五軸同步3D列印機無需輔助支架於高複雜度物件積層製造之應用

Abstract

近年來，數位製造技術受到了學術界和工業界的極大關注，它可以製造幾何形狀複雜的物件，且具有客製化製造與多種材料選擇的優點。熔融沈積成型（Fused Deposition Modeling）和光固化成型（Stereolithography Apparatus）是數位製造中較為廣泛使用的兩個技術，因為此兩種技術在成本和品質之間有取得很好的平衡，其中熔融沈積成型（FDM）是3D列印眾多方法中最受歡迎的一種技術，也是本論文中所使用與探討的積層製造技術，但是熔融沈積成型（FDM）技術採用逐層方式堆疊製造，其中在製造過程中需要為懸空的部分添加支撐結構以防止列印失敗，支撐結構的添加減慢了列印的速度，亦增加列印材料之費用，並會在成品表面上留下痕跡，這會使得在去除支撐材時損壞成品的表面品質。由於打印方式是逐層疊加的，因此列印模型的強度在垂直於層的方向上受到限制，特別是當外力從不同方向施加時，層與層之間不良的粘合性成為抵抗外力的弱點。本文中所提出的演算法在我們台大智慧機器人及自動化實驗室開發的五軸同步3D列印機上進行實驗，並克服了以上敘述的兩個問題。 為了克服支撐結構的問題，在硬體和軟體方面有各種相關的研究成果，近年來各種機器人製造系統被引入積層製造中，本文中的五軸同步3D列印機是龍門式設備，可以實現多軸3D列印。將給定的模型基於幾何性質進行分割，形成數個子零件，每個子零件可以達到無支架需求的列印，而每個子物件的G-code則透過切層軟體獲得，後續本論文中所提出的五軸列印軌跡生成演算法，用來獲得完整的五軸同步3D列印的G-code，我們成功地透過各種實體模型來展示無支撐列印的結果。 對於強度不足的問題，我們提出了基於表面列印軌跡的同步五軸列印演算法。五軸列印具有不同方向列印的功能，因此與僅在固定方向上進行列印相比，列印物件的強度可透過表面列印被大大提升，用於破壞性實驗的測試樣品成功地於五軸同步表面列印中完成，最後透過三點彎曲試驗和拉伸試驗的破壞性實驗，對列印的樣品進行強度分析，並顯示出表面列印可以提高列印模型的強度。

Digital manufacturing technologies have received significant attention from both academia and industry in recent years. It can produce geometrically complex objects directly from 3D model data. Manufacturing customization and the use of various materials are the advantages of digital manufacturing. Fused Deposition Modeling (FDM) and Stereolithography Apparatus (SLA) are two widely used approaches in digital manufacturing because they achieve a very good balance between the cost and quality. FDM is the most popular one among the numerous methods of 3D printing. In this thesis, we use FDM basic principle to conduct additive manufacturing (AM) process. However, FDM technology is in layer-by-layer manner, where supporting structures need to be added for overhanging areas during the manufacturing process. The addition of supporting structures, not only increases material costs but also slows down the speed of fabrication and introduces artifacts onto the finished surface, which can damage the actual product upon removing the supporting material. The strength of the printed models is restricted in the direction of perpendicular to the layers since the printing style is in layer by layer fashion. The poor adhesion between the layers becomes a weakness to resist external force, especially when the force exerted from different directions. In this thesis, the algorithms are proposed to solve these two issues and implemented under the five axes synchronous 3D printing machine developed in our NTU Intelligent Robotics and Automation Lab. For overcoming the issue of supporting structures, there are various researches to improve in the aspects of hardware and software. Various robotic fabrication systems have been introduced in recent years. The developed five axes synchronous 3D printing machine is a gantry-type equipment to conduct multi-axis synchronous 3D printing in our experiment. A geometry-based decomposition method is used to divide a given model into several sub-components. Each sub-component can be printed under self-support, which means that the sub-component can be printed without supporting structures. The G-code format of each sub-component is obtained by slicing software separately. An algorithm of five axes printing trajectory generation is proposed to combine the G-code of each sub-component. The five axes printing trajectory is implemented in synchronous five axes printing machine to demonstrate the results of printing without supporting structures. Algorithms for synchronous five axes printing based on the surface printing trajectory have been proposed to overcome the lack of strength issue. Five axes printing can achieve the goal of printing in different orientations so that the strength of the printed parts is greatly enhanced in comparison with the printing in a fixed direction only. The five axes synchronous 3D printing has been successfully demonstrated with physical object printing. The strength analysis of printed parts is also performed under the three-point bending test and the tensile test to show the evidential results of improving the strength of the printed object models.