【作者】 辛宗生；

【导师】 郭艳玲；

【作者基本信息】 东北林业大学 ， 机械设计及理论， 2011， 博士

【摘要】 选区激光烧结(Selective Laser Sintering, SLS)借助于计算机辅助设计与制造,采用分层制造叠加原理,将固体粉末直接成形为三维实体零件。用聚合物及其复合粉末成形功能件是SLS技术的一个重要发展方向,具有广阔的应用前景。虽然国内外研究者对聚合物及其复合粉末的制备与SLS成形进行了较为深入的研究,但仍存在许多技术性难题急需解决,由此针对木塑复合材料进行选区激光烧结关键性技术的系统研究具有一定的前瞻性。综述了快速成形技术产生的背景、国内外研究现状和发展趋势,重点阐述和分析了选区激光烧结技术国内外的研究现状、工作原理和工艺特点,在此基础上提出了本课题的研究目的和意义。重点解决木塑快速成形件性能及关键技术的问题,达到降低材料成本和扩大快速原型材料应用范围的目的。综合借鉴现有的有关界面相容和烧结理论方面的成果,仔细分析了木粉、热熔胶(PES)和塑料(PP)的特性,重点研究了它们混合后的相容性及烧结特性,在此基础上进行了混粉的制备和工艺流程的制定。通过试验和分析,采取了一定措施改善木塑界面的相容性。通过研究提出了改善木塑界面相容性有二种途径：通过碱化方法对木纤维进行表面处理,降低与疏水性聚合物间的相斥作用；添加合适的界面相容剂。通过试验和SEM分析,指出了在木塑复合材料烧结过程中存在范德华力、静电力和毛细管力等力且这些力的作用促使木塑粉末颗粒的有效接触,形成烧结颈,产生分子链段这一现象,揭示出分子链段内旋转是聚合物烧结的物质主要迁移机制这一本质,且发现随着温度的升高,分子链段的柔性增加,刚性减小这一特性。通过理论和试验,较详细分析了木塑复合材料在选区激光烧结过程中所产生的温度场、热应力及热应变场的变化趋势,并以能量密度的角度对热量传输和分布作了一定的阐述。通过试验和理论分析,系统地研究了SLS成形件的精度问题,分别讨论了成形件精度的各种组成部分及其形成原因和影响,概括出成形件的误差包括机器系统的误差,CAD模型误差,工艺误差及次级烧结和Z轴“盈余”所产生的误差。着重指出成形零件的主要形状误差是成形翘曲,成形翘曲主要是由层与层之间收缩的不连续引起；翘曲分为一维翘曲和二维翘曲。在成形机上烧结木塑复合材料并形成试件,进而对试件进行力学性能的测试、扫描电镜SEM的分析及烧结工艺参数的优化试验,试验表明：木塑复合材料的拉伸强度、弯曲强度、拉伸模量和弯曲模量均随着木粉和MAH的加入量的变化而变化；相容剂的使用有利于复合材料力学性能的提高；采用优化烧结工艺参数成形的烧结件密度大,力学性能大大提高。通过解决上述关键性技术难题,促进了国内SLS用聚合物及其复合粉末的发展,填补了国际和国内利用木塑复合材料进行激光烧结技术的空白,对推动我国SLS技术的整体进步,进一步扩展SLS技术在各个行业中的应用具有一定的意义。更多还原

【Abstract】 The Selective Laser Sintering is based on the principle of laminated manufacturing and superposition and also take advantage of CAD&CAM technology to make solid powder into three-dimensional parts. Using polymers and compound powder to make functional components is one of the typical directions of SLS development and has promising prospects on application. Although domestic and international researchers have studied on this technology in depth, there are still considerable critical technical problems need to be solved. So to speak, research on the critical issue of SLS on wood-plastic composite materials is promising.This article gives a brief introduction for the definition of rapid prototype and background for generation, present situation of research both in domestically and foreign country and developing trends, especially have a discussion and analysis on SLS technology’s present situation of research both in domestically and foreign country, principles of working and characteristics of process, what’s more, based on the former research, it demonstrates the purpose and significance of this issue. The purpose of the article is mainly on solving the problems of properties and critical technology of rapid prototype components based on wood powder to reach the objective of reducing cost and enlarge the area of application of rapid prototype material.This article refers to the present achievement of interface-compatible and interface-sintering principles and carefully analyzes the properties of wood powder, PES and PP, mainly researching on the compatibility after mixture and it’s sintering principle, and base on this, I conducted the making of mixed powder and its process.Through test and analysis, the compatibility of interface between wood-plastic has been improved. According to the research, there are two methods with which we can improve the compatibility. One method is that we can process the surface of wood fibers by alkalization to reduce the repulsion with hydrobolicity, meanwhile, the interfacial compatiblizer should be used. Through test and SEM analysis, we conclude that the force such as van force, electrostatic force and capillary force and so forth make material contact efficiently while sintering, meanwhile it attains sintering neck and molecule segment, and it’s internal rotation is the main mechanism of material migration of polymers sintering. Molecule segment’s flexibility increases and it’s strength decreases with the increasing of temperature.This article has a specific analysis on the temperature field of wood-plastic powder bed, thermal stress and strain field in the process of SLS, and discusses heat transmission and distribution from the perspective of power density. The article talks about the precision problem of formed parts in SLS systematically though test and theory, and discusses all composing parts of precision, its forming reason and its effects respectively, which makes me draw the following conclusions that the errors of formed components consists of the error of machine’s system, CAD mold, process, secondary sintering and surplus within Z axis. It points out that the main shape error of formed components is mainly due to forming warp age which is caused by the inconsistency of contract among layers, and we can divide one-dimensional warpage and two-dimensional warpage.To sintering the compound material and finally manages to make the test components,then did some mechanics property test,analysis with SEM,as well as sintering process parameter optimization, the tests shows that with the change of wood-plastic powder and MAH, the wood-plastic powder’s stretching, bending and impact strength are changed. Compatibilizer is good for the improvement of mechanics property of compound materials. The using of optimized sintering parameter can bring us high density test parts whose mechanics property has been improved greatly at the same time.This research promotes the development of domestic polymers and its compound powder used in SLS and fills in the blank of application of wood-plastics material in laser sintering, and does well for boosting the progressing of domestic SLS technology, and also has significance in improving the using of SLS technology in all professions.更多还原