激光选区熔化成型件尺寸精度研究及在免组装机构直接制造中的应用

发布时间：2018-02-20 15:11

本文关键词： 激光选区熔化尺寸精度工艺参数免组装机构　出处：《华南理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：激光选区熔化(Selective Laser Melting,SLM)能够直接成型致密度高、机械性能优良、结构复杂的金属构件,具有传统加工方法无法比拟的很多优点,但是其成型件尺寸精度不高是该技术的一大缺陷。为了改善SLM成型件的尺寸精度,本文首先分析了SLM成型的尺寸误差来源,然后研究了工艺参数对成型件尺寸精度的影响,最后采用优化的工艺参数成型了尺寸精度良好的免组装机构。全文研究内容和成果如下:1)系统分析了SLM成型的尺寸误差来源。主要包括前期数据处理误差、SLM加工成型误差、后处理误差。前期数据处理主要有以下误差来源:CAD模型转换成STL文件格式、支撑添加不当、分层处理。SLM成型加工过程中主要有以下误差来源:机器误差、激光深穿透、光斑直径、材料收缩变形、粉末粘附、加工参数、材料性能以及一些其他的细节因素。后处理过程中主要有以下误差来源:支撑去除、零件环境的改变、打磨、抛光、修补、涂覆等。2)研究了工艺参数对SLM成型件尺寸精度的影响。在光斑补偿为0时,尺寸精度随激光功率、体能量密度的增大而降低;随扫描速度、扫描间距的增大而升高。在扫描策略方面,S形单方向扫描要好于Z形单方向扫描;层错扫描和正交扫描要好于单方向扫描;勾边操作会降低成型件尺寸精度;S形正交层错扫描要好于轮廓偏移扫描。建立了光斑补偿与扫描误差、体能量密度之间的对应关系式,采用该关系式优化光斑补偿值,改善了SLM成型件的尺寸精度。3)研究了SLM成型典型几何结构和间隙结构的成型能力与尺寸精度。获得了厚度为0.15mm的方板,直径为0.1mm的圆柱,直径为0.4mm的竖直圆孔,直径为0.5mm的悬垂圆孔,边长为0.5mm的悬垂方孔,跨度为3mm的水平悬垂结构,极限尺寸为0.2mm的间隙特征。方板、尖角、圆柱的尺寸误差随尺寸增大而增大;竖直圆孔的尺寸误差随尺寸增大从负误差变为正误差后继续增大;悬垂圆孔的圆度误差随尺寸增大而增大;间隙特征的尺寸精度随倾斜角度的增大而升高,随能量密度的增大而降低。4)成型了高精度免组装机构——兰花手链和双曲柄连杆传动式自行车。优化了免组装机构的结构特征,改善了组装形态、摆放方式、支撑结构,成型的免组装机构尺寸精度保持在±0.1mm范围之内。
[Abstract]:Laser selective Laser melting (SLM) can directly form metal components with high density, excellent mechanical properties and complex structure, which have many advantages that can not be compared with traditional processing methods. In order to improve the dimensional accuracy of SLM, this paper first analyzes the source of dimensional error of SLM forming, and then studies the influence of process parameters on the dimensional accuracy of forming parts. Finally, an assembly free mechanism with good dimensional accuracy is formed by optimizing process parameters. The main contents and results of this paper are as follows: 1) the source of dimension error of SLM molding is analyzed systematically, which mainly includes the error of pre-processing data processing and the forming error of SLM machining. The error of post-processing. There are the following error sources: STL model converted into STL file format, improper support addition, and the following error sources in the process of delamination processing: machine error, laser penetration, Spot diameter, material shrinkage and deformation, powder adhesion, processing parameters, material properties, and some other detail factors. The main error sources in the post-processing process are: support removal, part environment change, polishing, mending, mending, The effect of process parameters on the dimensional accuracy of SLM molded parts is studied. When the spot compensation is 0:00, the dimensional accuracy decreases with the increase of laser power and bulk energy density, and with the scanning speed, the dimension accuracy decreases with the increase of laser power and bulk energy density. In terms of scanning strategy, the scanning strategy of S shape is better than that of Z type single direction scan, and that of slice fault scan and orthogonal scan is better than that of single direction scan. The trimming operation can reduce the dimension accuracy of the forming parts and the S-shape orthogonal lamination fault scanning is better than the contour offset scan. The corresponding relationship between spot compensation and scanning error, volume energy density is established, and the compensation value of light spot is optimized by the formula. The forming ability and dimensional accuracy of typical geometric structure and clearance structure of SLM forming were studied. The square plate with thickness of 0.15 mm, the cylinder with diameter of 0.1 mm and the vertical hole with diameter of 0.4 mm were obtained. The diameter of the circular hole is 0.5 mm, the side length of the hole is 0.5 mm, the span of the horizontal drape structure is 3 mm, the clearance characteristic of the limit size is 0.2 mm. The dimension error of the square plate, the sharp angle and the cylinder increases with the increase of the size. The dimension error of vertical circular hole increases with the increase of size from negative error to positive error, the roundness error of vertical circular hole increases with the increase of size, and the dimensional accuracy of clearance characteristic increases with the increase of inclined angle. With the increase of energy density, a high-precision no-assembly mechanism, orchid bracelet and double-crank linkage drive bicycle is formed. The structural characteristics of the no-assembly mechanism are optimized, and the assembly form, arrangement, and supporting structure are improved. The dimensional accuracy of the moulded non-assembly mechanism is kept in the range of 卤0.1 mm.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG665

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