【作者】 刘勇；

【导师】 朱荻；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 随着科学技术以及微机电系统的发展,零件尺寸越来越趋于微小型化。从产品尺度特征来划分,通常将1-1000μm的系统称为微系统,其相对应的微细加工技术已成为各工业发达国家广泛关注和重点投入的研究热点。微结构中的重要一类是金属微结构,产品微型化、精密化和高新技术产品的研制生产对微尺度金属复杂结构件加工技术有着迫切的需求。因此,发展针对微尺度的,具有三维加工能力、能够加工金属及其合金材料的微细加工方法已经成为当前微细制造领域迫在眉睫的研究课题。本文结合微细电解加工技术和微机械铣削的基本思想,提出一种新的微细加工方法:微细电解铣削加工。原理上阴极电极不会损耗,采用微米级直径的柱状电极,可加工出数微米至数十微米尺度的复杂微结构件。提出的技术主要面向航空航天、精密仪器、生物医疗等领域。本文的主要内容包括以下几个方面:(1)建立了微细电解铣削加工的理论模型。在分析了纳秒脉冲电流微细电解加工基本原理的基础上,基于界面双电层理论,建立了微细电解铣削加工分步控制数学模型,为后续的加工试验提供了重要的理论指导,并对影响加工性能的因素进行了分析。(2)搭建了一套三维微细电解铣削加工系统。该加工系统具备高分辨率低速微进给、三轴联动、高回转精度、短路检测与保护和绝缘抗振等功能,并基于Labwindows/CVI虚拟仪器平台开发了一套与机床硬件配套的三维微细电解铣削加工控制与检测软件系统。(3)提出了在线制备两种微电极的新工艺。一是基于电化学刻蚀技术,提出了多阶柱状电极的制备方法,建立了多阶柱状电极的数学控制与预测模型,制备出一系列不同阶数的末段直径为10μm的柱状电极;二是利用单脉冲火花放电技术,通过控制放电能量,成功加工出了一系列微球头柱状电极,末端球形圆度好,并具有镜面级的表面粗糙度。最后,基于有限元电场仿真,分析了不同形状微电极的多种应用场合。(4)进行了微细复杂结构的电解铣削加工工艺试验。在以高温合金GH3030为主的多种材料上进行了微细电解铣削加工工艺试验,分析了加工电压、脉冲宽度、脉冲周期、电极直径、电解液参数等对加工的影响规律。根据理论模型,应用了薄分层铣削策略,研究了铣削层厚度对起始点形状精度、加工稳定性及加工效率的影响。应用优化的参数成功加工出特征尺寸为5μm,形状精度高、表面质量好的微细三维微阶梯型腔和高精度的凹半球结构。(5)利用旋转的微螺旋电极在高温合金GH3030上进行了微小结构的高速电解铣削加工工艺试验。重点研究了电极转速对加工精度、加工稳定性和表面粗糙度的影响。另外,分析了加工电压、脉冲宽度、电解液参数等对加工的影响规律。应用优化的参数成功加工出特征尺寸为40μm,形状精度高、表面质量好的典型微小结构。更多还原

【Abstract】 With the development of science and technology and Micro-Electro-Mechanical System (MEMS), parts and components become more and more miniaturized size. The system dimension, which is between 1 and 1000μm, is usually called micro system according to the scale features of the products. The corresponding micro machining technology has become a research hotspot in the industrially developed countries.The metal micro-structure is an important class of micro structures. Product miniaturization, precision and development of high-tech product have the urgent demand to the micro metal processing technology of micro scale complex structures. Therefore, the development for a micromachining technology, which has the capability to machining three-dimensional structures on metals and alloy materials, has become a hot issue in the micro-manufacturing field.Micro electrochemical milling (MECM), which is a combination of micro milling and electrochemical micro machining, is proposed as a new method of micro machining technology in this paper. Because of no electrode wear, the micrometer scale cylindrical electrode can be used as the tool in MECM, and the complex structures of micrometer or tens micrometer can be fabricated. The new technology can be used in the field of aerospace industry, precise instrument, biomedical devices and so on. The doctoral dissertation consists of five sections, including:(1) The fundamental theory of MECM is investigated. The theoretical model of MECM is founded, which is an important theoretical guidance for the following experiments, based on the charging process of interfacial electric double layer. In addition, the effects of various parameters on machining quality are analyzed, and then the correlative technical solutions are proposed.(2) A set of 3D machining system of MECM is established. The machining system has the following characteristics, such as micro-feeding with high-resolution and low speed, triaxiality linkage, high rotational accuracy, short-circuit detection and protection, vibration insulation and so on. The real-time control and data acquisition system for 3D micro electrochemical milling is founded using devices of virtual instruments, and the software of the system is designed based on Labwindows/CVI.(3) Two new methods of fabricating the micrometer scale electrodes used in MECM are investigated. First, the fabricated method of the micro multi-stepped cylindrical electrode is analyzed. Then, a mathematical control model for fabricating the micro multi-stepped cylindrical electrode is set up. It is proved that the experimental and theoretical values have a good agreement by the experiment of a third-stepped microelectrode. After that, based on the above multi-stepped cylindrical electrode, the type of micro cylindrical electrode with a spherical end, which has good roundness and mirror-class surface quality, is fabricated by using single electric discharge technology and through controlling the discharge parameters. Finally, based on electric field analysis, various applications are analyzed by using different micro electrodes.(4) Sets of experiments are carried out to fabricate micro complex structures on various metals, such as, nickelbase superalloys GH3030, nikel and stainless steel. The impacts of applied voltage, pulse on time, pulse period, electrode diameter, electrolyte parameters on the machining process are experimentally investigated. According to the theoretical model, strategy of milling by thin layer is applied. The impacts of layer thickness on the shape accuracy, machining stability and machining efficiency are experimentally investigated. Finally, using the optimized parameters, some high-precision micro 3-D staircase structures with minimum feature size of 5μm and hemispherical cavities are fabricated successfully.(5) A series of experiments are carried out to fabricate small structures on nickelbase superalloys GH3030. The effects of rotation rate on machining quality are experimentally investigated emphatically. In addition, the impacts of applied voltage, pulse on time, electrolyte concentration on the machining accuracy are experimentally investigated. Finally, using the optimized parameters, some small structures with high shape accuracy, good surface quality and minimum feature size of 40μm are fabricated successfully.更多还原