散热条件对FDM成型精度的影响及表面化学抛光工艺研究

发布时间：2018-03-18 21:54

本文选题：熔融沉积　切入点：成型精度　出处：《山东大学》2017年硕士论文　论文类型：学位论文

【摘要】：熔融沉积成型(Fused Deposition Modeling,FDM)是国内外应用最广泛的增材制造技术之一。随着该技术的快速发展,实际应用过程中对成型件表面粗糙度的要求越来越严格。其中温度控制是顺利成型的基础,然而实际成型过程瞬态温度分布难以精确控制,因散热不足造成制件表面缺陷的问题经常发生。本文研究了散热条件对FDM制件成型精度的影响,并在此基础上进一步研究了针对聚乳酸材料(Poly Lactic Acid,PLA)成型件的化学抛光机理及工艺条件。熔融沉积成型零件的层间坍塌错位与成型过程材料的温度变化过程密切相关,通过分析影响成型精度的主要因素,揭示了大斜率小截面典型特征成型过程中零件出现侧面层软化和坍塌错位问题的机理。针对成型零件不同部位对冷热需求相反的矛盾,分析传统温度控制方案的不足之处,提出将半导体制冷技术应用于上述成型过程的散热控制。半导体制冷片冷端作用于小截面正打印层,热端应用于已成型层的持续保温。研究表明,这种方法既可以避免大斜率小截面的打印缺陷,同时减小了成型零件快速冷却导致的翘曲变形程度。以环保材料PLA为例,研究了熔融沉积成型零件化学抛光后处理的反应机理和工艺条件,分析不同抛光方式的特点,对抛光的化学反应过程进行模型假设和实验观察验证。结果表明,所建立的模型揭示了抛光前后表面制件侧面相邻层的溶解流动及形貌变化规律,并为制定化学抛光工艺提供参考依据。研究了化学抛光对成型零件抗拉性能的影响。研究发现,水平成型方向对试样的最大抗拉力几乎无影响,化学抛光后试样抗拉性能发生明显变化,其中拉伸强度大幅下降,断裂延展性有一定提高。
[Abstract]:Fused Deposition Modeling (FDM) is one of the most widely used material increasing manufacturing technologies at home and abroad. With the rapid development of this technology, In the process of practical application, the requirements of surface roughness of molded parts are more and more strict, among which temperature control is the basis of smooth forming, but the transient temperature distribution in actual forming process is difficult to control accurately. The problem of surface defects caused by insufficient heat dissipation occurs frequently. The influence of heat dissipation conditions on the forming accuracy of FDM parts is studied in this paper. On this basis, the chemical polishing mechanism and process conditions of poly-lactic acid (Poly Lactic Acid-PLA) molded parts are further studied. The interlaminar collapse dislocation of melt deposition molding parts is closely related to the process of material temperature change during the forming process. By analyzing the main factors affecting the forming accuracy, the mechanism of the side layer softening and collapse dislocation in the process of forming the typical characteristics of large slope and small cross section is revealed. In view of the contradiction between the different parts of the forming part and the opposite demand for cold and heat, Based on the analysis of the shortcomings of the traditional temperature control scheme, it is proposed that the semiconductor refrigeration technology be applied to the heat dissipation control of the above molding process. The cold end of the semiconductor refrigeration film acts on a small section of the positive print layer. The hot end is applied to the continuous heat preservation of the formed layer. The study shows that this method can not only avoid the printing defects of large slope and small cross section, but also reduce the degree of warping caused by rapid cooling of the forming parts. Take the environmentally friendly material PLA as an example, The reaction mechanism and process conditions of chemical polishing of melt deposition forming parts were studied. The characteristics of different polishing methods were analyzed. The model hypothesis and experimental observation of the chemical reaction process of polishing were carried out. The results showed that, The established model reveals the dissolution flow and morphology of adjacent layers of surface parts before and after polishing, and provides a reference for the formulation of chemical polishing process. The effects of chemical polishing on the tensile properties of molded parts are studied, and it is found that the influence of chemical polishing on the tensile properties of molded parts is studied. The direction of horizontal forming has little effect on the maximum tensile strength of the samples. The tensile properties of the samples after chemical polishing are obviously changed, in which the tensile strength is greatly decreased, and the fracture ductility is improved to a certain extent.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG175

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