Electrochemical Machining Process Research Articles

Influence of Cryogenic Coated Copper Tool Electrode in Electrochemical Micro Machining process of Stainless Steel 316

Electrochemical micro-Machining (ECMM) is best suited for machining micro level profiles as it provides several advantages like better precision, less wear and machinability of wide range of materials. Using various levels of process parameters like voltage, electrolyte concentration, frequency and duty cycle, electrochemical micro machining was performed using untreated and cryogenic treated electrodes and its effect on various response parameters while machining Stainless Steel 316 are studied. From results obtained, the cryogenic treated tool electrode had a high MRR,9.8% of lower overcut,11.2 % of lower conicity and 3.8% of higher circularity compared to untreated tool electrode because the treated tool has high electrical conductance, high corrosion resistance and smaller grain size. The optimized values for Cryogenic Treated tool was achieved when applied voltage was 10V, electrolyte concentration was 30 g/L, frequency was 50 Hz and duty cycle was 33%.

High‐Dissolution Mechanism of Ti–48Al–2Cr–2Nb Alloy in Electrochemical Machining from a Nonlinear Dynamic Perspective

High‐rate dissolution process of Ti–48Al–2Cr–2Nb alloy in electrochemical machining exhibits strong nonlinear dynamic characteristics, but the quantitative relationship between these nonlinear characteristics and surface topography, as well as the electro‐dissolution mechanism, is unknown. Therefore, the fractal and recursive features of dissolution behavior and quantitative characterization of the dissolved surface topography were investigated. Additionally, an electro‐dissolution mechanism model in electrochemical machining process was presented. Applying a higher potential of 11 V can enhance the stability of the electrochemical system, resulting in a smoother and uniform surface. The saturation correlation dimension, surface roughness, and integral area of lacunarity initially decrease before increasing with higher electrolytic pressure, while laminarity and determinism show an initial increase followed by a decrease. These five characteristic parameters reach their optimal values at an electrolyte pressure of 0.4 MPa, indicating that achieving a stable and deterministic electrochemical system is crucial for obtaining a uniform smooth surface. These nonlinear dynamic characteristic parameters can be considered as in‐situ monitoring parameters for surface quality in ECM. The anodic dissolution process comprises three stages: initial passive film dissolution and breakdown, rapid dissolving with surface coarsening, and stable dissolving with polishing.

Material corrosion characteristics of heat-treated SLM-ed Hastelloy X in electrochemical machining process

Selective laser melting (SLM) technology and electrochemical machining (ECM) offer new methods for producing nickel-based superalloys with complex structures and high surface quality, including Hastelloy X parts. However, SLM-fabricated parts exhibit significant anisotropy, and there are no effective criteria for evaluating material corrosion characteristics in actual ECM due to the detachment of research and application, making the parameter selection challenging in actual ECM. To address this issue, this article proposes a comprehensive evaluation system based on the corrosion characteristics in the actual machining process and investigates the effect of heat treatment temperature on the corrosion characteristics of Hastelloy X in ECM. The results show that at a heat treatment temperature of 1000°C, machining efficiency, accuracy, and localization can all be achieved at a good level with good consistency in different directions at the expense of a certain machining accuracy. The 800℃ heat-treated specimen exhibits strong corrosion resistance, providing a significant advantage in machining localization and accuracy. When the heat treatment temperature exceeds the solid solution temperature (more than 1175℃), the mechanical properties and corrosion characteristics of the specimen are significantly degraded. The results of various material testing methods, including electrochemical testing, EBSD, XRD, and EDS indicate that changes in grain size due to recrystallization and the galvanic effect of precipitates are the primary causes of these changes.

Corrosion, wear and machinability studies on scrap aluminium alloy wheel based metal matrix composite

Recycled materials, especially scrap aluminum alloy wheels with reinforcement castings, are gaining applications in various fields such as aerospace, naval, military, and automobile. In this research, Honda car alloy wheels are stir-cast with 5% alumina as reinforcement and subjected to corrosion, wear, and machinability studies. Corrosion studies were conducted to evaluate the corrosion current density (ICorr), corrosion potential (ECorr), and corrosion rate for the cast aluminum metal matrix composite. The wear studies with different loads, i.e., 50 N, 60 N, 70 N, and 80 N, were performed on the specimen and investigated the coefficient of friction, frictional force, and pin temperature. The sliding load has a significant effect on wear performance, and for the sliding load of 80 N, the wear recorded was 2574.83 µm. The electrochemical machinability studies with voltage, duty cycle, and concentration of citric acid electrolyte are performed on the machining rate and surface corrosion factor. Analysis of the electrochemical machining process with PROMETHEE-II shows that 7 V, 60% duty cycle, and 30 g/L electrolyte concentration are estimated to be the best combination for a higher machining rate and a lower surface corrosion factor. KEY WORDS: Alumina, Machining rate, Nyquist plot, Electrochemical machining, PROMETHEE-II Bull. Chem. Soc. Ethiop. 2024, 38(4), 1163-1175. DOI: https://dx.doi.org/10.4314/bcse.v38i4.27

On the Modified Electrochemical Machining Process with a Partially Insulating Cathode

On the Modified Electrochemical Machining Process with a Partially Insulating Cathode

Experimental investigation of micro-machining of borosilicate glass using an ultrasonic assisted rotary electrochemical discharge machining (UA-RECDM) process

Electrochemical discharge machining is an advanced micro-machining process for machining of conductive as well as non-conductive hard and brittle materials, e.g. glass, ceramics, silicon wafer, etc. The present work explores the machining of glass using an in-house developed novel ultrasonic assisted rotary electrochemical discharge machining setup. The setup has specialized features, such as using ultrasonic vibrations to tool the electrode and incorporating rotary motion for manipulating the workpiece. Experiments were conducted using a one factor at a time approach by varying the tool feed rate, the amplitude of the vibrations and the rotation of the workpiece as process parameters. The quality of the machining output was evaluated by observing two key parameters: the overcut and the circularity of the hole. It was observed that as the workpiece rotation speed increased from 40 rpm to 60 rpm, the overcut in the machined samples decreased from 181.378 μm to 163.564 μm. The rotary motion of the workpiece caused a seeping action of the electrolyte in the hydrodynamic regime, leading to the formation of a thin gas film and the stabilization of the discharging process. The morphology of the machined hole exhibits better circularity, low heat-affected zones, minimum micro-cracks and smooth edges at its periphery due to stable discharge formation.

Enhanced fabrication of conical array via two-stage through mask electrochemical machining process

In response to the issues of low processing precision, poor surface quality, and low array uniformity in the fabrication process of metal array conical structures, this paper proposes a two-stage enhanced process for fabricating metal array conical structures using through-mask electrochemical machining (TMECM). The micro-convex structure with high consistency can be quickly obtained through the first electrochemical machining (ECM), and then the mask is removed and the micro-convex structure is modified twice. The top diameter of the micro-structure is reduced by using the phenomenon of electric field concentration in the ECM process, and the top curvature radius of the micro-structure is further reduced, so as to increase the height diameter ratio of the micro-structure and improve the surface quality. The results show that during the initial ECM, when the machining time is 35 s, the voltage is 20 volts, the flow rate of the acid etching solution is 1 m /s, the duty cycle is 50 %, and the frequency is 200 Hz, the stable machining of the metal array conical structure can be achieved. In the secondary electrochemical surface modification, it was found that under the conditions of working solution containing 2 mol/L nickel-based etching agent, pulse voltage of 20 V and processing time of 35 s, the method effectively improved the surface quality of the workpiece and ensured the stable manufacturing of the micro-conical array structure. The prepared microstructure height was 198 μm and the top diameter was 28 μm.

Mechanisms and characterization of a novel hybrid laser-enhanced particle laden electrochemical fabrication process for high quality micro-dimples on germanium wafers

The first-generation semiconductor materials represented by silicon (Si) and germanium (Ge) still hold a dominant position in many fields, including micro-electromechanical systems (MEMS) and integrated circuits (ICs). The processing of these materials continues to attract significant research attention for improvements in quality and efficiency. This study proposes a novel hybrid laser-enhanced particle-laden electrochemical machining (LEPL-ECM) process, whereby pulsed laser irradiation is utilized to selectively and locally enhance the electrical conductivity of Ge at specific locations. A neutral electrolyte jet, containing abrasive diamond particles, is applied to the location on the wafer surface opposite the laser irradiation, facilitating a localized and enhanced electrochemical dissolution. The effect of micro-particle erosion effectively removes the generated oxides and potential passivation layers, ensuring continuous and efficient electrochemical reactions. Consequently, high-quality micro-dimples with an entrance diameter of about 380–800 μm, a depth of around 138–300 μm, and a quasi-mirror surface with the roughness (Sa) of as low as 59.8 nm can be achieved within 90 s. Furthermore, the effects of the applied voltage, laser power and processing time on the resulting dimple characteristics and surface quality are discussed, along with a detailed morphology characterization. Dense micro-pits, radial streamlined micro-grooves and a special transitional region have been observed on dimple center, sidewall and near the edge, respectively, and the formation mechanism have been analyzed. Finally, a simulation of the electrolyte jet induced fluid pressure and velocity as well as the particle trajectory and distributions within and surrounding the dimple structure was conducted, which reveals that the synergistic mechanism associated with the hybrid material removal process involves both electrochemical corrosion and abrasive erosion.

Study on Improving Electrochemical Machining Performances through Energy Conversion of Electrolyte Fluid

Electrochemical machining (ECM) is regarded as a promising and cost-effective manufacturing method for difficult-to-cut materials with complex shapes and structures. The flow-field state of machining gaps is considered a key factor affecting machining performance in ECM engineering practice and has been widely studied. However, little attention has been given to the fluid energy of electrolytes during the ECM process. This study mainly focuses on the influence of the conversion between dynamic and static pressure energy of electrolyte fluid on ECM performance. The simulation results show that by changing the degree of convergence of the electrolyte outlet, the dynamic and static pressure energy of the electrolyte can be effectively adjusted, and increased static pressure energy can be obtained by sacrificing dynamic pressure energy. The experimental results show that electrolyte energy conversion can achieve better surface quality and material removal rate (MRR). However, excessive sacrifice of fluid dynamic pressure energy will also worsen the ECM performance. By combining MRR and Ra, moderate fluid energy conversion can achieve better machining performance, with a degree of convergence of around 50%–70%. The experimental results also show that moderate energy conversion of the electrolyte fluid can improve the utilization efficiency of electrical energy in the ECM process. This may be because the static pressure of the electrolyte can effectively compress the volume of gas products and reduce the electrical resistivity of the machining gap. These conclusions can provide some useful assistance for ECM engineering practice.

Electric field simulation in the electrochemical machining of a thin-walled part cavity

The article is aimed at simulating an electric field in the interelectrode gap during the electrochemical machining of a thin-walled part cavity for aerospace equipment. The study involved simulating the process of electrochemical cavity machining at a constant voltage in a steady-state mode in the COMSOL Multiphysics environment. The simulation was carried out for the scheme of electrochemical machining with a movable cathode and vertical and horizontal feeding to the workpiece surface undergoing machining while maintaining a constant interelectrode gap. The following simulation conditions were adopted: 12Cr18Ni10Ti stainless steel as the material of the cathode tube; AlMg6 aluminum alloy as the material of the thin-walled part; NaNO3 solution as the electrolyte. When simulating the electric field in the interelectrode gap, the heat exchange process was taken into account. The simulation of the electric field in the electrochemical cavity machining of a thin-walled part yielded a macro that allows the process simulation to be adapted to different input process conditions. As a result of the simulation, the following distribution patterns were obtained: current density in the cathode, potentials, electric field in the interelectrode gap and adjacent area, and process temperature of electrochemical machining. The simulation results show that the electric field lines are directed toward the cathode from the workpiece periphery. This means that anodic dissolution of material occurs in a given region, which characterizes the law concerning the distribution of potentials in an electrochemical cell. The temperature distribution pattern obtained in the simulation revealed that a temperature increase in the machining zone is insignificant. An increase in electrolyte temperature is shown to result in a proportional increase in wall temperature. Thus, the conducted study provides a theoretical insight into the examined process.

INFLUENCE OF THE ELECTROLYTE FLOW AND CLEANING AIR PRESSURE ON THE OVERCUT IN BIPOLAR PULSED ELECTROCHEMICAL MICRO-MACHINING PROCESSES

This paper presents an experimental investigation on the reduction of overcutting in the bipolar pulsed electrochemical pulsed machining process. It is described how this unconventional manufacturing method, which involves the anodic dissolution of a metal part immersed in an electrolytic medium, can be improved by incorporating compressed air as a residue-cleaning medium and modifying the electrolyte flow rate to reduce overcutting. These results can be helpful for the inclusion of these variables in process control systems and generate significant improvements in the fabrication of components at micrometer scales. Keywords: micromachining, electrochemical machining, overcut, electrolyte, automatic processes.

CONTROL DE MICRO MECANIZADO NO CONVENCIONAL BASADO EN ANÁLISIS DE PARÁMETROS MULTIVARIABLES UTILIZANDO UN SISTEMA DE INFERENCIA DIFUSA

Non-conventional manufacturing processes, such as pulsed electrochemical machining, are strategies for manufacturing metal components that optimize tool life. This is achieved by implementing non-traditional techniques based on electrolysis to remove metal in a controlled environment without generating contact between the tool and the workpiece. These characteristics allow a reduction in the resources required for the development of components with complex morphology on high-strength materials in many application fields, such as aerospace, medical, and precision tools. However, the characteristic features of non-linearity in this kind of process increase the complexity of the development of automatic control through traditional algebraic techniques in the regulation of uniform material wear. In this context, a non-traditional solution based on techniques derived from artificial intelligence bounded by fuzzy logic and genetic algorithms is presented for the tuning and automatic control of the pulsed electrochemical machining process. Furthermore, the efficiency is evaluated by analyzing the over-cutting phenomenon and the precision in developing linear polygonal machining on a micrometer scale. Keywords: Modern manufacturing, fuzzy logic, automatic control, electrolysis, genetic algorithms.

Effect of the hollow electrode on the material removal rate of titanium alloy (grade 1) in the electrochemical machining (ECM) process

This study examined the material removal rate (MRR) affected by the variables of the electrochemical process including electrode type, voltage, electrolyte type, electrolyte concentration, and gap. Titanium alloy was employed as the workpiece, while copper was utilized as the cylindrical electrode. The input parameters were established according to Taguchi’s methodology. An analysis of variance (ANOVA) using a linear regression model was dependent on making sense of the experiment’s findings. the solid electrode achieved the maximum material removal rate (MRR) value (0.0857) g/min, while the hollow electrode with (1500 l/hour) flow rate achieved the minimum material removal rate (MRR) value (0.00002) g/min. the material removal rate (MRR) was directly proportional to the voltage. Maximum material removal rate (MRR) occurred at a concentration of (75 g/l) for the (NH4C) electrolyte, while minimum material removal rate (MRR) occurred at a concentration of (50 g/l) for the (NH4Cl) electrolyte. It has been observed that the contributing factors in controlling material removal rate (MRR) were as follows; (66.67%) for the voltage, (5.89%) for the electrode, (5.72%) for the electrolyte concentration, (3.24%) for the type of electrolyte, and (3.07%) for the gap.

A State-of-the-Art Review on the Recent Advancements in the Electrochemical Abrasive Flow Machining Process

Abrasive flow machining (AFM) is a non-conventional machining method used for the fine finishing of complex external/internal surfaces of metallic parts. Generally, this process has a low material removal rate (MRR) and is a more time-consuming process. So, to overcome this problem, various researchers employed hybridization of the abrasive flow machining process (AFM) with a distinct nontraditional machining process. Hence, this paper aims to provide a detailed review of the electro-chemical assisted AFM (ECA2FM) process, which is a combination of electrochemical machining and abrasive flow process. Then, the effect of processing parameters such as grit size and type, the total number of cycles, current, voltage, abrasive type and size, extrusion pressure, design of workpiece holding device and proper tooling on the material abrasion and surface finishing is summarized. Thereafter the Progressive outlook on the integration of electrochemical AFM with magnetic energy is given. Finally, the emerging applications of the electrochemical AFM process are discussed.

Research on simulation method of multiple time scales dissolution process in tube electrode pulse electrochemical machining

Tube electrode pulsed electrochemical machining (TE-PECM) has received widespread attention as an electrochemical perforation technique that is widely used for machining deep small holes/oblique small holes such as air film holes in blades. However, the TE-PECM process is characterized by complex multi-physics field coupling relationships and multiple time scales for multi-physics interactions, making the simulation of the pulsed electrolytic processing process computationally huge and difficult to perform. To accurately describe the multi-physical field coupling relationship for pulsed electrochemical processing. In this paper, a k-ε gas-liquid two-phase flow model has been introduced to model the interpolar gas-liquid two-phase flow field variation law, and on this basis, a coupled multi-physics field model for pulsed electrochemical machining processing is established to provide an accurate description of the interpolar multi-physics interaction mechanism. A quasi-steady-state iterative simplification algorithm based on heat source averaging is proposed to solve the problem that the time scale span of the dissolution process leads to a huge amount of simulation calculations. The simulation analyzes the dissolution characteristics at the micro time scale and macro time scale and compares them with the full precision method. The results show that the simulation accuracy of the two methods is the same, but the simulation calculation time of the simplified algorithm is reduced by two-thirds. The experimental platform was designed and built to carry out a series of experiments under different processing times, and the results effectively verified the correctness of the simulation method.

Micro-ECDM Performances Analysis Using Fuzzy Logic and ANFIS During Micro-Channel Fabrication on Silica Glass

Higher accuracy and meticulousness are highly demandable in modern industrial field during micro-machining performances by electrochemical discharge machining (ECDM) process. The paper deals with the experimental fuzzy logic control (FLC) analysis as well as artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) analysis during micro-channel fabrication on silica glass. A comparative analysis of FLC, ANN as well as ANFIS has been performed and experimental error prediction has been propounded to estimate minimum error possibilities such as mean absolute error (MAE), root mean square error (RMSE) and regression value (R). Computational time training dataset, minimum sample size and prediction time are also illustrated in this paper. In this paper, ANN, FLC and ANFIS models are analyzed for tool wear rate (TWR) and heat-affected zone (HAZ). 3D Rule Viewer and regression analysis as well as validation of test results and characteristics graph between performances with number of epochs of ANN model also are included in this paper for TWR and HAZ. Influence of process parameters like voltage, duty ratio, pulse frequency and electrolyte concentration on Surface Viewer of TWR and HAZ is also illustrated. It is found that ANFIS has great effectiveness of prediction of error during micro-ECDM process.

Improvement on surface quality of Inconel-718 slits via laser cutting and wire electrochemical machining processes

In the paper, we present a combined gas–assisted laser machining and wire electrochemical machining (W-ECM) process to improve the surface quality of slits produced in Inconel-718, a high-strength nickel-based alloy widely used in aircraft engine parts. First, a laser cutting was applied to produce the slit structure in Inconel-718, where the power and feed rate were varied to identify the optimal processing parameters. Subsequently, the slits were processed by a custom-developed W-ECM process. The results were evaluated by characterizing the surface roughness and kerf width of the slits. Through this combined approach, a 90% average improvement on surface finish was achieved with a 10% increase in kerf width. In addition, the typical striation marks and thermal damages from laser machining processes were entirely eliminated in all slits. The new process is precise and low-cost, which may find important applications in high-precision laser machining applications.

Implementation of robotic electrochemical machining in freeform surface machining with material removal rate prediction using different machine learning algorithms

Robots are used as machine tools via some advanced properties such as versatility, adaptation and mobility with other control systems. These advantages can be the solution to overcome the encountered problems in electrochemical machining (ECM). In this manner, the usability of a new machining method that is Robotic electrochemical machining (RECM) in freeform surface machining is investigated. Firstly, ECM parameters and their effects on the material removal rate (MRR) is discussed and compared with the literature. Experimental results showed that MRR variation for RECM acts similar characteristics with conventional ECM processes. The increase in voltage, electrolyte conductivity and feed rate increase MRR. The highest effect on MRR for both materials is voltage, electrolyte conductivity, and feed rate, respectively. Secondly, three different machine learning models are designed as Gaussian Process Regression (GPR), regression tree and deep neural network (DNN) models and the relationships between their actual and predicted values are discussed. The performance of the DNN model is better than other models with a correlation of determination values equal for Inconel 718 and AISI 1040. Furthermore, the DNN model with four input parameters outperforms developed models such as GPR and DTR with optimized hyperparameters regarding the R2, MSE, RMSE, and MAE. The change in height in the Z-axis and the surface roughness of the machined surfaces are also measured. The results show that the decrease in the Z axis is homogeneous, that is, uniform machining occurs and also the surface roughness has improved. Therefore, RECM can be a solution to machine free-form surfaces for different materials with high predictability.

Simultaneous electrochemical and electrodischarge machining process: An approach to sustainable manufacturing

Manufacturing of Net Finished Shape (NFS) microholes in Inconel 718 materials with faster machining rate can offer significant benefits in terms of reduced waste, improved efficiency, and lower production costs, which are essential for sustainable manufacturing. However, the existing manufacturing method, namely electrochemical machining (ECM), results in slow machining with uncontrolled dissolution, leading to increase production time, energy consumption, and carbon emission associated with the manufacturing process. The current manuscript investigates the reason attributes for these problems through potentiodynamic polarization test. Subsequently, a new machining process known as Simultaneous electrochemical and electrodischarge machining (SECEDM) has been proposed. This frugal manufacturing-based machining process offers high machining rate (MR) and better overall hole circularity (OHC) through the synergistic effect of anodic dissolution and electrochemical discharges. The obtained results reveal that the SECEDM process offers nearly 261 % and 141 % higher MR and 1.23 % and 3.78 % better OHC than electrochemical machining (ECM) and electrodischarge machining (EDM), respectively. Moreover, SECEDM outperforms the simultaneous micro-EDM and micro-ECM process (SEDCM) process by seven times in machining rate and promotes localized dissolution than ECM. Overall, SECEDM's benefits, including its high machining rate, superior surface quality, sustainability, eco-friendliness, and elimination of the need for secondary finishing processes, make it an ideal candidate for the next-generation manufacturing process.

Flow Visualisation and Evaluation Studies on Metalworking Fluid Applications in Manufacturing Processes—Methods and Results

Metalworking operations rely on the successful application of metalworking fluids (MWFs) for effective and efficient operation. Processes such as grinding or drilling often require the use of MWFs for cooling, lubrication, and chip removal. Electrochemical machining processes require electrolyte flow to operate. However, in those machining operations, a fundamental understanding of the mode of action of MWF is lacking due to the unknown flow dynamics and its interaction with the material removal during the process. Important information on the behaviour of MWFs during machining can be obtained from specific experimental flow visualisation studies. In this paper, promising flow visualisation analysis techniques applied to exemplary machining processes (grinding, sawing, drilling, and electrochemical machining) are presented and discussed. Shadowgraph imaging and flow measurements, e.g., particle image velocimetry, allow the identification of typical flow and MWF operating regimes in the different machining processes. Based on the identification of these regimes, efficient machining parameters and MWF applications can be derived. In addition, detailed experimental analyses of MWFs provide essential data for the input and validation of model development and numerical simulations within the Priority Programme SPP 2231 FluSimPro.