基于双电层电容的微细电解加工间隙的在线检测

根据微细电解加工中工具电极下端面面积远小于工件表面的非对称特征,在水基中性盐钝性电解液侧流冲入和金属电极处于钝化状态的条件下,提出了一种基于双电层电容的微细电解加工间隙的在线检测方法．在微细工具电极和／或工件上不外加传感器的前提下,利用工具电彬溶液界面上双电层电容值随加工间隙增大而单调递增的变化关系,精确、快速地实现加工间隙的在线检测．在冲液速度为1．058m／s的条件下,当加工间隙在O．100μm时,可在数毫秒内在线检测出微细电解加工间隙的大小,数值仿真与实验测量值之间的最大相对误差小于10％．为实现高精度、高质量、稳定的微细电解加工提供必要条件．     

采用疏水材料侧壁绝缘电极的微细电解加工实验

微细电解加工中工具电极和工件之间的加工间隙是影响加工效果的核心因素.工具电极侧壁施加绝缘膜的工艺方法,可显著改变侧面加工间隙内的电场分布,提高加工精度,同时保持原有的加工效率,有着良好的应用前景.本文基于仿真方法,分析了绝缘膜对端面加工间隙和侧面加工间隙的影响规律,研究了绝缘膜疏水性质对电解加工中产生的氢气泡运动的吸附作用对微细电解加工的影响.在直径为数十到数百微米的钨丝侧壁制备出可用于微细电解加工的几微米厚的硅胶疏水材料侧壁绝缘薄膜.在硝酸钠电解液中,实现了不锈钢材料上将微气泡附着于电极前端与绝缘膜结合处、保护绝缘膜和约束杂散腐蚀的微细电解端面分层扫描加工效果.     

三维微细电火花伺服扫描加工工艺

为提高三维微细电火花加工的加工效率,从而达到工业应用目的,采用放电间隙伺服控制实时补偿电极损耗的技术路线,提出了三维微细电火花伺服扫描加工方法．基础实验验证了伺服扫描加工每层加工深度的一致性,研究了横向扫描加工速度对加工深度的影响规律．在小于1mm2加工区域内的三维结构加工实验结果显示,伺服扫描加工可以便捷地实现三维微小结构的加工成型．进一步在工件与电极之间附加激振,可大幅度地提高放电脉冲的有效利用率以及加工效率．采用φ100μm的钨丝电极,在铜试件上加工深度300μm的典型三维形状,加工时间小于50min．     

微细槽的电化学铣削加工

为了研究不锈钢微细槽的电化学铣削加工技术,使用微细的、旋转的圆柱电极作为电化学加工的阴极,采用脉冲电压电化学加工技术用类似铣削加工的方法加工微细槽.研究了脉冲宽度对电极和微细槽侧面加工间隙的影响,并对微细槽铣削加工过程中的电场和流场进行了分析.在相同的电压幅值和平均电压条件下,脉冲宽度越大,侧面加工间隙越大.电场和流场分析表明,微细槽的侧面加工间隙和侧面倾斜度随着脉冲宽度的减小以及进给速度的增加而减小.当脉冲宽度小于工件表面双电层充电时间常数时,采用钝化电解液能够减小电化学杂散腐蚀和微细槽的侧面倾斜度.当脉冲宽度为0.4μs、进给速度为24μm/min时,微细槽的侧面倾斜度很小,侧面加工间隙达到10μm.实验结果表明,采用超短脉冲电化学铣削加工方法和合适的电解液,能够提高微细槽的加工精度.     

微细电化学加工技术

开展了微细电化学加工技术的试验研究工作,内容包括微细电铸和微细电解加工．讨论了微细电化学加工的工艺特点和主要技术步骤．针对若干典型微结构,提出了相应的微细电化学加工方法和技术方案,采取了纳秒脉宽脉冲电流、电化学微铣削等手段,结合若干实例进行了加工试验,例如：微缝电解加工、微轴电解加工、微针尖电解加工及微齿轮模具模芯电铸成型等,获得了很好的试验结果．提出的加工方法在金属零件微制造方面有着重要的应用前景．     

飞秒激光双光子微细并行加工方法

飞秒激光三维微细加工技术具有真三维的制作能力和亚微米的加工分辨率等特点,因此获得越来越多的关注,但其串行工艺加工效率低是其技术难点．为了提高加工效率,搭建了一套飞秒激光并行加工平台,利用微透镜阵列实现飞秒激光分束聚焦,初步实现了双光子微细并行加工,在光敏树脂和玻璃上分别并行加工出多个二维结构,加工单点分辨率达到1．25μm．针对实验结果,对实验的加工一致性和分辨率进行分析,提出了进一步提高加工效率和加工一致性的方法．     

基于超纯水电化学加工的扫描直写技术

为了充分发挥电化学加工以离子状态去除材料的加工机理,实现其在微细、精密,甚至是纳米加工领域中的应用,针对绿色制造和微细加工的需求,提出以超纯水为电解液的微细电化学加工方法．采用阳离子交换膜促进超纯水解离,提高电化学加工过程中电流密度;利用微探针作为工具电极,通过数控机床控制运动轨迹保持与阳极表面的间距恒定,以不同路径横向扫描工件,即可在工件阳极表面加工出2D／3D几何结构．并通过试验加工字母“PW-ECM”,验证了超纯水作为电解液进行电化学扫描直写加工技术的可行性．     

纳秒脉冲激光对水下靶材的掩模微细刻蚀加工

在激光的传输光路中加入掩模板,采用纳秒脉冲激光对水下靶材进行了掩模微细刻蚀加工,与飞秒激光微细加工相比可显著提高加工效率,加工精度由掩模保证.在所构建的试验系统中,分别在空气中、纯水中和盐溶液中进行了加工试验,在水流的作用下,激光辐照的多余热量被带走,加工边缘热影响区明显减小.同时,水下激光辐照还会在加工区域造成光学击穿,产生等离子体冲击波,在水层的约束限制作用下,加工表现出了明显的冲击波力学效应.通过这种热-力学的复合效应,使金属材料表面产生材料去除和变形的加工效果.最终在质量分数为15%的NaNO3的溶液中,利用热-力学效应和化学反应的复合作用,实现了线宽120μm左右、热影响区小、成形精度较好的微细刻蚀加工.     

飞秒激光三维微细加工技术

双光子吸收几率与光强度的平方成正比,因此,双光子吸收引发光致聚合局限在紧密聚焦的焦点区域,通过控制焦点的扫描运动可实现高精度三维加工。基于该原理,提出了一种利用飞秒激光进行微细加工的技术。根据此技术,建立了飞秒激光三维微细加工系统,该系统包括光源系统、显微镜系统、实时监测系统和精密移动系统等。研究发现,该系统加工的直线线宽最小可达500nm;加工线宽与加工速度成反比;激光功率为2mW时,最大和最小临界加工速度分别为80μm/s和1μm/s;制备出线宽1μm,宽度5μm的“CHINA”复杂结构,以及杆间距、层间距均为5μm的三维木堆型光子晶体结构。实验证实,该技术是一种非常灵活的微细加工技术。     

铝合金电解加工工艺特性实验研究

对铝合金电解加工工艺特性进行基础实验研究.通过分析影响电解加工平衡间隙的因素,利用正交试验对加工电压、电解液温度及工件进给速度对平衡间隙的影响进行了研究.实验表明:加工电压与工件进给速度的影响较大.并同时利用实验对电解加工中的重要参数平衡状态下的实际体积电化当量ηω进行了计算.     

Machining of circular micro holes by electrochemical micro-machining process

Machining of micro holes with micro electrochemical machining (micro ECM) process has been carried out with an indigenously developed set up. This paper describes relevant problems and solutions for the circular micro holes machining process on 304 stainless steel sheets with 60 lm thickness using high speed steel cylindrical tool of diameter 500 lm and using dilute H2SO4 as electrolyte.The taper angle variation of the machined hole is analyzed and reported for different experimental setting parameters. The minimum value of the taper angle of machined holes is achieved at the parameter setting of
0.4 mol/L H2SO4, 700 kHz, 600 ns and 21 V, for stainless steel sheets and HSS tool.     

阴极侧壁绝缘对微孔电化学加工精度的影响

在微孔电化学加工中,阴极侧壁区域的工件阳极溶解极易导致加工锥度的产生.为了提高阳极溶解的定域性,采用阴极侧壁绝缘电极进行微孔电化学加工的实验研究.采用直径80～100μm的侧壁绝缘阴极,在0.5mm厚度的不锈钢板（1Cr18Ni9Ti）上加工出一系列微孔.结果表明,阴极侧壁绝缘可以很好地减少加工锥度,从而提高微孔电化学加工精度.此外,减小脉冲宽度及加工电流密度、降低电解液浓度也有益于加工精度的改善.     

ECM-abrasive polishing of metals

The combined action of abrasives and electrochemical machining (ECM) results in a better surface finish than that could be achieved by using abrasives alone. From an initial roughness of R_tm 30 to 50 nm, flat carbon steel and stainless steel specimens could be finished to a roughness of R_tm 0-4 μm. The procedures in conducting the experiments and analysing the data are discussed in this paper.     

新型静电驱动双向平动MEMS变形镜(英文)

设计了一种新型静电驱动双向平动的MEMS变形镜,其结构包括3部分:中央下电极,4个静电驱动杠杆结构以及反射镜面(上电极).该变形镜有两种驱动模式:向下驱动模式和向上驱动模式.在向上驱动时,4个杠杆结构实现了位移的放大;向下驱动时,利用了非线性弹性系数法扩展了镜面的平动范围.采用表面硅工艺完成了变形镜的加工.通过白光干涉仪对变形镜的测试表明:在向上驱动模式下,变形镜在驱动电压为31 V时位移达到1.1μm;在向下驱动模式下,变形镜在6 V的驱动电压下位移达到1.1μm.变形镜的总行程为2.2μm,达到了同样工艺下传统变形镜的3倍左右.     

Effect of deep cryotreated tungsten carbide electrode and SiC powder on EDM performance of AISI 304

Abstract

Powder mixed electric discharge machining (PMEDM) is a further advancement of conventional EDM process in which electrically conductive powder is suspended in the dielectric fluid to enhance the material removal rate (MRR) along with the surface quality. Cryotreatment is introduced in this process for improving the cutting tool properties as well as tool life. In this investigation, EDM is performed for the machining of AISI 304 stainless steel using cryotreated double tempered tungsten carbide electrode when SiC powder is suspended in the kerosene dielectric. The influence of process parameters viz. pulse on time, peak current, duty cycle, gap voltage and powder concentration on tool wear rate (TWR), surface roughness (R_a), and MRR has been studied. Metallographic analysis was carried out for the machined surfaces. By the addition of powder concentration and cryotreated double tempered electrode, significant improvement in the machining efficiency has been found out. When cryotreated electrode used MRR, TWR and R_a decreased by 12%, 24% and 13.3%, respectively and when SiC powder used MRR increased by 23.2%, TWR and R_a decreased by about 25% and 14.2%, respectively.     

High-speed machining of martensitic stainless steel using PcBN

The performance of PcBN cutting tool during its application in the mass production of components made from AISI 440B stainless steel has been considered. The experimental tests have been performed at cutting speed ranging between 350–500 m/min at dry cutting conditions. The machining operations that have been explored included facing, turning, grooving and boring and the 3D topography of the machined surface are presented. The results show that good surface finish similar to grinding and dimensional accuracy can be achieved with PcBN tools.     

Excimer laser micromachining of oblique microchannels on thin metal films using square laser spot

Excimer laser micromachining of thin metal films with a sacrificial polymer coating is a novel technique that produces features with smooth edges. Using this technique, oblique microchannels are fabricated by workpiece dragging and using a square laser spot, where the axis of traverse of the workpiece is not parallel to the edges of the square laser spot. The microchannels have serrated edges that are particular to the shape of the mask producing the spot. The edge roughness of the channels, machined with a square laser spot of side 100 μm, is found to be most affected by the fluence–spot overlap interaction, and the channel width by spot-overlap and the angle of tilt of the traversed path. Polymer coated metal films underwent close to ideal machining, aided by the clamping action of the polymer layer. Through this technique of machining post polymer coating, the edge roughnesses of the microchannels have been curtailed to less than 10 μm, and channel widths to 150 μm. This technique may be used in fabrication of oblique and circular patterns using excimer laser micromachining with rectangular and square laser spots.