高频窄脉冲电流微细电解加工

微细电解加工是微细加工领域很有发展前景的微细加工技术之一。适合于微细电解加工的装置被研制出来, 它包括机床进给机构、线电极电火花磨削在线制作微细电极装置、短路检测模块、脉冲电源及其他一些辅助装置, 其中,高频窄脉冲电源是微细电解加工最重要的核心技术之一。根据微细电解加工的特点,设计了微细电解加工 MOSFET脉冲电源,该微能脉冲电源能很好地满足微细电解加工的要求。运用该微细电解加工装置进行加工试验, 在低的加工电压和低的钝化电解液浓度条件下,利用高速旋转的微细电极加工微小孔和像小铣刀一样进行微细电解铣削加工微结构,得到了满意的工艺效果,因而进一步说明电解加工在微细加工领域很有发展潜力。     

纳秒脉冲微细电化学加工的理论及试验

根据电化学反应原理,探讨纳秒脉冲电化学加工的特点及其实现微细加工的机理.建立纳秒脉冲微细电化学加工的理论模型,并分析电解液浓度、加工间隙、脉冲参数和加工电压等因素对微细电解加工的影响作用.构建微细电化学加工系统,包括微细加工机床、纳秒脉冲电源、电解液循环系统、运动控制部分和加工检测部分.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和降低加工电压可以提高微细电解加工的精度.在自制的微细电化学机床上,实现工具电极和工件微结构的连续加工.将加工间隙控制在5 μm以内,加工出中间有20 μm×30 μm×30 μm棱台的微型腔和30 μm槽宽的十字形孔,分析加工起始点对成形精度的影响,并提出解决方法.试验证明纳秒脉冲微细电解加工可以很好地满足微机电系统(Micro electromechanical system,MEMS)微器件的加工要求.     

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。     

电解加工在微细制造技术中的应用研究

电解加工是利用阳极金属电化学溶解原理来去除材料的制造技术,这种微去除方式使得电解具有微细加工的可能,这里着重探讨了高频窄脉冲微细电解加工技术、电液束微细电解加工技术和利用电解制备微细电极的工作原理,技术特点,应用领域和加工精度,并详细的讨论了目前微细电解加工脉冲电源和加工设备的研制和发展。     

厚镍板的微细电解线切割加工技术研究

采用超短脉冲电流技术进行微细电解线切割加工,脉冲电压是决定所能加工厚度的关键因素之一,提高超短脉冲电压可以在有效抑制杂散腐蚀的同时切割加工厚度比较大的工件。构建了线电级往复运丝的微细电解线切割试验系统;工件为800μm的镍板,线电极为直径10μm的钨丝;采用正交试验研究了脉冲电压、脉冲宽度、脉冲周期和电解液浓度对加工精度的影响;选用实际最优参数在厚800μm的镍板上切割加工出了宽度约为35μm的悬臂梁结构。     

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。     

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。     

线电极微幅振动电解线切割研究

通过线电极叠加轴向微振动促进加工间隙中的电解产物排除,改善线电极电解线切割的稳定性,提高加工效率。自行研制线电极微幅振动电解加工系统,阐述线电极微幅振动电解加工原理,建立加工间隙产物排除的数学模型,揭示线电极叠加轴向微幅振动是排除电解产物、更新电解液的有效途径之一,分析线电极叠加轴向微幅振动对加工稳定性、加工效率和加工精度的影响。针对线电极叠加轴向微幅振动和不叠加振动两种情况进行了对比试验,试验结果表明,振幅8μm、频率10Hz的振动参数有利于改善线电极电解线切割稳定性,提高加工效率。与不叠加振动相比,线电极叠加轴向微幅振动情况下,线电极电解线切割可以在较小的电压、脉冲宽度和较大的脉冲周期下稳定进行,有效地缩小切缝宽度,提高了加工精度。采用优化后的振动参数和加工参数,在不锈钢工件(0Cr18Ni9)上加工出12μm的微缝以及形状复杂的微渐开线齿轮和微螺旋结构。     

金属微结构的电解铣削加工技术研究

随着微机电系统的发展,微细加工技术成为了当今世界的研究热点。对微细电解铣削加工技术进行了深入研究,在难加工材料镍基高温合金上进行了一系列微细电解铣削加工工艺试验。首先,基于微细电解铣削加工原理,自行研制了一套高精度微细电解铣削加工系统。其次,分组试验并分析了各主要参数,如铣削层厚度、加工电压、脉冲宽度、电极直径,以及电解液浓度等对形状精度和加工精度的影响规律。最后,通过优化加工参数,成功加工出了数个典型三维平面及曲面微结构,形状精度高,加工稳定性好,充分展现了微细电解铣削工艺在加工复杂金属微结构方面的巨大潜力。     

大长宽比微细槽的微细电解铣削实验研究

为了提高大长宽比微细槽电解加工的稳定性和加工精度,在304不锈钢薄板上进行了微细槽的电解铣削加工正交实验,并利用极差值法分析了加工电压、脉冲宽度和进给速度等对侧面加工间隙的影响程度大小,并得到工艺参数的优化组合,在此基础上进行了大长宽比微细槽的电解铣削加工。结果表明:在该工艺条件下,加工过程稳定,加工精度较好,可重复性较高。     

Pulse electrochemical polishing for microrecesses based on a coulostatic analysis

Electrochemical polishing using a pulsing current is a potential alternative process for polishing micro patterns or microrecesses generated by pulse electrochemical machining. Pulse electrochemical polishing processes are attractive compared to conventional electrochemical polishing processes based on a continuous current because they allow instantaneous electrochemical reaction by applying ultrashort voltage pulses. However, there have been few attempts for calculating preferable pulse durations of the electrochemical process. To predict the preferable pulse durations, the specific polarization resistance and time constant should be obtained from a charging/discharging analysis of electrical double layer. This study describes a means of controlling physical and electrical conditions to achieve polished micro pattern or microrecess with lustrous and smooth surfaces while maintaining their original micro-scale shapes.     

高频群脉冲电解加工中IGBT反向尖峰电压的数学模型

在高频群脉冲电解加工电源的研究中发现电源的核心元件IGBT在关断瞬间会出现反向尖峰电压,由于对他的适当 控制对提高电解加工的精度和加工产品的表面质量起着至关重要的作用,针对这个问题我们建立了反向尖峰电压的数学模 型。本文就此数学模型进行了介绍,同时阐述了该模型的建立对抑制反向尖峰电压的作用。     

基于脉冲电源的金属电化学线切割工艺研究

为了提高金属电化学线切割精度,将脉冲电源应用到切割加工中,根据电化学加工原理,并以切割缝宽为切割效果的评价标准,建立了脉冲电源切割理论模型,得出了影响缝宽变化的工艺参数,主要有:电源的电压幅值、脉冲宽度、占空比和进给速度等。并在此基础上对参数进行了优化加工实验。研究结果表明,在保证加工稳定的条件下,通过降低电压、调小脉冲宽度和占空比的方法,加工出的切割缝宽比直流电源加工出的缝宽明显减小,该方法将有望直接用于小尺寸零件的加工。     

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.     

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.     

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。     

An experimental study on micro-EDM in low-resistivity deionized water using short voltage pulses

Deionized water has been used as dielectric fluid for micro-electrical discharge machining (micro-EDM) because it gives higher material removal rate and lower tool wear than hydrocarbon oil. Moreover, it is a relatively low-cost and eco-friendly substance. Therefore, deionized water tends to be more favorable for micro-EDM. However, it causes weak electrochemical reaction during micro-EDM due to its slight conductivity. This leads to the unanticipated additional material removal from the workpiece which affects the machining shape and quality. The study in this paper aims to suppress the electrochemical reaction in die-sinking micro-EDM using deionized water by employing short voltage pulse. Experiments were carried out to fabricate micro-holes using the developed nanosecond pulse circuit. Different pulse parameters were applied to identify the main factor affecting the electrochemical reaction rate. Machining gap was found to be thinner and workpiece surface adjacent to the rim of micro-holes were found to be free of defects caused by material dissolution when pulse duration reached a critical value. Moreover, the influence of pulse parameters on material removal rate and machined shape was also investigated. Besides, energy-dispersive X-ray spectroscopy analysis showed that the machined surface using deionized water was less affected from material migration during micro-EDM process in comparison to hydrocarbon oil.     

Feed rate of wire electrochemical machining using pulsed current

The effect of various parameters on the feed rate in electrochemical machining has been investigated. Parameters considered were velocity of the electrolyte flow, nozzle diameter, material, diameter and tension of the wire, pulse period and peak value of the applied voltage. On the assumption that the feed rate is limited by accumulation of generated sludge or gas, the feed rate equation and favourable pulse conditions were derived and verified experimentally. The rate was improved by applying a shorter pulse period than the ‘residential’ time of the electrolyte between electrodes. Above the critical pressure, at which the feed rate is a maximum, the adverse effects of wire vibration cannot be neglected. Measures proposed to prevent it were reduction of nozzle diameter and length of wire span, and increase in applied voltage and wire tension.     

Experimental investigation of kerf characteristics through wire electrochemical spark cutting of alumina epoxy nanocomposite

Alumina epoxy nanocomposite (AENC) is an emerging class of composites with a wide range of functionality and applicability; however, managing AENC using a machine is difficult because of its special mixed characteristics. The presence of extremely hard alumina particles in soft epoxy matrix enhances material properties. The present work investigates the kerf characteristics of a straight cut made in AENC through Wire electrochemical spark cutting (WECSC) process. The kerf characteristics, such as kerf deviation and taper, are used to measure the cut quality. The applied voltage, electrolyte concentration, wire velocity, pulse on-time and pulse off-time are varied, and their effects on the kerf characteristics are experimentally investigated in a developed setup. Influencing parameters for straight cutting of AENC are applied voltage, concentration of electrolyte and wire velocity.