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Bearing steel (GCr15) is widely used in key parts of mechanical transmission for its excellent mechanical properties. Electrochemical machining (ECM) is a potential method for machining GCr15, as the machining process is the electrochemical dissolution of GCr15 regardless of its high hardness (>50 HRC). In ECM, NaNO3 solution is a popular electrolyte, as it has the ability to help in the nonlinear dissolution of many metallic alloy materials, making it useful for precision machining. However, due to high carbon content of GCr15, the electrochemical dissolution of GCr15 is unique, and there is always a black layer with high roughness on the machined surface, reducing the surface quality. In order to improve the electrochemical machining of GCr15 with a high surface quality, the surface characteristics of GCr15 in ECM were investigated. The anodic polarisation curve in the NaNO3 electrolyte was measured and electrochemical dissolution experiments were conducted with different current densities. SEM, XRD, and XPS were employed to analyse the surface morphology and composition formed on the machined surface at different current densities. The initial results showed that there were two parts (black part and bright part) formed on the machined surface when a short circuit occurred, and the test results suggested that the black part contained a mass of Fe3O4 while the bright part was composed of mainly Fe and Fe3C. Further investigation uncovered that a black flocculent layer (Fe3O4) always formed in a low current density (32 A/cm2) with high roughness. With the current density increased, the amount of black flocculent layer was reduced, and Fe3C particles appeared on the machined surface. When the current density reached 81 A/cm2, the entire flocculent oxide layer was removed, only some spherical Fe3C particles were inserted on the machined surface, and the roughness was reduced from Ra7.743 μm to Ra1.783 μm. In addition, due to exposed Fe3C particles on the machined surface, the corrosion resistance of the machined surface was significantly improved. Finally, circular arc grooves of high quality were well manufactured with current density of 81 A/cm2 in NaNO3 electrolyte. [ABSTRACT FROM AUTHOR]

In order to shorten the cathode design cycle, reduce design cost and improve forming accuracy for all-metal screw drill stator electrochemical machining (ECM), this paper proposed a precision forming cathode design method based on particle swarm optimization BP neural network (PSO-BP). The cathode design algorithm model of all-metal screw drill stator electrochemical machining was established, completed the camber feed cathode design. By using self-developed large scale horizontal CNC electrochemical machining equipment, under the condition of voltage 19 V, electrolyte 15%NaCl, electrolyte temperature 35 ± 1℃, electrolyte inlet pressure 1.6 MPa, and feed speed 10 mm/min, the stable and reliable electrochemical machining processing of the 4-m length of 38CrMoAlA all-metal screw drill stator was completed. The contour forming accuracy is ± 0.03 mm, and the surface roughness is Ra0.848 μm. Research showed that it is an efficient and feasible method to design the electrochemical machining camber feed cathode of all-metal screw drill stator using PSO-BP neural network. [ABSTRACT FROM AUTHOR]

Bearing steel (GCr15) is widely used in key parts of mechanical transmission for its excellent mechanical properties. Electrochemical machining (ECM) is a potential method for machining GCr15, as the machining process is the electrochemical dissolution of GCr15 regardless of its high hardness (>50 HRC). In ECM, NaNO3 solution is a popular electrolyte, as it has the ability to help in the nonlinear dissolution of many metallic alloy materials, making it useful for precision machining. However, due to high carbon content of GCr15, the electrochemical dissolution of GCr15 is unique, and there is always a black layer with high roughness on the machined surface, reducing the surface quality. In order to improve the electrochemical machining of GCr15 with a high surface quality, the surface characteristics of GCr15 in ECM were investigated. The anodic polarisation curve in the NaNO3 electrolyte was measured and electrochemical dissolution experiments were conducted with different current densities. SEM, XRD, and XPS were employed to analyse the surface morphology and composition formed on the machined surface at different current densities. The initial results showed that there were two parts (black part and bright part) formed on the machined surface when a short circuit occurred, and the test results suggested that the black part contained a mass of Fe3O4 while the bright part was composed of mainly Fe and Fe3C. Further investigation uncovered that a black flocculent layer (Fe3O4) always formed in a low current density (32 A/cm2) with high roughness. With the current density increased, the amount of black flocculent layer was reduced, and Fe3C particles appeared on the machined surface. When the current density reached 81 A/cm2, the entire flocculent oxide layer was removed, only some spherical Fe3C particles were inserted on the machined surface, and the roughness was reduced from Ra7.743 μm to Ra1.783 μm. In addition, due to exposed Fe3C particles on the machined surface, the corrosion resistance of the machined surface was significantly improved. Finally, circular arc grooves of high quality were well manufactured with current density of 81 A/cm2 in NaNO3 electrolyte.

Foamed metal materials are introduced as a novel tool to manufacture cathodes for the electrochemical machining (ECM) of involute internal spline made from difficult-to-cut materials. This paper analyzes the porosity density and electrolyte flow characteristics of foamed metal cathodes. The geometric and mathematical model of the involute internal spline by ECM is built, and electric field simulations are conducted by using the COMSOL Multiphysics software to determine the ECM results. Based on the simulation results, suitable initial process parameters are obtained and relative process experiments are carried out. The experiment results demonstrate that foamed metal material can be used to fabricate tool cathodes for ECM of involute internal spline. When the machining voltage is 10 V, the electrolyte type is 2% NaCl + 8% NaNO3 solution, and cathodic feed rate is 1.00 mm/min, the involute internal spline machined by axial ECM can achieve better profiles that meet the finishing accuracy and precision requirements. The experimental application of foamed metal cathode lays a new technical foundation for ECM to manufacture complex internal structures and from design theory to contemporary industrial praxis. [ABSTRACT FROM AUTHOR]

• Modal analysis is conducted on the prototype blade at its first-order frequency. • Blades machined at different current densities were subjected to detailed surface-integrity evaluation. • Fatigue testing and fracture surface analysis is conducted on the blades. • The failure mechanism of blades machined by ECM was characterized. Blades made from Inconel 718 (IN718) are generally machined using electrochemical machining (ECM), and the high-cycle fatigue (HCF) of such blades significantly impacts the service life of aeroengines. In this study, modal analysis was performed to obtain the blade modal shape and stress distribution at first-order frequency, after which blades were machined at different current densities (9.5 A/cm2, 18.2 A/cm2, 34 A/cm2, 46.7 A/cm2, 61.2 A/cm2, 70.1 A/cm2) and then subjected to detailed surface-integrity analysis and fatigue tests. No surface defects (e.g., intergranular corrosion, recast layers) were observed, the microhardness was unchanged, and new residual stress was not found to be introduced to the machined surfaces. The machined surfaces were uneven and contained micro-pits, and high current density contributed to better surface quality. At a constant load of 520 MPa, the blade machined at 70.1 A/cm2 had the best fatigue life of 1.4×106. The blades fractured because of micro-pits, and as the surface quality of the blades improved, so did their fatigue performance. Therefore, the fatigue failure mechanism characterized in this work provides a reference for the HCF behavior of blades machined by ECM. [ABSTRACT FROM AUTHOR]

Electric discharge machining (EDM) is a type of high-precision machining usually applied to hard-material machining for mold manufacturing and in the aerospace industry. Longer process times typically reduce facility efficiency. The use of electrochemistry machining (ECM) can overcome this challenge to efficiently machine large workpieces. Some industries have adopted and combined these two processes for Inconel 718 material machining. However, the use of coordinate-measuring machine times to determine the machining accuracy of these two processes is difficult. This study matched process features by analyzing the electric driving pulses of ECM and EDM. Fitting intelligent sensing signals that respond to dimensional measurements can be used to analyze electrical pulse signals. For analyzing a cross-process model using extracted key features of the process, our feedback-based system determines lower machining measurement errors and improves geometric size. Finally, the processing time of experiments can be reduced by 80%, and our proposed model has a prediction accuracy of approximately 0.01 mm 2 . [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing technology can be used to easily and rapidly produce complex shapes. In this study, an electrode tool used for electrochemical machining (ECM) was fabricated using a 3D fused deposition modeling (FDM) printer. The electrode tool was made from acrylonitrile butadiene styrene (ABS), a low-cost material commonly used in 3D printing. Since the electrode printed with ABS material is non-conductive, additional conductive coating was applied to the tool surface. Electrical conductivity characteristics and coating thicknesses were analyzed with respect to the number of coatings to identify optimal coating conditions. The ECM performance of the fabricated electrode was then compared with that of a conventional copper electrode tool. The effect on the shape of the 3D printing electrode during machining according to the type of coating was analyzed. The thermal effect of the current applying had to be considered, and a suitable coating type was selected based on the experimental results. The fabricated ECM electrode can achieve significant machining quality to the existing electrode performance, and through the results of this study, it was possible to increase sustainability in the manufacturing industry with advanced machining technology. [ABSTRACT FROM AUTHOR]

In view of the difficult machining characteristics of titanium alloys and the limitations of sequential EDM/ECM machining, taking NaNO3 salt solution with low conductivity as the working fluid, the simultaneous machining of EDM and ECM (SEDCM) assisted by abrasive particles was carried out. Firstly, the effects of the electrical conductivity of the working fluid, the abrasive material, and particle size on material removal rate (MRR), tool wear rate (TWR), surface roughness (Ra), and surface morphology of SEDCM were investigated. Then, SiC abrasive with particle size of 50 μm was selected to add in the working fluid of SEDCM, owing to the unique properties of SiC in comparison with Al and Cu abrasive particles. The effect of process parameters, such as peak current, pulse on time, abrasive concentration, and gap voltage, was optimized using Taguchi-based grey relational analysis. The multi-objective optimization of MRR, TWR, and Ra was converted into the optimization of a single grey relational grade. Finally, based on the grey relational grade, the optimal combination of peak current, pulse on time, abrasive concentration, and gap voltage was predicted and verified by experiments. The results show that the comprehensive machining effect is better when the conductivity of working medium is 300 μS/cm, as long as other electrical parameters and experimental conditions are the same. Compared with Cu and Al abrasives, SiC abrasive has the lowest tool wear rate and the best surface quality, even with the worst material removal rate. Moreover, MRR, TWR, and Ra were obviously improved at the optimal parametric combination of peak current 1.5A, pulse on time 15 μs, abrasive concentration 5 g/L, and gap voltage 40 V by implementing Taguchi-based grey relational analysis. [ABSTRACT FROM AUTHOR]

In order to solve the problem of uneven gap distribution and flow pattern in the complex parts with multi-stage internal cone hole in electrochemical machining, a method of computer simulation–assisted cathode design is proposed. The electric field and flow field models of machining gap are established respectively, and the simulations of different cathode profiles are carried out. When the cathode cone angle is 2°, the electric field distribution between the cathode and the workpiece is reasonable, and the electrolyte distribution in the machining gap is uniform. With the conditions of processing voltage 10 V, electrolyte inlet pressure 1.5 MPa, electrolyte temperature 28 ℃, and cathode feed speed 5 mm/min, the electrochemical machining (ECM) processing of multi-stage internal cone hole is carried out by using the optimized cathode. The results show that the surface of the workpiece has no flow pattern, the dimensional forming accuracy is better than 0.1 mm, and the surface roughness reaches Ra 0.697 μm. Research shows that the optimization of cathode structure with computer simulation can shorten the cathode development cycle and reduce the cost of cathode design effectively in ECM, which provides an efficient and feasible method for the optimization of complex cathode structure. [ABSTRACT FROM AUTHOR]

Electrochemical machining (ECM) is a preferred advanced machining process for machining Monel 400 alloys. During the machining, the toxic nickel hydroxides in the sludge are formed. Therefore, it becomes necessary to determine the optimum ECM process parameters that minimize the nickel presence (NP) emission in the sludge while maximizing the material removal rate (MRR). In this investigation, the predominant ECM process parameters, such as the applied voltage, flow rate, and electrolyte concentration, were controlled to study their effect on the performance measures (i.e., MRR and NP). A meta-heuristic algorithm, the grey wolf optimizer (GWO), was used for the multi-objective optimization of the process parameters for ECM, and its results were compared with the moth-flame optimization (MFO) and particle swarm optimization (PSO) algorithms. It was observed from the surface, main, and interaction plots of this experimentation that all the process variables influenced the objectives significantly. The TOPSIS algorithm was employed to convert multiple objectives into a single objective used in meta-heuristic algorithms. In the convergence plot for the MRR model, the PSO algorithm converged very quickly in 10 iterations, while GWO and MFO took 14 and 64 iterations, respectively. In the case of the NP model, the PSO tool took only 6 iterations to converge, whereas MFO and GWO took 48 and 88 iterations, respectively. However, both MFO and GWO obtained the same solutions of EC = 132.014 g/L, V = 2406 V, and FR = 2.8455 L/min with the best conflicting performances (i.e., MRR = 0.242 g/min and NP = 57.7202 PPM). Hence, it is confirmed that these metaheuristic algorithms of MFO and GWO are more suitable for finding the optimum process parameters for machining Monel 400 alloys with ECM. This work explores a greater scope for the ECM process with better machining performance. [ABSTRACT FROM AUTHOR]

In this study, the electrochemical machining (ECM) of the 304 stainless steel with the response surface methodology (RSM) approach for designing, analyzing and mathematical modeling was used. The electrolyte type, concentration and current parameters were considered as the machining parameters. The mathematical model for the responses was presented and based on the type of electrolyte including NaCl, NaNO3 and KCl. The results showed that the current has the highest effect on Surface Roughness (SR) and Material Removal Rates (MRR) and respectively it improves them to 0.465μm and 0.425gr/min. The electrolyte concentration has the highest effect on Over Cut (OC) and causes to increase its values. Under the conditions of NaCl electrolyte, 1 molarity concentration and 55 A current, the optimum condition 0.4006 gr/min MRR, 0.75 mm OC and 0.465mm SR was achieved.

Due to more freedom in design and flexibility in production, parts produced by additive manufacturing (AM) technologies offer a huge potential for the manufacture of turbomachinery components. Because of the layer by layer built structure, internal defects such as cracks or gaseous pores can occur. These defects considerably reduce the mechanical properties and increase the importance of quality control, especially in the field of turbomachinery. Therefore, in this study, an electrochemical defect analysis (EC-D) of additive manufactured components is introduced, performed, and validated in comparison to a nondestructive X-ray testing of the same part. A test rig was developed, which allows an alternation between electrochemical machining and subsequent optical documentation of each removed layer. The documentation of the surface and the macroscopic defects in the AM-parts are captured by an integrated camera system. [ABSTRACT FROM AUTHOR]

Electric discharge machining (EDM) is a type of high-precision machining usually applied to hard-material machining for mold manufacturing and in the aerospace industry. Longer process times typically reduce facility efficiency. The use of electrochemistry machining (ECM) can overcome this challenge to efficiently machine large workpieces. Some industries have adopted and combined these two processes for Inconel 718 material machining. However, the use of coordinate-measuring machine times to determine the machining accuracy of these two processes is difficult. This study matched process features by analyzing the electric driving pulses of ECM and EDM. Fitting intelligent sensing signals that respond to dimensional measurements can be used to analyze electrical pulse signals. For analyzing a cross-process model using extracted key features of the process, our feedback-based system determines lower machining measurement errors and improves geometric size. Finally, the processing time of experiments can be reduced by 80%, and our proposed model has a prediction accuracy of approximately 0.01 mm2.

Electrochemical machining (ECM) is one of the main methods for manufacturing gamma-titanium aluminum (γ-TiAl) alloy blades of new-type aero-engines. Tool-vibration-assisted pulsed electrochemical machining (VPECM) is an important method to improve the manufacturing accuracy. In order to determine the influence of processing parameters on the VPECM quality of γ-TiAl TNM alloys, multi-field simulations with different parameter combinations of peak voltage, feed rate, duty cycle, and tool vibration frequency were carried out. The influence of bubble rate and temperature increase on the conductivity distribution in the machining gap under different parameter combinations was analyzed. Then, orthogonal experiments with the above four processing parameters were carried out. The experimental results of surface roughness, replication accuracy, and average current density in the pulse width were interpreted by a grey relational analysis, and the best parameter combination was determined. Finally, four blade-shaped γ-TiAl TNM alloy specimens were processed by using the optimized parameter combination, which had good replication accuracy and surface quality.

Electrochemical machining (ECM) is a noncontact removal machining method based on electrolytic action, can be effectively used to remove metallic materials, regardless of the material hardness. Due to its excellent features, ECM is usually used to realize the shape generation of difficult-to-cut metallic materials. However, when processing certain typical difficult-to-cut materials, such as titanium alloy and tungsten carbide, an oxide film is formed on the workpiece surface, which hinders the further dissolution of the material. Passivation due to oxide film formation generally occurs under a low current density. During the generation of a complicated shape through small tool electrode scanning, the low-current-density area around the peripheral area of the tool eventually covers the complete machining area. Consequently, the passivation becomes highly intense, and a suitable shape may not be generated. To solve this problem and realize the shape generation of titanium alloys in scanning ECM, the characteristics of the oxide film and its influence on material dissolution when using a suction tool were investigated based on current distribution calculations and machining experiments. A model for the scanning ECM of titanium alloys and guidelines for designing the scanning tool and determining machining conditions were proposed. The effectiveness of the proposed model and guidelines were validated through experiments with a suction tool.

Electrochemical machining (ECM) using tube electrodes is an effective approach for the rough machining of turbo engine blisks. The uniformity of the channel allowance decisively influences the accuracy of subsequent ECM precision for the blisk. A voltage regulation strategy to minimize allowance differences in the ECM is proposed. Simulation and experimental investigations are performed to determine the relationships between the channel width and the applied voltage. Comparative experiments using the conventional constant voltage method and the proposed voltage regulation method are performed. The experimental results show that the allowance differences on the back and basin surfaces of the blade are reduced by 47.81% and 51.57%, respectively, using the proposed method. Thus, the experimental results verify that the voltage regulation strategy is effective for the ECM of blisk channels. [ABSTRACT FROM AUTHOR]

Electrochemical machining (ECM) is a non-traditional machining technology that is widely used in the manufacturing of key components in the aviation industry. The current efficiency is defined as the ratio of the observed amount of dissolved metal to the theoretical amount predicted from Faraday's law. In ECM, the current efficiency curve relates the dissolution rate of the anode material and the current density. Accurate measurement of the current efficiency curve is the basis for anode shape prediction and cathode tool design. However, in conventional measurement methods, the phenomenon of edge stray corrosion introduces significant measurement errors. Improving the current efficiency is thus a challenging task for any electrophysical or electrochemical machining process. To improve the measurement accuracy, this paper proposes a current efficiency curve measurement with a casing-type anode. In the proposed measurement method, the anode is designed in two parts: the mandril and the casing. The edge stray corrosion effect is mainly concentrated on the casing, and only the current distribution on the mandril is considered in the calculation of current efficiency. The measurement simulations of the conventional and the proposed methods were carried out. The simulation results show that the casing-type method significantly improves the accuracy of current efficiency measurements, and the current efficiency curve of 304SS was obtained. [ABSTRACT FROM AUTHOR]

Micro rotary structures have attracted increasing attention in many industrial applications. However, the fabrication of complex micro rotary structures with high strength, high hardness, and low rigidity, poses a significant challenge to traditional machining methods. To solve this difficult problem, this study proposes a novel method of fabricating complex micro rotary structures by using wire electrochemical grinding (WECG), which is an anodic dissolution process and has no machining force. WECG, a type of ECM, has some major advantages over wire electrical discharge grinding (WEDG): no electrode wear, absence of residual stress, good surface quality, low machining cost, and high machining efficiency. Firstly, this study investigated the influences of the process parameters on the dimensional accuracy of the micro grooves produced, then optimized these process parameters. A qualitative simulation of WECG was conducted to reveal the reason for the trumpet-like micro grooves fabricated by WECG. Finally, based on the optimal process parameters, several different kinds of rotary structures were successfully produced by WECG. The experimental results demonstrate that WECG is a promising method for fabricating complex rotary structures of difficult-to-cut materials at low cost and with high efficiency.

Electrochemical machining (ECM) is a preferred advanced machining process for machining Monel 400 alloys. During the machining, the toxic nickel hydroxides in the sludge are formed. Therefore, it becomes necessary to determine the optimum ECM process parameters that minimize the nickel presence (NP) emission in the sludge while maximizing the material removal rate (MRR). In this investigation, the predominant ECM process parameters, such as the applied voltage, flow rate, and electrolyte concentration, were controlled to study their effect on the performance measures (i.e., MRR and NP). A meta-heuristic algorithm, the grey wolf optimizer (GWO), was used for the multi-objective optimization of the process parameters for ECM, and its results were compared with the moth-flame optimization (MFO) and particle swarm optimization (PSO) algorithms. It was observed from the surface, main, and interaction plots of this experimentation that all the process variables influenced the objectives significantly. The TOPSIS algorithm was employed to convert multiple objectives into a single objective used in meta-heuristic algorithms. In the convergence plot for the MRR model, the PSO algorithm converged very quickly in 10 iterations, while GWO and MFO took 14 and 64 iterations, respectively. In the case of the NP model, the PSO tool took only 6 iterations to converge, whereas MFO and GWO took 48 and 88 iterations, respectively. However, both MFO and GWO obtained the same solutions of EC = 132.014 g/L, V = 2406 V, and FR = 2.8455 L/min with the best conflicting performances (i.e., MRR = 0.242 g/min and NP = 57.7202 PPM). Hence, it is confirmed that these metaheuristic algorithms of MFO and GWO are more suitable for finding the optimum process parameters for machining Monel 400 alloys with ECM. This work explores a greater scope for the ECM process with better machining performance.

This paper proposes a combined milling process of electrical discharge ablation machining (EDAM) and electrochemical machining (ECM) as an alternative to the low efficiency problem of less efficient electrical discharge machining (EDM) and to reduce the recast layer of EDAM. The working medium was a mixed aerosol of NaCl solution and oxygen, which has electrolytic and dielectric characteristics. The mechanism was analyzed: the combined milling process was a mixed process of EDAM, ECM, and EDAM-ECM combined machining. The EDAM-ECM combined machining can be divided into three stages: the electrolysis stage, discharge channel formation stage, and rapid ablative removal stage of metal substrate. Experiments were performed to compare conventional EDM milling, EDAM milling, and combined milling of EDAM and ECM. Results showed that the material removal rate (MRR) of the combined milling was 11.5 times that of EDM milling, and it increased by 18.7% compared with EDAM milling. The relative tool wear ratio (RTWR) decreased by 46.6%, and the thicknesses of the recast layer on the bottom and side were reduced by 61.2% and 49.2%, respectively, compared with EDAM milling. [ABSTRACT FROM AUTHOR]

Electrochemical machining (ECM) is an important method to drill film cooling holes in difficult-to-machine materials such as high-temperature nickel-based alloy. However, physical field parameters of ECM, such as flow field characteristics and temperature field distribution in the interelectrode gap, cannot be directly monitored, which makes it difficult to improve the accuracy of ECM. In this paper, the effect of processing voltage, electrolyte inlet pressure, and electrode feed rate on machining accuracy was studied through experiments. According to the gas–liquid two-phase flow theory and mathematical model of convective heat transfer, the volume fraction of hydrogen and electrolyte temperature field were simulated and analyzed by COMSOL Multiphysics software. The results indicate that the electrolyte temperature plays a dominant role in all factors affecting the processing effects when only the processing voltage or electrolyte inlet pressure changes. When only the electrode feed rate changes, volume fraction of hydrogen dominates the effects. This has guiding significance for practical production, and can improve the accuracy of ECM by controlling the temperature of the electrolyte and the volume fraction of hydrogen. [ABSTRACT FROM AUTHOR]

The discharge craters and recast material are the characteristics of the surface machined by using EDM, which deteriorate the surface quality and other properties such as fatigue strength of the workpiece. In this study, a new combined machining method which utilizes a thin foil as tool electrode and combines EDM and ECM into a single process for slicing workpiece is proposed and investigated through experiments. The method can improve the surface quality by using ECM to remove the discharge craters and recast layer of EDM surface. The advantages of utilizing a foil instead of a wire as tool electrode for slicing the workpiece is that tool vibration can be considerably reduced and the efficiency of electrochemical dissolution increased. The experimental results show that good surface quality can be obtained by eliminating the craters and recast layer of EDM surface without sacrificing the cutting efficiency. Two factors of the combined machining, namely the height and the feed rate of the foil electrode, which have significant influence on the final surface quality are investigated. The taper of the kerf, kerf width, and tool wear are discussed experimentally. The combined machining with a thin foil as tool electrode provides a promising method for workpiece slicing in the future. [ABSTRACT FROM AUTHOR]

The Mechano-Electrochemical Milling (MECM) process combines Electrochemical Machining (ECM) with a mechanical cutting process. The exploitation of the strengths of both proven technologies offers opportunities for more efficient machining of both existing and new hard-to-cut materials. Notwithstanding research has been done on the material removal rate and material removal mechanisms of this new process, the mutual influences of the two material removal components on the electrolyte behaviour in the working gap are still unclear and are subject of investigation in this paper. Phenomena such as bubble formation, a more irregular flow and a more complex surface topography during machining have a direct influence on the combined material removal mechanism and the resulting machined surface. Investigation of these phenomena is done through online high-speed observation of the electrolyte behaviour in the working gap during MECM under a series of different parameter conditions. These observations, together with other online and offline measurements such as current-voltage and infrared imaging, allow to better explain the process behaviour. [ABSTRACT FROM AUTHOR]

Though much work has been done in input-output mapping and input parameter optimization of different manufacturing processes, very sparse work is available in obtaining multiple optimal process parameter combinations of these processes i.e. multimodal optimization. Multimodal optimization is necessary as a single optimal process parameter combination may theoretically satisfy the objective function, but it might not be applicable in real life and may lead to unstable experimentation conditions. In this paper, a new approach based on supervised clustering is presented for multimodal optimization. In the presented approach, k-means clustering algorithm is first used to cluster selected initial points. Next, the optimization is performed in a small radius surrounding these cluster centers. New cluster centers are then formed from select points of the previous iteration and the optimization results. The proposed technique aims to find multiple optimal solutions by taking advantage of the fact there is a high density of points with favorable objective value clustered around a peak or a valley. The presented approach is then applied for multimodal optimization of some benchmark problems as well as a case study of input parameters optimization of electrochemical micro-machining. The results from the benchmark problems and the case study validate the effectiveness and robustness of the proposed approach. [ABSTRACT FROM AUTHOR]

The electrochemical machining (ECM) technology is applied to the rifling processing field to solve the problem that new structure rifling with gradually changing grooves cannot be processed. By establishing the mathematical and geometric models of flow field in ECM gap, the distribution state of the deep spiral hole with gradually changing groove flow field in ECM gap was studied. By analyzing the simulation results of the flow field, it can be seen that the electrolyte is not evenly distributed in ECM gap and the electrolyte flow rate is insufficient at the tail of cathode process zone. Therefore, the cathode structure was secondarily improved to improve the electrolyte flow field distribution, so as to establish an optimized cathode model. Carry out ECM experiments of the deep spiral hole with gradually changing grooves and test experiment results under different parameters. The relationship between process parameters and deep spiral hole with gradually changing groove size can be obtained by analyzing the test results. The test results show that when the voltage varies from 12 to 18 V, the section shape of gradually changing groove rifling is respectively changed to 0.54 mm in diameter and 0.31 mm in groove width; for every 2-V increase in voltage, the average increase in diameter is 0.18 mm and in groove width is 0.10 mm. The simulation in ECM gap by using COMSOL is effectively shortening the cathode development cycle. The realization of ECM deep spiral hole with gradually changing grooves lays a technical foundation for the leap from design theory to engineering practice. [ABSTRACT FROM AUTHOR]

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Electrochemical discharge drilling (ECDD) is a hybrid machining process for fabricating small holes in nickel-based superalloys. In this study, the effects of solution conductivity on tool electrode wear during ECDD process are investigated. The experiments are performed using deionised water and NaNO3 solutions with different conductivities as working fluids. Machining current waveforms and hole-drilling results are analysed. The aim of this study is to investigate the reduction in tool electrode wear while obtaining good quality drill holes by ECDD with suitable solution conductivity. Experimental results show that the ECDD process using a NaNO3 working fluid with a conductivity of approximately 4.0 mS/cm results in optimal quality holes with the low tool electrode wear, and the tool electrode relative wear ratio is reduced by 65.4% as the working fluid conductivity changes from 0.005 to 4.0 mS/cm. [ABSTRACT FROM AUTHOR]

Electrochemical machining (ECM) is a promising nontraditional machining method for shape generation, which has many advantages such as capable of processing difficult-to-cut metallic materials without residual stress, good surface quality, high efficiency, no tool wear, etc. However, in many cases, problems of relatively poor machining accuracy and possible environmental risks hinder further application of this process. Hence an electrolyte suction tool has been proposed for ECM, which is expected to give a solution to these problems by restraining the electrolyte flow within the suction tool. In this paper, the effects of different electrolyte flow modes in suction tool on characteristics of ECM process were investigated both theoretically and experimentally. A multi-physics model coupling with a turbulent two-phase flow field and an electrical field was established for the ECM with the suction tool. A set of observational experiments and machining experiments were designed and conducted to clarify the characteristics of the electrolyte flow field and verify the results of simulation. The results show that under the inward flow mode (IFM), much surrounding air is sucked into the machining area and a relatively stable gas-liquid zone is formed, leading to poor machining characteristics. Meanwhile, the electrolyte is confined to a small area under the outward flow mode (OFM), which effectively improves both surface quality and machining accuracy of the ECM process. • A multi-physics model coupling with a turbulent two-phase flow field and an electric field was established to study the characteristics of ECM with suction tool and the validity of simulation was proved by experimental results. • From observation results, the influence of direction of the electrolyte flow on the sucked air and the bubble collapse was found. • The relationship between the electrolyte flow mode and the machined surface was made clear. [ABSTRACT FROM AUTHOR]

In this study a multiphysics simulation model of the pulsed electrochemical machining (PECM) with oscillating cathode is shown. The focus of this study is on the implementation of machine tool-specific control characteristics in combination with physical phenomena and material removal. As a result, the implementation of the machine tool control characteristics leads to an increase of simulation accuracy of the multiphysics model. The simulation results are compared with results of previous simulations and experimental investigations. [ABSTRACT FROM AUTHOR]

Abstract When polishing workpiece with inner corner feature using electrochemical machining (ECM) process, the surface quality at corner area is much poorer than that at other areas, and the surfaces of upstream area and of downstream area are much different. In this paper, the characteristics of this corner area phenomenon was investigated. Since the current density has a great influence on the surface roughness in ECM process, understanding the current density distribution on workpiece surface helps to analyze the corner area phenomenon and clarify process characteristics. Current density distribution considering the influences of several factors such as corner shape and inter electrodes gap (IEG), bubbles and electrolyte flow, were obtained with simulation and verified by experiments. ECM polishing with different fillet radius of the corner under different current densities were carried out. The observation experiments of machining by-products flowing with electrolyte flushing between machining gap, as well as the measurement of current densities at different areas, were conducted. The experimental results showed accordance with the simulation results. It was found the corner shape greatly influence the current density thus the surface roughness at the corner area, while the transport and accumulation of gas bubbles with electrolyte flow is one of the main reasons for the difference of surface roughness between the upstream area and the downstream area. Highlights • The ECM polishing characteristics of corner area phenomenon was investigated. • The current density distribution considering the influences of several factors such as corner shape and inter electrodes gap (IEG), bubbles and electrolyte flow, were obtained with simulation and verified by experiments. • It was found the corner shape greatly influence the current density thus the surface roughness at the corner area. [ABSTRACT FROM AUTHOR]

In order to solve the problems of flow field divergence, short circuit, and poor forming precision in electrochemical machining (ECM) large-diameter special-shaped inner spiral tube with pull reverse flow-cathode structure, a pull downstream cathode structure is proposed which has the function of changing working teeth and converging electrolyte flow field. The gap flow field simulation model was established, and then comparing and analyzing the gap flow field between pull downstream cathode model and the pull reverse flow cathode model. The simulation results show that pull downstream cathode structure is better than pull reverse flow-cathode structure in the gap electrolyte velocity, pressure, and streamline under the condition of 15 m/s electrolyte inlet velocity and electrolyte outlet pressure with atmospheric pressure. We also analyzed the stress and displacement of these two different cathode structures. The simulation results show that the maximum stress is 0.350 MPa and the maximum displacement is 4.275 × 10−5 mm with pull downstream cathode. However, the maximum stress of traditional pull reverse flow cathode is 0.428 MPa and the maximum displacement is 5.6355 × 10−5 mm. Finally, under the conditions of 12 V, 20 mm/min cathode feed speed, 15 wt% NaCl electrolyte with temperature 30 °C, and inlet pressure 1.5 MPa, the 2000 mm qualified sample was machined stably and reliably by pull downstream cathode. It indicates that it is feasible to machining large-diameter special-shaped inner spiral tube with the new pull downstream cathode structure. [ABSTRACT FROM AUTHOR]

The dissolution mechanism of pure chromium at high current density characteristic for electrochemical machining processes is studied. The combination of electrochemical, microscopic, and spectroscopic techniques leads to a comprehensive interpretation of the dissolution mechanism. The polishing quality increases with increasing nitrate concentration and current density, respectively. The oxygen evolution amounts up to 45% of the consumed anodic charge and the apparent valence of the chromium dissolution decreases with increasing applied potential down to z = 3.5. The authors explain this phenomenon by a passive dissolution of chromium via Cr3+ followed by a chemical oxidation of Cr3+ to dichromate under nitrate reduction to nitrogen. [ABSTRACT FROM AUTHOR]

A tremendous amount of work has been done in the recent years in the optimization of input parameters, however, current optimization techniques can only provide a single optimal input process parameter combination. Although alternative techniques have been developed to provide multiple solutions with identical objective values, these techniques have low efficiency when searching for multiple solutions. In this paper, a two-stage filter split-optimization approach is proposed to obtain multiple solutions, at a higher efficiency than for a single-objective optimization problem. The aforementioned tasks are accomplished by first performing an initial split-optimization and then performing a second optimization after excluding input parameters from having their range split into sub-ranges based on the results of the initial optimization. The proposed approach enables the algorithm to explore input parameters that have a more significant impact on the objective function, thereby enabling it to find multiple optimal solutions more efficiently. The proposed approach was validated by using it to optimize the input process parameters of an electrochemical machining problem with five input parameters. The results from the case study show that though the proposed approach provided fewer optimal solutions it was able to obtain them at twice the efficiency when compared to the original method.

Electrochemical machining (ECM) is a non-traditional machining technology that is widely used in the manufacturing of key components in the aviation industry. The current efficiency is defined as the ratio of the observed amount of dissolved metal to the theoretical amount predicted from Faraday’s law. In ECM, the current efficiency curve relates the dissolution rate of the anode material and the current density. Accurate measurement of the current efficiency curve is the basis for anode shape prediction and cathode tool design. However, in conventional measurement methods, the phenomenon of edge stray corrosion introduces significant measurement errors. Improving the current efficiency is thus a challenging task for any electrophysical or electrochemical machining process. To improve the measurement accuracy, this paper proposes a current efficiency curve measurement with a casing-type anode. In the proposed measurement method, the anode is designed in two parts: the mandril and the casing. The edge stray corrosion effect is mainly concentrated on the casing, and only the current distribution on the mandril is considered in the calculation of current efficiency. The measurement simulations of the conventional and the proposed methods were carried out. The simulation results show that the casing-type method significantly improves the accuracy of current efficiency measurements, and the current efficiency curve of 304SS was obtained.

In order to improve the efficiency of turbine blade repairing, protection processes of non-machined surface in Electrochemical Machining (ECM) based on blade repairing were studied. Mathematical model of electric field was developed to obtain current density distribution on anode surface, and to study the repairing principle and consequently analyze the defects forming mechanism by conventional electrolytic repair process. Sacrificial layer process was proposed to protect the non-machined surface in this work and an experimental system was developed to shape overlay welded TC4 blades. The results show that directly shaping process and insulated layer process produce stray dissolution and "stair" defects respectively,while sacrificial layer process achieves acceptable machining performance. With shaping time of 60s, the efficiency is improved; shaped blades have higher precision and surface roughness is Ra≤0.6μm, and with higher repeatability, the design requirements can be met.

Short-pulsed laser-induced periodic surface structures (SPLIPSSs) have the possibility to control tribology, wettability and biocompatibility. Nevertheless, the optimal structure depends on each functionality, which has not been clarified. The hybrid process with a short-pulsed laser and electrochemical machining (SPLECM) is, then, proposed to fabricate micro/nano hybrid structures and to modify the surface composition for providing high functionalities with material surfaces. Electrochemical machining is a well-established micro-elution and deposition method with noncontact between a workpiece and a tool. In this study, the effects of electrolytes on SPLIPSSs were investigated experimentally by the picosecond laser irradiation on 304 stainless steel substrates in various electrolytes. The geometry of SPLIPSSs depended on the types and the concentration of electrolytes. In the case of copper nitrate solution and copper sulfate solution, LIPSSs and spheroidization of copper were obtained. This study demonstrated the possibility of SPLECM to fabricate micro/nano structures and to control surface composition.

Electrochemical machining (ECM) cathode cross tank and return hole design is very crucial to machining aerospace closed integral impeller. In order to improve the precision of electrochemical machining closed integral impeller outside flow channels, the 3D cathode geometry model is developed by UG software, and the cathode structure flow field is simulated by COMSOL software. Through the flow field simulation, the width of cathode cross tank, the diameter, and the number of the electrolyte return holes were optimized. From the velocity cloud diagram, the simulation results show that the flow field is more stable and uniform under the parameters of electrolyte inlet pressure 0.4 MPa, 1.0-mm cross tank width, and the number of electrolyte return hole is 36 with 1.0 mm diameter. To verify the accuracy of the simulation result, the verified experiment was carried out. Finally, the experiment results were consistent with the simulation data. It indicates that electrolyte flow field simulation is an effective method to optimize cathode structure design. Utilizing this method can optimize the cathode structure and enhance the flow field stability during the processing of ECM. It can also reduce the cathode design cycle and cost. [ABSTRACT FROM AUTHOR]

Low machining accuracy has been a technical bottleneck for the application and promotion of electrochemical machining (ECM). Since the 1990s, it has been recognized by scholars that high-frequency pulsed power supply can improve the precision of ECM. But, in terms of the experimental results of our study, a new discovery was found that the increasing of the frequency has no effect on improving the machining accuracy of ECM. Comparing with the DC power supply, the experiment results show that the machining accuracy under pulsed power supply is decided by effective average voltage value, regardless of the frequency of the pulsed waveform, the duty cycle, and the pulse peak. [ABSTRACT FROM AUTHOR]

In this research, a three-dimensional (3D) finite element method (FEM) model based on Faraday’s law and moving mesh technique is proposed to simulate the channel machining process in Scanning Micro Electrochemical Flow Cell (SMEFC) and jet electrochemical machining (jet-ECM). The scarcity of available FEM models for the channel fabrication by electrochemical machining (ECM) with confined electrolyte is identified through a brief review of ECM simulation with moving electrode. The detailed information on the model establishment is then presented, including the fundamental principle, the way to construct the geometrical model of the moving electrolyte droplet during the machining process, the boundary settings and some key assumptions. Thanks to the introduction of the virtual electrolyte layer and the moving mesh technique, confined machining of channels by SMEFC can be simulated. In the experimental validation phase, species of the electrolyte (NaNO 3 and NaCl), the dimension of the hollow electrodes and the electrochemical equivalent of the workpiece, the machining voltages and feed rates are compared in terms of the channel cross-sectional profiles and errors. The flow field and heat transfer still need to be considered in order to simulate the case with NaNO 3 electrolyte in the future. This proposed 3D simulation model can improve the understanding and applicability of channel machining by SMEFC, since the current density distribution and the change of workpiece shape can be calculated simultaneously. With some modifications, this method can be as well extended to the channel machining by jet-ECM. Two case studies of micro scale and meso scale jet-ECM are simulated respectively. The proposed simulation method is a potential way to understand and improve the channel machining process by ECM with confined electrolyte. [ABSTRACT FROM AUTHOR]

Electrochemical machining (ECM) is characterized amongst other things, by extremely high current densities and a high dissolution rate of material. Due to the extreme current densities under ECM conditions, tungsten carbide forms adherent, supersaturated, viscous films of polytungstates close to the interface. This film is permanently dissolved by electrolyte flow and is reproduced at the electrode surface. The dissolution proceeds in an active state up to 30 A cm−2. An additional layer is formed at higher current densities which means that there is a passive state and the presence of high-field oxide films with thicknesses around 10 nm. The complex interaction between current, field strength, and oxide thickness yields a constant resistance to the oxide film. The formation of an oxide film is also indicated by the onset of oxygen evolution which consumes about 20% of anodic charge. The interaction of ionic currents (oxide formation and dissolution) and electronic currents (oxygen evolution) is small due to completely different conduction mechanisms. [ABSTRACT FROM AUTHOR]

Jet electrochemical machining (Jet-ECM) is a flexible method for machining complex microstructures in high-strength and hard-to-machine materials. Contrary to mechanical machining, in Jet-ECM there is no mechanical contact between tool and workpiece. This enables Jet-ECM, like other electrochemical machining processes, to realize surface layers free of mechanical residual stresses, cracks, and thermal distortions. Besides, it causes no burrs and offers long tool life. This paper presents selected features of Jet-ECM, with special focus on the analysis of the current density during the machining of single grooves in stainless steel EN 1.4301. Especially, the development of the current density resulting from machining grooves intersecting previous machining steps was monitored in order to derive systematic influences. The resulting removal geometry is analyzed by measuring the depth and the roughness of the machined grooves. The correlation between the measured product features and the monitored current density is investigated. This correlation shows that grooves with the desired depth and surface roughness can be machined by controlling current density through the adjustment of process parameters. On the other hand, current density is sensitive to the changes of working gap. As a consequence of the changes of workpiece form and size for the grooves intersecting premachined grooves as well as the grooves with a lateral gap, working gap, and current density change. By analyzing monitoring data and removal geometry results, the suitability of current density inline monitoring to enable process control is shown, especially with regards to manufacture products that should comply with tight predefined specifications.

The increasing demand for high-performance materials, in for example aerospace and biomedical industries, calls for more efficient and capable technologies. This paper describes a new technology, namely Mechano-Electrochemical Milling (MECM), which combines electrochemical machining (ECM) with a mechanical cutting process. The process behaviour has been investigated experimentally based on the machining of two Titanium alloys, Titanium grade 2 and Titanium grade 5. The material removal mechanism was investigated through analysis of the machined surface and removed material. Besides the slightly higher material removal rate in MECM compared to ECM, the MECM process results in more stable process conditions. [ABSTRACT FROM AUTHOR]

To get micro holes with high aspect ratio on metal alloys by electrochemical machining (ECM) process, the mutual restricted problems between machining localization and efficiency are researched. By analyzing the thickening process of passive film, the mechanism of gas inhibition and dissolution promotion (GIDP) is explored. Thereby, a three-electrode pulse power supply (PPS) is designed to acidize on the workpiece/solution interface, for both better machining localization and efficiency. Micro ECM experiments, using the three-electrode PPS in neutral salt solution as electrolyte, are carried out on 304 stainless steel and 18CrNi8 alloy, in which a micro hollow electrode is used to flush electrolyte under high-pressure supply. It is found that the material removal rate (MRR) is increased by at least 80% and surface roughness R is dropped by 40%, compared to those of two-electrode PPS. Micro array holes with diameter of about 175 μm are machined through metallic plates with thickness of 0.5 and 1.1 mm respectively. The micro array holes obtained have high consistent precision, good surface quality, and aspect ratio up to 6.5. Experimental results show the feasibility of micro ECM techniques proposed for micro hole with high aspect ratio. [ABSTRACT FROM AUTHOR]

A unique micro electrochemical machining (ECM) method based on a scanning micro electrochemical flow cell (SMEFC), in which the electrolyte is confined beneath the tool electrode instead of spreading on the workpiece surface, has been developed and its feasibility for fabricating mesoscale channels has been investigated. The effects of the surface conditions, the applied current, the feed rate, the concentration of the electrolyte and several geometrical parameters on the machining performance have been investigated through a series of experiments. The cross-sectional profile of the channels, the roughness of the channel bottom, the width and depth of the channel, the microstructures on the machined surface and the morphologies of the moving droplet have been analyzed and compared under different machining conditions. Furthermore, experiments with different overlaps of the electrolyte droplet traces have also been conducted, in which the SMEFC acts as a "milling tool". The influences of the electrode offset distance (EOD), the current and the feed rate on the machining performance have also been examined through the comparison of the corresponding cross-sectional profiles and microstructures. The results indicate that, in addition to machining individual channels, the SMEFC system is also capable of generating shallow cavities with a suitable superimposed motion of the tool electrode. [ABSTRACT FROM AUTHOR]

The electrochemical machining (ECM) is used to solve the difficult machining problem of metal screw pump stator inner hole; the mathematical model of electrolyte flow field in machining gap is established, and the distribution of electrolyte flow field in ECM machining gap of processing screw pump stator inner hole is simulated by using COMSOL simulation software. The simulation results show that, at the end of the machining gap, the electrolyte is not full, therefore setting up the added liquid hole on the cathode working zone by optimizing the cathode structure in the relevant machining gap zone to improve the distribution of flow field. Finally, the experiments are carried out which were conducted with different voltage and feed rate parameters; the test piece is sliced and measure it after the experiments, based on the measurement results to adjust the process parameters. The experiments result show that, when the processing voltage is 16 V and the feed rate is 6 mm/min, the distribution of electrolyte flow field in machining gap is more uniform, and the test piece size reached the product requirements. The simulation greatly shorten the cathode design cycle and optimize the structure of cathode by using COMSOL. [ABSTRACT FROM AUTHOR]