微细电火花加工系统及其工艺技术

开发了一套微细电火花加工系统,该系统不仅能加工微细轴、微细孔,还能实现微三维结构的微细电火花加工。研究了针对该系统的微细电火花加工工艺技术,研究了放电电压、放电电容等工艺参数,主轴转速,以及工作液介质对微细电火花加工效率、相对电极损耗率的影响规律。采用旋转削边电极技术大大提高了进行大深径比微细孔加工时的加工效率。进行了大量的加工实验,加工出了最小直径为6μm的微细轴以及最小直径为10μm的微细孔;通过对电极损耗的在线补偿策略研究,实现了微三维结构的加工,加工出了外径为4mm、具有24个叶片的微型涡轮盘及具有微三维结构的微细梁,充分证实了该系统的广泛适用性。     

微细电火花加工及其关键技术

综述了微细电火花加工的基本原理及最新研究进展。比较了LIGA技术与微细电火花加工的特点与应用。简要分析了微细电火花加工的关键技术：微细电极的在线制作、微进给装置、微小能量的脉冲电源、微小电极的运动轨迹规划、电极的损耗及补偿策略。展望了微细电火花加工在微三维结构加工中的应用前景。     

一种新型卧式微电火花机床的设计与实验研究

针对微电极制作的效率问题,提出了一种快速在线微电极加工成形的方法,设计了一种新型卧式微电火花机床。该机床由金刚石砂轮超精密在线电极磨削、线电极电火花在线电极磨削共同完成微米级电极的高效精密制作,该机床组成部分还包括基于CCD的在线光学尺寸检测与测量系统、精密运动与进给系统、纳秒级独立式脉冲放电电源与放电状态检测反馈系统组成。在该机床上进行了微电极制作、微小孔加工以及微电火花铣削等实验,加工出直径为15μm微细轴和直径为50μm微小孔。     

微细电火花加工机床关键技术

研制开发两台高精度、高性能,具有自主知识产权的微细电火花加工机床,并对微细电火花加工机床的几个特有关键技术进行了深入研究.基于压电陶瓷的宏微伺服进给系统能实现分辨率为3.42 nm的微进给,并且能实现振动式进给,以改善微细电火花加工的间隙状态,提高微细电火花的加工效率和加工质量.结合块电极反拷与线电极反拷的微细工具电极反拷系统,可高效高精度地现场制作微细电极,电极直径最小可达4 μm.基于多传感器信息融合技术的放电间隙状态监测技术,能很好地解决微细电火花加工间隙状态的监测与识别问题.RC脉冲电源不存在维持电压现象,这一最新发现为降低单脉冲放电能量难题提供一个新的解决途径,使得基于RC方法开发的超微能脉冲电源的单脉冲放电能量最小降至皮焦级,为微细电火花加工奠定了良好的基础.最后的微细电火花加工试验表明,所开发的微细电火花加工机床性能稳定,且加工质量良好,尤其适合加工孔径为50～200 μm的微细孔.     

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。     

电火花成形机床微细加工相关探索

首先简要介绍了电火花微细加工目前的发展状况。并概括地分析了商品电火花成形机用于微细加工所具有的一些特殊优势。最后通过微轴的加工实例来证实其进行实用微细加工的可行性。     

采用蠕动式微进给机构的微细电火花加工装置

介绍了一种采用蠕动式微进给机构的微细电火花加工装置，尝试微细火花加工的实用化和装置本身的微小型化。内容包括该装置机构的设计制作及初步的加工实验结果，特别是蠕动式微进给机构提高输出推力、适用于微细电火花加工的设计实现。     

小型数控微细铣床的研制及铣削试验研究

总结了现有微小零件加工技术的局限性,阐述了微细铣削加工的优势,并自主构建了一台适于微小零件制造的小型三轴数控微细铣床,铣床本体尺寸为400mm×400mm×260mm,工作空间为50mm×50mm×50mm。介绍了组成微细铣床的六大子系统的性能,对微细铣床系统进行精度测试,该铣床的定位精度达到1μm,满足微细铣削加工的精度要求。使用硬铝LY12进行微直槽及薄壁、微同心圆槽的铣削加工试验。加工试验结果显示:该微细铣床已经具备加工介观尺度的高深宽比微小零件的能力。     

微细电火花加工中微细电极的制作与检测技术研究

分析了微细电火花加工技术中各种微细电极制作方法的特点,提出了一种加工效率与尺寸精度相兼顾的微细电极在线制作方法.充分利用微细电火花加工机床的数控和接触感知功能,探索并提出了一种微细电极的在线检测方法,并对检测误差进行了分析.实验表明,该方法具有广泛的实用性.     

基于多功能微机床的复合微细电火花模块设计及实验研究

针对实验室块反铐加工中出现的难以加工较细的微细工具电极问题,根据现有多功能微机床进行设计,按照模块化设计思路,设计出了微细电火花复合加工模块,该模块包括在线块电极磨削加工与在线电极磨削加工两部分。采用块电极磨削与线电极磨削相结合的方法,通过运用不同电源模式实现块反铐加工粗加工、线电极作为中、精磨削的微细电火花电极制作流程,采用蒸馏水为工作液,研究电参数对工具电极影响,并通过该实验验证了该加工工艺方法,且能稳定加工出长直径为50μm、长径比大于84的微细工具电极。     

Fabrication of large scale nanostructures based on a modified atomic force microscope nanomechanical machining system

The atomic force microscope (AFM) tip-based nanomechanical machining has been demonstrated to be a powerful tool for fabricating complex 2D∕3D nanostructures. But the machining scale is very small, which holds back this technique severely. How to enlarge the machining scale is always a major concern for the researches. In the present study, a modified AFM tip-based nanomechanical machining system is established through combination of a high precision X-Y stage with the moving range of 100 mm × 100 mm and a commercial AFM in order to enlarge the machining scale. It is found that the tracing property of the AFM system is feasible for large scale machining by controlling the constant normal load. Effects of the machining parameters including the machining direction and the tip geometry on the uniform machined depth with a large scale are evaluated. Consequently, a new tip trace and an increasing load scheme are presented to achieve a uniform machined depth. Finally, a polymer nanoline array with the dimensions of 1 mm × 0.7 mm, the line density of 1000 lines/mm and the average machined depth of 150 nm, and a 20 × 20 polymer square holes array with the scale of 380 μm × 380 μm and the average machined depth of 250 nm are machined successfully. The uniform of the machined depths for all the nanostructures is acceptable. Therefore, it is verified that the AFM tip-based nanomechanical machining method can be used to machine millimeter scale nanostructures.     

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。     

Experimental attempts of sub-micrometer order size machining using micro-EDM

So far, parts larger than several micrometers can be machined by micro-electrical discharge machining (micro-EDM). However, with the growing demands for even smaller parts, sub-micrometer order machining or even nanometer order machining are increasingly required in various industrial areas. In order to meet these requirements, the study on sub-micrometer order manufacturing has become considerably important. In the present study, experimental attempts of sub-micrometer order size machining using micro-EDM was performed, in which the smallest possible size that can be achieved for machined parts was examined, and the factors affecting the manufacturing of sub-micrometer parts were investigated. The results showed that insufficient positioning accuracy, smallest discharge energy and the machined shape error due to the influence of gap control and thermal deformation are not suitable for sub-micrometer machining. Disregarding positioning accuracy and machined shape error, cemented tungsten carbide (WC) and cemented tungsten carbide made of super fine particles (SWC) are relatively better than tungsten (W) from the viewpoint of material structure and influence of residual stress. In particular, SWC is more suitable than WC because both crystal grains size and size of defects among grains are smaller. Setting the polarity of workpiece negative was found to contribute to achieving sub-micrometer machining if the material removal rate is disregarded. Based on these investigation results, sub-micrometer machining using SWC was attempted. The minimum diameter obtained was about 2.8 μm.     

A Feasibility Study on the Micro Eletro-Discharge Machining Process for Photomask Fabrication

A feasibility study of micro electro-discharge machining (micro-EDM) technology has been conducted for its possible contri-bution in the photomask industry. A series of experimental runs was performed on three specimens using a micro-EDM system with built-in wire electro-discharge grinding. Different thicknesses of chromium films were coated on borosilicate glass substrates. Unwanted chromium metal was machined through to the transparent glass substrate, leaving behind the desired pattern. In this study, lines were machined at different voltages, using electrodes of 20 _m in diameter, and no significant wear of electrodes was observed. The machined regions on the specimens were quantified in terms of linewidth deviation and light transmission. The experimental results showed that the linewidth deviations for all three specimens are below the 10% cut-off threshold. The best average light transmission obtained from this experiment was 75.8% at 90 V. The results gathered so far, suggests that the application of micro-EDM to produce a photomask is an acceptable process.     

柱切换LC-MS/MS分析吸毒尿样中的吗啡、O6-单乙酰吗啡、可待因、乙酰可待因

建立在线固相萃取即柱切换LC-MS/MS方法,分析吸毒者尿样中的吗啡、O⁶-单乙酰吗啡、可待因、乙酰可待因。以吗啡-d₃为内标,预处理柱为Oasis HLB 2.1 mm×20 mm×25 μm,分析柱为Xterra MS C₁₈ 2.1 mm×150 mm×3.5 μm,用水作预处理流动相,分析流动相用含甲酸铵和甲酸的水、乙腈梯度洗脱,质谱采用电喷雾离子源,正离子MRM扫描。100 μL尿样直接进样分析,尿样中吗啡、O⁶-单乙酰吗啡、可待因、乙酰可待因的检测限为 0.3～1 μg/L,线性关系良好,相关系数γ在0.999 1以上。     

Experimental study on micro EDM-drilling of Ti6Al4V using helical electrode

There is a growing interest in the machining of micro-holes with high aspect-ratio in difficult-to-machine alloys for the aerospace industry. Processes based on electro discharge machining (EDM) and developed for the manufacture of both micro-electrode and micro-hole are actually used, but most of them involve micro-EDM machines. In this work, the influence of EDM parameters on material removal rate, electrode wear, machining time and micro-hole quality when machining Ti6Al4V is studied. Due to an inefficient removal of debris when increasing hole depth, a new strategy based on the use of helical-shaped electrodes has been proposed. The influence of helix angle and flute depth with respect to process performance has been addressed. Main results include 37% reduction in machining times (hole diameter 800 μm) when using electrode helix angle of 45° and flute-depth of 50 μm, and an additional 19% with flute-depth of 150 μm. Holes of 661 μm diameter and as much as 6.81 mm depth, which yields in aspect ratio of 10:1, have successfully been machined in Ti6Al4V.     

Fabrication of micro rods by twin-mirroring-wire tangential feed micro electrical discharge grinding

In micro electrical discharge machining (micro-EDM), the precision fabrication of cylindrical micro rods is difficult to achieve with a high processing efficiency. In order to overcome this challenge, this paper proposes a new processing method, which is denoted as twin-mirroring-wire tangential feed micro electrical discharge grinding (TMTF-WEDG). The machining principle, characteristics, and realization of the new method are firstly introduced. Then, the advantages of TMTF-WEDG in terms of machining efficiency and accuracy are demonstrated. The experimental results have shown that the machining efficiency can be increased to more than 70% in comparison with conventional tangential-feed wire electrical discharge grinding. It has also been proved that a minimum removal of material corresponding to a reduction of less than 1 μm in the diameter of a micro rod can be obtained by TMTF-WEDG. This considerably helps in improving the accuracy and repeatability of the machining process. A deviation of less than 1 μm on the diameter of a micro rod has been obtained in a length range of 800 μm. The process repeatability in machining five micro rods has been established to be below 2 μm. The proposed method is therefore of great significance for improving the machining efficiency and ensuring a high precision in the shaping process of cylindrical micro rods.     

基于免形状测量模式的复杂形状测量机设计

为了高精度高效率地测量数学模型未知的复杂几何形状,介绍了"免形状测量模式",分析了该测量模式对仪器的基本要求,基于该模式设计了一台移动工作台式测量机。测量机以直线电机为驱动元件,以高精度长光栅为测量元件。为减小被测件重量对测量机的影响,设计了封闭式真空负压的空气静压气浮导轨和共平面的H形二维结构。设计了具有制动功能的Z轴和气浮隔振等关键部件。仪器量程为300 mm×300 mm×300 mm,测量不确定度为1.8μm,能测量数学模型未知的复杂几何形状。     

Precise Micro-Assembly Through an Integration of Micro-EDM and Nd-YAG

Micro-EDM (micro electro-discharge machining) integrated with Nd-YAG laser as a novel process for precise micro-assembly is presented in the paper. In the integrated system the individual micro-parts assembled can be machined using micro-EDM, and accurately moved to the desired position using ultra-precision motion control, and fuse bonded with a laser beam. This process is demonstrated through two cases of a precise endless diamond wire saw defined as a pin-to-pin and a pin-to-plate micro-mould using the novel integrated system. As a result of this on-line assembly process, the pin–plate positioning accuracy and perpendicularity can be maintained, and a smooth pin–pin joint can also be obtained.     

Study on burr formation in micro-machining using micro-tools fabricated by micro-EDM

The purpose of this study is to study burr formation in micro-machining using micro-tools. The micro-tools employed are fabricated by micro-EDM using the wire electro-discharge grinding (WEDG) method in the micro-EDM/milling machine we had already developed. Micro tungsten-carbide tool with a minimum of 31-μm in diameter had been fabricated. The simple-shaped micro-tool fabricated is able to perform the micro-machining operation which is a combination of micro-milling and grinding processes. Micro-slot and micro thin-walled structure had been produced on Al 6061-T6 materials successfully. Burr formation in micro-machining is investigated experimentally and classified into four types: primary burr, needle-like burr, feathery burr and minor burr. Formation mechanisms of these burrs and the relationship between their existence and the machining condition are discussed.