臺灣博碩士論文加值系統

近年來3D列印技術越來越流行，並且運用於各種產業，如航太業、工業甚至醫學工程方面，其主要優點為客製化及快速製作，以達到縮短產品週期並提高產品設計之自由度。但是隨著產品的多樣性與複雜性，單純的加工以無法獨力製作完成，因此我們設計出複合加工機(加法及減法)，用以完成多樣且複雜的產品。並且產品可能是由多個零件或多個物件所構成的，但目前所使用的3D列印都是多個物件同一層先印完再移動至下一層，噴頭會在物件間頻繁移動，不但消耗能源而且拖累完成的時間，因此，在此論文中，我們將提出加法製作多物件流程優化之演算法以及減法路徑規劃完成客製化雕刻。
首先，在加法製作流程優化分為三大步驟，1.針對每個物件作放置之最佳化，以減少列印時所產生支架達到節省材料與去除支架的程序，2.多物件進行集裝優化(bin packing)規劃物件擺放位置，並且結合最短路徑演算法(travelling salesman problem)，有利於噴嘴移動過程中，可以使噴嘴有效率之移動，3.加法路徑優化配合硬體上的最大限制，使得列印更加有效率，對比常見方法在演算法中大量減少在物件間移動的頻率，不僅可以節省製作時間外，還可以節約能源。在加減法製作流程，當列印加工完成後並將物件資訊轉換至減法坐標系，並將物件所要雕刻區域利用保角映射(conform mapping)作攤平展開得到二維平面，並使用彈簧質量模型(spring mass model)基於三角形邊長做優化以減小攤平曲面之誤差，接下來二維圖形投影至攤平的二維平面上，再將平面轉換至物件表面，以取得減法路徑軌跡，以完成加減復合之工程，並實現在我們實驗自行開發的龍門式複合加工機上。

In recent years, three dimensional (3D) printing is the fastest growing technology. Nowadays, it has been largely applied in aerospace industry, industry and medicine engineering, etc. Additive manufacturing (AM) technologies not only reduce the new product development cycle, but also develop unique style models to satisfy users’ requirements. However, the additive manufacturing cannot complete the diversity and complexity products independently. We design the hybrid 3D printing machine including the additive and subtractive processes to complete the products. And the products may be composed of the many parts or objects. In the common slicing software, the 3D printers print an object layer by layer. However, when multiple objects are printed at the same time, the nozzle moves among objects and always increases enormous distance of the transition travel. Therefore, in this thesis, we propose a novel addition process optimization algorithm and develop the trajectory planning of the subtractive process to carve the customized logo or image.
In the beginning, the optimization of the addition process is divided into three main steps. 1. The optimization for locating each specific object is implemented to minimize the supports during the printing procedure. This step can efficiently save the materials and consume less time for remove the supports. 2. Two dimensional packing problem for planning location of multiple objects is combined with the traveling salesman problem to promote the spray efficiency of nozzle. 3. With consideration of the workspace and hardware limitation, the printing time is apparently decreased by addition path optimization. Compared with the common path planning strategy, the advantage of the proposed path planning minimizes the frequency of movement among each object. This proposed algorithm effectively decreases time consuming on printing and saves energy consuming furthermore. For subtractive process, the object information can be obtained from additive process and is transformed to subtractive coordinate system. The sculpture region of the 3D object is initially expanded into 2D space by conform mapping, and the vertices of the flattening plane are adjusted to appropriate positions using spring mass model with edge-based flattening algorithm to minimize distortion of flattening plane. Then the 2D image can be intuitively projected onto the expanded plane by geometrical transformation. The projected product in 2D space can be reversely transformed into 3D space, where the reconstructed surface is fitted onto the original surface of the object. Therefore, the subtractive part can run along the path that is generated by above steps. We have demonstrated the success of the proposed methods by using the development of hybrid 3D printing machine consisting of additive and subtractive processes in our NTU robotics and automation lab.

誌謝 I
中文摘要 II
ABSTRACT III
TABLE OF CONTENTS V
LIST OF FIGURES VIII
LIST OF TABLES XI
CHAPTER 1 INTRODUCTION 1
1.1 INTRODUCTION 1
1.2 MOTIVATION AND OBJECTIVE 2
1.3 LITERATURE REVIEW 4
1.3.1 Flattening Surface 4
1.3.2 Additive Process 4
1.3.3 Subtractive Process 5
1.3.4 Path Generation and Planning 6
1.4 ADDITIVE MANUFACTURING METHODS 7
1.4.1 Fused Deposition Modeling (FDM) 7
1.4.2 Stereo Lithography Apparatus (SLA) / Digital Light Processing (DLP) 9
1.4.3 Selective laser sintering (SLS) 10
1.4.4 Selective laser melting (SLM) 11
1.4.5 Laser metal deposition (LMD) 12
1.4.6 Compare with additive manufacturing methods 13
1.5 THESIS ORGANIZATION 14
CHAPTER 2 THE HARDWARE AND SOFTWARE 15
2.1 HARDWARE 15
2.1.1 Mechanism Design 15
2.1.2 Robot Coordinate System 16
2.1.3 System Structure 18
2.2 SOFTWARE 24
2.2.1 STL (STereoLithography) Format 24
2.2.2 Slicing Software 25
2.2.3 Direct Numerical Control (DNC) 28
2.3 MATERIAL 29
2.3.1 PLA (Polylactic Acid) 29
2.3.2 ABS (Acrylonitrile Butadiene Styrene) 30
2.3.3 PLA vs. ABS 31
CHAPTER 3 MULTI-HETEROGENEOUS OBJECTS FABRICATION FOR ADDITIVE PROCESS 32
3.1 SYSTEM STRUCTURE 32
3.2 MODEL EXTRACTION AND ANALYSIS 33
3.3 COLLISION CONSIDERATION 35
3.4 PRINTING STRATEGY EVALUATION 40
3.5 PLANNING LOCATION OF MULTIPLE OBJECTS 43
3.5.1 2D Packing Algorithm 43
3.5.2 Genetic Algorithm 44
3.5.3 Cost Function Definition 49
3.6 PRINTING PROCEDURE OPTIMIZATION 51
3.6.1 Printing path Optimization 51
3.6.2 Motion Velocity Control 52
CHAPTER 4 PROJECTION ALGORITHM BASED ON FLATTENING SURFACE FOR SUBTRACTIVE PROCESS 55
4.1 SYSTEM STRUCTURE 56
4.2 PROJECTION ALGORITHM BASED ON FLATTENING METHOD 57
4.2.1 Conformal mapping 58
4.2.2 Vertices unifying procedure in u-v plane 61
4.2.3 Adjust flattening surface 62
4.2.4 2D logo is mapped into the flattening surface 64
4.2.5 Obtain the trajectory of the shape of logo in 3D space 64
4.3 SYSTEM INTEGRATION PROCESS 65
4.3.1 Additive Coordinate System 65
4.3.2 Subtractive Coordinate System 65
4.3.1 Coordinate Transformation 67
CHAPTER 5 EXPERIMENTAL RESULTS AND DISCUSSIONS 69
5.1 MULTI-HETEROGENEOUS OBJECTS FABRICATION 69
5.1.1 Experimental Setup 69
5.1.2 Experimental Results 72
5.2 PROJECTION ALGORITHM BASED ON FLATTENING SURFACE 77
5.2.1 Experimental Setup 77
5.2.2 Experimental Results 81
CHAPTER 6 CONCLUSIONS AND FUTURE WORK 88
CHAPTER 7 OTHER APPLICATIONS 89
REFERENCES 90
VITA 94

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