Electrochemical Discharge Machining Research Articles

Cathode shape prediction for uniform electrochemical dissolution of array tools for ECDM applications

ABSTRACT The effect of various cathode shapes, i.e., flat-plate, conical, and spherical-shaped cathodes, on the electrochemical dissolution (ECD) behavior of the 3 × 3 area-array tool electrode is presented. The allowed variation in all tip heights is less than 30 μm. Initially, the finite element method (FEM) was used to predicts the reduction in size and heights of the 3 × 3 tips. The spherical shape cathode exhibited uniform current density distribution around the tips, resulting in the consistent dissolution for a longer time than other cathode shapes. Detailed experiments were also performed to predict the dissolution behavior. Experimental results confirmed a similar dissolution behavior. The flat-plate electrode was not suitable in the ECD of array tool electrodes as the difference between the outermost and central tip heights was more than 130 µm, while the difference was less than 30 µm with a spherical-shaped cathode. Electrochemical discharge machining (ECDM) was carried out using the area-array electrodes made by the spherical and flat plate cathodes. The energy channelized by the uniform tips during the ECDM resulted in uniform material removal beneath all the tips, resulting in consistent crater formation. In contrast, a single crater was formed when the non-uniform tips were used.

Influence of electrochemical discharge machining parameters on machining quality of microstructure

As a nontraditional processing technology, electrochemical discharge machining (ECDM) can process glass and engineering ceramics precisely. This technology has proven to be a potential process for glass 3D microstructure. However, the key to expanding the application of ECDM is how to improve machining accuracy. This research conducted micro-hole and microgroove machining. Power voltage and frequency influence on hole processing efficiency, hole entrance diameter, and hole limit depth was explored. We considered four factors affecting ECDM—the voltage and frequency of the pulse power supply, the tool electrode feed rate, and the rotation speed. We studied their influence on the roughness of the microgrooves. The results show that machining efficiency, entrance diameter, and limit depth of micro-holes increased with the increase in voltage but decreased with the increase in power frequency. The results show that the roughness of microgrooves has an apparent positive correlation with the power voltage. In contrast, it had an evident negative correlation with the power frequency and electrode speed. The bottom surface roughness of microgrooves can be as minor as 0.605 μm. Various complex 3D microstructures on the glass surface by layer-by-layer method proved the great potential of ECDM.

Multi-spark simulation of the electrochemical discharge machining (ECDM) process

Multi-spark simulation of the electrochemical discharge machining (ECDM) process

Experimental investigation into tool wear behaviour of line-array tool electrode during the electrochemical discharge micromilling process

A tool-workpiece gap during the electrochemical discharge machining (ECDM) process is a critical parameter for successfully fabricating microchannels using line-array tool electrodes. Tool wear during the ECDM process increases the tool-workpiece gap and result in non-uniform array microchannel depths or intermittent machining due to reduced heat flux transferred into the workpiece. Hence, proper selection of a tool material that results in uniform tool-tips height/tool-workpiece gap for a longer machining time is essential, especially for the line-array tool electrodes. In this article, the tool wear behaviour of four different materials, i.e., brass, SS304, molybdenum, and tungsten, during fabrication of longer (>15 mm) and deeper (>200 μm) array microchannels using multi-pass ECDM process is reported. The tool wear behaviour at varying machining time/pass numbers was investigated, keeping all other process parameters constant. The experimental results found that the brass electrode's wear rate was relatively faster, and the line-array tool electrode becomes unusable for the ECDM process after 15 min of total machining time. The wear behaviour of molybdenum and tungsten tool materials was similar and resulted in intermittent or no microchannels formation after 35 min of machining time. At the electrolyte-air interface, necking of the tips and subsequent breaking at different machining times was observed for the brass, molybdenum, and tungsten tool materials. Comparatively uniform tips height, microchannel depths, and negligible necking were observed for the SS304 tool electrode after 65 min of machining time. Therefore, SS304 is a suitable tool material for fabricating longer and deeper array microchannels using the multi-pass ECDM process. Moreover, the fabrication of a dual serpentine flow field was demonstrated in the glass workpiece using customized SS304 line-array tool electrodes.

Performance of SiC and Al2O3 Loose Abrasives in the Electrochemical Discharge Machining Process

Electrochemical Discharge Machining (ECDM) has combined characteristics of ECM and EDM which is effectively been used for machining electrically nonconductive, hard, and brittle materials like glass, quartz, and ceramics. However, the industrial application of this process is limited due to difficulty in machining micro holes with higher machined depth. To improve the machining performance of the ECDM process, loose abrasive particles have been mixed in an electrolyte while machining blind holes on soda–lime glass. This study is mainly focused on investigating the effect of process parameters (voltage and electrolyte concentration) on the responses (volume of material removed, machined depth and overcut) using CCRD. The significance of process parameters on the responses has been evaluated using ANOVA. A second-order regression equation has been developed for predicting the relation between input process parameters and quality characteristics (i.e. volume of material removed, diameter overcut, and machined depth). It is observed that the addition of Al2O3 abrasives has improved the volume of material removed and machined depth. On the other hand, the addition of SiC abrasives into the electrolyte has reduced the diametric overcut due to their specific characteristic.

Influence of Different Tool Electrode Materials on Electrochemical Discharge Machining Performances.

Electrochemical discharge machining (ECDM) is an emerging method for developing micro-channels in conductive or non-conductive materials. In order to machine the materials, it uses a combination of chemical and thermal energy. The tool electrode’s arrangement is crucial for channeling these energies from the tool electrode to the work material. As a consequence, tool electrode optimization and analysis are crucial for efficiently utilizing energies during ECDM and ensuring machining accuracy. The main motive of this study is to experimentally investigate the influence of different electrode materials, namely titanium alloy (TC4), stainless steel (SS304), brass, and copper–tungsten (CuW) alloys (W70Cu30, W80Cu20, W90Cu10), on electrodes’ electrical properties, and to select an appropriate electrode in the ECDM process. The material removal rate (MRR), electrode wear ratio (EWR), overcut (OC), and surface defects are the measurements considered. The electrical conductivity and thermal conductivity of electrodes have been identified as analytical issues for optimal machining efficiency. Moreover, electrical conductivity has been shown to influence the MRR, whereas thermal conductivity has a greater impact on the EWR, as characterized by TC4, SS304, brass, and W80Cu20 electrodes. After that, comparison experiments with three CuW electrodes (W70Cu30, W80Cu20, and W90Cu10) are carried out, with the W70Cu30 electrode appearing to be the best in terms of the ECDM process. After reviewing the research outcomes, it was determined that the W70Cu30 electrode fits best in the ECDM process, with a 70 μg/s MRR, 8.1% EWR, and 0.05 mm OC. Therefore, the W70Cu30 electrode is discovered to have the best operational efficiency and productivity with performance measures in ECDM out of the six electrodes.

Fabrication of micro-mechanical planar cantilever beam-mass structures on quartz substrates using an ECDM process

Electrochemical discharge machining (ECDM) processes have been used to realize miniature structures such as micro-channels and micro-holes on non-conductive materials such as quartz and Pyrex for a variety of applications. However, for realizing mechanical/physical sensors, actuators, energy harvesters, and resonators on glass substrates, free-standing devices with movable components such as beam-mass structures and cantilevers are required. There has been a negligible focus on developing miniature glass-based devices with movable components primarily due to the non-linear material removal rate (MRR) of the ECDM processes, requiring continuous measurement, tracking, and maintaining the working gap in the range of a few micrometers during micromachining. A couple of techniques were proposed to address maintaining a constant working gap, however, using costly equipment with complex feedback mechanisms. We report a two-stage experimental approach – without using feedback mechanisms and additional equipment – to realize micro-mechanical planar cantilever beam-mass structures on thick quartz substrates in the present work. In the first stage, the process parameters such as applied voltage, tool travel rate (TTR), and initial working gap ( Wg) are optimized for fabricating broader and deeper micro-channels using needle-shaped tools. In the second stage, using the optimized parameters, an array of micro-channels is fabricated. The cumulative depth, corresponding depth, and the width of each layer of the channels are measured, and this data is utilized for fabricating planar beam-mass structures on quartz substrates. We envisage that the experimental results of the present study would be beneficial for ECDM researchers to fabricate glass-based miniature devices with movable components without using complex tools and equipment.

An Optimization Strategy to Improve Performance in Electrochemical Discharge Machining of Borosilicate Glass Using Graph Theory Algorithm and Desirability Index

An Optimization Strategy to Improve Performance in Electrochemical Discharge Machining of Borosilicate Glass Using Graph Theory Algorithm and Desirability Index

Experimental and numerical investigations of material removal process in electrochemical discharge machining of glass in discharge regime

Electrochemical discharge machining (ECDM) can be applied as a non-traditional processing technology for machining non-conductive materials such as glass and ceramics, based on the phenomena of evoked electrochemical discharges around the tool electrode. The material removal mechanism of ECDM is noticeably complex and difficult to experimentally characterize. In this paper, finite element models were proposed to predict the material removal in the ECDM discharge regime. First, the single-pulse discharge on a tapered electrode was modeled. It was found that about 30.5% of the discharge energy is transferred to the workpiece. The continuous discharge on a cylindrical electrode was thereafter modeled according to this phenomenon, in which the removal of a layer of the workpiece material starts from the projected contour of the edge of the electrode end and extends inward during the ECDM processing. The effective discharge ratio for material removal was calculated to be 10.1%. The drilling depths of holes at different applied voltages were predicted by the proposed finite element method. It was found that the predicted values were consistent with the experimental results.

Optimization the Machining Parameters of Electro Chemical Discharge Machining of NiTi Shape Memory Alloys

The electrochemical discharge machining (ECDM) is a combination effect of electrochemical machining in which metal is removed through the electrochemical process and electrical discharge machining in which metal is removed by rapid current discharges between two electrodes which are separated by a dielectric liquid and subject to an electric voltage. Difficulty of machining nickel titanium alloys by conventional methods such as; the significant tool wear, the need of highly experienced operators, and an excessive degradation in the material performance due to the high thermal and mechanical effects of these methods. For these, reasons non-conventional methods such as electrical discharge machining and electro chemical machining are often used to fabricate NiTi alloys with better machining results. The experiments were conducted with various conditions of voltage (50,60,70 and 80)V, dielectric solution concentration (30 and 40% of NaOH) and nanoparticles silver, and copper content (0.5% Cu, 0.5% Ag, 0.5% Cu and Ag) in the (55% Ni-45%Ti) alloy samples. The machining experiments were designed according to Taguchi's design of experiments (L32). Grey relational analysis was used to optimize the responses of the ECDM process. Material removal rate (MRR), tool wear rate (TWR), and surface roughness (Ra) represent the response parameters for machining of the alloy samples prepared by the powder metallurgy route. To achieve the objectives of this research work MiniTab17 software was employed. The optimal conditions were: voltage of 50V, solution concentration of 40% and the sample (NiTi+0.5%Cu+0.5%Ag) have the highest effect on machining characteristics with MRR value of 0.04991mg/sec., tool wear rate value of 0.00125mg/sec., and surface roughness of 0.0117μm.

Effect of sensing mechanism on machining performance of ECDM process

ABSTRACT Electro Chemical Discharge Machining (ECDM) has been introduced as an un-conventional hybrid process in last few decades for machining of materials which are electrically non-conducting as well as conducting. In the current work, an effort is carried out to modify the microfeatures produced in ECDM machining with a sensor mechanism. An ECDM setup is fabricated with a sensor mechanism in order to reduce the irregularities in the micromachining process. The microholes machined with a sensor mechanism has shown improvement in terms of circularity. A multiobjective optimisation is carried out with Grey Fuzzy Reasoning Analysis (GFRA) in order to obtain maximum Material Removal Rate (MRR) with minimum Radial Over Cut (ROC). The experimental study has shown that ROC has been reduced to greater extend with improvement in material removal through optimisation of process parameters using GFRA. From the GFRA analysis, at an optimised parameters combination, a higher MRR of 0.075 mg/min with minimum ROC 0.01 mm is obtained for borosilicate glass workpiece.

Impact of gas film thickness on the performance of RM-ECDM process during machining of glass

ABSTRACT Nowadays, the extensive use of glass-based materials for biomedical, micro-fluidic, and MEMS applications grabbed great attention. The use of glass substrate for the above-said applications required subtractive processing to fabricate essential microstructures. Electrochemical discharge machining (ECDM) is an emerging hybrid micromachining process employed to machine the glass work-material. In ECDM, the thermal energy released by the tool electrode in the form of electrochemical discharges due to the electrical breakdown of hydrogen gas film takes away the material from the work surface. The thickness of hydrogen gas film plays a crucial role in deciding the discharge characteristics and subsequent thermal energy amount. Thus, in the present research work, an experimental investigation on hydrogen gas film thickness during the triplex hybrid process of rotary mode (RM) ECDM has been carried out. A high-speed imaging technique was utilized to capture the images of the gas film. These captured images were processed through Matlab’s edge detection toolbox to measure its thickness. Central composite design (CCD) of response surface methodology (RSM) was used to design the experimental plan. Applied voltage, tool rotation rate, and electrolyte concentration were taken as input parameters. To investigate the influence of gas film thickness on energy channelization behavior during RM-ECDM process, a material removal rate (MRR) and L/D ratio (diameter to depth ratio of machined holes) were taken as the response characteristics. A desirability approach was used to optimize the input parameters.

Multi Response Optimization of ECDM Process Parameters for Machining of Microchannel in Silica Glass Using Taguchi–GRA Technique

In this work, machining of microchannel in silica glass was successfully carried out using electro chemical discharge machining (ECDM) process. The experiments were planned according to L27 orthogonal array with applied voltage, stand-off distance (SOD), electrolyte concentration, pulse frequency and pulse-on-time (TON) as control factors. The material removal rate (MRR), overcut (OC) and tool wear rate (TWR) were considered as response characteristics. In this study the effects of control parameters on MRR, OC and TWR have been investigated. The increase in applied voltage, electrolyte concentration and pulse on time lead to the improvement in the output characteristics which is attributed to formation of heavily crowded hydrogen bubbles and further coalescence of hydrogen bubbles promotes the occurrence of sparks which resulted in higher values of MRR, OC and TWR. The multi-objective optimization of ECDM was carried out through grey relational analysis (GRA) method. Optimal combination of process parameters achieved from GRA was 45 V applied voltage, 25 wt.% electrolyte concentration, 1.5 mm SOD, 400 Hz pulse frequency and 45 μs TON. ANOVA for GRG study revealed that the applied voltage (70.33%) was most significant factor affecting output responses followed by electrolyte concentration (11.69%), pulse frequency (4.98%) and SOD (4.13%). Furthermore, the regression equations were formulated for the optimum combination to predict the collaboration and higher-order effects of the control parameters. In addition, confirmation test was conducted for the optimal setting of process parameters and the comparison of experimental results exhibited a good agreement with predicted values. The microstructural observation of machined surface for the optimum combination was carried out.

Fabrication of micro holes in Yttria-stabilized zirconia (Y-SZ) by hybrid process of electrochemical discharge machining (ECDM)

In the present work, the electrochemical discharge machining (ECDM) process with an integrated approach of electrolyte flow and pressurized feeding is demonstrated to produce micro-holes in Yttria-stabilized zirconia (Y-SZ). The mechanism of material removal reveals that the material is primarily removed due to the thermal spalling phenomenon over the melting and evaporation. Unlike the other glass based ceramic materials, the contribution of chemical etching phenomenon is found to be almost negligible in removing the material from Yttria-stabilized zirconia work substrate. The incorporation of electrolyte flow in the ECDM process increases the machining efficiency by improving hole depth by 42% and reducing diameter by 33% for the same processing durations. The improved frequency of electrochemical discharges (ECD’s) due to the supply of electrolyte is responsible for removing the material in controlled manner without causing any fracture at the hole edges. Moreover, the supply of electrolyte reduces the tool wear, which results in consistent machining conditions for longer machining durations. The maximum penetration speed obtained in this investigation was 126 μm/min.

A study based on electrochemical discharge assisted by hollow electrode and micro-nano bubble to process transparent non-conductive brittle materials

To overcome the difficult part of sapphire drilling, this research proposes two auxiliary processing. The first solution is investigating the influence of the addition of micro-nano bubbles to the original electrolyte. It is confirmed that the micro-nanobubble assists ECDM. For glass processing, the processing time using micro-nanobubble electrolyte is 31% faster than the processing time using ordinary electrolyte. As for the current response for the first 20 s, the average current intensity increased by 26.7%. Another method is to use hollow electrodes to absorb the processed slag and replenish the electrolyte during the processing. We use a high-speed camera to acquire images and current simultaneously and found that when using hollow electrodes, the time between the formation of a gas film and the generation of electric sparks in the way of replenishing the electrolyte is the shortest. The time of replenishing electrolyte is 34.5% faster than that of not replenishing. In addition, the thickness of the gas film is reduced by 54%. In addition, for the influence of gas film thickness and current value on processing efficiency. Finally, two auxiliary methods are combined to realize the feasibility of electrochemical discharge machining of sapphire. Compared with the case without auxiliary methods, the depth is increased by 3.8 times. When the voltage increases, the maximum depth reaches 440.8 μm.

A novel approach for removal of delaminated fibers of a reinforced composites using electrochemical discharge machining

Fiber reinforced composites, also referred as fiber reinforced plastics (FRPs) have gained considerable importance in engineering applications due to their unique qualities like high strength and stiffness at lesser weight, chemical inertness, thermal resistance, corrosion resistance, and electrical resistance. Though the machining of FRPs is not recommended, many times it is inevitable and the primary machining process like drilling is essential. This can cause delamination of the fibers thereby adversely affecting the mechanical properties of the composite and requires additional secondary finishing operation. The present investigation explores electrochemical discharge machining (ECDM) as a one of the novel technique to remove the delaminated fibers from such composites. Using ECDM the protruded delaminated fibers from a drilled hole in FRP have been precisely eliminated. Two different approaches viz. top machining and inside machining were followed for this purpose. Process evaluation was done in terms of its ability to remove the delaminated fibers and the extent of thermal damage (heat affected zone and hole overcut) to the workpiece. Both approaches have shown considerable potential of removal of delaminated fibers precisely.

Effect of tool-electrode material in through-hole formation using ECDM process

ABSTRACT An experimental investigation comparing the effect of tool electrode materials on the formation of microholes in glass by the pulse electrochemical discharge machining is presented. Two different materials, i.e., Molybdenum and High carbon steel (HCS), were used in the experiments carried out in 10% wt KOH electrolyte. Other parameters such as machining voltage, pulse frequency, tool feed rates were systematically varied. A lower mean discharge current was noticed when the molybdenum tool having higher electrical conductivity was used. The average reductions in the hole overcut, taper angle, and the heat-affected zone in the microholes were 30%, 55%, and 58%, respectively, when the Molybdenum tool was used compared to the HCS tool. For both tool materials, the hole overcut was measured to be minimum when a tool feed rate of 4 µm s−1 was used. The microhole diameter and heat-affected zone were increasing with the increment in the applied voltage irrespective of the tool electrode material. Due to the higher melting point, molybdenum electrodes had less tool erosion and, therefore, more suitable than the HCS tools for electrochemical discharge machining applications.

Experimental Investigation and Analysis on Borosilicate Glass Using Electrochemical Discharge Machining Process

Electrochemical discharge machining process (ECDM) is a non-traditional machining process which has widely used in medical, electronics and aerospace industry. This paper discuss about the various different methods using same process i.e. electrode immersion depths along with electrolytic stirring effects in ECDM are discussed. The various process parameters considered during the experiment (applied voltage, electrolyte concentration and electrode immersion depths); on the other side response parameters consider as material removal, tool wear and surface finish. Experimental results indicate the adequate material removal with equivalent electrode cross sectional areas as well as fine immersion depths. Electrode immersion depth ratios, electrolyte concentration and electrolyte-stirring effect on borosilicate glass using NaOH as the electrolyte mediums show some improvement in process results. The addition of stirring effect to the electrolyte along with proper immersion depths of the electrodes resulted in improvement of the process performance mainly the improvement in surface finish values up to around four times than the normal ECDM process. The FESEM micro graphs of the fabricated micro channels reveal some interesting modes of material removal. EDS were studied for analysis of debris through this process.

Experimental investigations of energy channelization behavior in ultrasonic assisted electrochemical discharge machining

The present work analyzes the energy channelization behavior during the triplex hybrid process of ultrasonic assisted electrochemical discharge machining (UA-ECDM). In this work, a high frequency (35 kHz) low amplitude configuration of ultrasonic vibrations has been employed to investigate the ECDM process. The underlying energy channelization mechanism during the UA-ECDM process has been demonstrated while considering the evidence from high-speed imaging of gas film, discharge signals, optical images, simulation results, structural and compositional analysis of machined work material. The controlled assistance of ultrasonic in the ECDM process shifts the energy paradigm from the edges to the center of the tool electrode. Moreover, in the UA-ECDM process, the material is removed by additional cavitation and high-pressure evacuation actions along with melting, vaporization, and chemical etching phenomenon. An improved frequency of spark discharges indicates the initiation of breakdown phenomena in upward and downward strokes of ultrasonic vibrations. Energy channelization index and specific energy were taken as the performance indicators. The incorporation of ultrasonic vibrations consumed 2.23 times less energy than the ECDM process to remove a unit material per unit time. The energy channelization index with ultrasonic assistance is also improved by five times. The incorporation of ultrasonic vibrations in the ECDM process reduced the heat-affected zone and produced the machined surfaces without the alkali deficient layer. The article reports the parametric effect and their contribution to the response characteristics. The involvement of high electrochemical discharge energy with ultrasonic assistance exhibits better results in higher material removal rate and depth/diameter ratio due to the parallel provision for the evacuation of sludge/debris and electrolyte replenishment in the machining zone.

Optimization of process parameters in Electro Chemical Discharge Machining of silica glass through Analysis of Means

In recent years, the Electro Chemical Discharge Machining (ECDM) process has advanced as a substitute for machining of conductive and non-conductive materials. Optimization of the process parameters plays a crucial role in improving the quality of the processed components. The machining of microchannel in silica glass has been successfully attempted in present work by considering Analysis of Means (ANOM) of ECDM process parameters. The experiments were planned using Taguchi’s L9 orthogonal array with applied voltage, stand-off distance (SOD), electrolyte concentration (EC) and pulse on time (TON) as process parameters. The Material Removal Rate (MRR), Machining Depth (MD) and Overcut (OC) were observed as output characteristics. The ANOM study revealed that the error between experimental and predicted values of MRR, MD and OC are 4.22%, 1.92% and 3.46% respectively. Stand-off distance was found to be the most significant factor followed by pulse on time, applied voltage and electrolyte concentration from ANOVA. Confirmation test was performed by setting the optimum combination of process parameters and the predicted values from regression analysis exhibited a good agreement with experimental results.