生物医用材料聚醚醚酮熔融沉积成型系统的结构设计及工艺优化

发布时间：2018-06-17 01:52

本文选题：聚醚醚酮 + 熔融沉积成型　；参考：《电子科技大学》2017年硕士论文

【摘要】：新兴特种高分子材料聚醚醚酮(Poly Ether Ether Ketone,PEEK)以其优异的机械性能、生物相容性、耐磨性、耐蚀性以及杨氏模量与人体骨骼相近等诸多优点,被视为骨损伤修复和骨骼代替的理想材料,适合在人体内长期植入。然而,目前PEEK材料自身只能采用注塑或激光烧结成型技术成型制造,限制了其在临床医学骨科手术中的应用。而熔融沉积成型(Fused Deposition Modeling,FDM)作为一种基于增材制造的先进加工技术,拥有高度定制化、制件周期短、制件结构复杂等工艺特点,克服了PEEK人工骨制作困难、无法定制的缺点,将是未来临床医学一个重要的研究方向。针对PEEK熔点高、粘度大的材料特点以及一般FDM设备无法完成PEEK打印的技术瓶颈,本文开发出了一套适用于PEEK的FDM系统,并对成型工艺进行优化。为满足PEEK材料的熔融沉积成型工艺条件,从整机设计参数入手,对新型PEEK FDM打印装备的机械系统进行结构设计,包括传动系统、机身结构、成型热床、喷头系统等,并完成各个机构的三维建模与装配。本文改进了加热系统及温控系统,优化了喷嘴流道内部结构。采用有限元分析软件ANSYS对喷头系统结构做模态分析,得到结构模态参数,为喷头系统的结构优化提供依据。采用流体动力学软件FLUENT研究了PEEK熔融沉积成型过程中在喷头流道内的流动情况,模拟得到PEEK熔体的温度、速度、压力分布云图。结果显示,成型温度影响材料的粘度、温度梯度以及加热速率,成型速度与流道压力的大小成正比,喷嘴口速度分布呈中心向外逐步减小。基于热力学原理模拟了FDM成型过程的温度场及应力场。根据其工艺特点,运用参数化编程语言(APDL)以及“生死单元”技术实现不同成型路径、成型速度、成型温度等仿真条件参数控制,完成FDM成型过程的热应力耦合分析。分析对比不同成型参数条件下的成型结果,其中提高成型环境温度和沿短边扫描成型能有效降低成型过程中产生的热应力,为PEEK熔融沉积成型工艺参数的优化提供理论依据。运用本文设计的FDM系统完成PEEK标准拉伸件打印。为分析成型温度、分层厚度、成型速度、材料填充料对PEEK成型件机械性能的影响,设计四因素三水平9组正交拉伸试验,分别将拉伸强度和断裂伸长率作为综合工艺指标做极差对比并得到最优工艺参数水平组合,为工艺优化提供实验依据。
[Abstract]:Poly ether ketone (PEEK), a new special polymer material, has many advantages such as excellent mechanical properties, biocompatibility, wear resistance, corrosion resistance and Young's modulus. As an ideal material for bone repair and bone replacement, it is suitable for long-term implantation in human body. However, peek material can only be made by injection molding or laser sintering molding, which limits its application in orthopedic surgery in clinical medicine. As an advanced processing technology based on adding material, the fused deposition molding (FDM) has the characteristics of high customization, short manufacturing period and complicated structure, which overcomes the difficulties of making peek artificial bone and cannot be customized. It will be an important research direction of clinical medicine in the future. In view of the characteristics of peek material with high melting point and high viscosity, and the technical bottleneck that ordinary FDM equipment can not complete peek printing, a set of FDM system suitable for peek is developed in this paper, and the molding process is optimized. In order to meet the technological conditions of melt deposition forming of peek material, the mechanical system of new type peek FDM printing equipment is designed from the design parameters of the whole machine, including transmission system, fuselage structure, forming hot bed, sprinkler system, etc. And complete the three-dimensional modeling and assembly of each mechanism. In this paper, the heating system and temperature control system are improved, and the internal structure of nozzle runner is optimized. The finite element analysis software ANSYS is used to analyze the structure of the nozzle system, and the modal parameters of the structure are obtained, which provides the basis for the structural optimization of the nozzle system. The fluid dynamics software fluent was used to study the flow of peek melt in the nozzle channel, and the temperature, velocity and pressure distribution of peek melt were simulated. The results show that the molding temperature affects the viscosity, temperature gradient and heating rate of the material, the molding speed is proportional to the pressure of the flow channel, and the velocity distribution of the nozzle decreases gradually in a central direction. Based on the thermodynamic principle, the temperature field and stress field of FDM forming process are simulated. According to its technological characteristics, the parameterized programming language APDL) and the "birth and death unit" technology are used to realize the control of simulation parameters such as different forming paths, molding speed, molding temperature, etc. The thermo-stress coupling analysis of FDM molding process is completed. By analyzing and comparing the forming results under different forming parameters, it is found that increasing the ambient temperature and scanning along the short edge can effectively reduce the thermal stress in the forming process, which provides a theoretical basis for the optimization of the process parameters of peek melt deposition molding. The FDM system designed in this paper is used to print peek standard stretch parts. In order to analyze the influence of forming temperature, delamination thickness, forming speed and filling material on the mechanical properties of peek, nine groups of orthogonal tensile tests with four factors and three levels were designed. The tensile strength and elongation at break were compared as the comprehensive process indexes and the optimum process parameters were obtained. The experimental results provided the experimental basis for the process optimization.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ317;R318.08

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