Electrochemical Machining Process Research Articles

Study of Micro-groove Generation on Titanium Alloy (Ti6Al4V) using Novel WEDM and WECM Sequential Electro Micro Machining (SEMM) Technique

Abstract The micro-part manufacturing can be accomplished by the execution of different micro-machining techniques. The sequential machining is one of the most promising techniques which dictate the structured approach towards the fabrication of highly precise micro-features in sophisticated components. The newly coined Sequential Electro Micro Machining (SEMM) technique has been implemented for the improvement of overall machining efficiency and enhancement in surface characteristics of the part during machining. In the chain of sequential machining, the present research paper has introduced a novel sequential combination of micro Wire Electro Discharge Machining (µWEDM) and micro Wire Electro-Chemical Machining (µWECM) processes. The µWEDM process was carried out on the standard wire cut EDM machine, whereas µWECM was performed on indigenously designed and developed system setup. The micro-grooves on difficult to cut material such as titanium alloy (Ti6Al4V) was initially generated by applying µWEDM process. The µWEDM is a thermal process, where the shaping of micro-groove was accomplished rapidly due to the existence of high-intensity spark discharges. The spark produced also generates recast layer comprising of cracks, micro-pores and numerous micro-craters in the heat affected zone of the machined region. During experimentation, the micro-groove using µWEDM process was cut at different machining voltages. In order to make out the best sequential machining combination, the machining voltage at which the least surface defects occurred on micro-groove was selected for sequencing with the subsequent process. In present experimentation, the least width overcut of the groove was obtained at 10V. The µWECM process was then applied to ameliorate the surface defects and other irregularities imparted to micro-groove during the µWEDM process. The effects of machining process parameters in µWECM, such as applied voltage, machining time and duty ratio on µWEDMed part was investigated. The sequential machining experiments were then conducted by choosing the best input process parameters in both the processes. The experimental results thus obtained after the application of diversified sequential micro-machining processes revealed an improved machining efficiency and high surface quality of micro-groove. Thus the µWEDM process for shaping the groove and µWECM process for finishing the groove was conducted successfully

Improving quartz micro-machining performance by magnetohydrodynamic and zinc-coated assisted traveling wire-electrochemical discharge machining process

In this industrial revolution era, machining of advanced non-conducting material like quartz is difficult and costly with existing conventional machining processes. Further its high hardness, brittleness and non-conducting nature add-up to machining difficulties. Traveling Wire-electrochemical discharge machining (TW-ECDM) process has a good potential of machining of quartz material. TW-ECDM process is a hybrid and complex combination of electrochemical machining (ECM) and wire-electrical discharge (W-EDM) machining process. However, due to poor electrolysis process, sparking phenomenon is not steady and uniform at higher machining depth. In the present work, the authors have tried to investigate the feasibility of Magnetohydrodynamic (MHD) assisted TW-ECDM process for machining of quartz. This MHD approach produces the magnetic field which helps to improve the electrolysis process, accuracy, and efficiency. Also, first-time zinc-coated brass wire of diameter 0.15 mm has been used to improve the machining performance. A hybrid approach of Taguchi robust design and ANOVA was used to analyze the process performance. Experimental results reveal that the MHD approach enhances the material removal rate (MRR) and reduces the surface rousghness (Ra) as compared to without MHD approach. The improvement in MRR was found from 25.35% to 83.72% and Ra reduced from 9.06% to 28.79%/ Additionally, an experimental result shows that quartz machined by TW-ECDM with MHD approach yielded longer and straight machined cut with less kerf width. Henceforth, the proposed hybrid MHD and zinc-coated brass wire approach is simple, easy, economically viable, environmental friendly and does not require any major changes in the existing machining setup. Moreover, the length of cut, kerf width and machine profile were also analyzed by scanning electron microscope.

Effect of loose abrasive mixed electrolyte on the aspect ratio of blind holes drilled in soda-lime glass by ECDM process

Electro-Chemical Discharge Machining (ECDM) process has the potential to machine various features and 3D surfaces on glass. However, machining of high aspect ratio micro holes is a challenging problem in ECDM process. In ECDM process, the machining rate mainly depends on the availability of the electrolyte at the electrode tip. Machining accuracy like taper, entry and exit diameter of the hole at high depths is rigorously affected due to lack of electrolyte at the machining zone resulting in more taperness. Low surface qualities (i.e. more over cut and tapered micro holes) are few limitations of the process. To enhance the machining capabilities a novel approach of PMECDM has been conducted. Present study is mainly focused on behavior of abrasive particles while machining soda lime glass, also studied effect of process parameters on the responses such as machining depth, outer diameter and aspect ratio. Also, the study led to analyze the effect of thermal properties of abrasives on machining performance of ECDM process. The maximum machined depth achieved was 2.31 mm in 5 min, and tremendous reduction of outer diameter from 1237.37 μm to 712.8 μm. Response surface methodology has been used to plan the experiments and ANOVA has been used to analyze the impact of each process parameters on machined depth and outer diameter of the micro holes.

Machining issues on Electrochemical Spark Machining—A review

Electrochemical Spark Machining is a hybrid advance machining process of Electrochemical Machining and Electric discharge machining which can machine conducting materials as well as non-conducting materials. Electrochemical Spark Machining is focused for melting, vaporizing, and chemical etching the undesirable material from the workpiece. It is appropriate for micromachining of complex geometry with a high aspect ratio. In recent years, researches have studied several aspects of machining related to ECSM. This review paper is an effort to understand the key issue related to machining on ECSM. The review reports that the kind of electrolyte, applied voltage, tool materials, tool rotation affect the machining process in terms of surface roughness, aspect ratio, and MRR. The review paper finally lists down certain areas for future research in ECSM.

Geometrical Analysis of Wire Electrochemical Machining for the Manufacture of Turbine Disc Slots

The advantages of sinking electrochemical machining (ECM), e.g. best surface integrity, are always faced with the cost-intensive initial effort for the component specific design of a machining device and its tool geometry. However, this disadvantage does not apply to wire ECM where no task-specific tool design is required for cutting 2.5-dimensional geometries like fir tree slots in turbine discs. An industrial application is still being hindered by insufficient flushing concepts. However, a previous study showed that the flushing approach of High Speed Wire Electrical Discharge Machining (HSWEDM) is also successfully transferable to wire ECM. Workpiece heights up to 40 mm could be machined with a cutting rate of Vw = 20 mm2/min. Nevertheless, these investigations were only performed with straight cuts, radii were not examined. Therefore, in this paper the geometrical accuracy of the wire ECM process is analyzed using the example of two different turbomachinery disc slot geometries with 20 mm and 40 mm heights by a coordinate measuring machine.

Numerical and experimental study of discharge mechanism in the electrochemical discharge machining process

Electrochemical discharge machining (ECDM) is a modern machining process which can be applied to the special materials with unique properties. Glass and ceramics are major applications of the mentioned process. ECDM includes variant mechanisms of material removal (MR) in which discharge (thermal) mechanism plays the most important role in comparison to other mechanisms. This research introduces a new approach to simulate the discharge phenomenon and the consequent volume of removed material. Despite previous researches which implemented a simple thermal simulation based on Gaussian distribution, the current model considers different constitutive phenomena of discharge (plasma) and presents a more realistic numerical model. Electric current, electromagnetic field, and heat transfer are major effective phenomena on the plasma behavior which are considered in simulations and evaluated simultaneously, for all components of ECDM configuration. Special experiments are designed to validate the predictions of the model. The single discharge mode of the ECDM process is applied and two main parameters of hole diameter and MR are measured to compare with computed results. Consecutive actual images and current signal diagrams determined 37 V as a critical voltage to appear the discharge phenomenon. Results showed that the developed model has errors of 14.33 % and 31.52 % in the prediction of hole diameter and MR, respectively.

Numerical and experimental analysis of high-aspect-ratio micro-tool electrode fabrication using controlled electrochemical machining

Numerical and experimental analysis of high-aspect-ratio micro-tool electrodes fabrication using a controlled electrochemical machining (ECM) technique is reported. The evolution of the tool electrode shape was first predicted using a finite element method-based numerical simulation and then validated with the detailed experiments. The effects of machining voltages and the machining durations on the change in the tool electrode profile were investigated. High-carbon steel was chosen as an electrode material due to its lower cost, good electrical conductivity, and easy availability. A 5% (i.e., 5 gm of NaCl in 100 ml of deionized water) NaCl solution was used as the electrolyte. The tool profiles predicted using the FEM-based numerical model showed an excellent matching trend with the ECM experimental results. The role of the black surface film formed on the electrode surface was found to be significant. The tool electrodes having an average diameter of 60 µm and an aspect ratio of more than 75 were fabricated at the optimized machining parameters. These single-tip micro-tool electrodes were used to create through-hole in a 400-µm-thick glass substrate by electrochemical discharge machining. The obtained ECM process parameters were used to create multiple electrodes having a tip size of 130 µm and having a smooth surface. These through-holes were filled with copper to form 3D interconnects, i.e., through-glass vias, which are required in the radio-frequency MEMS applications and 3D packaging.

A facile electrochemical machining process to fabricate superhydrophobic surface on iron materials and its applications in anti-icing

Iron materials are widely applied in electrical-tower. However, the freezing rain adhering to the electric-tower in winter can raise a huge potential safety hazard to the power facilities. Therefore, how to make ironworks possess anti-icing property has become a difficult problem. In order to resolve the aforementioned issue, a facile, low-cost and environment-friendly electrochemical machining method was developed to fabricate superhydrophobic surface on iron materials to endow anti-icing capacity in the freezing rain. After fluoroalkylsilane (FAS) modification, superhydrophobic surface could be obtained. The morphology of the surface film was examined using scanning electron microscopy (SEM) equipped with an energy-dispersive spectroscopy (EDS) and laser confocal microscope. The chemical composition was investigated by X-ray photoelectron spectroscopy (XPS). The influence of the applied processing time on wettability was also studied. The results showed that a rough surface, which consisted of many step-like structures, was formed on the surface of iron by the proposed electrochemical method. After FAS modification, the surface showed good superhydrophobicity with the water contact angle of 162° and water sliding angle of 3.33°. The mechanism of the generated rough structures was also discussed. Moreover, the static and dynamic anti-icing tests were conducted. The results showed that the superhydrophobic surface can not only significantly delay the freezing time, but also prevent the cold water from freezing on the iron surface, which could be a good solution to the freezing rain issue.

Synthesis of Zinc Oxide Nanoparticles Through Hybrid Machining Process and Their Application in Supercapacitors

An electrochemical discharge machining process to produce zinc oxide (ZnO) nanoparticles (NPs) under varying voltage and duty factors has been investigated. The morphological and optical characterizations of the generated ZnO NPs were carried out. It was observed that the production rate of NPs and their size increased with an increase in voltage. The ZnO NPs produced at 120 V showed the maximum production rate larger NPs. The field-effect scanning electron microscope images of the NPs revealed a nanorod-like structure, large conical shape rods and hexagonal wurtzite-like structures. The ZnO NPs generated at 120 V and 20% duty factor presented less agglomeration of NPs compared to other NPs generated by varying electrical parameters. The crystal size of the ZnO NPs were found to vary from 31.08 nm to 50.37 nm. The ZnO NPs were also tested for use in a supercapacitor electrode, and the results showed that the specific capacitance of the electrode was 708.75 F/g at a current density of 1 A/g and a retained capacity of 90.42%.

Effect on Material Removal Rate and Surface Finish in ECM Process When Machining Stainless Steel-316 with Cu Electrode

Electrochemical Machining process is one of the popular non-traditional machining processes which is used to machine materials such as super alloys, Ti-alloys, stainless steel etc. Its working principle is based upon Faraday law of electrolysis. The aim of the present work is to optimize the ECM process parameters with the combination of SS 316 (job material) and Copper electrode (tool material). To explore the effect of ECM process parameters such as electrolyte concentration, voltage and current, feed rate on MRR and surface finish (Ra) of the job, total 27 experiments were conducted as per experimental scheme. The results of these experiments revealed that increase in electrolyte concentration decrease the mrr and surface roughness initially increases then decreases. Further, increase in current increases mrr initially and then decreases, surface roughness also increases. It is also noticed that increase in Feed rate mrr decreases and then increases, also surface roughness decreases then increases. Through RSM analysis it is found that the optimum conditions for maximum MRR, and minimum Surface roughness (Ra) is electrolyte concentration 150gm/lit, Voltage 13.5 V & feed 0.8 mm/min. The findings are discussed in the light of previous researches and subsequently conclusions are drawn.

Development of association rules to study the parametric influences in non-traditional machining processes

Non-traditional machining (NTM) processes have already emerged out as the suitable substitutes for the conventional metal removal methods due to their capability of generating complicated shape geometries on diverse difficult-to-machine engineering materials. For these NTM processes, it is always proposed that they should be operated while setting their various input parameters at the optimal levels for achieving better machining performance. In this paper, the application of a data mining tool in the form of development of association rules is explored to determine the best machining conditions for three NTM processes, i.e. electrochemical machining process, ultrasonic machining process and electrical discharge machining process. These rules, presented as simple ‘If-Then’ statements, would also guide the concerned process engineers in investigating the effects of various NTM process parameters on the considered responses. It is observed that the most preferred parametric combinations identified based on the generated association rules closely match with those as perceived by the past researchers.

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.

The effects of magnetic field and ethanol addition on the electrochemical discharge machining

This paper is about adding magnetic and ethanol to explore the accuracy of electrochemical discharge machining processing quartz glass. The tool electrode is tungsten carbide rod, the auxiliary electrode is platinum, the power source uses square wave pulse voltage, the KOH electrolyte is added with ethanol, and the tool is added with 3 T magnetic force. The experimental results show that ethanol can stabilize the square wave power supply wave shape, which can reduce the contact angle between the electrode and the bubble. The low contact angle electrolyte can increase the wettability of the tool electrode and improve the electrochemical processing stability. Therefore, under the action of ethanol and a magnetic field, the processing result can be improved, so that the generated bubbles are reduced and the film gets thinned. When the voltage frequency is higher, the film formation thickness will decrease, and the magnetic force and voltage will induce the magnetohydrodynamics of the electrolyte, which will make the electrolyte and bubble flow around the electrode relatively stable, the circumference around the aperture is flat, and the roundness is obviously improved. The overall improvement in the taper of the machined hole is increased by about 30%, and the amount of undercut of the hole is reduced.

MODELING AND PARAMETER OPTIMIZATION IN ELECTROCHEMICAL MACHINING PROCESS: APPLICATION OF DUAL RESPONSE SURFACE-DESIRABILITY APPROACH

Selection of appropriate machining parameters which result in desired outcomes plays a key role in effective utilization of the electrochemical machining (ECM) process. In this paper, in order to correlate between ECM process parameters and cost functions, comprehensive mathematical models were first determined based on response surface methodology (RSM). Voltage, tool feed rate, electrolyte flow rate and concentration of NaNO3 solution were considered as the machining parameters while material removal rate (MRR) and surface roughness (Ra) were considered as cost functions. To do this, three scenarios of machining performances, Ra≤0.9µm, 0.9µm≤Ra≤ 1.8µm, and 1.8µm≤Ra≤2.7µm, were considered for optimization search based on desirability functions. The goal is to find the optimum set of machining parameters in order to maximize the MRR while keeping Ra in specified ranges simultaneously. The results show that the errors between experimental and anticipated optimal values are less than 8.16% and hence confirm the effectiveness of the proposed approach. Keywords − − , , ,

Quasi-Homogenous Model of Electrochemical Machining of Turbine Engine Parts

Abstract In order to increase the efficiency of jet engines hard to machine nickel-based and titanium-based alloys are in common use for aero engine components such as blades and blade integrated disks (BLISK). Electrochemical Machining (ECM) provides an economical and effective method for machining high strength and heat-resistant materials into complex shapes with high material removal rate without tool wear and without inducing residual stress. This article presents the physical and mathematical models of electrochemical shaping used in the manufacture of turbine engine parts. The modelling is based on the assumption that the multi-phase mixture filling the gap is treated as two-phase quasi-homogenous medium. The model describes the workpiece shape evolution in time, distribution the local gap size, flow parameters such as the static pressure and the velocity, temperature and void fraction as result of gas generation. The major features of the numerical computer program are briefly described with a selected example of machining a typical turbine blade. The results of computer simulation of effects of setting parameters ECM on accuracy-machined profile are discussed. The improvement of accuracy has been reached by using described sequence of ECM and Pulse ECM processes.

Experimental Investigations on Aircraft Blade Cooling Holes and CFD Fluid Analysis in Electrochemical Machining

The flow field distribution in an interelectrode gap is one of the important factors that affect the machining accuracy and surface quality in the electrochemical machining (ECM) process for aircraft blades. In the ECM process, some process parameters, e.g., machining clearance, processing voltage, and solution concentration, may result in electrolyte fluid field to be complex and unstable, which makes it very difficult to predict and control the machining accuracy of ECM. Therefore, 30 sets of experiments for cooling hole making in ECM were carried out, and furthermore, the machining accuracy and stability of cooling hole were concentrated. In addition, the flow channel of the geometrical model of the gap flow field was established and analyzed according to the electrolyte flow state simulation by CFD. The effects of the flow velocity mode on the machining accuracy and stability for cooling hole making were investigated and determined in detail.

Multi-physics Simulation of Heat Transfer in Pulse Electrochemical Machining (PECM) Process

A multi-physics model is presented for numerical simulation of temperature evolution during quasi steady state (QSS) in pulse electrochemical machining (PECM) process. A fluid model consisting of wall-model and Reynolds-averaged Navier-Stokes equations is used for solving low-Re electrolyte flow near the wall and turbulent flow of electrolyte in the middle channel. A method that the boundary conditions and bulk sources are averaged in time is introduced to make the time-steps not dictated by the time scale of the pulses and SS calculations cheap. The influence of reaction heat sources, joule heat source and inlet flow rate on temperature evolution has been investigated. Simulation results indicate that the influence of reaction heat source on electrode temperature is greater than the eletrolyte and most of the joule heat is carried away by the electrolyte flow.

Electrochemical machining behaviour of AA6063-TiC composites by using response surface methodology

Abstract In this research work, the production and machining of aluminium metal matrix composites were investigated. AA6603 base metal and TiC as reinforcement at propositions ranging from 0 to 9 wt% are used. The material being proposed for the application in aerospace industries and to obtain critical surface finish levels, electro chemical machining process is adopted. The surface roughness is measured as the response by varying the % of reinforcement, voltage and electrolyte concentration. ANOVA, response surface methodology and regression analysis has been carried to identify the most contributing parameter, optimal combination and prediction of deviation from experimental values.

Improvement of leading-edge accuracy by optimizing the cathode design plane in electrochemical machining of a twisted blade

Cathode design plays an important role in the electrochemical machining of aero engine blades and is a core issue influencing machining accuracy. Precision electrochemical machining of the leading edge of a twisted blade is particularly difficult. To improve the electrochemical machining accuracy of the leading edge, this article deals with cathode design by optimizing the design plane based on the three-dimensional potential distribution in the inter-electrode gap. A mathematical model is established according to the electrochemical machining shaping law, and the formation of the blade leading edge is simulated using ANSYS. The simulation results show that the blade leading-edge profile obtained with the optimized planar cathode is more consistent with the blade model profile. The optimized planar cathode and a non-optimized planar cathode are designed and a series of corresponding electrochemical machining experiments is carried out. The experiments show that the electrochemical machining process is stable and that the surface quality near the leading edge of the samples is slightly better than that of the body surface. Compared with the non-optimized planar cathode, the allowance difference at the leading-edge vertex is decreased by 0.062 mm. Using the optimized planar cathode allows fabrication of a workpiece whose shape is similar to that of the designed twisted blade.

Bayesian Optimized Deep Convolutional Network for Electrochemical Drilling Process

Electrochemical machining is a promising non-traditional manufacturing process to make high-quality parts. The benefits of minimal thermally and mechanically induced stresses, free of burr, and a low surface roughness are appealing for industry and research institutes. However, the combined chemical reaction, electric field, fluid mechanics, and material properties involve a significant number of independent parameters which are difficult to analyze in order to draw comprehensive conclusions. To our current knowledge, process responses such as the material removal rate, optimal feed rate, and cutting profile cannot be represented accurately by analytical solutions. In recent years, deep learning has had tremendous success in analyzing sophisticated systems. The improved computation efficiency and reduced size of the training dataset required for deep learning have enabled various prediction models in the manufacturing industry. In this paper, a new approach is developed using the deep convolutional network with the Bayesian optimization algorithm to predict the diameters of the drilled hole from an electrochemical machining process. The Keras application programming interface (API) was used to build the deep convolutional network; the feed rate, pulse-on time, and voltage were used as input parameters to provide a fair comparison with a neural network from previous research. Random dropout layers were added to prevent overfitting of the network. Instead of tuning the network parameter by trial and error, the Bayesian parameter optimization algorithm was implemented to find the optimal set of parameters of the deep convolutional network that yields the minimum mean square error. The proposed algorithm was compared with a previously developed neural network with partially embedded physical knowledge. Improved training speed and accuracy were observed in comparison with the traditional neural network. The prediction model using the proposed deep learning algorithm demonstrated better prediction accuracy and provided a more systematic way to select the hyperparameter for the deep convolutional network.