Electrochemical Discharge Machining Process Research Articles

Electrochemical discharge machining: fumes generations, properties and biological effects

Electrochemical discharge machining (ECDM) is a non-conventional machining process which is highly susceptible for machining of various materials irrespective of their properties. This process is successfully attempted for machining of micro-holes and micro-channels on ceramics, composites and super-alloys for micro electromechanical system, lab-on-chip devices and aerospace applications. However, since the development of ECDM process, the environmental aspects and its effect on human health are least reported. Therefore, the analysis and characterization of fumes particles, gases and compounds generated in breathing zone of ECDM process is the key route for its conversion to sustainable and green manufacturing process. This paper describes the fumes mass concentration, morphology of fume particles, average size and chemical composition in ECDM process with alkaline electrolytes such as KOH. The morphological analysis of fumes particles in ECDM process exhibits different shapes such as spherical, irregular, rectangular, agglomerations and flower shell structure. The energy dispersive spectroscopy (EDS) is carried out to predict chemical composition of fumes particles generated in ECDM process. The EDS analysis and Fourier transform infrared spectroscopy of fumes particles reveal the presence of different toxic elements and compounds such as Cr, Mg, Ti and Fe, which have carcinogen effects on environment as well as on human health.

Electrochemical Discharge Machining Technology Applied for Turning Operation

In hybrid electrochemical discharge machining (ECDM) process machining of electrically conducting and non-conducting materials takes place in an alkaline electrolyte with the introduction of a tool electrode and an auxiliary electrode. In this paper an alternative of ECDM process, Electrochemical Discharge Turning (ECDT), is proposed to machine a cylindrical job which rotates continuously against a stationary or moving tool electrode. The material removal mechanism of ECDT process is similar to ECDM process, but ECDT employs ECDM components with rotary cylindrical workpiece immersed in an electrolytic solution. The present paper highlights the design and development of ECDT set-up which can be applied for turning operation. The proposed ECDT set up can also be utilized for making grooves of different shapes and sizes on cylindrical parts of electrically non-conducting materials.

A multiphase simulation study of electrochemical discharge machining of glass

Micromachining of glass has gained importance due to numerous applications of glass in microfluidics, optics, electronics, and biotechnology industry. Electrochemical discharge machining (ECDM) is an emerging nontraditional process which has the potential for micromachining of glass with minimal surface damages. Material removal during the machining of glass by ECDM involves thermal machining by electrical discharges between the tool and the gas film. The energy of these discharges is influenced by the gas film characteristics and affects the machining results. In this study, a combined approach of finite element simulation and experimentation is used to study the ECDM process to understand the impact of gas film characteristics on the overcut in machining. The multiphase simulation setup incorporates a combined electrochemical system of glass and electrolyte. The changes in the gas film characteristics due to the variations in the level of electrolyte and the corresponding changes in the overcut are studied. It was observed that the gas film thickness increased with an increase in the level of electrolyte and the gas film stability showed an opposite trend. This resulted in an increase in the overcut in the machining with the increase in the level of electrolyte. This trend observed in the simulation was validated with experimentation.

A Theoretical analysis on Electro Chemical Discharge Machining using Taguchi Method

The Electrochemical discharge machining (ECDM) is a growing machining process that develops from the processes like electrochemical machining (ECM) and electric discharge machining (EDM), used in micro machining of usually non-conductive materials such as quartz, glass, composites and ceramics. In recently time the need of non-conductive materials has been grown rapidly in the field of aerospace, medical, electrical and optical applications. Such as these applications implicate machining with higher reliability and higher accuracy, ECDM process has lavish scope in this area. Some further methods also that can machine non-conductive materials but they have certain limitations. In the current time ECDM is an emerging process, continuously researchers are trying to improve and amend it as a better way for non-conducting materials. Currently this paper carried out a study on continuous improvements in ECDM in machining of glass in the ECDM, has been show their effect on material removal (MR). A Taguchi analysis on machining of borosilicate glass has also been obtained, wherein it is illustrated that increase in feed rate and electrolyte concentration increases the MR.

Metaheuristic approach in machinability evaluation of silicon carbide particle/glass fiber–reinforced polymer matrix composites during electrochemical discharge machining process

The advanced manufacturing and machining techniques are adopting a population-based metaheuristic algorithm for production, predicting and decision-making. Using the same approach, this paper deals with the application of bees algorithm and differential evolution to forecast the optimal parametric values aiming to obtain maximum material removal rate during electrochemical discharge machining of silicon carbide particle/glass fiber–reinforced polymer matrix composite. The bees algorithm follows swarm-based approach, while differential evolution works on a population-based approach. The experimental design was prepared on the basis of Taguchi’s methodology using an L16 orthogonal array. For the experimental analysis, the main variables in the process, that is, electrolyte concentration (g/L), inter-electrode gap (mm), duty factor and voltage (volts), were selected as main input parameters, and material removal rate (mg/min) was adjudged as output quality characteristic. A comparative investigation reveals that the maximum material removal rate was obtained by the parametric value proposed by differential evolution that follows the bees algorithm and Taguchi’s methodology. Furthermore, the results prove that the differential evolution algorithm has better collective assessment capability with a rapid converging rate.

Experimental Investigation and Analysis of Electrochemical Discharge Machining (ECDM) On Fiberglass Reinforced Plastic (FRP)

Electrochemical discharge machining (ECDM) is a hybrid machining process widely used for machining of non-conducting materials such as glass, quartz, ceramic and other semiconducting materials used in MEMS devices. In this study, ECDM operation is conducted on fiberglass reinforced plastic material with a mixture of NaOH + KOH as electrolyte in equal proportions. Input process parameters such as voltage, duty factor, electrolyte concentration and tool rotation were optimized so as to achieve high material removal rate (MRR). The focus is on experimental investigation and gray relational analysis of ECDM process with flow and without flow of electrolyte. With continuous flow of electrolyte supplied during machining, it is observed that MRR increases albeit being very less.

Fabrication of micro-slits using W-ECDM process with textured wire surface: An experimental investigation on kerf overcut reduction and straightness improvement

In this work, a vertical configuration of wire electrochemical discharge machining (W-ECDM) process with textured wire surface was used to machine the micro-slits on glass. The effects of process parameters like applied voltage, pulse on time, electrolyte concentration and feed rate were experimentally investigated on the size and geometry of micro-slits in terms of kerf overcut and straightness. The discharging mechanism for textured and smooth wire surfaces have been evidenced by the simulation results and high speed imaging. The simulation results revealed that the textured surface of wire electrode resulted in intensification of localized electric fields over the entire machining face of wire electrode. Thus, the breakdown of gas film from the textured surface of wire electrode generates spark discharges from the entire face of wire electrode. The underlying material removal mechanism of W-ECDM process during micro-slitting operation has been proposed and illustrated with appropriate schematics. Additionally, second-order regression models were developed to determine the relationships between input process parameters and responses. Features plots were used to correlate the response characteristics with respect to input process parameters. Desirability approach was used to optimize the parametric ranges for minimum kerf overcut and maximum straightness. The parametric combination of applied voltage of 48 V, pulse on time of 3 ms, feed rate of 3 mm/min and electrolyte concentration of 15% wt./vol. is recommended to machine the micro-slits with minimum kerf overcut of 105 μm and maximum straightness of 94.42%.

Numerical and experimental investigations into microchannel formation in glass substrate using electrochemical discharge machining

Microchannels formed in non-conductive substrates like fused silica, glass and quartz, etc, have wide applications in the field of micro-fluidic and lab-on-chip applications due to their optical transparency, chemical inertness, and biocompatible nature. Electrochemical discharge machining (ECDM) has emerged as a potential low-cost fabrication method to fabricate microfeatures in these materials, compared to conventional laser etching techniques. In this paper, numerical simulation and experimental fabrication of microchannels in a glass substrate using the ECDM based micromilling technique is demonstrated. Stainless steel needle as tool electrode is used in alkaline electrolyte medium. The effects of process parameters viz. tool feed rate, pulse frequency and machining voltage on material removal rate (MRR) and surface roughness (SR) of the microchannels were analysed. The experimental results showed that the MRR and SR increases with an increase in machining voltage and tool feed rate but reduces with an increase in the pulse frequency. Simulations using FEM-based model showed similar trends in MRR with that of experiments. A comparison between the cross-section profiles obtained by the experimental work and predicted profile by the numerical simulation showed some deviation between them due to the Gaussian heat flux assumption in the numerical model. Optical images showed that KOH performance is comparatively better than NaOH with respect to thermal damage and width of cut. Further, multi-objective optimization was performed using utility theory coupled with Taguchi’s method to optimize the process parameters. Moreover, the capability of the ECDM process was demonstrated in fabricating various other micro-features such as sinusoidal channel, letter engraving, etc in a glass substrate, which can be extended to other brittle materials like quartz, fused silica, ceramic, etc.

Machining of Carbon Fibre Reinforced Polymer Composite by Electrochemical Discharge Machining Process

Carbon Fibre Reinforced Polymer (CFRP) composite is highly applicable in aeronautics, defence and electronics industries application due to their better mechanical properties. Still, the micro-drilling of CFRP composite is challenge to research society due to its semi-conductive and fibrous nature. In this work, the author’s successfully drilled micro-holes in CFRP composite using Electrochemical Discharge Machining (ECDM) process. The experiments were designed on the basis of Taguchi’s method using L9 orthogonal array. The experiments were carried out with process parameters such as electrolyte concentration, applied voltage, inter electrode gap and material removal rate as response characteristic. The surface characteristics of drilled hole were studied by Scanning Electron Microscope (SEM) micrograph. Additionally, the dominant effects of process parameters on MRR were evaluated using Analysis of Variance (ANOVA).

Modelling and Multi-Objective Optimization during ECDM of Silicon Carbide Reinforced Epoxy Composites

The silicon carbide (SiC) reinforced epoxy composites has evidenced their reputation as advanced composite material in domain of strength and durable nature. But, presence of SiC particles as reinforcement in epoxy composites wanes the machinability by increasing tool wear in conventional drilling process. For the reduction in tool wear and improvement in machinability, it becomes necessary to use non-conventional machining method which can elude direct tool-composite interaction. In domain of non-conventional machining methods, the electrochemical discharge machining (ECDM) process is emerging as potential contender for machining of nonconductive, hard and brittle fibrous materials. In this paper, artificial neural network-based hybrid model was generated for prediction and optimizing material removal rate (MRR) and taper during ECDM of SiC reinforced epoxy composites. The input parameters considered for the process were selected as voltage, electrolyte concentration, inter-electrode gap and duty factor whereas MRR and taper were obtained as response parameters. The experimentation was performed based on response surface methodology (RSM) using central composite design. RSM and ANN models were used to predict the MRR and taper during ECDM. The input parameters were optimized for higher MRR and minimum taper using desirability function. The obtained results for optimal solution were validated with the neural network model. The validation exemplifies the influence that machining methods focussed on artificial intelligence have on optimizing progressions.

Traveling Wire Electrochemical Discharge Machining (TW-ECDM) of Quartz Using Zinc Coated Brass Wire: Investigations on Material Removal Rate and Kerf Width Characteristics

In this era, advanced non-conducting materials are gaining importance due to their superior properties. However, it is difficult to micro-machine these materials inefficiency and also economically still persists with currently used advanced non-traditional machining processes. Non-traditional machining processes are typically unfeasible for quartz material owing to its properties such as high strength, high melting point, high temperature-resistance, chemical stability and brittleness. Traveling wire electrochemical discharge machining (TW-ECDM) process is newly developed non-traditional machining process and has great potential for machining of quartz ceramics. Coated wire has been used to reduce the wire breakage and improves the efficiency. The input important input parameters have been selected for this process as applied voltage, electrolyte concentration and wire speed. Taguchi robust design was perform to identify the optimal parametric conditions using L9 orthogonal array. Signal to noise (S/N) ratio and ANOVA were used to find the optimal parametric conditions and relative contribution of the input parameters respectively. Also, the surface finish was analyzed by scanning electron microscope (SEM). First time, coated wire with diameter of 0.15 mm has been used during TW-ECDM process. These obtained results present in this article will provide new guidelines to the micro-manufacturers, engineers and researchers.

Experimental investigations into triplex hybrid process of GA-RDECDM during subtractive processing of MMC’s

ABSTRACTThe use of Al-6063 SiCp metal matrix composites (MMCs) in electronic packaging applications, heat sinks for printed circuit boards and for microwave housings necessitates certain degree of machining operations to meet the specifications of the product. The various conventional and non-conventional machining processes had been used to machine the MMCs. But all such processes have their limitations in providing the desired outcomes. Therefore, the present research endeavor, a new process variant of ECDM for the machining of Al-6063 SiCp MMCs. The developed grinding assisted rotary disk electrochemical discharge machining (GA-RDECDM) process integrates the concept of triplex hybridization. In GA-RDECDM, an abrasive coated rotary disk was used as a tool electrode. The abrasive coated disk provides micro gaps between the tool electrode and work material surface and thereby it results in thin and stable gas film formation. The breakdown of thin and stable gas films produce high frequency, low intensity discharges and consequently improves the machining performance. The additional abrasion action imparted by rotating disk ensures the continuation of ECDM process. The influence of various process parameters including applied voltage, pulse on time, electrolyte concentration and the disk rotation rate on width over cut (WOC) and depth were experimentally investigated. Multi criteria optimization using desirability approach predicts the parametric combination of applied voltage of 99V, pulse on time of 3 ms, electrolyte concentration of 17%wt./vol. and disk rotation rate of 30 rpm as the optimum setting for fabrication of slits on the MMCs. The underlying process mechanism is also investigated and presented with appropriate illustrations. The major contribution of the present research work is the development of a novel method for the fabrication of the slits on MMCs.

Fabrication of precise micro-holes on quartz substrates with improved aspect ratio using a constant velocity-feed drilling technique of an ECDM process

In the present study, a detailed experimental investigation is carried out on a constant velocity-feed drilling technique of an electrochemical discharge machining (ECDM) process to fabricate micro-holes on quartz substrates. First, cylindrical micro-tools of four different diameters (145 µm, 195 µm, 300 µm and 400 µm) with varying tool feed rates (TFRs) (0.3 µm s−1–1.9 µm s−1) are considered to study their influence on the precision of fabricated micro-holes while using a 30 wt% NaOH solution as an electrolyte, a machining voltage of 30 V and an initial working gap of 5 µm. Minimum micro-hole diameter and overcut were achieved at a TFR 0.8 µm s−1 for the cylindrical tools of all diameters. Considering 0.8 µm s−1 as an optimal TFR, the influence of tool shape on the quality metrics was investigated using a spherical shaped tool electrode having a ball diameter of 145 µm and a spindle diameter of 90 µm. A micro-hole realized using the spherical shaped tool shows that the entrance diameter, entrance overcut, central diameter and central overcut are reduced by 12%, 29%, 28% and 67% respectively as compared to that realized using a cylindrical tool for the same process parameters. Micro-holes with improved precision and aspect ratio are achieved without using cost intensive equipments, feedback mechanisms, coated tools and tool rotation.

Investigations on quantification and replenishment of vaporized electrolyte during deep micro-holes drilling using pressurized flow-ECDM process

Electro-chemical discharge machining (ECDM) process has ability to drill micro-holes, nonetheless has limitation of lower depth with appreciable hole quality. The reason thereof is poor replenishment of vaporized electrolyte inside the machining zone with an increment in drilling depth. Few approaches have been reported to replenish the electrolyte in ECDM process. However, quantification of the vaporized electrolyte from the machining zone at different parametric conditions, and its replenishment with precise control is not revealed. In order to address these limitations of ECDM process, this article reports development of pressurized flow-ECDM (PF-ECDM) process. In this development fresh electrolyte is injected through a tubular electrode with precisely controlled electrolyte flow rate (EFR) into the machining zone during ECDM. Also, a novel approach is used to predict the range of EFR by quantifying the electrolyte vaporization rate at various thermal energy inputs. A comprehensive investigation is conducted to bring forth the effect of EFR on machining performance (i.e. depth and entrance diameter of the hole). The results of investigation reveal that the injected fresh electrolyte enhances the machining performance over conventional ECDM process. Also, the EFR is found to be dependent on provided thermal energy inside the machining zone. Hence, noticeable improvements in the process performance are realized at a particular value of EFR (i.e. adequate EFR) for specific parametric conditions. The multi criteria optimization is also performed using desirability function approach to obtain the optimum process parameters for PF-ECDM process. Eventually, a micro hole of 2478 μm depth is achieved using PF-ECDM process.

Electrochemical discharge machining: A review on preceding and perspective research

Electrochemical discharge machining has been proved to be efficient micro-machining process and significantly used for the machining of non-conductive materials. The miniaturized products have gained advantages in Lab-on-a-chip devices and microelectromechanical system because of advancement in technology. The challenge to produce micro features has been suitably addressed by electrochemical discharge machining and emerged as potential contender in generating micro holes and micro channels on electrically non-conductive materials. This article includes state-of-art review on different domains of electrochemical discharge machining, which includes work piece, electrolyte, behaviour of tool electrode, gas film formation, machining quality along with recent hybridizations in electrochemical discharge machining process. The conclusion focuses or summarizes the future research trends for enhancement of electrochemical discharge machining efficiency and tackles problems encountered in machining.

A Study of the Materials Removal Mechanism of Grinding-Aided Electrochemical Discharge Machining of Metal Matrix Composites

In order to research the workpiece materials removal mechanism of Grinding-assisted Electro-chemical Discharge Machining(G-ECDM) of Metal Matrix Composites (MMCs), a good deal of single pulse experiments has been performed in this paper. The crater volume, convex edge, debris, machined surface of G-ECDM have been taken into considerationand it turns out to be that the grinding effect removes the convex edge of the Electro-chemical Discharge Machining (ECDM) crater during the machining of MMCs, the result show that the material removal rate (MRR) of G-ECDM is much higher than that of ECDM and Electrical Discharge Machining (EDM). When compared to the normal ECDM process, it is found that though the Al4C3 phase can be detected in this ECDM condition, no Al4C3 are observed in the processed surface, which indicates a better surface quality. The reason of this phenomenonhas been analyzed theoretically and experimentally. Based on these results, mechanism of the G-ECDM of MMCs was disclosed in this study.

Genetic Algorithm Based Optimization of ECDM Process for Polymer Matrix Composite

The acceptability of polymer matrix composites for various industrial applications has been increased over the years due to their better mechanical properties. However, nonconductive nature and fibrous residuals produced during micro drilling of these materials has become major challenge for the research fraternity. The conventional machining of these materials causes high tool wear due to presence of abrasive particles. Recently, the electrochemical discharge machining (ECDM) process has emerged as potential contender for the machining of nonconductive hard and brittle materials. Keeping in mind all these challenges, the present research work focuses on micro drilling of PMCs using ECDM process. The experimentation was planned as per Taguchi’s methodology using L9 orthogonal array. Voltage, electrolyte concentration and duty factor were considered as process parameters whereas material removal rate and taper were observed as output quality characteristics. The regression equation and coefficients were obtained using regression analysis. Using this regression equations, further solutions were obtained by genetic algorithm.

Effect of tool diameter in ECDM process with powder mixed electrolyte

Electro Chemical Discharge Machining (ECDM) combines the basic principles of Electro Chemical Machining (ECM) and Electro Discharge Machining (EDM) using the advantages of both the techniques to machine non-conducting, hard to machine materials like a variety of glasses, ceramics and composites. In the current paper, ECDM is carried out with powder mixed electrolyte with stales steel tool of various diameters. Output responses are measured according to MRR and ROC. From the experimental results smaller diameter tools has shown higher MRR with lower ROC.

Experimental study on the heat-affected zone of glass substrate machined by electrochemical discharge machining (ECDM) process

Electrochemical discharge machining (ECDM) is an unconventional microfabrication technology which is used for creating microchannels on glass workpieces. Since melting and evaporation are the main mechanisms of material removal in glass workpiece and fabrication of microchannels in ECDM process, the material properties of heat-affected zones (HAZ) would be changed. In this paper, microchannels were machined on soda lime glass in different machining conditions and the nano-indentation test, which is the key tool for identification of changes in material properties of HAZ, was conducted on machined workpieces for measuring the hardness of microchannels’ edges. Experimental results showed that applying a magnetic field in both 15 and 30 wt% electrolyte concentrations leads to an increase in the hardness of the channel edge up to 87 and 24%, respectively. In fact, in the presence of a magnetic field, a magneto-hydrodynamic convention is created, which affects the hydrogen gas bubbles’ movement. So, the electrical conductivity of the solution is enhanced and finally by occurring a more consecutive electrical discharge, a smaller heat-affected zone is created. In addition, due to generation of higher thermal energy, by increasing the electrolyte concentration and applied voltage level, the larger HAZ is created. Analyzing the load-displacement curves of nano-indentation test shows that the hardness of samples machined in the presence of KOH electrolyte is lower than NaOH electrolyte. The potassium ions are larger than sodium ions, leading to a decrease in the sample’s strength and increase in the HAZ.

Experimental investigation of magnetohydrodynamic effect in electrochemical discharge machining

Electrochemical discharge machining (ECDM) which is also known as spark assisted chemical engraving (SACE) is a machining process to machine non-conducting and brittle materials. Micro-ECDM presents several desirable properties featuring high flexibility, smoothly machined surfaces, and high drilling speed comparing with other micromachining technologies. The unstable gas film around the tool electrode in which the electrical discharges take place is unpredictable as the machining depth increases, resulting in inaccurate geometry and inconsistent machining. The material removal rate is significantly decreased due to insufficient electrolyte flow around tooltip in the hydrodynamic regime. These are the serious drawbacks of the process that need to be improved. This paper presents an analytical analysis of the magnetohydrodynamic (MHD) effect in the ECDM process. The mechanism of the magnetohydrodynamic effect in electrochemical discharge machining was investigated. The high-speed camera was used to record the formation of a gas film on the tool electrode with and without magnetohydrodynamics effect. The experimental results showed that the MHD effect induced by the magnetic field improved electrolyte circulation and higher machining efficiency was achieved. Furthermore, it was observed that the thickness of the gas film was decreased. The radius of the machined hole is reduced from 528 µm to 430 µm while the machining time was decreased from 50 to 16 s. The counter resistant feeding method and magnetic field can be applied simultaneously by the newly designed set-up. This hybrid method made significant enhancement in accuracy and throughput of the drilling process, as well as improving the roundness of the machined hole.