Surface characteristics of ECMed titanium work samples for biomedical applications

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???m, 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.     

渐开线内花键电解加工流场设计及工艺稳定性研究

为进一步提高渐开线内花键电解加工的工艺稳定性,基于数值分析方法探讨了电解液流动方式、工具阴极结构、电解液参数对流场分布的影响规律。数值分析结果表明：电解液侧向流动可以改善加工区入口处电解液流速分布均匀性;带有导流段的变截面阴极能够降低工件表面流速波动。针对工艺稳定性及加工定域性,开展了渐开线内花键电解加工试验研究。试验结果表明：进给速度可达2.1 mm/min以上,齿形误差可控制在0.015 mm以内,当加工深度为30 mm时,齿向误差在0.02 mm以内。该加工方式的效率及精度能够满足很多实际需求,具有明显的技术经济优势。     

微尺度弧形群缝电解加工试验研究

精密电解加工是剃须刀网罩上微尺度阵列弧形群缝的首选加工工艺,为提高电解加工精度和加工过程稳定性,基于电场分析,优化了工具阴极凸起宽度、凸起高度关键尺寸的设计;基于对流场的数值分析,优化设计了电解液流道结构,优选了电解液进出口压力参数,消除了流道内可能存在的缺液区和流线交叉区域,并据此研制了专用工装夹具。通过工艺试验,研究了端面初始间隙、平均电压,进给速度等关键工艺参数对群缝缝宽的影响。在研制的数控电解加工设备上加工出了缝宽0.24 mm的弧形群缝,且群缝的曲线形状精度高,加工过程稳定,已能够满足批量生产的需要。     

Parametric analysis on electrochemical discharge machining of silicon nitride ceramics

The electrochemical discharge machining (ECDM) process has a potential in the machining of silicon nitride ceramics. This paper describes the development of a second order, non-linear mathematical model for establishing the relationship among machining parameters, such as applied voltage, electrolyte concentration and inter-electrode gap, with the dominant machining process criteria, namely material removal rate (MRR), radial overcut (ROC) and thickness of heat affected zone (HAZ), during an ECDM operation on silicon nitride. The model is developed based on response surface methodology (RSM) using the relevant experimental data, which are obtained during an ECDM micro-drilling operation on silicon nitride ceramics. We also offer an analysis of variance (ANOVA) and a confirmation test to verify the fit and adequacy of the developed mathematical models. From the parametric analyses based on mathematical modelling, it can be recommended that applied voltage has more significant effects on MRR, ROC and HAZ thickness during ECDM micro-drilling operation as compared to other machining parameters such as electrolyte concentration and inter-electrode gap.     

Application of adaptive neuro-fuzzy inference system and cuckoo optimization algorithm for analyzing electro chemical machining process

Electrochemical machining process (ECM) is increasing its importance due to some of the specific advantages which can be exploited during machining operation. The process offers several special privileges such as higher machining rate, better accuracy and control, and wider range of materials that can be machined. Contribution of too many predominate parameters in the process, makes its prediction and selection of optimal values really complex, especially while the process is programmized for machining of hard materials. In the present work in order to investigate effects of electrolyte concentration, electrolyte flow rate, applied voltage and feed rate on material removal rate (MRR) and surface roughness (SR) the adaptive neuro-fuzzy inference systems (ANFIS) have been used for creation predictive models based on experimental observations. Then the ANFIS 3D surfaces have been plotted for analyzing effects of process parameters on MRR and SR. Finally, the cuckoo optimization algorithm (COA) was used for selection solutions in which the process reaches maximum material removal rate and minimum surface roughness simultaneously. Results indicated that the ANFIS technique has superiority in modeling of MRR and SR with high prediction accuracy. Also, results obtained while applying of COA have been compared with those derived from confirmatory experiments which validate the applicability and suitability of the proposed techniques in enhancing the performance of ECM process.     

Parametric analysis on electrochemical discharge machining of silicon nitride ceramics

The electrochemical discharge machining (ECDM) process has a potential in the machining of silicon nitride ceramics. This paper describes the development of a second order, non-linear mathematical model for establishing the relationship among machining parameters, such as applied voltage, electrolyte concentration and inter-electrode gap, with the dominant machining process criteria, namely material removal rate (MRR), radial overcut (ROC) and thickness of heat affected zone (HAZ), during an ECDM operation on silicon nitride. The model is developed based on response surface methodology (RSM) using the relevant experimental data, which are obtained during an ECDM micro-drilling operation on silicon nitride ceramics. We also offer an analysis of variance (ANOVA) and a confirmation test to verify the fit and adequacy of the developed mathematical models. From the parametric analyses based on mathematical modelling, it can be recommended that applied voltage has more significant effects on MRR, ROC and HAZ thickness during ECDM micro-drilling operation as compared to other machining parameters such as electrolyte concentration and inter-electrode gap.     

Investigation into electrochemical micromachining (EMM) through response surface methodology based approach

Electrochemical micromachining (EMM) could be used as one the best micromachining technique for machining electrically conducting, tough and difficult to machine material with appropriate machining parameters combination. This paper attempts to establish a comprehensive mathematical model for correlating the interactive and higher-order influences of various machining parameters, i.e. machining voltage pulse on/off ratio, machining voltage, electrolyte concentration, voltage frequency and tool vibration frequency on the predominant micromachining criteria, i.e. the material removal rate and the radial overcut through response surface methodology (RSM), utilizing relevant experimental data as obtained through experimentation. Validity and correctiveness of the developed mathematical models have also been tested through analysis of variance. Optimal combination of these predominant micromachining process parameters is obtained from these mathematical models for higher machining rate with acuuracy. Considering MRR and ROC simultaneously optimum values of predominant process parameters have been obtained as; pulse on/off ratio, 1.0, machining voltage, 3 V, electrolyte concentration, 15 g/l, voltage frequency of 42.118 Hz and tool vibration frequency as 300 Hz. The effects of various process parameters on the machining rate and radial overcut are also highlighted through different response surface graphs. Condition of machined micro-holes are also exhibited through the SEM micrographs in this paper. Pulse voltage pattern during electrochemical micromachining process has been analyzed with the help of voltage graphs. Irregularities in the nature of pulse voltage pattern during electrochemical micromachining have been observed and the causes of these irregularities are further investigated.     

混气电解加工探讨

电解加工是利用金属在电解液中发生阳极溶解反应而去除工件上多余的材料、将零件加工成形的一种方法。电解加工的加工精度不仅与加工间隙有关,还与机床、工艺装备、工具阴极、工件、工艺参数等诸多因素有关,通常采用混气电解加工、脉冲电解加工、小间隙电解加工和改进电解液等措施提高加工精度。其中混气电解加工是将具有一定压力的气体与电解液按一定比例混合在一起,然后将这种混合物加入到工件的加工间隙中去进行电解加工的一种方法。混气电解加工可以缩小加工间隙,提高电解加工的加工精度和复制精度,但混气电解加工的微观不平度和不直度还不理想。从气液混合比、混气电解加工的特性以及混气电解加工的工艺三个方面对混气电解加工的原理进行一定的探讨,希望摸索一种提高电解加工精度的方法。     

Micro wire electrochemical machining with an axial electrolyte flow

Micro wire electrochemical machining is a useful technique to produce high-aspect-ratio slit micro-structures. To improve processing stability, the axial electrolyte flow is adopted to renew electrolytes in the machining gap. A wire electrochemical micro-machining system with an axial electrolyte flow unit is developed. A mathematical model of tool feed rate is presented. To investigate the influence of electrolyte flow on processing stability and machining efficiency, comparative experiments were carried out. The influence of applied voltage and electrolyte concentration on machining accuracy is studied and the parameters such as electrolyte flow rate and applied voltage are optimized. Low initial machining gap is applied to decrease the stray current machining in the initial machining period. With the optimal parameters, the high-aspect-ratio micro spline and curved flow channel with the slit width of 160?μm have been fabricated on 5-mm-thick stainless steel (0Cr18Ni9). The width of the slit is uniform and the aspect ratio is 31.     

发动机叶片电解加工夹具结构设计与密封性能分析

探讨了叶片全方位电解加工时,夹具的总体结构设计、电解液流道布局、夹具体防腐蚀、导电和绝缘等影响叶片成型精度的若干关键问题;分析了夹具的密封性能对电解液压力、流速和加工稳定性的影响;通过叶片加工试验验证了所设计夹具的精度和可靠性。试验结果表明所设计的夹具定位准确,能加工出符合精度要求的发动机叶片;夹具的密封性能得到极大改善,在相同的进口压力下,加工腔及流道内的压力损失急剧减小,出口压力提高。     

Analysis of taper produced in side zone during ecd

The full capabilities of electrochemical machining (ecm) have not been utilized in production, mainly due to some inherent problems associated with tool design. For example, the side wall generated during electrochemical drilling (ecd) of a cylindrical hole is tapered. To study the effect of process parameters on the taper produced during ecd, experiments were performed using brass as cathode, low alloy steel forgings and castings as anode and aqueous solution of NaCl as electrolyte. From the analysis of the results, some useful conclusions have been derived that would be helpful in controlling the taper produced by bare tool, bare bit tool or coated tool.     

Analysis of taper produced in side zone during ecd

The full capabilities of electrochemical machining (ecm) have not been utilized in production, mainly due to some inherent problems associated with tool design. For example, the side wall generated during electrochemical drilling (ecd) of a cylindrical hole is tapered. To study the effect of process parameters on the taper produced during ecd, experiments were performed using brass as cathode, low alloy steel forgings and castings as anode and aqueous solution of NaCl as electrolyte. From the analysis of the results, some useful conclusions have been derived that would be helpful in controlling the taper produced by bare tool, bare bit tool or coated tool.     

Grinding-aided electrochemical discharge machining of particulate reinforced metal matrix composites

A grinding-aided electrochemical discharge machining (G-ECDM) process has been developed to improve the performance of the conventional ECDM process in machining particulate reinforced metal matrix composites (MMCs). The G-ECDM process functions under a combined action of electrochemical dissolution, spark erosion, and direct mechanical grinding. The tool electrode has a coating containing a hard reinforcement phase of diamond particles. The MMC employed in this study was Al₂O₃ particulate reinforced aluminum 6061 alloy. The material removal mechanism of this hybrid process has been analyzed. The results showed that the grinding action can effectively remove re-cast material deposited on the machining surface. The surface roughness (R _a) measured for the G-ECDM specimen was ten times smaller than that of the specimen machined without grinding aid (i.e., ECDM alone). Moreover, the material removal rate (MRR) of G-ECDM was about three times higher than that of ECDM under the experimental conditions of this study. The voltage waveform and crater distribution were also analyzed, and the experimental results showed that the G-ECDM process operates in a stable condition. The relative importance of the various processing parameters on MRR was established using orthogonal analysis. The results showed that MRR is influenced by the machining parameters in the order of duty cycle?>?current?>?electrolyte concentration. This study showed that the G-ECDM process is superior to the ECDM process for machining particulate reinforced MMCs, where a higher machining efficiency and a better surface quality can be obtained.     

超声辅助模板电解加工夹具设计及参数优化

在钛合金等难加工材料上加工高质量的群孔结构仍是一个难题,模板电解加工技术是解决此类问题的较理想方法,在其基础上引入了超声辅助技术,以进一步提高加工质量。设计一种专用超声辅助模板电解夹具,通过大量试验寻找关键参数的影响规律。研究结果表明,一定范围内超声频率越低,超声功率越高,则超声辅助优化效果越显著;超声辅助模板电解加工的最佳温度为45℃,最佳电解液压力为0.35 MPa。     

Weld profile,microstructure, and mechanical property of laser-welded butt joints of 5A06 Al alloy with static magnetic field support

Electrochemical discharge machining (ECDM) is a suitable process for the fabrication of microholes and microchannels in the nonconductive materials such as glass. In the ECDM milling, in some conditions, the tool is penetrated to the workpiece, which may lead to a breakage in the tool. In order to avoid the tool breakage, machining the parameters such as feed rate should be selected appropriately. In this study, the bending force applied on the tool was evaluated as a function of tool diameter, electrolyte concentration, presence of the magnetic field, and tool feed rate. The maximum feed rate, which keeps the bending tool force in the constant ranges, is desirable. According to the experimental results and combination of the machining parameters, the optimum feed rate was obtained. The results showed a decrease in the bending force by increasing the electrolyte concentration and elevating the applied voltage. In addition, the significant effect of a magnetic field on the reduction of bending force in the lower concentration of electrolyte (15 wt%) was observed.     

Electrochemical slurry jet micro-machining of tungsten carbide with a sodium chloride solution

Electrochemical slurry jet micro-machining (ESJM) is a new non-conventional process that couples abrasive slurry jet machining (ASJM) and electrochemical jet machining (ECJM) concurrently. A micro-jet of abrasive particles and electrolytic solution is made to impinge on the target while applying a DC potential between the jet nozzle and the workpiece. ESJM can be used to remove material that is difficult to machine through a combination of erosion, corrosion and synergistic effects. This study focuses on ESJM of tungsten carbide (WC) using a pH-neutral NaCl electrolyte rather than an alkaline solution which is more commonly used in the electrochemical processing of WC. For the studied process parameters, it was shown that the erosion due to ASJM alone was not able to erode the WC, and that the corrosion under ECJM was slow and produced unacceptably wide channels. The combined ESJM process however, was found to involve erosion of the developed oxide layer and subsequent exposure of un-corroded WC, leading to a much higher machining current density, corrosion rate, and machining localization than using ECJM alone. It was also found that the total abrasive kinetic energy, working voltage and solution concentration strongly affected the machining current density, material removal rate and aspect ratio (depth to width ratio). The results indicate that ESJM has a high potential to machine difficult-to-cut metals efficiently and economically.     

Cutting tool wear monitoring for reliability analysis using proportional hazards model

Electrochemical machining (ECM) is an important technology in machining difficult-to-cut materials and to shape free-form surfaces. In ECM, material is removed by electrochemical dissolution process, so part is machined without inducing residual stress and without tool wear. To improve technological factors in electrochemical machining, introduction of electrode tool ultrasonic vibration is justifiable. This method is called as ultrasonically assisted electrochemical machining (USAECM). In the first part of the paper, the analysis of electrolyte flow through the gap during USAECM has been presented. Based on computational fluid dynamic methods, multiphase, turbulent and unsteady electrolyte flow between anode and cathode (under assumption that cavitation phenomenon occurs) has been analysed. Discussion of the obtained solutions is the base to define optimal conditions of electrolyte flow in case of USAECM process. The second part of the paper is connected with experimental investigations of USAECM process. Classic experimental verification of obtained results in case of machining is extremely difficult, but influence of the ultrasonic vibration can be observed indirectly by changes in technological factors (in comparison to machining without ultrasonic intensification), whereas results of numerical simulation give possibility to understand reason and direction of technological factors changes. Investigations proved that ultrasonic vibrations change conditions of electrochemical dissolution and for optimal amplitude of vibration gives possibility to decrease the electrode polarisation.     

Electrochemical micro-machining of high aspect ratio micro-tools using quasi-solid electrolyte

With the outbreak of product miniaturization, there is an increasing demand for the fabrication of micro-tools in recent years. However, fabrication of accurate micro-tools with high aspect ratio is a great challenge for traditional processes due to their mechanical-thermal effects. Electrochemical micro-machining (EMM) has many advantages over other machining processes, which makes it a potential method to manufacture micro-tools. This paper proposes a novel EMM fabrication method of micro-tools with high aspect ratio, in which an agarose hydrogel of high intensity is employed as quasi-solid electrolyte. During the machining process, a tungsten rod is inserted into the quasi-solid electrolyte which is partially immersed into working electrolyte (2 mol/L NaOH solution) to maintain mass balance. The shapes of micro-tools fabricated in liquid electrolyte and quasi-solid electrolyte under same machining conditions are analyzed. Compared to liquid electrolyte, quasi-solid electrolyte has the advantages of improved precision and ability to manufacture high aspect ratio micro-tools. Besides, effects of main parameters, including vertical distance, duty factor, and pulse peak voltage, on the machining accuracy and efficiency are investigated experimentally. Finally, optimum parameters of 12 mm vertical distance, 50% duty factor, and 5 V pulse peak voltage are selected based on experiments. Using these parameters, a cylindrical micro-tool with an average diameter of 12 μm and aspect ratio of 408.33 is successfully fabricated.     

旋转超声电解复合加工小孔的仿真加工

为研究旋转超声电解复合加工小孔的成型过程,进行了旋转超声电解复合加工小孔试验,得到了不同加工时间孔的截面,并根据试验参数,进行了基于ANSYS的二维仿真加工和三维仿真加工。对小孔的入口直径、底面直径和加工深度进行了对比分析,结果表明由于三维仿真加工中采用了管电极,并考虑了电解加工中阴极超声高频振动对电解液电导率的影响,故其仿真结果更加接近试验值,间接证明了旋转超声电解复合加工小孔三维仿真加工的可靠性,展示了不同时刻的三维加工型腔,为旋转超声电解复合加工的成型过程和成型规律的研究提供了参考。     

微细孔电解加工控制方法及试验研究

基于微细电解加工的特点，介绍了一种微细电解加工系统。该系统能够将加工间隙控制到几微米到几十微米的范围内。根据电解加工以离子形式对材料去除的特性，进行微细电极、微细群电极的制备研究，并将其用于微细孔、群孔的加工中。试验分析了各工艺参数如电压、溶液浓度、加工间隙、进给速度等对微细孔电解加工精度的影响。结果表明，微细电解加工的侧面间隙随着加工电压的降低、溶液浓度的减小、脉宽变窄和初始加工间隙的减小而减小，改善了加工的定域性，加工精度得到提高。