【作者】 范晖；

【导师】 黄因慧；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2009， 博士

【摘要】 快速原型制造技术(Rapid Prototyping Manufacture, RPM)是20世纪80年代初发展起来的一项重要的制造技术,它采用离散堆积的技术思想,以叠层制造方式成形复杂的零部件或模具。自其闻世以来,制造出具有实际功能的金属零件,一直是RPM领域研究者的关注方向。电铸是另一种通过非接触性加工的电沉积方法制造金属零件的技术,它具有加工时无切削应力变形、无热影响区、无工具损耗、加工精度高、成本经济、适用范围广等优点,因此非常适合作为各种精密、异型、复杂等难以用传统加工方法制取或加工成本很高的金属零件的制造手段。本文将电铸和快速原型制造技术的核心思想“叠层制造”系统地结合起来,开发了一种成形金属零件的新方法—叠层模板电沉积成形技术。它的加工原理可表述为:首先通过对目标零件进行分层切片处理,制作出一组具有特定轮廓的屏蔽模板,金属阳离子逐层、选择性地沉积至模板限定的区域内,最终形成以模板型腔为侧面边界的金属零件。该技术融合了原型制造技术和电铸技术的优点,具有适于制造复杂形状零件,成品零件机械性能较好,加工成本低廉的特点。它主要针对毫米级加工尺度上的微小型金属结构器件制造,是特种成形技术领域内新型工艺研究的一次有益的探索。本文进行了叠层模板电沉积法成形金属铜零件的基础试验研究,并进行了以下主要工作:(1)提出了将叠层制造技术与电沉积技术相结合于一体制造金属零件的成形技术,阐述了叠层模板电沉积直接成形金属零件技术的成形原理;在对有关的电化学基本理论、快速成型技术、电沉积技术和方法分析和总结的基础上,立足于现有的试验条件,设计和实现具有可行性的加工方式和工艺路线。(2)针对试验具体环境,开展对叠层模板电沉积设备的试验研制,整个试验系统包括三个部分:加工控制系统、电铸液系统、电沉积系统。对现有的电化学加工平台设备进行改造、完善,并在其基础上进行专有设备的设计和制造,建立符合试验要求的叠层模板电沉积加工系统。(3)针对叠层模板电沉积的技术特点,选择适宜的分层算法并开展相关分层软件的设计,实现了对STL格式下任意CAD模型的分层切割操作,完成分层文件与模板数控加工系统的对接和兼容;同时,基于叠层模板电沉积中的操作环境,选取合适的模板材料,设计了模板的加工流程及在加工中的配置方式。(4)使用有限元仿真软件建立相关电场模型,初步分析电场分布在电极尺寸、辅助阴极、模板厚度等加工参数改变时的变化规律,并对试验中可能出现的问题进行预分析,为试验的进行提供参考依据。(5)系统研究了叠层模板电沉积中存在的工艺问题,包括最关键的问题—单层模板电铸中由于非均匀电场分布导致的沉积金属厚度极度不均。通过改变试验环境,包括设置旋转阴极和辅助阴极,改变电流参数以及采用脉冲电流和换向脉冲电流,特别是对换向脉冲电流的参数(正负脉冲的脉宽、频率、工作时间、关断时间以及电流密度)进行反复优化,并从理论上对负脉冲电流改善沉积层均匀性的作用进行了分析,获得了平整性好的模板电沉积层。(6)成形了一组具有不同形状和不同厚度的铜的零件,验证了叠层模板电沉积制造小型金属零件的可行性,并对试验样品进行了性能测试和精度测试,结果表明,零件具有较好的机械性能。最后,对该技术存在的不足作了分析,并提出了相应的改进方向和措施。更多还原

【Abstract】 Rapid Prototyping Manufacture (RPM) is an important fabrication technology using the concept of discrete-piling. It produces complicated parts or moulds in the manner of laminated fabrication. Since introduction of RPM in early 1980s, direct and economical production of metal parts satisfying market demand has been always pursued by RPM researchers worldwide. Electroforming is another widely accepted fabrication technology that employs electro-deposition, a non-contact processing method, to form metallic article, hence being advantaged in the following aspects including high accuracy to replicating sample mould, strong adaptability and solid mechanical behavior of the electroformed parts because of none of mechanical contact between tool and workpiece, therefore avoiding such defects as deformation, stress, tool-loss or heat-affected zone. Resultingly, in the engineering of small-sized and involuted metal parts, electroforming is more competent than conventional machining processes if dealing with operational difficulty and production cost.In this thesis, by systematically integrating the electroforming method with Laminated Object Manufacturing (LOM), the core concept of RPM, a novel technique to form metal part, namely laminated template electro-deposition (LTE) is presented. According to mechanism, the designated operational sequence of this technique begins with slicing of the target-part in STL format in order to make a series of patterned shielding templates. In the next step metal ion selectively deposits, layer by layer, into blank areas that templates determine and, finally, forms metal parts within templates inside-wall. LTE shares a few of properties with both RPM and electro-deposition, for instance, strong ability of producing complex metal articles, well behavior of finished products as well as low maintenance cost. As a valuable exploration into the field of metal part forming via special process, it is intentionally focused on the millimeter-scaled metallic structure production.In this thesis, the experimental research into producing copper parts are carried out and the major research works are as follows:1. The strategy combining LOM with electro-deposition method to form metal part and the mechanism of LTE were originally put forward. On the basis of understanding of the electrochemical theory, rapid prototyping technology and electrodeposition method, a set of feasible processing way and process route was drafted in line with current experimental conditions.2. In consideration of characteristics in LTE, an experimental system capable of fullfilling LTE requirement was constructed through updating the current electrochemical lab workbench and adding specially-built devices to this platform. This experimental system consists of three major parts: servo-control feed unit, electrolyte refreshing unit and electro-deposition unit.3. A slicing software that embeds an appropriately-selected hierarchical algorithm was achieved by programming tool. The software fully takes LTE requirement into account and allows any 3-d CAD model in STL-format for slicing. The study of software interface linking sliced files with NC machining system and the compatibility in data transmission were illustrated. The procedure of template-material selection, cutting process of patterned template and template configuration manner in experiment were repectively introduced.4. An experimentally-oriented computational model was established through finite element analysis software to estimate electric field distribution. Based on it, the dependence of experimental conditions such as electrode dimension, position of auxiliary cathode as well as template thickness on the electric field was analyzed and some potential problems were pre-analyzed to provide reference on the real operation of LTE.5. Studies of main technological problems in LTE experiment were demonstrated. The key obstacle was considered as how to avoid extremely uneven thickness of metal deposit layer, which is commonly generated by nonuniform electric-field distribution in planar deposition. A few of additional measures and assistant apparatus concerning the change of test environment, were tried, which includes setting rotating cathode and auxiliary cathode, variation of current parameters as well as adopting pulse current and reversing pulse current. Especially for reversing pulse current, the parameters such as pulse frequency of anodic and catholic, pulse width, the working time, off time and current density were variously modulated for optimization. The mechanism how the negative pulse current works to improve deposit uniformity was discussed. Experimental results reveal that these applied approaches favor formation of uniform and smooth deposit layer to some extent.6. The fabrication of a group of copper parts in varied shapes and thickness were presented to demonstrate the feasibility of using this method as an alternative small-sized metal part manufacturing technique. Mechanical tests and precision measurement were conducted on these samples, showing that the finished parts have well mechanical property. Methodology and solution for the improvement were proposed on the basis of imperfection analysis regarding this method.更多还原