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。     

高频窄脉冲微细电解加工实验研究

加工间隙是电解加工的核心工艺参数,利用在45钢薄片上打微细孔,通过实验分析来探索高频、窄脉冲微细电解加工中频率、电压和电解液浓度对加工间隙及电极截面和加工稳定性的影响规律。     

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.     

Wire electrochemical micromachining of high-quality pure-nickel microstructures focusing on different machining indicators

High-quality pure-nickel microstructures, which are characterized with multiple superior machining indicators, including machining homogeneity, machining surface roughness, and machining round edge, are now highly anticipated in the field of micromachines and microsystems. However, according to the published studies, a gap remains in achieving high-quality machining. In this paper, wire electrochemical micromachining (WECMM) is proposed for machining high-quality pure-nickel microstructures focusing on different machining indicators. The appropriate electrolyte is selected by combining analysis of the electrochemical characteristics and machining experiments involving microslits of pure nickel. In contrast with previous studies that usually focused on the machining homogeneity or machining surface roughness of the machining results, the effects of several critical machining parameters on the machining homogeneity, machining surface roughness, and machining rounded edge are studied comprehensively, and the relative results for different machining indicators are also revealed. Finally, the combinations of process parameters for manufacturing high-quality pure-nickel microstructures focusing on different machining indicators are identified, and corresponding high-quality pure-nickel microstructures are fabricated.     

微细工具电极在线制作技术及实验研究

本文提出了一种在线制作微型工具电极的新方法。该方法是基于电化学微加工,通过反复交换工具电极和工件的极性,进行相互加工获得与电化学微加工相适应的微型工具电极。由于该过程在线进行,因此可以避免因两次夹紧工具电极造成的位置误差和夹紧误差,并可以大大提高加工精度。该方法对于电化学展成微加工来说是非常重要的。通过实验,稳定的加工出了最小直径为20μm的工具电极。     

Investigation into fabrication of microslot arrays by electrochemical micromachining

Maskless electrochemical micromachining (EMM) is a prominent and unique surface texturing method to fabricate the arrays of microslots. This article investigates the generation of microslot arrays using maskless EMM method. The developed prototype maskless EMM setup consists of EMM cell, power supply connections, electrode holding devices and constricted vertical cross flow electrolyte system for the fabrication of microslot arrays economically. One textured cathode tool with SU-8 2150 mask is used to produce 22 microslot arrays. Influences of EMM process parameters including voltage, electrolyte concentration, inter electrode gap, flow rate and machining time on the machining performance that is, width overcut, depth and surface roughness (R_a) of microslot arrays are investigated. For lower width overcut, controlled depth, and lower surface roughness, machining with lower voltage, lower electrolyte concentration, lower inter electrode gap, higher flow rate and lower machining time are recommended. From the analysis, it is observed that the best machining conditions including inter electrode gap of 50?μm, applied voltage of 6 V, electrolyte concentration of 20?g L^?1, flow rate of 5.35 m³ hr^?1 and machining time of 1?min fabricate regular microslot array with mean width overcut of 24.321?μm, mean machining depth of 10.7?μm and mean surface roughness of 0.0101?μm.     

窄细槽分段速进给电解加工方法研究

针对小间隙电解加工过程中极间间隙不稳定导致加工效率低下甚至发生短路等问题,以窄细槽电解加工过程为研究对象,提出自适应于工件蚀除速度的电极进给分段速加工方法。建立极间电流与加工深度之间的理论关系模型,采用单因素实验法对理论模型进行修正,使其反映实际加工过程。依据电解过程中深度与电流的变化规律,建立电极进给速度实时修正方程,实现电解过程不同进给速度段的划分。采用速度线性矢量混合算法,构建速度控制方程,实现各段速间的平稳过渡,保证电极进给速度变化时极间电流的稳定。实验结果表明,分段速进给控制方法能有效避免小间隙电解过程中由于进给速度与工件蚀除速度不匹配而导致的短路现象,有效保证窄细槽电解加工效率与轮廓精度。     

基于六维力电解加工间隙在线检测试验研究

为了实时检测加工间隙,把流体作用在阴极上的六维力作为研究参数:设计通电解液不通电、通电加工两大类工况,从定性和定量两个角度分析六维力与加工间隙之间的关系;并以平面、斜面、叶片型面三种阴极进行试验加工,用最小二乘多变元线性拟合法,分别建立平面、斜面阴极加工的六维力与加工间隙之间的关系方程式,用叶片型面加工数据对建立的关系方程式进行检验与修正,得到最终的修正关系式:分析关系式各参量之间的关系,并得到结论:在15％的误差范围内,关系式可以用于在线检测加工间隙。     

A review on the conventional,non-conventional,and hybrid micromachining of glass

Glass, commonly known as a brittle material, has the potential to be used in many applications in semiconductor, biomedical, mold manufacturing, opto-electronics, automobile and aerospace industries due to its superior mechanical strength and excellent wear and thermal resistance. This review article aims to present a comprehensive overview on the micromachining of difficult-to-cut glass materials. The article includes the state-of-the-art reviews on conventional, non-conventional and hybrid machining of various types of glass materials at micro-scale. A comparative analysis of various conventional and non-conventional micromachining processes used for machining glass is presented. Discussions on the current research trends and challenges in micromachining of glass have been included. Finally, recommendation for future research in the areas of glass micromachining has been provided.     

Research of micro EDM/ECM method in same electrolyte with running wire tool electrode

A micro rod machining method which can switch between electrical discharge machining (EDM) and electrochemical machining (ECM) by attaching/detaching a diode to/from a bipolar pulse generator in parallel to the working gap was newly developed using a wire electrode made of tungsten. The problem of the wire electrode wear was eliminated by the use of the wire electrochemical turning (WECT) method in which the tungsten wire electrode is continuously running. The ultra-short bipolar pulse current was generated by the electrostatic induction feeding method where a pulse voltage is coupled to the working gap through a feeding capacitance. The machining characteristics of three types of wire guide; disk-shaped WC guide, laminated wire guide and cylindrical acrylic guide, were studied. The experimental results showed that the cylindrical acrylic guide has the best machining characteristics without the influence of guide wear and with less stray current flowing through the working gap. Using the cylindrical acrylic guide, the influences of the feeding capacitance C₁, and the total amplitude of the pulse voltage on the machining characteristics were studied. Finally, a stainless steel SUS 304 micro-rod with a high aspect ratio of 14 was fabricated efficiently by using the EDM and ECM modes for rough and finish machining in sequence with the same setup, pulse generator, and neutral electrolyte.     

脉冲电解加工间隙测控方法的研究进展

介绍电解加工间隙测控的意义及重要性 ;总结电解加工技术中加工间隙的测控方法 ;分析国内外加工间隙测控的现状及关键问题 ,提出一种可实现在线测控加工间隙的新思路———建立六维力、电流信号与加工间隙之间的关系方程式。     

高频群脉冲电化学微小型加工中的反向电流与压力波

针对脉冲电化学加工，建立了反向电流和压力波的数学模型，提出了高频群脉冲电化学加工方法。结果表明，充分发挥反向电流作用的电源频率在10～24kHz之间，压力波频率在400～1333Hz之间。反向电流仅与电极本身有关，它决定了高频群脉冲电化学加工的主脉冲频率；压力波则除了电极外，还与电解质性质和流速、极间间隙和电压等有关，它决定了高频群脉冲电化学加工的调制脉冲频率。根据模拟结果设计的实验表明，良好的加工质量来源于高频群脉冲带来的较小极间间隙。     

微细电解加工的精度及定域性研究

在分析微细电解加工特点的基础上,探讨了底面间隙和侧面间隙之间的关系,并研究了它们对加工精度和定域性的影响。通过对定域性评价指标的比较,提出了以定域蚀除率评价杂散蚀除的新概念。运用定域蚀除率分析了在利用纳秒脉冲电流进行微小孔的电解加工时,脉冲宽度和工具电极直径对加工定域性的影响。结果表明,减小脉冲宽度和占空比可以增强定域蚀除能力,提高加工精度。     

Recent developments and research challenges in electrochemical micromachining (µECM)

Electrochemical machining (ECM) and especially electrochemical micromachining (μECM) became an attractive area of research due to the fact that this process does not create any defective layer after machining and that there is a growing demand for better surface integrity on different micro-applications such as microfluidics systems and stress free drilled holes in automotive and aerospace manufacturing with complex shapes. Electrochemical machining is a non-conventional machining process based on the phenomenon of electrolysis. This process requires maintaining a small gap (size of a few μm)—the inter-electrode gap—between the anode (workpiece) and the cathode (tool electrode) in order to achieve acceptable machining results (i.e. accuracy, high aspect ratio with appropriate material removal rate and efficiency). This paper presents different problematic areas of electrochemical micromachining (often referred to as electrochemical micromachining or μECM). The aim of this paper is to address the problems met by the μECM technology developers and to present the current state-of-the-art solutions.     

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。     

微细电解加工的过程检测及精度控制

超短脉冲微细电解加工时,极间加工间隙很小,加工过程的稳定性是影响加工精度的重要因素。在所建立的加工控制系统中,采用两步短路对刀法精确定位电极初始间隙,利用霍尔电流传感器实时检测平均加工电流,动态控制电极的进给运动速度,从而保持不同加工条件下稳定加工的最小加工间隙。进行了微细结构的电解加工试验,通过检测加工过程的状态,保证了加工的稳定性,实现了线宽只有25μm的微细结构加工。     

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.     

High frequency group pulse electrochemical machining

In the process of machining ultrathin metal structure parts, the signal composition of high frequency group pulse, the influence of frequency to reverse current, and the design of the cathode in high frequency group pulse electrochemical machining (HGPECM) are discussed. The experiments on process were carried out. Results indicate that HGPECM can greatly improve the characteristics of the inter-electrode gap flow field, reduce electrode passivation, and obtain high machining quality. The machining quality is obviously improved by increasing the main pulse frequency. The dimensional accuracy reaches 30–40 μm and the roughness attained is at 0.30–0.35 μm. High frequency group pulse electrochemical machining can be successfully used in machining micro-parts. __________ Translated from Transactions of Beijing Institute of Technology, 2006, 26(7): 585–588 [译自: 北京理工大学学报]     

Experimental investigation on monitoring interelectrode gap of ECM with six-axis force sensor

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.     

Experimental and numerical analyses of the pressure distribution in electrochemical machining

Measurements have been made of the pressure distribution of the electrolyte solution flowing along the inter-electrode gap during electrochemical machining. A theoretical model for the pressure distribution, which takes into account the growth of the hydrogen gas layer along the cathode electrode, is proposed. A method of solution of the model, based on optimisation techniques, is discussed.The experimental results and the theoretical model are correlated in terms of the variation of the interelectrode gap, thereby providing a prediction of the pressure distribution together with values for gas void fraction index, the slope of the gas bubble layer and the friction factor.A comparison of the measured and predicted pressure variation is presented. Numerical values for the above parameters are then discussed in the light of other observations of the process.