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In order to improve the electrochemical machining (ECM) precision and efficiency of a closed impeller internal flow channel, the internal flow channel cathode shape and structure were optimized by gap flow field simulation. Firstly, the theoretical model and three-dimensional gap flow field simulation geometric model were set up. Next, the inter-electrode gap flow field simulation results were draw from the streamline, velocity, and pressure cloud picture. Secondly, the cathode and the frock clamp were designed according to the simulation results. Finally, the verification experiment was carried out to evaluate the cathode structure and the ECM process parameters, and the experimental results were consistent with the simulation results. The whole process is stable and no short-circuit phenomenon with the forward flow field machining pattern. The results show that the method of gap flow field simulation-assisted ECM cathode design is useful and economical for machining closed impeller internal flow channel. [ABSTRACT FROM AUTHOR]

This paper describes tungsten micro-rod machining using a neutral electrolyte and ultra-short-pulse bipolar current supplied by the electrostatic induction feeding method. The tungsten oxide layer can be removed by NaOH generated when the polarity of tungsten electrode is negative. The machining accuracy improves with higher electrolyte concentration, and there is less tool wear when platinum tool electrode is used. A micro-rod with a diameter of 7.1 μm and aspect ratio of 14 was fabricated successfully. The machinable minimum diameter was equivalent to that obtained by EDM. Furthermore, the current waveform could be optimized to increase the material removal rate. [ABSTRACT FROM AUTHOR]

In several fields of mechanical engineering internal precision geometries are applied. For this, application requirements like high shape accuracy, sufficient stability, high wear resistance or an increase of life time have to be fulfilled. However, there is also a demand on quick and precise manufacturing processes that are flexible in machining various internal geometries. Electrochemical machining (ECM) is a process which meets these requirements. This process allows surface structuring and shaping of metal components with high shape accuracy independently of the materials strength and hardness [1] . This study presents investigations on a developed process design for manufacturing internal precision geometries by pulsed electrochemical machining (PECM) with help of multiphysics simulations. The peculiarity of this process is the shaping of the workpiece by the lateral working gap. Multiphysics simulations were carried out to understand the respective interactions between several physical phenomena. Especially, fluid dynamical effects are described in detail within the developed model. Furthermore, Joule heating and cathodic hydrogen formation are included. The fluid flow ensures the removal of heat and hydrogen and a continual supply with fresh electrolyte, respectively. The electrical conductivity of the electrolyte is modeled as a function of hydrogen volume concentration and temperature. Hence, both effects, Joule heating and hydrogen formation, influence the current density distribution which in turn determines the material removal. [ABSTRACT FROM AUTHOR]

Electrochemical machining (ECM) has established itself as one of the major alternatives to conventional methods of machining difficult-to-cut materials and generating complex contours, without residual stress and tool wear. The working teeth of traditional internal spiral line cathode and its body are integrated, which can not change angle with the helix angle changing while processing internal - spiral line so the internal spiral line would be wide and cause overcut. The 48 working teeth divided into 10 turn-tables along the axial direction of assembled turn-table cathode is designed. When the different turntable rotated with different rate relative to cathode body around the axial direction, so that the working teeth keep its direction along length consistent with the internal spiral line in processed. The pedestal position between adjacent turntable working teeth will induce cavitations, separation and eddy flow, which impairs machining accuracy (MA) and surface roughness (SR) of ECM. The machining gap flow field between adjacent two turn-table working teeth is simulated by computational fluid dynamics (CFD) for working teeth shape, which is not optimized, and three design solutions optimized working teeth shapes in this investigation. Experimental results indicate that internally spiral line can be produced using the pedestal sits chamfered (R 0.4 mm) turn-table working teeth cathode (TWTC) to obtain good SR and high efficiency. [ABSTRACT FROM AUTHOR]

In this paper, issues concerning micro-discharge energy generation and micro-tool electrode manufacture in traditional micro-electrical discharge machining (EDM) are discussed, and a new electrostatic field-induced electrolyte jet (E-Jet) micro-electrical machining method is proposed. A major issue is that the discharge process is an extremely volatile way to remove material from a substrate, and because it happens on such a small scale it is difficult to distinguish the principal machining mechanism of this new discharge process. This paper investigates the machining mechanism by examining the topology and composition constitution of the machined surface obtained using NaCl solution and deionized water as the E-jet solution in positive-polarity and negative-polarity machining after both single and prolonged discharges. Different material removal mechanisms under different polarities and discharge times have been disclosed, and conclusions concerning the E-Jet EDM control conditions have been drawn. [ABSTRACT FROM AUTHOR]

Cooling holes are important structures in turbine blades for high-performance aircraft engines. Nickel-based superalloys such as Inconel 718 are widely used in manufacturing turbine blades. However, it is very challenging to manufacture cooling holes in Inconel alloys. Conventional machining process such as electrical discharge machining (EDM) and laser beam machining (LBM) are thermal processes, which lead to recast layer, heat-affected zone, and tensile residual stresses. Electrochemical machining is an alternative to machine cooling holes without thermal damage. This paper focuses on the process capability and effect size of vacuum extraction shaped tube electrolytic drilling (VE-STED) process to manufacture cooling holes of Inconel 718. The effect of key process parameters, i.e., applied voltage, electrolyte concentration, and tool feed rate on process efficiency, form accuracy, and process stability has been investigated. The effect size was determined using ANOVA. [ABSTRACT FROM AUTHOR]

Laser-chemical and electrochemical machining (ECM) have the common feature that material removal is based on the chemical dissolution on atomic scale. Although, the mechanisms of dissolution and surface modification are quite similar, physical main active principle and corresponding material loadings differ. During laser-chemical machining the material is heated locally and chemical reactions are enabled by heat going into the reaction. On the other hand in ECM the material is dissolved by an electric field support. For this reason, this paper presents the energy-based analysis and comparison of these two material loadings to process performance and material modifications. The results imply that the stability of an electrochemically evolved oxide layer is strongly depending on the local temperature. Furthermore, the results appear that the chemical reaction and thus the dissolution speed depends on the microstructural composition of the workpiece material. [ABSTRACT FROM AUTHOR]

Conventional machining of WC6Co carbide metal is challenging due to its mechanical properties. Electrochemical machining applying a continuous free jet and pulsed current (Jet-PECM) is a promising alternative for surface structuring of this material, because the resulting removal only depends on its electrochemical properties. Neither tool wear nor thermal or mechanical influence on the work piece is caused by this process. In this study the influence of current pulse parameters on the cross-sectional shape of straight-lined grooves machined with Jet- PECM in WC6Co was analyzed. Furthermore adequate machining strategies were derived and applied in order to generate surfaces with defined waviness. [ABSTRACT FROM AUTHOR]

Due to the hard working conditions in the gas turbine engines, after a certain time parts may break off, may worn out of service limits or may crack. While some of these parts are replaced with new ones, some are repaired with special techniques. Advanced methods of machining are a group of the techniques used in repair. In metal machining industry, workbenches are divided into two groups: traditional (lathing, boring, grinding etc.) and advanced. In this study advanced methods of machining like Electrochemical Machining (ECM), Electro Discharge Machining (EDM), Electrochemical Grinding (ECG) and Laser Beam Machining (LBM) are introduced, advantages and disadvantages are stated and applications on gas turbine engine repair are given. Also some examples of benefits gained by part renewal operations applied by Eskişehir 1st Air Support and Maintenance Center to F110-GE-100/129 turbofan engines which powers F-16 fighter of Turkish Air Force are given.

Electrochemical machining (ECM) of metals, particularly steels, plays an important role in numerous industrial applications. The alloy steels especially 20MnCr5 are used as good wear resistant in the applications of boxes, piston bolts, spindles, camshafts, gears, shafts and other mechanical controlling parts. Machining of above complicated shapes with conventional machine tools is cumbersome task. Hence, investigation was made to study the electrochemical machining characteristics of 20MnCr5 alloy steel. Hydrogen peroxide (HO) mixed aqueous NaCl was used as electrolyte in order to enhance the machining performance of ECM. The predominant ECM process parameters such as applied voltage ( V), inter-electrode gap (IEG) and electrolyte concentration (EC) were considered to study its influence on the material removal rate (MRR) and surface roughness ( R). Microstructure of surface of the 20MnCr5 steel specimen machined with ECM was studied to understand the effect of electrolyte during the machining. The contour plots were generated to study the effect of process parameters as well as their interactions. The optimized machined conditions found with particle swarm optimization (PSO)-desirability function (DF) optimizer were quite close with experimental results. Additional advantage of HO presence was noted that scales formed on flow path of electrolyte were completely removed. [ABSTRACT FROM AUTHOR]

γ-TiAl-based alloys have attractive properties regarding the specific strength at high temperatures. Thus, the demand for aero engine components such as turbine blades and discs out of this class of materials will increase over the next years significantly. Due to the hard machinability via conventional cutting processes one possible alternative is seen in the Electrochemical Machining (ECM). This paper contains basic research on the unpulsed electrochemical machinability of four typical γ-TiAl-based alloys. Therefor specific material removal rate is investigated as a function of current density and compared to the theoretical dissolution behavior according to Faraday's law. Finally investigations on surface integrity aspects of these alloys are presented and exemplarily compared to conventional cutting processes to show specific ECM process capabilities. [ABSTRACT FROM AUTHOR]

Abrasive flow machining is a fine finishing process, mainly for the finishing of complex internal/external surfaces of metallic parts. Like most of the finishing processes, this process is also a slow process due to low material removal rate. Hybridization of abrasive flow machining process (AFM) with other non-conventional machining (NCM) processes is being explored in the recent times, so as to overcome the main limitation of low material removal in the AFM process and to satisfy the stringent finish/functional requirements. The present study is about the development of a novel hybrid of electrochemical machining (ECM) and abrasive flow machining (AFM), for the fine finishing of internal holes or prismatic recesses. The new process has been termed as electrochemical-aided abrasive flow machining (ECAFM) process, and higher abrasion of the material was observed in this process due to the synergetic effect of ECM and AFM processes. Further in the present investigation, the various process parameters have been optimized for the response characteristic of material removal, based on Taguchi method and using standard L orthogonal array (OA) for the plan of experimentation. Overall, the ECAFM process has a very promising future in the industries in terms of its ability to finish fast even if the component is thin/delicate and made of hard alloys. [ABSTRACT FROM AUTHOR]

The initial planning of manufacturing process chains provides the opportunity to sustainably influence the energy requirement for the manufacturing of industrial products by selecting the process chain with the lowest energy consumption. However, the task is still challenging due to the need for energy consumption data of manufacturing equipment. In this paper, the analysis of the energy consumption of a manufacturing process is illustrated by the example of the Pulse Electrochemical Machining (PECM) process. A comparison of two machine tool generations of the same manufacturer shows the improvement in energy consumption. Based on the information gained from the analysis, an approach for the provision of energy consumption data is presented. [ABSTRACT FROM AUTHOR]

In this paper an interdisciplinary simulation model of the electrochemical machining (ECM) process for aero engine blades is set up. Simulation results of a compressor vane are presented and compared to optical measurements of actual manufactured workpieces. The simulation model is based on conservation equations for the electric field, fluid flow and heat transfer in combination with analytical functions for the influence of temperature and gas evolution on the specific electrical conductivity. Validation is done by optical in situ measurements. Finally construction rules for an inverse modelling approach are examined and simulation results of the calculated cathode geometry are presented. [ABSTRACT FROM AUTHOR]

Due to the increasing use of hard to machine nickel-based alloys in aircraft engines, electrochemical machining (ECM) is an important manufacturing alternative, especially in blade and blisk (blade integrated disk) production. However, caused by constantly changing properties of the electrolyte during machining, it is difficult to predict suitable tool electrode (cathode) geometry for a given workpiece contour a priori. Especially temperature and gas evolution affect the conductivity of the electrolyte significantly and thus lead to local deviations in dissolving rate. So this paper presents optical in situ measurements of electrochemical machining the nickel-based alloy Inconel 718 in terms of high- speed and thermography camera recordings. With the help of these measurements on the one hand a deeper process understanding is generated and on the other hand the findings will serve as input and validation for an interdisciplinary process simulation model based on conservation equations. Finally this model will be used to calculate a complex geometry and will be compared to experimental results. [ABSTRACT FROM AUTHOR]

The present work is focused on the electrochemical behavior of tungsten carbide cobalt in alkaline ammonia electrolytes under near-ECM conditions. Potentiodynamic measurements were carried out in an electrolyte mixture of sodium nitrate and ammonia. It could be shown that a homogenous dissolution of both phases, the hard phase tungsten carbide and the binder phase cobalt, is possible with this electrolyte mixture. Additionally, galvanostatic pulse experiments coupled with polarographic analysis of the waste electrolyte were carried out to investigate the current efficiency of the machining process. Current efficiencies between 70 and 100% can be achieved under the chosen conditions dependent on the current density. [ABSTRACT FROM AUTHOR]

This paper investigates the performance enhancement of electrochemical machining (ECM) process by oxygenated aqueous sodium chloride (NaCl) electrolyte. It is experimentally found that the performance parameters such as material removal rate (MRR) and surface roughness ( R) are greatly improved with this new mix of electrolyte. The oxygen gas is suitable to electrochemically react with aqueous NaCl solution to enhance the oxidation of metal oxides on the machined surface to increase the MRR. In this work, experimental investigations are conducted with both aqueous NaCl electrolyte and oxygenated aqueous NaCl electrolyte on the alloy steel specimen (20MnCr5). Largest MRR of 7.33 g/min with R of 1.90 μm is obtained in oxygenated NaCl environment compared to MRR of 1.98 g/min and R of 3.13 μm in aqueous NaCl environment with machining conditions of voltage (V) of 17 V, tool feed rate (F) of 0.5 mm/min, and electrolyte concentration (EC) of 142.5 g/l of water. Microstructure of surface of the specimen machined with oxygenated aqueous NaCl electrolyte is more homogeneous and promises a good surface quality. [ABSTRACT FROM AUTHOR]

A new hybrid fuzzy-Artificial Bee Colony algorithm (Fuzzy-ABC) for the optimization of electrochemical machining (ECM) process parameters is presented in this paper. The 6061Al/10%wt Al2O3/5%wt SiC composite is taken as a test specimen and its machining characteristics on ECM process are studied. Maximizing the material removal rate (MRR), minimizing the surface roughness (Ra) and minimizing the over-cut (OC) are the main indicators of quality of an ECM process and thus are considered as objectives. The main process parameters governing the ECM process are current, applied voltage, flow rate, tool feed rate, inter-electrode gap and electrolyte concentration. The central composite design of response surface methodology was employed in order to identify the effective machining parameters on the above objectives. Fuzzy Logic (FL) concepts provide a fairly accurate prediction, when sufficient information is not available. The artificial bee colony (ABC) algorithm is a new evolutionary computational technique provides better results to that of other algorithms. Hence, in this paper, fuzzy logic was integrated with artificial bee colony algorithm, thus making a new hybrid Fuzzy-ABC algorithm. The optimized values for ECM were obtained through the hybrid Fuzzy-ABC algorithm. Confirmatory experiments reveal that the experimental values are fairly close with optimized values. [ABSTRACT FROM AUTHOR]

Electrochemical machining (ECM) is a complex process including the flow field, electric field, and thermal field. The material removal is influenced by the multiphysics. However, the variation of each field is complex. With the development of the CFD, this problem can hopefully be solved. In the present, the multiphase flow model and the coupling multiphysics models were built to predict the variation of the electrolyte velocity, the volume fraction of each phase, temperature, and electric conductivity of electrolyte in the interelectrode during the internal spiral hole machining in ECM. The material removal rate (MRR), decided by the electric conductivity, which is influenced by the multiphysics, was also discussed. Simulation results denote that the flow state of electrolyte has the main effect on the disposal of sludge, rise of the electrolyte temperature, and void fraction of hydrogen reduces the electric conductivity of electrolyte and the MRR is also diminished. Experimental verification of the model using an inhouse-built electrochemical machining system for the internal spiral hole (measuring the height of spiral rib) reveals good correlation with theoretical predictions. The present model could predict the forming of the workpiece in ECM and has values for the real experimentation. [ABSTRACT FROM AUTHOR]

Monel 400 alloys are used in various fields such as aerospace industries, marine industries, etc. It is very difficult to machine Monel 400 alloys using conventional machine tools. The Electrochemical Machining (ECM), an advanced manufacturing process, is a natural choice for machining Monel 400 alloys. The present work is carried out to investigate the influence of ECM process parameters, such as applied voltage (V), inter electrode gap (IEG) and electrolyte concentration (EC), on material removal rate (MRR) and surface roughness (Ra) during machining Monel 400 alloys. An aqueous sodium chloride (NaCl) is used as a basic electrolyte in the electrochemical machining of Monel 400 alloys. The experimental strategy is based on a response surface methodology. The effects of process parameters as well as their interactions are investigated and the process parameters are optimized through the desirability function of the response surface methodology. The microstructure of the Monel 400 alloys specimen, machined with ECM, is studied to understand the effect of electrolyte and other parameters during the machining. [ABSTRACT FROM AUTHOR]

A novel concentrated magnetic field-assisted electrochemical machining (ECM) technology is proposed in this paper to machine contemporaneously seven workplaces' complex cavity with high efficiency and good precision. An ECM clamping apparatus with concentrated magnetic field, periodic magnetic field, and no magnetic field was designed. The magnetic field simulation was carried out. Comparing the results of the concentrated magnetic field to the periodic magnetic field, the magnetic field intensity of the former is increased by 9.8 % than the latter. The ECM cathode with the same gap was designed and manufactured. Under the conditions of 12 % NaNO, 14-V voltage, 0.8-MPa electrolyte pressure, temperature 32 °C, cathode feed rate 0.9 mm/min, initial machining gap 0.1 mm, and the S-03 special stainless steel workpiece material, the experiments with concentrated magnetic field, periodic magnetic field, and no magnetic field were carried out. The results show that the gap magnetic field strength was increased by 16.7 % in the concentrated magnetic field than in the periodic magnetic field. Through a sectioning test, the precision in the concentrated magnetic field is increased by 33.3 % compared with no magnetic circuit and increased by 14.8 % compared with the periodic magnetic field. The concentrated magnetic field-assisted ECM technology cannot only reduce the cathode design cycle and cost but also increase the process accuracy. [ABSTRACT FROM AUTHOR]

Selecting an appropriate electrolyte is very important for high-efficiency electrochemical machining novel S-03 special stainless steel aerospace component. A series of experiments were conducted with NaCl, NaNO, and their admixture solutions. This research focused on the relationship between current efficiency and current density. The current density effects on surface roughness, machining velocity, and grain boundary corrosion were analyzed. The results showed that: the current efficiency in NaCl electrolyte was 100 % with different concentrations. Under the conditions of 24 V voltage, 30 °C electrolyte, and 0.8 MPa electrolyte pressure, the 10 % NaCl electrolyte can obtain 3.6 mm/min cathode feed speed; the surface roughness is Ra 0.08 μm; and the material removal rate is 411.4 mm/min. Comparing forward flow to forward flow with added backpressure, we found that: the surface roughness value decreased sharply at 3.6 mm/min in NaCl electrolyte. [ABSTRACT FROM AUTHOR]

This study focused on increasing the freezing rate in cell vitrification cryopreservation by using a cryopreservation container possessing rigid mechanical properties and high heat-transfer efficiency. Applying a fast freezing rate in vitrification cryopreservation causes a rapid temperature change in the cryopreservation container and has a substantial impact on mechanical properties; therefore, a highly rigid cryopreservation container that possesses a fast freezing rate must be developed. To produce a highly rigid cryopreservation container possessing superior heat transfer efficiency, this study applies an electrochemical machining (ECM) method to an ANSI 316L stainless steel tube to treat the surface material by polishing and roughening, thereby increasing the freezing rate and reducing the probability of ice crystal formation. The results indicated that the ECM method provided high-quality surface treatment of the stainless steel tube. This method can reduce internal surface roughness in the stainless steel tube, thereby reducing the probability of ice crystal formation, and increase external surface roughness, consequently raising convection heat-transfer efficiency. In addition, by thinning the stainless steel tube, this method reduces heat capacity and thermal resistance, thereby increasing the freezing rate. The freezing rate (3399±197°C/min) of a stainless steel tube after interior and exterior polishing and exterior etching by applying ECM compared with the freezing rate (1818±54°C/min) of an original stainless steel tube was increased by 87%, which also exceeds the freezing rate (2015±49°C/min) of an original quartz tube that has a 20% lower heat capacity. However, the results indicated that increasing heat-transferring surface areas and reducing heat capacities cannot effectively increase the freezing rate of a stainless steel tube if only one method is applied; instead, both techniques must be implemented concurrently to improve the freezing rate. [ABSTRACT FROM AUTHOR]

The first attempt is to introduce nano particles mixed electrolyte in electrochemical machining (ECM) process on improving material removal rate (MRR) and minimum surface roughness (SR) of high carbon high chromium die steel (HCHCr) with 67 HRc. The intervening variables (MRR and SR) depending upon the process parameters of ECM like applied voltage, tool feed rate, electrolyte concentration composition and electrolyte flow rate. In this experimental work two electrolytes, namely plain aqueous sodium nitrate (NaNO3) and 40 grams of copper (Cu) nano particle mixed with plain aqueous sodium nitrate electrolyte. The experimental results provide evidence that Cu nano particles mixed aqueous NaNO3 electrolyte improves MRR and minimum SR of HCHCr die steel on maximum working conditions when compared to plain aqueous NaNO3 electrolyte under similar working condition. [ABSTRACT FROM AUTHOR]

Abstract: The anodic dissolution of hcp-cobalt in sodium nitrate solution under near-ECM conditions was investigated in situ by using a specially designed flow channel cell. The in situ investigation was focused on current densities of 5A/cm2 and 10A/cm2. Cobalt dissolves actively as cobalt (II) ion with a current efficiency close to 100%. In contrast to copper, the current–voltage relation does not show an active–passive transition. The dissolution strongly depends on the crystallographic orientation of the grains. The lowest dissolution rate was observed on plains vicinal to the basal plane {0001}. No gas evolution was observed. The surface roughness is determined by the micro roughness on the individual grains. [Copyright &y& Elsevier]

Abstract: In this contribution a novel approach to Electrochemical Micro Machining (EMM), utilizing a structured counter-electrode with an integrated microfluidic channel, is presented. The process is capable of transferring numerous structures in parallel. The structure was defined by SU-8 photoresist. A high fluidic channel from the same material simultaneously acting as a spacer was applied on top of the electrode. During the structuring process, 3M NaNO3 was pumped through the channel and the applied current density was 100A/cm2. Since the current density is significantly higher than in previous works, it can be assumed that the faradic component of material removal predominates the non-faradic part due to the double layer. A FEM simulation using COMSOL Multiphysics shows the dependence of the material removal rate to the concentration of Fe3+ ions. The influence of different process parameters on the etch profile and the spatial resolution is investigated in theory and in practical tests. Computational and experimental results show a removal rate of to (As=Ampere seconds) which is in accordance to the theoretical value of calculated with Faraday's first law for Fe3+ ions. [Copyright &y& Elsevier]

Abstract: Due to their particular mechanical and thermal properties titanium- and nickel-based alloys such as Ti–6Al–4V or Inconel 718 are in common use as blisk materials. Besides conventional milling in this paper two alternative technologies for roughing operations in blisk manufacture – electro discharge machining (EDM) and electrochemical machining (ECM) – are presented. Therefore material removal rates in sinking-EDM (SEDM) and ECM as well as cutting rates in wire-EDM (WEDM) are determined for the above mentioned materials and class of geometries. With these results, an extensive cost-analysis is made where different production technologies are compared for analogical blisk geometries. It is demonstrated that for distinct geometries, materials and batch sizes unconventional manufacturing technologies are economic alternatives to existing milling strategies. [Copyright &y& Elsevier]

Special stainless steel 00Cr12Ni9Mo4Cu2 has multiple composition and inhomogeneous tissues; short circuiting will frequently occur when using conventional electrolyte processing. This article analyzes the reason why the process of machining is difficult from the material composition and structure. We used the NaNO and NaClO electrolyte composite to select the appropriate concentration, and then by using the orthogonal experiment and gray relational analysis method, we discussed how the voltage, feed speed, and electrolyte pressure solved the problem of the material removal rate (MRR), surface roughness (SR), and side gap. Under optimal conditions of 20 V, an electrolyte composite concentration of 178 g/l NaNO and 41 g/l NaClO, a feed rate of 0.7 mm/min, and an electrolyte pressure of 0.8 MPa, a material removal rate of 100.8 mm3/min, a surface roughness of Ra 0.8 μm, and a side gap of 0.16 mm were produced. Given the same voltage, with an increasing cathode feed rate, the MRR was shown to increase while the surface roughness value and the side gap decreased. Under the same cathode feed rate, the MRR decreases, while the side gap and the surface roughness increase as the electrochemical machining application voltage increases. This study proves that using a certain concentration of electrolyte composite is a simple, low-cost, and feasible approach in improving efficiency and quality. [ABSTRACT FROM AUTHOR]

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 blisks (blade integrated disks). Here Electrochemical Machining (ECM) is a promising alternative to milling operations. Due to lack of appropriate process modeling capabilities beforehand still knowledge based and a cost intensive cathode design process is passed through. Therefore this paper presents a multi-physical approach for modeling the ECM material removal process by coupling all relevant conservation equations. The resulting simulation model is validated by the example of a compressor blade. Finally a new approach for an inverted cathode design process is introduced and discussed. [Copyright &y& Elsevier]

Abstract: This paper describes a micro ECM system using the electrostatic induction feeding method. With this method, since the pulse voltage is coupled to the tool electrode by capacitance, the pulse duration of the electrolytic current is determined by the rise and fall time of the voltage pulse and is thus significantly short, realizing short gap width. A servo feed system was also developed based on the measurement of the gap voltage. Wear of the tungsten tool was negligibly small because of the oxide layer formed on the tool, allowing micro-holes with sharp edges and straight walls to be drilled. [Copyright &y& Elsevier]

This paper focuses on the grid cathode design in electrochemical machining (ECM) in order to develop a new cathode design method for realizing a breakthrough: one cathode can produce different workpieces with different profiles. Three types of square cells, 25 mm x2.5 mm, 3 mm x 3 mm, and 4 mm x 4 mm in size and three types of circular cells, with diameters of 1.5, 2.0, and 2.5 mm are utilized to construct the plane, slant, and blade grid cathode. The material of the cathode and anode is CrNi18Ti9 and the ingredients of the electrolyte are 15% NaCl and 15% NaNO3. A large number of experiments are conducted by using different grid cathodes to analyze the effects of the shape and size of the grid cell on the machining process. In addition, we compare the workpiece quality and machining error between using the grid cathode and the unitary cathode and discuss the reasons for the errors in order to obtain a better surface quality of the workpiece. Our research supports the conclusions that the grid cathode can be used to manufacture workpieces with complex shapes, the workpiece quality is better if the square cell is smaller and, for the same equivalent area, the circular grid cathode produces a better quality workpiece than the square grid cathode. [ABSTRACT FROM AUTHOR]

Abstract: In order to increase the efficiency of jet engines hard to machine titanium- and nickel-based alloys are in common use for blade and disk materials. With Electrochemical Machining (ECM) highest material removal rates can be achieved at best surface qualities. However for tool design, knowledge of local material dissolution is indispensable. This paper deals with basic research on the electrochemical machinability of selected modern titanium- and nickel-based alloys for aero engine components. Therefor experimental results of feed rate as a function of current density for an ECM sinking operation with a cylindrical tool electrode and external flushing are compared to the theoretical dissolution behavior according to Faraday's law. Furthermore surface properties were examined in terms of SEM and EDX analysis of the rim zone. [Copyright &y& Elsevier]

Abstract: Electrochemical machining (ECM) is one of the non-conventional machining processes which is mostly used to machine difficult-to-machine materials such as super alloys, Ti-alloys, stainless steel, alloy steel etc. The major requirement of the process is that work piece should be electrically conducting in nature. A large number of parameters influence material removal rate (MRR) and surface roughness (SR) of parts produced by ECM. Usually, tool makers use thumb rules and machine manuals to set optimal parameters for the process. In this work, response surface methodology is adopted to study the effect of four important parameters such as current, voltage, flow rate of electrolyte and inter-electrode gap on MRR and SR. Statistically validated regression equation are developed relating response like MRR and SR with input parameters. Finally, a non-dominated sorted genetic algorithm is used to find out the optimal process parameters that simultaneously maximize MRR and minimize SR. The set of Pareto solutions provide flexibility to the tool makers to choose the best setting depending on applications. [Copyright &y& Elsevier]

In order to resolve the problem of single machining object existing in traditional electrochemical machining (ECM) with unitary cathode, a grid cathode composed of circular cells is used to produce the workpieces with different shapes. Three types of circular cells, Φ1.5 mm, Φ2.0 mm, and Φ2.5 mm, are utilized to construct the plane, slant, and blade cathode. The material of the cathode and the anode is CrNiTi, and the ingredient of electrolyte is 15% NaCl and 15% NaNO. The machining balance current and the balance time are acquired and analyzed, the machining process and the workpiece quality are compared between using the grid cathode and the unitary cathode. Moreover, the machining errors and the error reasons of workpiece surface are analyzed. Research shows that the grid cathode can be used to manufacture workpieces with a complex shape, and the workpiece quality is better if the circular cell is smaller. If the circular cell is small enough the workpiece quality is almost equal to it machined by the unitary cathode. [ABSTRACT FROM AUTHOR]

Abstract: During the anodic dissolution of pure copper in sodium nitrate under near-ECM conditions the influence of the crystallographic orientation of individual grains on the dissolution behaviour was simultaneously investigated. Two different states can be distinguished – the active and the transpassive state. The dissolution shows a continuous transition from one state to the other, depending on the current density j c which itself is determined by the velocity of the electrolyte. For j < j c the active state is marked by an orientation dependant anodic dissolution. Above the critical density j c the crystallographic orientation of the grains is no longer an influencing factor and therefore a homogenous dissolution takes place. This is called the transpassive state which will be analysed in this paper in detail. For this, in-situ-experiments combining electrochemistry and optical microscopy together with EBSD investigations and current efficiency measurements had been undertaken. [Copyright &y& Elsevier]

Abstract: The influence of crystallographic orientation on the anodic dissolution of copper in sodium nitrate under near ECM conditions was investigated in situ by a specially designed electrochemical flow channel cell. The investigation was limited to the active dissolution range where a distinctive influence of the microstructure on the anodic dissolution was expected. It was clearly shown that the topography strongly depends on the crystallographic orientation. The dissolution rate of less-packed {100} planes is higher than of the close-packed {111} planes. Additionally, a gas evolution as side reaction was temporarily observed. This process happens preferentially on {111} planes. [Copyright &y& Elsevier]

To realize on-line monitoring interelectrode gap, six-axis force sensor was embedded into main spindle of machine tool to measure force signals on cathode exerted by electrolyte. The force signals, three forces, and three moments in X, Y, Z directions, respectively, are considered as research parameters. On one hand, the forces exerted on the tool cathode by electrode are measured with six-axis force sensor as electrolyte flow system is activated and electrode is deactivated. On the other hand, the forces are tested when electrolyte flow system and electrode are both activated. Then, the relation between six force components and interelectrode gap are analyzed. Machining experiments using three types of tool, e.g., plane tool, slant tool, and blade tool, have been carried out to deduct experiential equations between six force components and gap according to least squares method. Furthermore, the experimental data with blade tool are put into experiential equation with slant tool to examine validity of measuring gap in ECM. The relation of parameters in equations is analyzed and a conclusion is drawn: in the range of 15% error, machining experiential equation with slant tool can be used to on-line measure the interelectrode gap in ECM. [ABSTRACT FROM AUTHOR]

Electrochemical machining (ECM) process has great potential on account of the versatility of its applications. ECM is being widely used in the manufacturing industry because hard metals can be machined regardless of the mechanical property of a work piece. Titanium is broadly used in a number of fields such as aerospace, power generation, automotive, chemical including petrochemical, and sporting goods. Apart from these applications, it has tremendous prospective in dental, medical industries, and biomedical engineering. The biological performance of titanium implant depends on their surface topography and form accuracy that includes various surface parameters. ECM is one of the alternative machining processes that can be applied to the machining of titanium implant for biomedical applications. The aim of this paper is to present experimental result of surface characteristics obtained on titanium samples, utilizing developed cross-flow electrolyte supply system in electrochemical machining. It is observed that electrolyte flow velocity and voltage between electrodes are some of the influencing parameters, which affect the surface characteristics. Titanium oxide layer has been generated on the machined surface, which facilitates the improvement of the corrosion and chemical resistance of titanium implant. Effects of electrolyte flow velocity and voltage during electrochemical machining process for generation of various surface characteristics have been successfully studied through experimentation. In the present work, the obtained surface roughness values on the titanium sample machined by ECM were in the range of 2.4 to 2.93 μm, which is within acceptable value for the implants. Effects of electrolyte flow velocity and voltage on the material removal rate and machining accuracy in the form of overcut are also presented in the paper. [ABSTRACT FROM AUTHOR]

Abstract: Electrochemical machining (ECM) is a manufacturing process that offers a number of advantages (e.g. no mechanical stress) over its nearest competitors as certain trends in production move towards the micro scale. Maintaining optimum ECM process conditions ensures higher machining efficiency and performance. This paper presents the development of a fuzzy logic controller to add intelligence to the ECM process. An experimental ECM drilling rig, at University of Manchester, was improved through the integration of a fuzzy logic controller into the existing control system. Matlab (Fuzzy Logic Toolbox) was used to build a fuzzy logic controller system, which controls the feed rate of the tool and the flow rate of the electrolyte. The objective of the fuzzy logic controller was to improve machining performance and accuracy by controlling the ECM process variables. The results serve to introduce innovative possibilities and provide potential for future applications of fuzzy logic control (FLC) in ECM. Hybrid controllers that integrate fuzzy logic into the control system allow for “human like” decision-making intelligence to be incorporated into ECM controllers. The focus of this paper is the feasibility of FLC in ECM, but the results have the potential of being applied to EMM. As the future of ECM moves towards electrochemical micromachining (EMM), the need for process uncertainty control in this area may be met by FLC, which has advantages over conventional methods of process control. [Copyright &y& Elsevier]

Abstract: We have carried out the electrical discharge machining (EDM) of submicron holes using ultrasmall-diameter electrodes. Two types of electrode were used: tungsten electrodes fabricated by the combination of wire electrodischarge grinding and electrochemical machining, and silicon electrodes originally designed as probes for scanning probe microscopes. The diameters of the former and latter were 1μm or less, and less than 0.15μm, respectively. Holes were drilled using a relaxation-type pulse generator at an open-circuit voltage of less than or equal to 20V with the machine''s stray capacitance as the only capacitance. Using tungsten electrodes, holes of less than 1μm in diameter and more than 1μm in depth were successfully drilled. A 1.3-μm-wide slot was also fabricated by drilling many holes with a small pitch. It was possible to drill holes of approximately 0.5μm diameter using silicon electrodes because the electrode diameter was less than those of the tungsten electrodes. These holes have the smallest reported diameter for holes drilled by EDM, indicating the possibility of submicron- and nanoscale machining by EDM. [Copyright &y& Elsevier]

Non-conventional machining is increasing in importance due to some of the specific advantages which can be exploited during machining operation. Electrochemical machining (ECM) appears to be a promising technique, since in many areas of application, it offers several special advantages including higher machining rate, better precision and control, and a wider range of materials that can be machined. The present work is, therefore, initiated to investigate the influence of some predominant electrochemical process parameters such as applied voltage, electrolyte concentration, electrolyte flow rate and tool feed rate on the metal removal rate (MRR), and surface roughness (Ra) to fulfill the effective utilization of electrochemical machining of LM25 Al/10%SiC composites produced through stir casting. The contour plots are generated to study the effect of process parameters as well as their interactions. The process parameters are optimized based on Response Surface Methodology (RSM). [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the application of micro electrochemical machining (ECM) for the micromachining of internal features is investigated. By controlling pulse conditions and machining time, micro features are machined on the side wall of a micro hole. These methods can easily machine a micro hole with larger internal diameters than the entrance diameter, which is very difficult to do by the conventional processes. A micro disk-shaped electrode with an insulating layer on its surface is also introduced to machine microgrooves inside the hole. This method is similar to the turning lathe process. The purpose of this study was to confirm the various possibilities of making complex internal structures in a micro hole by micro ECM. [Copyright &y& Elsevier]

Abstract: Brief design and manufacture considerations are detailed for a hybrid electrochemical grinding unit adapted from a vertical machining centre using a 40,000rpm spindle and 500A DC generator. Subsequently, experimental work is presented on the influence of tool bond systems, superabrasive grit type and electrical parameters when simultaneous ECM/grinding Udimet 720 using 10–15mm diameter plain points. Single layer electroplated CBN tools produced G-ratios and maximum normal cutting forces of ∼451 and ∼45N, respectively, compared to ∼128 and 557N for equivalent diamond wheels. Data on workpiece roughness and overcut are also presented as are initial results for a fir tree shaped tool. [Copyright &y& Elsevier]

Abstract: The practical application of electrochemical machining (ECM) is still limited because of its lack of accuracy, difficulty of proper tool design and insufficient control of the operating parameters. Application of low frequency vibration to the tool electrode in electrochemical machining is one of the effective techniques for improving accuracy and quality of the machined surface. This paper presents an analytical approach to establish mathematical model in an endeavor to asses the mechanism of metal removal for this novel and hybrid technique. The effect of input parameters and machining conditions on the effectiveness of tool vibration during ECM has been fully investigated. The analytical model reveals that there could be a great complexity in the relationship between the tool amplitude and the equilibrium gap size, which could lead to tool damage, if the problem has not been carefully considered. [Copyright &y& Elsevier]

Abstract: Electrochemical machining (ECM) offers the unique advantage of better accuracy and high surface integrity of hard-machined components. A new technique has been developed to utilize a simultaneously moving and rotating electrode to remove a specific amount of material from pre-machined holes and rods of hardened steel specimens. One of the electrodes was provided with two simultaneous movements, traverse speed and rotational speed. The electrolyte was pumped into the gap between the tool and the workpiece, through a matrix of fine holes distributed along one of the electrode surface. A mathematical model has been proposed for accurately estimating the thickness of the workpiece layer under different working conditions. Experimental results revealed that this technique could lead to the removal of a surface layer thickness up to 200μ, which consequently classified this method as a super-finishing process. Finally, the results of the experiments and the simulation are compared with each other. The obtained results are an endeavour to enhance the controllability of the ECM process. [Copyright &y& Elsevier]

In the numerically controlled electrochemical contour evolution machining (NC-ECCEM) process the workpiece is machined by a simple, small and non-profiled tool-cathode controlled by a NC system to move along a contour trace to evolve into a desirable shape of surface. This machining technology synthesizes the advantages of both electrochemical machining (ECM) and numerical control (NC) techniques, as well as overcoming their own different disadvantages. The geometric model, the modelling method and its numerical solution, regarding the NC-ECCEM process using a rotary tool-cathode, are introduced in this paper. A series of results similar to the actual experimental results are obtained. The model deduced in this paper is useful for analyzing the NC-ECCEM process. [Copyright &y& Elsevier]