Theoretical and Experimental Investigation of Laser Milling Assisted with Jet Electrochemical Machining

In laser milling assisted with jet electrochemical machining(LMAJECM),the source of energy is a pulsed laser beam aligned coaxially with a jet of electrolyte,which focuses optical energy on the surface of workpiece.The impact of jet of electrolyte develops a state-of-art work to perform operations such as electrolytic etching,effective cooling,and transportation of debris.Therefore,a special jet cell is designed to obtain stable jet as to be a kind of noncontact tool,i.e.,electrode.According to the theoretical model of on-off pulse time process,laser machining and electrolytic anodization are simulated by finite element analysis(FEA)method.Grooves on a 0.5mm thick 321 stainless steel sheet produced by LMAJECM is performed with pulsed Nd:YAG laser at the second harmonic wavelength.Compared with laser milling under ambient atmosphere conditions,the recast layer and burrs are effectively diminished.And the accuracy of depth is dedicated to laser milling,whilst that of width is dominated by jet electrochemical machining.It is demonstrated that LMAJECM can be a highly potential approach for fabricating 3-D micro components.

Analysis of the current density characteristics in through-mask electrochemical micromachining(TMEMM) for fabrication of micro-hole arrays on invar alloy film

Invar alloy consisting of 64% iron and 36% nickel has been widely used for the production of shadow masks for organic light emitting diodes（OLEDs） because of its low thermal expansion coefficient（1.86 × 10^-6cm/°C）.To fabricate micro-hole arrays on 30 lm invar alloy film,through-mask electrochemical micromachining（TMEMM） was developed and combined with a portion of the photolithography etching process.For precise hole shapes,patterned photoresist（PR） film was applied as an insulating mask.To investigate the relationship between the current density and the material removal rate,the principle of the electrochemical machining was studied with a focus on the equation.The finite element method（FEM） was used to verify the influence of each parameter on the current density on the invar alloy film surface.The parameters considered were the thickness of the PR mask,inter-electrode gap（IEG）,and electrolyte concentration.Design of experiments（DOE） was used to figure out the contribution of each parameter.A simulation was conducted with varying parameters to figure out their relationships with the current density.Optimization was conducted to select the suitable conditions.An experiment was carried out to verify the simulation results.It was possible to fabricate micro-hole arrays on invar alloy film using TMEMM,which is a promising method that can be applied to fabrications of OLEDs shadow masks.

Experimental Investigation on Complex Structures Machining by Electrochemical Micromachining Technology

Electrochemical micromachining （EMM） technology for fabricating micro structures is presented in this article. By applying ultra short pulses, dissolution of a workpiece can be restricted to the region very close to the electrode. First, an EMM system for meeting the requirements of the EMM process is established. Second, sets of experiments is carried out to investigate the influence of some of the predominant electrochemical process parameters such as electrical parameters, feed rate, electrode geometry features and electrolyte composition on machining quality, especially the influences of pulse on time on shape precision and working end shape of electrode on machined surface quality. Finally, after the preliminary experiments, a complex microstructure with good shape precision and surface quality is successfully obtained.

表面织构电解加工技术研究进展

表面织构在能源、光学、电子、信息技术、生物和摩擦学等领域具有重要应用,其加工工艺是制造技术研究的重要内容。由于所加工表面织构具有无毛刺、翻边等优点,电解加工成为表面织构的重要制造技术方法和技术研究热点,故详细介绍了五种典型表面织构电解加工技术在方法创新、材料去除机制、加工过程建模及加工工艺等方面的研究进展,给出了电解加工表面织构的典型结构和材料,指出提高加工效率和加工自动化程度是未来表面织构电解加工技术的发展趋势。

超声横振辅助微细电解加工关键技术研究

针对深窄槽微细电解加工中存在电解产物排出困难的问题,提出了一种超声横振辅助微细电解加工方法。该方法利用工具电极产生横振使加工间隙的流场产生周期性变化,增强了电解加工间隙内电解产物传质能力,提高了深窄槽微细电解加工效率及加工稳定性。为研究该工艺的加工特性,研制了一套超声横振辅助微细电解加工装置,其关键技术是实现3种工作模式的超声-电解同步电源。基于研制的超声横振辅助微细电解加工装置,本文以深窄槽加工实验为研究对象,探究了电源的不同工作模式对深窄槽的影响规律。实验结果表明超声横振有利于提高深窄槽加工的传质能力,同步超声模式1有利于进一步提高工件的溶解量和微细电解加工的传质能力,同步超声模式2则有利于提高深窄槽的加工精度。最后,加工出槽宽为432.9μm,深宽比为11.9的深窄槽。

Electrochemical micromachining of micro-dimple arrays on cylindrical inner surfaces using a dry-film photoresist

The application of surface textures has been employed to improve the tribological performance of various mechanical components. Various techniques have been used for the application of surface textures such as micro-dimple arrays, but the fabrication of such arrays on cylindrical inner surfaces remains a challenge. In this study, a dry-film photoresist is used as a mask during through-mask electrochemical micromachining to successfully prepare micro-dimple arrays with dimples 94 lm in diameter and 22.7 lm deep on cylindrical inner surfaces, with a machining time of 9 s and an applied voltage of 8 V. The versatility of this method is demonstrated, as are its potential low cost and high efficiency. It is also shown that for a fixed dimple depth, a smaller dimple diameter can be obtained using a combination of lower current density and longer machining time in a passivating sodium nitrate electrolyte.

Electrochemical micromachining of microgroove arrays on phosphor bronze surface for improving the tribological performance

A high friction coefficient and a low wear rate of contacted surfaces are essential elements to friction pairs between the stator and the rotor in ultrasonic motors. It has been shown that surface textures have a significant effect on improving the tribological performance of friction pairs.In this paper, microgroove arrays are introduced to the stator surface for improving the tribological performance of friction pairs between the stator and the rotor in ultrasonic motors. Microgrooves were fabricated on a phosphor bronze surface by through-mask electrochemical micromachining（TMEMM）. Parameters, namely, the electrolyte inlet pressure, applied voltage, pulse duty cycle,and frequency, were varied to investigate their influences on the dimensions and morphology of the microgrooves. Results showed that the width and depth of the microgrooves were strongly affected by the applied voltage and frequency, while the morphology of the microgrooves was dependent on the electrolyte inlet pressure and the pulse duty cycle. Compared with a smooth surface, the friction coefficient increased from 0.245 to 0.334 and less abrasion was obtained when a surface was textured with microgrooves of which the width and depth were 185.6 and 57.6 lm,respectively. Microgroove arrays might play an important role in enhancing the performance of ultrasonic motors.

Investigation of the influence of ultrasonic stirring on mass transfer in the through-mask electrochemical micromachining process

Surface texturing is a widely accepted approach for friction reduction between mechanical components. Through-mask electrochemical mieromachining is a simple and reliable process for metal surface texturing in which mass transport conditions have profound influence on final machined quality. An ultrasonic stirrer is usually adopted for mass transfer enhancement. However, understanding of the effects of ultrasonic stirring on mass transfer is limited, and is far from sufficient for developing guidelines for its practical application. In this work, the influences of ultrasonic stirring parameters on mass transfer have been investigated numerically and experimentally. With the numerical method, periodic pressure change in the electrolyte over time has been obtained, showing that ultrasonic stirring results in drastic transient pressure change in electrolyte fluid fields. Parameters related to ultrasonic frequency, vibration amplitude, and the depth of anode surface immersed in the electrolyte solution influence pressure amplitude. Validation experiments have been conducted and etched surface profile and morphology characterized, which show that the experimental observations are in agreement with numerical predictions. With the optimized mass transfer, well-defined micro-pits array of 30 gm and a smooth etched surface on tin-bronze substrate in large scale have been demonstrated.

3D multiphysic simulations of energy field and material process in radial ultrasonic rolling electrochemical micromachining

The radial ultrasonic rolling electrochemical micromachining(RUR-EMM)combined rolling electrochemical micromachining(R-EMM)and ultrasonic vibration was studied in this paper.The fundamental understanding of the machining process especially the interaction between multiphysics in the interelectrode gap(IEG)was investigated and discussed by the finite element method.The multiphysics coupling model including flow field model,Joule heating model,material dissolution model and vibration model was built.3D multiphysics simulation based on micro dimples process in RUR-EMM and R-EMM was proposed.Simulation results showed that the electrolyte flowed into and out IEG periodically,gas bubbles were easy to squeeze out and the gas void fraction deceased about 16%to 54%,the maximum current density increased by 1.36 times in RUR-EMM than in R-EMM in one vibration period of time.And application of the ultrasonic vibration increased the electrolyte temperature about 1.3–4.4%in IEG.Verification experiments of the micro dimple process denoted better corrosion consistency of array dimples in RUR-EMM,there was no island at the micro dimple bottom which always formed in R-EMM,and an aggregated deviation of less than 8.7%for the micro dimple depth and 4%for the material removal amount between theory and experiment was obtained.

The coupling effect of slow-rate mechanical motion on the confined etching process in electrochemical mechanical micromachining

By introducing the mechanical motion into the confined etchant layer technique(CELT), we have developed a promising ultraprecision machining method, termed as electrochemical mechanical micromachining(ECMM), for producing both regular and irregular three dimensional(3 D) microstructures. It was found that there was a dramatic coupling effect between the confined etching process and the slow-rate mechanical motion because of the concentration distribution of electrogenerated etchant caused by the latter. In this article, the coupling effect was investigated systemically by comparing the etchant diffusion, etching depths and profiles in the non-confined and confined machining modes. A two-dimensional(2 D) numerical simulation model was proposed to analyze the diffusion variations during the ECMM process, which is well verified by the machining experiments. The results showed that, in the confined machining mode, both the machining resolution and the perpendicularity tolerance of side faces were improved effectively. Furthermore, the theoretical modeling and numerical simulations were proved valuable to optimize the technical parameters of the ECMM process.

Investigation on surface structuring generated by electrochemical micromachining

Surface geometrical features and their function- ality depend on the manufacturing process which is employed for fabrication of surface structures. Maskless electrochemical micromachining （EMM） is used to generate various surface structures for diminishing and controlling friction and wear to increase the lifetime, reliability, and efficiency of mechanical systems. This paper presents a method for the generation of structured surfaces on stainless steel （SS-304） surfaces by using maskless EMM. The micropatterned tool is composed of 800 μm diameter circular holes in a 5 × 5 matrix form. The indigenously developed EMM set up consists of an EMM cell, electrical power supply system, and a controlled vertical cross-flow electrolyte circulation arrangement to control the influence of process parameters during the generation of the micro features of structured surfaces. The single structured cathode tool is used for the mass production of structured surfaces with a short fabrication time in the industrial context by avoiding the use of an individual masking process for each workpiece. The process has been characterized in terms of the effects of predominant process parameters such as machining voltage, electrolyte concentration, duty ratio, pulsed frequency, and machining time on the machined surface characteristics such as current efficiency, machining accuracy, and depth of the circular pattern on the stainless steel surfaces. A mathematical model is also developed to determine the theoretical depth of the dimple pattern and correlate the theoretical depths with actual depths as obtained by experimentation. Moreover, an effort has been made to study the structuringcharacteristics on the basis of micrographs obtained duringthe EMM.

超声辅助微细电解加工间隙空化微射流对材料蚀除的影响

为探究超声辅助微细电解加工(UAEMM)间隙电解液内产生的空化微射流对材料蚀除的影响,建立微射流冲击工件表面流固耦合模型,通过数值仿真研究高速微射流冲击下工件表面微观塑性形变规律以及微变形对电场分布的影响规律,并进行了超声空化实验验证。研究结果表明:微射流冲击工件表面产生若干深度约0.12μm、凸起约0.04μm的空蚀坑;在外加电场下,空蚀坑凸起处的电流密度和蚀除深度较原始工件表面处提高1.2倍;进一步的凹坑成形加工实验结果表明,在超声振幅10μm、加工时间5 s、加工间隙50μm工况下,与微细电解加工相比,UAEMM凹坑蚀除深度从20μm提高到100μm,同时成形凹坑底部粗糙度R_(a)从290 nm降低到40 nm;超声能场下间隙大量空化微射流促进了微细电解加工效率、加工后工件表面质量。

太赫兹微金属矩形波导凹型微腔电化学制造技术研究

随着太赫兹技术的发展,对高工作频段太赫兹金属矩形波导的需求日益迫切,然而,因其腔体端面尺寸和圆角半径较小、表面粗糙度要求严格,精密加工极具挑战性。文章针对太赫兹微金属矩形波导制造用的凹型微腔精密制造问题进行了研究,利用微细电解线切割加工技术、电化学沉积金及电化学沉积铜等电化学制造技术的组合,实现了端面尺寸为124.3μm×253.2μm、表面粗糙度Ra<0.1μm、圆角半径R<8μm的1THz金属矩形波导凹型微腔的制造,为高工作频段的组合式太赫兹金属矩形波导制造奠定了基础。

活塞环表面微坑电解加工技术的基础研究

研究表明摩擦副表面的织构可以有效地改善表面摩擦学性能,提出了采用阴极掩模微细电解方法在活塞环表面加工阵列微坑的加工工艺。试验研究了不同绝缘层厚度和加工电压对曲面微坑尺寸的影响。选用优化的加工参数,进行了曲面微坑电解加工试验,在活塞环表面得到平均直径为250μm,深度为10μm的阵列微坑。参照发动机中活塞环/缸套摩擦副的工作原理,采用该加工方法加工出表面面积率不同,深度不同的多个活塞环试样进行摩擦试验。试验结果表明,与光滑曲面相比,带有适当面积率和深度的阵列微坑的试样表面可以有效地降低摩擦因数,起到抗磨减摩的作用。

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。

基于多功能加工平台的微细电解加工(英文)

电解加工在加工过程中因难以控制加工形状而很少应用在微细加工领域.为了对微细电解加工可行性进行探索,设计了多功能微细加工平台.利用多功能微细加工平台可为微细电解加工在线制作电极,采用低加工电压、低浓度的钝化电解液、高频窄脉冲电源和高速旋转的微细电极,进行了微细电解加工实验,取得了很好的工艺效果.加工间隙是影响加工精度的关键因素,设计了一个加工间隙控制伺服系统,以保证微小的加工间隙.在厚为100μm的不锈钢薄片上用微细电解打孔加工出直径为65μm的微小孔.利用微细电解加工时电极无损耗,提出采用简单圆柱微细电极进行微细电解铣削,加工出较高精度的微结构,取得了较好的工艺效果,从而验证了该微细电解加工装置的微细加工能力和方法的可行性.

微细电解加工实验研究

针对微细电解加工中脉冲电源技术,电解液成分配比,以及加工间隙检测、控制等问题开展了微细电解加工技术的试验研究工作.首先讨论了微细电解加工的工艺特点和主要技术步骤,然后利用高频窄脉冲电源进行了加工实验.通过实验现象和实验结果的研究分析,提出了改进加工实验的方案,通过实验证明了本方案和技术路线的可行性,并获得了很好的微结构加工试验结果.通过微细电解加工实验的研究,为微细电解加工的生产应用提供了依据,显示出微细电解加工方法在金属零件微制造方面有着广阔的应用前景.

基于多功能加工平台的微细电解加工工艺

利用多功能微细加工平台的微细电火花加工技术为微细电解加工在线制作微细电极,在低浓度钝化电解液、低加工电压和高频窄脉冲电流加工条件下,利用高速旋转工具电极和微电流密度下电解钝化作用,实现了微米级的微细电解加工.通过工艺实验,研究电压、电解液浓度和进给速度等参数对加工间隙的影响,优化工艺参数.在优化加工条件下,在厚为100μm的不锈钢薄片上微细电解钻削出65μm的微小孔.针对成型电极在微细加工中暴露出的缺点,提出了利用旋转微细电极像微铣刀一样进行微细电解铣削新工艺,加工出高精度型孔和悬臂梁等微结构.

电化学微细加工监控系统的研究

在虚拟仪器软件平台上研制了电化学微细加工监控系统,系统采用霍尔电流传感器采集加工电流,并实时准确显示过程数据曲线,根据电流突变快速响应,系统的定位精度和重复定位精度均小于5μm。和传统电化学加工控制系统相比,具有硬件简单、灵活性好、性价比高、稳定可靠等特点。

微机电系统的微细加工技术

详细阐述了硅微加工工艺以及近几年内国际上开发的一些新的加工技术,如3D电化学微加工、EFAB工艺等,并提出了目前这些方法中存在的缺陷。