本文選題：熔融沉積　切入點：成型精度　出處：《山東大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：熔融沉積成型(Fused Deposition Modeling,FDM)是國內(nèi)外應(yīng)用最廣泛的增材制造技術(shù)之一。隨著該技術(shù)的快速發(fā)展,實際應(yīng)用過程中對成型件表面粗糙度的要求越來越嚴(yán)格。其中溫度控制是順利成型的基礎(chǔ),然而實際成型過程瞬態(tài)溫度分布難以精確控制,因散熱不足造成制件表面缺陷的問題經(jīng)常發(fā)生。本文研究了散熱條件對FDM制件成型精度的影響,并在此基礎(chǔ)上進一步研究了針對聚乳酸材料(Poly Lactic Acid,PLA)成型件的化學(xué)拋光機理及工藝條件。熔融沉積成型零件的層間坍塌錯位與成型過程材料的溫度變化過程密切相關(guān),通過分析影響成型精度的主要因素,揭示了大斜率小截面典型特征成型過程中零件出現(xiàn)側(cè)面層軟化和坍塌錯位問題的機理。針對成型零件不同部位對冷熱需求相反的矛盾,分析傳統(tǒng)溫度控制方案的不足之處,提出將半導(dǎo)體制冷技術(shù)應(yīng)用于上述成型過程的散熱控制。半導(dǎo)體制冷片冷端作用于小截面正打印層,熱端應(yīng)用于已成型層的持續(xù)保溫。研究表明,這種方法既可以避免大斜率小截面的打印缺陷,同時減小了成型零件快速冷卻導(dǎo)致的翹曲變形程度。以環(huán)保材料PLA為例,研究了熔融沉積成型零件化學(xué)拋光后處理的反應(yīng)機理和工藝條件,分析不同拋光方式的特點,對拋光的化學(xué)反應(yīng)過程進行模型假設(shè)和實驗觀察驗證。結(jié)果表明,所建立的模型揭示了拋光前后表面制件側(cè)面相鄰層的溶解流動及形貌變化規(guī)律,并為制定化學(xué)拋光工藝提供參考依據(jù)。研究了化學(xué)拋光對成型零件抗拉性能的影響。研究發(fā)現(xiàn),水平成型方向?qū)υ嚇拥淖畲罂估缀鯚o影響,化學(xué)拋光后試樣抗拉性能發(fā)生明顯變化,其中拉伸強度大幅下降,斷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.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG175

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本文編號：1631466