguchi-grey relational analysis and verified from confirmation test. It has also been inferred that the multi-response characteristics such as material removal rate, surface roughness and overcut can be effectively improved through the grey relational analysis.

Experimental investigation and multiphysics simulation on the influence of micro tools with various end profiles on diametrical overcut of holes machined using electrochemical micromachining for a predetermined optimum combination of process parameters

Electrochemical micromachining (EMM) process is generally applied to shaping of electrically conductive materials which has been gaining popularity in the production of biomedical, MEMS, aerospace and nuclear components. The dimensional accuracy is affected by various process parameters of EMM and by the end profile of the cathode (tool) used to machine the feature. In this study, it is proposed to investigate the EMM process to know the influence of various process parameters on the diametrical overcut of the machined hole and the optimum combination of process parameters to produce holes with minimum diametrical over cut. A bare electrode with flat end is used for this purpose. Later, insulated electrode with flat end and bare electrodes with various end profiles are used to drill holes at the optimum combination of process parameters on Titanium grade II sheet to identify the most suitable micro tool to produce holes with minimum diametrical overcut and minimum stray machined zone. The EMM process of drilling holes using insulated electrode with flat end and bare electrodes with various end profiles are simulated at the optimum combination of process parameters using COMSOL Multiphysics V4.2a software. Results justified the use of multiphysics simulation to understand the process before conducting experiments so that costly trial and error experiments can be reduced to a minimum.

Experimental Investigation of Electrochemical Micromachaning Process Parameters on Pure-Titanium Using Taguchi-Grey Relational Analysis

Non-conventional machine are nowadays plays a vital role in manufacturing complex shaped products and to produce the product with high accuracy the electrochemical machining is widely used to machine complicated shapes for electrically conducting difficult-to-machine materials such as super alloys, Ti-alloys, alloy steel, tool steel, stainless steel, etc. such titanium-based alloys are in common use for aero engine components such as blades and blisks (blade integrated disks). Therefore, in this present work to investigate the influence of some predominant electrochemical process parameters such as applied voltage, electrolyte concentration, Micro-tool feed rate and duty cycle on the metal removal rate , overcut and surface roughness to fulfill the effective utilization of electrochemical machining of Pure-titanium. The purpose of this study is to investigate the influence of process parameters on machining characteristics and optimize the combination of those parameters using Taguchi-grey relational analysis. From this result, it is observed that process parameters have significant role in Electrochemical Micromachining process and the optimization values has been found using proposed multi-response methodology.