Electrochemical Machining System Research Articles

Investigating the use of 3D printed tools for electrochemical machining: Lessons learned and future improvements

This paper describes the use of 3D printing in the production of tool electrodes for use in electrochemical machining (ECM). The majority of ECM jobs require the use of a unique form tool, production of which represents a significant expense. Additive manufacturing processes such as 3D printing offer the potential to lower cost of production and allow design of more complex tool electrode geometries. The tool electrodes used in this research effort were printed in polylactic acid (PLA) and subsequently fit with a copper electrode to serve as the electrical connection terminal for the tool. The tool surface intended for use as the electrode for ECM was coated with an electrically conductive paint before being copper electroplated to form a conductive surface. These 3D printed tool electrodes were successfully demonstrated to machine hardened tool steel in a prototype ECM machine, although challenges remain. This paper describes the development of ECM tools from 3D printed tool blanks, the prototype ECM system that was constructed to demonstrate use of the tool blanks, and the results of applying the 3D printed blanks to machine hardened tool steel. Next steps including potential improvements to tool electrodes are also discussed.

Design and analysis of erosion in electrochemical machining tool

The electro chemical machining system is the type of system in which it is used in the machining operations. In our project we have analyse the erosion in the electro chemical machining tool. The main disadvantage of the electrochemical machining system is that, due to repeated use of electrochemical machining tool there may be occurance of erosion in the machining tool. This effect is due to the presence of oxygen content in the electrolyte. We compared different types of metal like beryllium copper, copper tungsten, copper and brass with the electrolyte combination of sodium chloride and sodium nitrate. Normally the electrolyte used in the electro chemical machining system is that the sodium chloride and sodium nitrate [5]. So that we have used to compare the metals and electrolytes and used to find the best among them. Finally we have concluded that the beryllium copper has the best results. So the use of berylliumcopperwiththeelectrolyteofsodiumchloridewill havethereductionintheerosion.

Scaling approach towards electrochemical micromachining: a method to evaluate similarity

The electrochemical micromachining (ECMM) system is a modern equipment well thought out as the phenomenon of conventional electrochemical machining (ECM) system in microscale. The ECM system and ECMM system are similar, but the practice method and mechanism involved in the ECM system are analogous to those of the ECMM system, i.e., the differences in machining conditions and machining performance give rise to a factor called the scale effect. In this paper, ECMM has been applied with the advantageous concept called scale effect. Single factor experiments are conducted in which voltage, duty ratio, and tool feed rate are considered as the input factors for the exploration of the different grades of scale effect through the material removal rate, circularity, and overcut. The scale effects that occurred during machining are found using the similarity precision of the micro- and macrosystems based on the similarity theory. Quantitative evaluation of the scale effects is done for the ECMM process. The evaluation showed greater similarity precision indicating a larger significant scale effect. The output values of MRR, circularity, and overcut were normalized which also showed a positive scale effect. The research on scale effects delivers benefits in engineering such as optimizing the processing parameters involved and improving the machining performances of ECMM.

Experimental research on improving accuracy of electrochemical machining of deep narrow grooves

Deep narrow metal grooves have wide application prospects in the field of aeronautics and astronautics. Electrochemical machining (ECM) has a unique advantage in the fabrication of deep narrow grooves due to its advantages of no cutting heat, no cutting force, and high machining efficiency. But, there is significant stray current corrosion in the side wall of the deep narrow groove, which restricts the enhancement of the processing accuracy. In the interest of improving the processing accuracy of the deep narrow groove, the effects of compound feed and matching of pulse and oscillation (MOPAO) on the average current density distribution of the deep narrow groove side wall were studied based on finite element analysis (FEA) of the electrostatic field. The finite element simulation results show that the homogeneity of the deep narrow groove could be significantly improved with the increment of the oscillation amplitude, and the processing accuracy could be improved by prolonging the pulse turn-off time. Moreover, contrast experiments on the deep narrow groove ECM were carried out based on a self-developed ECM system. The experimental results indicate that the matching of pulse and oscillation can remarkably improve the processing accuracy, and smaller average groove width and better groove width uniformity can be obtained in comparison with the compound feed. Moreover, the maximum groove width is 2.78 mm, the minimum groove width is 2.73 mm, the length-width ratio reaches 11:1, and the depth-width ratio reaches 9:1 using the machining mode of MOPAO.

Effect of magnetic field on anodic dissolution in electrochemical machining

The authors modeled the electrochemical reactions of ECM with magnetic field using COMSOL commercial software. They studied the effect of filed strength and direction on the electrolyte mass transfer rate and the anodic dissolution amount. The mathematical models of the electrolyte rate distribution and the anodic dissolution amount were established. Simulation results indicated that the magnetic field would enhance the mass transfer rate and anodic dissolution amount and that the direction of the field will play a bigger part than the intensity in this connection. Experiments were also conducted to verify the model accuracy. Their experimental results were in good consistency with those of simulations. It is observed that the direction of the magnetic field that has a decisive say in altering the electrochemical machining system and this conclusion will potentially promote the application of magnetic field assisted electrochemical machining. The magnetic field works favorably to electromagnetic anodic dissolution reactions by improving both the mass transport rate and the corrosion rate.

Electrochemical machining of a narrow slit by cathodic compound feeding

Narrow slits are widely used in aerospace, instrument and meter, and heat-transfer equipment. Electrochemical machining (ECM) has the advantage of being free of tool wear, heat-affected zone, and machining deformation, and is suitable for high-precision machining of narrow slits. However, conventional cathodic continuous linear feeding causes serious stray removal at the narrow slit side wall and results in poor forming precision. This paper presents a new compound feeding method with vibration superimposed on a continuous linear feeding method and investigates the electrochemical machining of a narrow slit using this method. Its influence on narrow slit formation based on the numerical analysis of an electric field is studied as well. The results indicate that compound feeding is superior to linear feeding in terms of less stray removal and a smaller slit width. Comparative experiments of the compound and linear feeding with voltage pulses are also conducted based on a self-developed ECM system, with vibration frequencies from 0 to 50 Hz and vibration amplitudes from 0 to 2 mm. The results demonstrate that not only the average slit width and side-wall slope are smaller, but also the localization of the narrow slit electrochemical machining can be significantly enhanced by compound feeding.

Electrolyte Maintenance Technology Platform: Applying Learning Across Electrochemical Machining and Stripping Processes

In industrial electrochemical processes, there is commonly a need to maintain the electrolyte, so as to avoid excess costs associated with electrolyte replacement and waste disposal. Faraday is engaged in the development of a range of technologies aimed at electrolyte maintenance: 1) Recycling Electrochemical Machining ((R)ECM) for maintenance of electrochemical machining electrolyte to enable a zero-discharge process, 2) adjustment of a chrome stripping process to ensure that hexavalent chromium is not formed in the electrolyte during stripping, and 3) recycling of the components of a high velocity oxy-fuel coating during stripping. In each case, we are applying the principles of pulse-reverse electric fields, as necessary, as well as innovative racking and fixturing design to ensure good primary current distribution, to achieve the desired performance results. We will discuss how lessons learned in each project are applied to the other projects to enhance the chance of success. Electrochemical machining (ECM) is suited for machining parts fabricated from “difficult to cut” materials and/or parts with complicated and intricate geometries. However, the conventional DC ECM process generates large amounts of sometimes hazardous waste. To develop a (R)ECM process, we select an electrolyte whereby the machined material is soluble and avoids sludge formation by precipitation. The ECM unit operation is coupled to an EW unit operation where the machined material is collected as metal. The ECM and EW unit operations are adjusted to keep the soluble metal concentration in a range where the ECM process is not adversely effected and the EW operation is efficient and economical. Consequently, metals are recovered, waste is avoided and water usage is minimized. We have demonstrated integrated operation of the (R)ECM process where the soluble metal concentration is maintained in a pre-determined range by 1) simultaneous (R)ECM operation by adjusting the ECM unit operation in the presence of constant EW unit operation, 2) simultaneous (R)ECM operation by adjusting the EW unit operation in the presence of constant ECM unit operation, and 3) sequential operation of the ECM and EW unit operations. Faraday recently installed a β-scale Recycling Electrochemical Machining ((R)ECM) system at the U.S. Army Benet Laboratory. The (R)ECM system is sized to recover up to 0.5 m3per year of metal from an electrochemical machining operation. The (R)ECM system couples an electrochemical machining unit operation with an electrowinning (EW) unit operation for recovery of metals, elimination of waste, and minimization of water usage. Consequently, the RECM system is consistent with the U.S. Army’s “Vision for Net Zero”. Faraday is developing a Chrome Stripping technology for rapid removal of chrome from landing gear parts and other aircraft components, while maintaining the functional requirements of those parts, and eliminating or reducing hexavalent chromium formation to below OSHA PELs. Similarly to the (R)ECM technology, by integrating an Electrowinning unit, we will enable direct recovery of the “stripped” chromium metal from the electrolyte, return the electrolyte to the stripping process, and be a drop-in replacement for the current stripping process. Work has demonstrated removal of chrome from high strength steel substrates using a weak acid electrolyte while eliminating hexavalent chromium, without adversely affecting the substrate surface. We are optimizing the technology, and will design and build a pilot-scale facility to strip larger parts, perform compatibility testing for functional performance metrics, demonstrate replating after stripping, recover the chrome and enable a zero-discharge process Finally, Faraday has demonstrated the feasibility of an ElectroStripping/ElectroWinning technology, able to decrease the electrolytic stripping time of a high velocity oxygen fuel (HVOF) coating from an Inconel 718 substrate from 72 hours to 4 hours, without adversely affecting the substrate surface. The capability to maintain the electrolyte and recover stripped metals was also demonstrated. In future work, we will optimize the stripping process for WC-Co coatings, by improving the cell configuration and racking and fixturing, electrolyte, and waveform parameters. Acknowledgements: This study is supported by the US Army (W15QKN-12-C-0116), and the US Air Force SBIR Program (FA8222-16-C-0006, FA8117-15-C-0019). The financial support of Faraday Technology, Inc. corporate R&D is also gratefully acknowledged.

Sustainable Electrochemical Machining for Metal Recovery, Elimination of Waste, and Minimization of Water Usage

Faraday is developing and installing a β-scale Recycling Electrochemical Machining ((R)ECM) system at the U.S. Army Benet Laboratory. The (R)ECM system is sized to recover up to 0.5 m3 per year of metal from an electrochemical machining operation. The metals of initial interest include: 1) beryllium-free nickel-copper alloy (C18000), 2) Cr-Mo alloy steel (SAE4150), 3) nickel alloy (IN718) and 4) tantalum tungsten (Ta10W) alloy. The (R)ECM system couples an electrochemical machining unit operation with an electrowinning (EW) unit operation for recovery of metals, elimination of waste, and minimization of water usage. Consequently, the RECM system is consistent with the U.S. Army’s “Vision for Net Zero”[1]. Electrochemical machining (ECM) is suited for machining parts fabricated from “difficult to cut” materials and/or parts with complicated and intricate geometries. Conventional, direct-current (DC) ECM typically operates with neutral salt electrolytes whereby the machined material is generally precipitated from the machining electrolyte as metal oxide/hydroxide sludge. This sludge is generally transported off-site and disposed in a land-fill. Depending on the alloying components in the machined metal, the sludge is often designated as a hazardous material. Furthermore, the rifling of a gun barrel by ECM generates ~350 gal of centrifuged sludge per ~250 in3 of material removed [2]. This represents greater than 300X volume multiplier of waste sludge relative to the amount of material removed. As recently noted, the generation and disposal of the sludge is a major impediment to the widespread use and implementation of ECM operations [3]. Faraday has previously demonstrated the ability of pulse current/pulse reverse current (PC/PRC) waveforms electrochemically machining materials while achieving a high quality surface finish (Figure 1) [4],[5]. Smooth surfaces are typically not possible in conventional DC ECM. The PRC waveforms control the ECM process and consequently ECM with PRC is adaptable to a variety of electrolytes. To develop a (R)ECM process, we select an electrolyte whereby the machined material is soluble and avoids sludge formation by precipitation. The ECM unit operation is coupled to an EW unit operation where the machined material is collected as metal. The ECM and EW unit operations are adjusted to keep the soluble metal concentration in a range where the ECM process is not adversely effected and the EW operation is efficient and economical. Consequently, metals are recovered, waste is avoided and water usage is minimized. In the presentation, we will summarize the initial electrolyte selection studies for C18000, SAE4150, IN718 and Ta10W materials. In additionally, we will demonstrate integrated operation of the (R)ECM process where the soluble metal concentration is maintained in a pre-determined range by 1) simultaneous (R)ECM operation by adjusting the ECM unit operation in the presence of constant EW unit operation, 2) simultaneous (R)ECM operation by adjusting the EW unit operation in the presence of constant ECM unit operation, and 3) sequential operation of the ECM and EW unit operations. Finally, the status (R)ECM system design and installation at Benet Laboratories will be reviewed.

Recycling Electrochemical Machining for Metal Recovery and Elimination of Waste

This paper will discuss progress in development by Faraday of an integrated technology to recover and recycle metals from electrochemical machining (ECM) operations. ECM is suited for low mass removal, high value-added manufacturing steps that cannot be easily performed using conventional machining, whether due to workpiece material properties, tooling limitations, or high surface integrity requirements. Sludge byproducts formed during conventional ECM processes are difficult to recover from the electrolyte, and discarding the sludge results in the loss of potentially valuable “waste” metal as well as entrained electrolyte salts. The FARADAYIC® Recycling ECM [(R)ECM] technology, which is based upon patented FARADAYIC®cell designs and pulsed waveforms, is proposed as a novel augmentation of ECM to allow operation at conditions where both (a) sludge formation is avoided and (b) recovery of the machined metals in compact, solid form is enabled. Conventional, direct-current ECM typically operates with neutral salt electrolytes, which affords two particular advantages: the sludge formation itself is beneficial as it limits the dissolved metal concentration, in turn effectively eliminating any metal re-deposition onto the tool/counter­electrode; and empirical observation from industrial ECM practice is that neutral electrolytes generally yield superior surface finish as compared to acidic or alkaline electrolytes [[i]]. Faraday has previously demonstrated the capability of carefully tuned, pulsed FARADAYIC® waveforms to achieve extremely high quality surface finish in acidic and alkaline electrolytes, as well as neutral salt solutions. Also, separately tuned waveforms should allow on the one hand minimal re-plating on the tool in the ECM cell, and on the other an efficient electrowinning (EW) recovery process in an integrated electrowinning cell. As will be described, the FARADAYIC®(R)ECM technology successfully exploits both of these capabilities, enabling near-complete internal recycle of electrolyte and recovery of metals in compact, solid form. Figure 1 schematizes the (R)ECM process flow: blanks are machined into finished parts in the ECM cell and the dissolved metal is recovered in the EW cell, while substantially all of the electrolyte is retained within the system. Faraday initiated (R)ECM development efforts by screening candidate electrolytes for metal solubility limits and facility of metals electrodeposition using Hull cell tests. After initial electrolyte down-selection, ECM of 1″x1″ coupons was performed using various FARADAYIC® waveforms both to test the achievable surface finish and also to generate “live” ECM-derived electrolytes with which to reconfirm their suitability for the metal recovery function. The best-performing electrolyte for each material was then used in a larger “pilot-scale” (R)ECM system, in which high-rate ECM and in situ EW unit operations were tested, first separately and then in an integrated fashion. Beryllium-free nickel-copper (C18000) and Cr-Mo alloy steel (SAE4150) were separately machined in electrolyte to concentrations between 800-3500 ppm and subsequently recovered by electrowinning in solid, metallic form devoid of hydroxides/hydrated oxides, without intermediate electrolyte processing. Metal concentrations were maintained within a target operating window defined by polishing performance exhibited in the coupons studies (1500-2000 ppm) by appropriate adjustments to the electrical parameters of one of the (R)ECM unit operations. Development of FARADAYIC® (R)ECM for other alloys including 316L stainless steel and Inconel®718 is currently underway. [[i]] Wessel, “Electrochemical machining of Gun barrel Bores and Rifling” Naval Ordnance Station, Louisville, KY, September 1978; http://handle.dtic.mil/100.2/ADA072437. Figure 1

Analytical and Experimental Study of Electrochemical Micromilling

Electrochemical micromachining (ECMM) is a non-conventional manufacturing method suitable for the production of microsized components on a wide range of conductive materials. ECMM improves dimensional accuracy and simplifies tool design for machining hard, high strength, heat resistant, and conductive materials into complex shapes. Extremely small interelectrode gaps of the order of few microns are required in ECMM for better dimensional accuracy. However, excessively small interelectrode gaps may lead to complications, such as short-circuiting, which disrupt the stability of ECMM process. This necessitates the need for better understanding of the interelectrode gap dynamics. This paper presents a mathematical model for the analysis of interelectrode gap under non-steady state conditions in micromilling of steel using the ECMM process. Experimental verification of the mathematical model was conducted using an in-house built micro electrochemical machining system. The model is capable of predicting the machining results to within 1- 5 µm error (10- 50%).

Multiphysics research in electrochemical machining of internal spiral hole

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.

Analysis of stress-etching quality based on nanosecond pulse laser electrochemical machining

Nanosecond pulse laser electrochemical etching can remove the electrolytic products of laser irradiated region and so improve the processing stability and processing efficiency. The stress-etching characteristics and the material removal mechanism for aluminum alloy workpiece were investigated theoretically and experimentally by the use of a laser electrochemical machining system. For comparison of processing topography between laser direct etching in air and laser electrochemical machining, the scanning electron microscopy and the optical profilometry were used to detect and analyze etching morphological characteristics of machining areas. Based on the principle of mechanics and electrochemistry, stress-etching principles of laser electrochemical machining were studied. In this study, the effects of processing parameters and machining method on machining quality were explored, and a complex microstructure was processed successfully with reasonable processing parameters. The results show that laser electrochemical machining with better stability can reduce surface roughness and improve machining quality effectively.

Modeling and fabrication of micro tools by pulsed electrochemical machining

Accurate and precise micro tools are essential for the micromachining of complex micro features in a wide range of engineering materials including metals and ceramics. Existing micro tool fabrication processes suffer from drawbacks such as surface cracks, residual stress and deformations. Electrochemical machining of micro tools is proposed in this work to overcome these limitations. In this research, a mathematical model has been developed to predict the diameter of the micro tool fabricated. Experimental verification of the model using an in-house built micro electrochemical machining system reveals good correlation with theoretical predictions. Using the procedure described in this paper, very high aspect ratio (280–450) tungsten micro tools have been produced.

Development of a Prototype of Electrochemical Machining

Electrochemical machining (ECM) is the controlled removal of material by anodic dissolution in an electrolytic cell in which the workpiece is the anode and the tool is the cathode. The ECM presents the advantages: three-dimensional surfaces with complicated profiles can be easily machined in a single operation, irrespective of the hardness and strength of the material. ECM offers a higher rate of metal removal as compared to traditional and nontraditional methods, especially when high machining currents are employed. There is no wear of the tool, which permits repeatable production. This work shows a study of development of a prototype of electrochemical machining (ECM) developed at the Federal University of Uberlândia Minas Gerais-Brazil. A state-of-the-art ECM system is the art of assemblage of facilities including a proper ECM machine, a power supply, a process parameter control system, and an electrolyte preparation, feed and purification system. With the prototype developed, the material removal rate (MRR) was studied. The MRR was influenced by tool feed rate and type of electrolyte.

Design and its Experiments of Micro Electrochemical Machining System

A micro Electrochemical Machining (ECM) system has been developed, and macro/micro complex feed mechanism has been presented in order to achieve high-resolution. A nanosecond pulse power supply for micro-ECM has been developed, and the minimum pulse width can reach 50 ns. Complementary chopper circuit has been designed to avoid waveform distortion, which can achieve higher pulse frequency. A series of ECM experiments using the machining system have been carried out, and results of tests have proved that high-resolution spindle, and high frequency, short pulse width power supply help to achieve better quality surface, higher machining accuracy.

Fabrication of Micro-Structures by Micro-ECM

The machining of materials on microscopic scales is considered to be great importance to a wide variety of fields. Electrochemical Micro-machining (EMM) appears to be promising to machine the micro-structures in future due to the material is dissolved at the unit of ion. This paper is focused on developing a micro electrochemical machining system in which the micro-structures such as micro-cylinder, multiple micro-electrodes, micro-holes and micro-slot were processed. The micro-electrodes were prepared in a precisely controlling the electrochemical etching process. Mathematical model controlling the diameters of electrodes was built up. Furthermore, the obtained micro-electrodes were selected as the cathode tool for micro holes drilling and micro-slot milling using pulse power in Micro-ECM.

Cathode Design of Aero-Engine Blades in Electrochemical Machining Based on Characteristics of Gap Distribution

Cathode design is a difficult problem must be faced and solved in ECM. We develop a new numerical approach for cathode design by employing a finite element method and this approach has been applied in the cathode design of aero-engine blades in ECM. The mathematic models of the electric filed and electrolyte flow filed distribution in EMC process are described primarily. Then the realization procedure of this approach is presented，in which the effects of electric filed and electrolyte flow filed distribution within the inter-electrode gap domain are concentrated. In order to verify the machining accuracy of the designed cathodes, the experiments are conducted using an industrial scale electrochemical machining system. The experimental results demonstrate that the machined blade have high surface quality and dimensional accuracy which proves the proposed approach for cathode design of aero-engine blades in ECM is applicable and valuable.

Theoretical and experimental research into electrochemical micro-machining using nanosecond pulses

Based on the principle of electrochemical reactions,the characteristic and mechanism of nanosecond pulses electro-chemical micro-machining are investigated and the theoretical model of micro-electrochemical machining(ECM) is founded.The affections of electrolyte concentration,electrodes gap and pulse parameters on the result of electrochemical micro-mach-ining are discussed.The practical electrochemical machining system is developed.It consists of micro-machining equipment,nanosecond pulse power supply,electrolyte circulating system,movement control component and process monitoring compon-ent.The effects of pulse on-time and voltage on the side gap of electrodes are investigated with experiments.The result of exp-eriments show that decreasing pulse duration and voltage can enhance the localization and improve electrochemical micro-machining accuracy.On the self-developed equipment,tool ele-ctrode and workpiece are sequentially machining in electro-chemical method.Inter-electrode gap is restrained less than 5 μm.A crisscross micro-groove with 30 μm width and the mic-ro-structure with size 20 μm×30 μm×30 μm is produced.The influence of starting point upon forming precision is analyzed.The experimental results prove that micro-ECM can well meet the demand of micro machining.

Experimental investigation on the influence of electrochemical machining parameters on machining rate and accuracy in micromachining domain

Non-conventional machining is increasing in importance due to some of the specific advantages which can be exploited during micromachining operation. Electrochemical micromachining (EMM) appears to be a promising technique, since in many areas of application, it offers several special advantages that include higher machining rate, better precision and control, and a wider range of materials that can be machined. A better understanding of high rate anodic dissolution is urgently required for EMM to become a widely employed manufacturing process in the micro-manufacturing domain. An attempt has been made to develop an EMM experimental set-up for carrying out in depth research for achieving a satisfactory control of the EMM process parameters to meet the micromachining requirements. Keeping in view these requirements, sets of experiments have been carried out to investigate the influence of some of the predominant electrochemical process parameters such as machining voltage, electrolyte concentration, pulse on time and frequency of pulsed power supply on the material removal rate (MRR) and accuracy to fulfil the effective utilization of electrochemical machining system for micromachining. A machining voltage range of 6 to 10 V gives an appreciable amount of MRR at moderate accuracy. According to the present investigation, the most effective zone of pulse on time and electrolyte concentration can be considered as 10–15 ms and 15–20 g/l, respectively, which gives an appreciable amount of MRR as well as lesser overcut. From the SEM micrographs of the machined jobs, it may be observed that a lower value of electrolyte concentration with higher machining voltage and moderate value of pulse on time will produce a more accurate shape with less overcut at moderate MRR. Micro-sparks occurring during micromachining operation causes uncontrolled material removal which results in improper shape and low accuracy. The present experimental investigation and analysis fulfils various requirements of micromachining and the effective utilization of ECM in the micromachining domain will be further strengthened.

超純水のみによる電気化学的加工システムの開発と平坦化加工プロセスヘの応用

An electrochemical machining system using ultrapure water has been developed, designed for planarization machining and free-curvature-shape machining. The machining system is composed of three units: an electrochemical machining apparatus, an ultrapure water refining and circulation unit, and a high-pressure ultrapure water supply unit. The machining apparatus is equipped with an XYθ table and a Zφ machining electrode. A cylindrical or a spherical electrode is used for the machining electrode. The machining chamber is continually filled with refined ultrapure water by the refining and circulation unit. During machining experiments, process by-products, bubbles, and the like around the machining point can be efficiently removed by the high-pressure ultrapure water supply unit. Using this machining system, planarization experiments have been performed on copper plates, which are known to be easily etched, via application of a positive voltage. The effects of various machining parameters (current density, rotating speed of the electrode, etc.) on the roughness of the etched surface are investigated. It was found that the use of a high-pressure ultrapure water supply nozzle is effective in the planarization process. Furthermore, it was also found that there is an ideal set of conditions with respect to the combination of current density and rotating speed of the electrode. Copper plate surface roughness (Ra) was successfully reduced from 164 nm to 10 nm by planarization machining, with the optimal set of parameters.