电极平动式电解孔加工技术研究

从电解液流动角度对影响电解孔加工过程的主要原因进行了分析 ,提出利用电极平动来改善电解加工过程稳定性和提高加工精度 ,研制了电极平动系统 ,进行了加工试验。试验结果表明 ,电极的平动运动使得电解液分布变得均匀 ,消除了空穴和分离流等弊端 ,改进了过程稳定性 ,显著提高了加工精度。     

Study of electrochemical machining characteristics of Al/SiCp composites

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).     

Wire electrochemical machining using reciprocated traveling wire

Wire electrochemical machining (WECM) is a cutting process in which the workpiece acts as an anode and the wire as a cathode. WECM is typically used to cut plates and exhibits a great advantage over wire electro-discharge machining, namely, the absence of a heat-affected zone around the cutting area. The enhancement of WECM accuracy is a research topic of great interest. In WECM, the homogeneity of the machined slit has a decisive influence on the machining accuracy. This is the first study in which the integration of pulse electrochemical machining (ECM) and a reciprocated traveling wire electrode was used to improve the homogeneity of this slit. The experimental results show that the combination of pulse ECM and a reciprocated traveling wire electrode could enhance the accuracy of WECM and that generally a low applied voltage, pulse duty cycle, and electrolyte concentration; an appropriate traveling wire velocity; and a high pulse frequency and feeding rate enhance the accuracy and stability of WECM. Finally, a microstructure with a slit width of 177 μm, with a standard deviation of 1.5 μm, and with an aspect ratio of 113 was fabricated on a stainless steel substrate measuring 20 mm in thickness.     

Optimize the flow field during counter-rotating electrochemical machining of grid structures through an auxiliary internal fluid flow pattern

Flow field distribution plays a vital role in electrochemical machining (ECM) because it can directly affect the machining stability and accuracy of ECM. In counter-rotating electrochemical machining (CRECM), the uniformity of the flow field is difficult to control due to the complicated and changeable flow channel shape. Through the simulation of the conventional lateral fluid flow pattern, it is found that the complexity of the flow channel with grid structures makes the flow field of machining area strongly disordered, which leads to the low velocity zones and dead zones. Based on the simulation results, a new electrolyte flow pattern with an auxiliary internal fluid is proposed, which can remarkably improve the uniformity of flow field by apply supplementary electrolyte to the machining area. Experimental results show that the new flow pattern effectively improves the machining stability of CRECM, and enhances the machining precision of grid structures, the sidewall taper angle is reduced from 29.3° to 7.7°.     

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.     

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。     

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.     

An experimental study on the effect of magnetic field orientations and electrolyte concentrations on ECDM milling performance of glass

In this work, effects of magnetic field orientation, machining voltage and electrolyte concentration on electrochemical discharge machining (ECDM) performance have been studied. The microchannels have been machined on the glass substrate; microchannel's depth and surface quality have been taken as indexes of machining characteristic. Experimental results show that the Lorenz force of magnetic field affects a direction of bubble's motion, consequently, changes the electrochemical discharge behavior of electrolyte. The presence of magnetic field causes magnetohydrodynamic (MHD) convection which, by its turn, accelerates the repulsion of the bubbles from the cathodic surface. However, it should mention that the direction of bubble movement depends on the magnetic field orientation. If the magnetic field orientation induces upward Lorenz force (downward Lorenz force), the gas bubbles will repel from (will attract to) inter-electrode area. The obtained results demonstrate that when the magnetic field applies, the machined surface will be smoother for the lower concentration values of electrolyte and higher machining voltages. Enhancements of both the machining voltage and electrolyte concentration increase the machining depth. For the same values of applied voltages, application of magnetic field will also increase the machining depth in a certain machining process duration; this will be intensified for the lower values of electrolyte concentration. The results of this study explain how the combination of the magnetic field orientation and the values of machining voltage and electrolyte concentration should be defined in order to increase both the channel depth and surface quality.     

微细群缝的精密电解加工研究

以某辐射状分布微细群缝结构的电解加工为研究对象，讨论了电解液、工件材料、加工速度等因素对加工精度的影响，结合研制的加工电极设计流场分布，优化加工参数，实现了以较高的效率加工出缝宽小至0．27mm的微细群缝结构，缝宽一致均匀，加工稳定性和重复性均好。     

超短脉冲电流微细电解加工技术研究

利用电化学腐蚀方法,在自制的电解加工机床上连续实现微细工具电极的制作和工件的加工,通过试验研究了超短脉冲的电压幅值和脉冲宽度对侧面加工间隙的影响。结果表明,减小脉冲宽度,降低加工电压,可以提高微细电解加工的精度。利用优化的加工参数,进行了微小孔加工、微细直写加工以及成形电极微细加工的实验。     

Discussion of ultrashort voltage pulses electrochemical micromachining: a review

One of the most effective way of electrochemical machining (ECM) accuracy increase is to carry out process with application of voltage pulses. In one of the variants of ECM, ultra short (nono- or picosecond range) voltage pulses are applied. It gives possibility to achieve high localization of electrochemical dissolution process and allows to machine microparts with accuracy less than 0.01 mm. However, because of the process principles, this variant of ECM has number of limitations which stop its wider application in micromanufacturing industry. Based on the literature review, the physical principles of ultrashort voltage pulses electrochemical machining were presented and anodic dissolution localization issues were discussed. Also, differences between other electrochemical machining variants were underlined. It gave possibility to identify limitations and future perspectives of industrial applications.     

微细电解加工用中空电极的制备

为了改进加工间隙内电解产物的排出条件和加速电解液的更新,提出了一种嵌套式微细中空电极的精确可控焊接制备工艺。仿真分析了电极的过流特性,优化了电极长度,并进行了性能测试及加工实验。通过穿丝、黏结、嵌套尺寸及位置调整和焊接工序,制备出加工段内径为65μm、外径为130μm、长3.25mm左右,后段便于装夹和连通的嵌套式中空电极。在供液压力为1.15 MPa时,其出口流速可达10m/s左右。利用制备的中空电极,开展微细孔电解加工实验,在0.5mm厚不锈钢片上加工出最小入口孔径约为157μm,出口孔径约为133μm的微细孔,并将其延伸应用于微结构加工中,铣削出了长554μm、宽160μm、深224μm的微细T型槽。实验结果表明:制备的微细中空电极有效提高了加工间隙内电解液的流动特性,且连/导通可靠、装夹方便,适用于高深宽比微结构的电解加工。     

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。     

阵列微沟槽的场域离散脉冲电解加工技术

针对难加工金属材料表面阵列非贯穿型微沟槽的高效高质量加工难题,提出一种场域离散脉冲电解加工方法,所加工沟槽具有表面质量好、尺寸微小、槽数多、沟槽前后非贯穿的特点。使用绝缘栅栏隔板作为活动掩模板对各微沟槽加工区进行离散,同时遮蔽非加工区,从而实现流场隔离和非加工区电场屏蔽等效果,有效提高沟槽的加工稳定性、精度和一致性。通过设计专用夹具,对影响加工精度的关键因素进行了单因素工艺实验研究,并利用Comsol Multiphysics软件对电解加工的流场和电场进行了仿真分析。仿真和试验结果显示:场域离散加工方法的流场和电场都比传统的掩膜电解加工、电解转印加工好。成功地在1min内加工出9条宽538.76μm,深25.78μm,过切量为19.38μm的阵列微沟槽,证实了该方法的有效性。采用短加工时间、低脉冲电压幅值、高脉冲频率、小脉冲占空比等工艺参数,有利于提高沟槽的加工精度。通过场域离散电解加工技术,可以实现对非贯穿型微沟槽的高效率、高质量、低成本加工。     

Investigations aiming to increase electrochemical machining accuracy

Under conditions of electrochemical sinking, the standard deviation of inter-electrode gap thickness decreases with the decrease of machined area, while the machining accuracy increases. Advantage may be taken of this fact when using an electrode with a working area smaller than its machined area and when using different electrode kinematics than for sinking. For instance, the working electrode should move above the machined area at a velocity v_p. Theoretical and expeirmental research shows, that electrochemical machining (ECM) processes can show a significant increase of machining accuracy when compared to classical electrochemical sinking. This results mainly from the fact that parameters of the process can be chosen in such a way that the uneven distribution of physical properties in the machining space does not radically affect changes of inter-electrode gap thickness. Because the productivity of the discussed case is lower than for classical electrochemical sinking, it should be applied for finishing operations in which a small material excess is removed.     

采用BP神经网络的叶片电解加工精度预测

工件成型精度的预测是实际电解加工的重要研究课题,快速、准确地选取加工参数并预测出工件的形状精度可以减少试验次数,缩短试制周期,降低生产成本。本文以某型发动机叶片为研究对象,对影响电解加工精度的主要加工参数进行了分析,结合工艺试验的数据建立了BP网络模型,并采用该模型进行了不同加工参数组合下叶片型面的预测。结果表明,该模型的预测精度比较高,具有一定的工程实用性。     

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.     

Electrochemical machining of the spiral internal turbulator

Electrochemical machining (ECM) is promising to machine the complex surface due to the advantages of no tool wear, stress free, and good machining accuracy. In this study, a machining method of the spiral internal ribs by ECM is presented. Firstly, the ECM experimental system is developed, which consists of electrolyte supply module, power supply unit, and workpiece-holding device. Then, a shaped cathode was used to process the spiral-turbulated hole on the built system. The shaped cathode was prepared by means of ultraviolet-curing mask method considering the expected spiral turbulator’s shape. Furthermore, parameters affecting the machining accuracy in shape duplication and machining efficiency are analyzed and discussed, especially the voltage and electrolyte concentration which have the main effect on the processed results.     

Flow field design and experimental investigation of electrochemical machining on blisk cascade passage

Electrochemical machining (ECM) provides an economical and effective way for machining heat-resistant, high-strength materials into complex shapes that are difficult to machine using conventional methods. It has been applied in several industries, especially aerospace, to manufacture blisk. The electrolyte flow field is a critical factor in ECM process stability and precision. To improve the process stability and the efficiency of blisk cascade passages, ECM with a radial feeding electrode, a rational electrolyte flow mode for electrochemical machining called “Π shape flow mode”, is discussed in the paper. Three flow field models are described separately in this report: traditional lateral flow mode, positive flow mode and Π-shaped flow mode, and the electrolyte velocity and pressure distribution vectors for each flow mode are calculated by means of a finite element fluid analysis method. The simulation results show that the electrolyte flow is more uniform with the Π-shaped flow mode. The deformation of the cathode, which is caused by the pressure difference, is also analysed in this report. The cascade passage ECM with a radial feeding electrode was experimentally tested out to evaluate the rationality of the flow field, and the fluctuation of current during the process was less than 1 %, which means that the process that uses the Π-shaped flow mode is stable. The feeding velocity of the cathode with the Π-shaped flow mode is approximately 70 % higher than that with the other two flow modes, and the incidences of short circuiting are obviously decreased. The surface roughness of the blisk hub is only 0.15 μm, and the machining error of the hub is less than 0.1 mm. The results demonstrate that using the Π-shaped flow mode can enhance the quality, stability and efficiency of blisk cascade passage ECM.     

OPTIMIZATION OF ELECTRO-CHEMICAL MACHINING PROCESS PARAMETERS USING GENETIC ALGORITHMS

ECM and ECM-based processes (derived and hybrid processes) are one of the most widely used advanced machining processes (AMPs) to make complicated shapes of varying sizes in the products made of electrically conducting but difficult-to-machine materials such as superalloys, Ti-alloys, alloy steel, tool steel, stainless steel, etc. These materials are extensively used in aerospace, automobile, space, nuclear, defense, cutting tools, dies and mold making applications. ECM offers some unique advantages over other conventional and advanced machining processes but its use incurs relatively higher initial investment cost, operating cost, tooling cost, and maintenance cost. Use of optimum ECM process parameters can significantly reduce the ECM operating, tooling, and maintenance cost and will produce components of higher accuracy which is very important in some critical areas such as aerospace, space, defense, nuclear applications. Therefore, choice of optimum process parameters is essential to ensure the most cost-effective, efficient, and economic utilization of ECM process potentials. This paper describes optimization of three most important ECM process parameters namely tool feed rate, electrolyte flow velocity, and applied voltage with an objective to minimize geometrical inaccuracy subjected to temperature, choking, and passivity constraints using real-coded genetic algorithms. Comparison of the obtained optimization results with the results of past work in this direction shows an improvement in terms of geometrical accuracy.