粉凝式積層製造系統用液滴控制機構的創新設計與實作

Abstract

現在的醫療進步如此快速，在手術過程中所需要的材料也跟著醫療的進步，慢慢地淘汰不適用的材料，骨移植術中填補病患骨頭的空缺所需的材料也是如此，碳酸鈣材料被發現可被人體降解吸收，降解出來的鈣離子有助於骨骼的生長。近年來，快速製作人體骨骼模型的3D積層製造技術逐步被開發應用，大多採用噴墨頭技術將平舖在2D移動平台的粉質成型材料(例:碳酸鈣等)依繪製的3D幾何模型分層凝結成型。但考慮到溶液中有較大分子成份物質時，噴嘴直徑需適度增加或液滴成型或噴灑方式需另行因應開發。 本論文主要是探討此技術有別於常用的微級液滴而著眼於1μm~500μm等級的液滴所需要的水凝式3D粉末積層列印製造所需的噴頭設計;本研究採取經濟實用的設計構想，以常見的連續式泵浦噴頭噴出的水柱搭配特殊的液滴產生器，即改良連續式泵浦噴頭成為可控制的微小液滴產生器，在此噴頭前方加裝液滴控制閥，使連續的水柱變成直徑約0.1mm的液滴。 本論文設計不同造型的液滴控制閥，透過有限元軟體ANSYS系統的Fluent流體力學模組模擬不同液滴控制閥對連續式泵浦噴頭噴出的水柱形成液滴的效果，我們採用Fluent系統中的多相流模型與動網格分析模組進行流場的分析，多相流模擬水與空氣之間的相互作用，可以模擬水柱噴出水的樣子，動網格可以模擬液滴控制閥的移動，透過Fluent的多相流與動網格模擬液滴控制閥產生的微小液滴動態流場與液滴的形狀，據以進行液滴控制閥的評估與設計改良。經由液滴產生器的流場分析與實驗測試，本研究已設計出能將連續水柱有效產生微小液滴的液滴控制閥，由模擬與實際實驗結果顯示所設計的模組具有適量控制液滴體積與成形的效果，並且可完成2D平板與3D造型的水凝粉末積層製造的實際成效，可提供生醫領域等3D粉末積層列印技術的應用與參考。

This paper proposes an innovative droplet generator with a special designed cyclical valve to form a powder additive manufacturing system. The design of the proposed droplet valve is provided for the powder coagulation ball of about 1μm~500μm, The micro droplet generator had been developed by combining a common continuous type liquid pump, nozzle and a proposed liquid droplet control value. By using the droplets control valve mounted on the head of the nozzle, the specified diameter of the generated droplet is restricted in about 0.1mm. In this study, different shapes of droplet control valves were designed assisted by the analysis and simulation of Fluent. Fluent is one of the useful fluid dynamics analysis software provided by ANSYS. For simulating the dynamic moving processes of the control valve, the function modules of multiphase flow model and moving mesh analysis module have been selected to analyze the flow phenomenon of the droplet. The interaction between water and air was also simulated and demonstrated by multiphase flow simulation. Thus the spraying route of the water column and generated droplet could be simulated. The geometry and dimension of the shape design of control valve is one of the focus of the study, The current parameters were concluded after systemized evaluation by using Fluent simulation. After several flow analysis and experimental testing, this study has designed a water droplets control valve that can effectively produce tiny droplets from water column. The successful powder coagulated experimental models have demonstrated the accepted function results of the proposed method and droplet control device. The simulation and actual experimental results by means of the vision observation of high speed camera show that the designed control module can cyclically provide the consistent amount of liquid droplets to from a 3D powder model. The prototype of the 3D hydrogel powder additive manufacturing machine has also been built to demonstrate the results. All the results could be references to biomedical or 3D printing technology.