陳漢明臺灣大學：機械工程學研究所馮煒良Fung, Wai-LeongWai-LeongFung2007-11-282018-06-282007-11-282018-06-282005http://ntur.lib.ntu.edu.tw//handle/246246/61348在生產過程中，有一些物件，既不能以兩片公母模來製造，亦不能用多片模塊來生產，就稱之為不可脫模物件。為了製造這一類不可脫模的物件，就必須先把其分割，使其每一片都能製造。為此我們提供了一個方法，根據可脫模性和可視性，把被定義為不可脫模的薄殼物件，分割為數個可脫模物件，而每一個分割出來的物件都能被傳統的兩片公母模所製造。本研究中我們所採用的是三角網格的模型，而輸出則是一些三角網格群組。 本研究中所提出的方法主要由兩個部份所組成。第一個部份論述水平切割的方法。物件沿ｚ軸被數個水平面所切割使得每一個切割面都得到一個輪廓。然後分析每一個切割面的輪廓，再經過本研究所提出的一個合併方法，得到了脫模方向集合。第二個部份則介紹一個切割物件的方法，利用第一個部份所得的脫模方向集合，把物件切割為數個可脫模部份。In the manufacturing process, some objects, which cannot be produced either by two-piece or multi-piece moulds, are considered as non-mouldable. An additional disassembly process to these objects should be introduced in order to make these objects manufacturable. This thesis describes a method to divide a non-mouldable thin-shell object into several mouldable pieces suitable for traditional two-piece moulding based on the surface visibility and mouldability. Triangle facet model is used in this method and the output result is a set of triangle facets. The proposed method is composed of two steps. In the first step, the object is sliced horizontally along the Z direction and a set of two-dimensional contours is obtained. Each slice is then analyzed and a set of parting directions of the object is determined with the proposed combining method. Afterwards, the object is sub-divided into several pieces according to their corresponding parting directions in the last step.Contents Chinese abstract 1 English abstract 2 Contents 3 List of figures 5 List of tables 7 Chapter 1 Introduction 8 1.1 Background and motivation 8 1.2 Related work 9 1.2.1 Parting direction 9 1.2.2 Parting line 10 1.2.3 Parting surface 11 1.2.4 Multi-piece mould 11 1.3 Organization of the thesis 12 Chapter 2 Visibility and mouldability 14 2.1 Visibility 14 2.2 Mouldability 15 Chapter 3 Determination of a parting range of a surface in two-dimensional cases 17 Chapter 4 Determination of the parting direction sets 21 4.1 Two-dimensional cases 21 4.2 Extension to three-dimensional cases 25 Chapter 5 Dividing the object into pieces 34 5.1. Without splitting scheme 34 5.2. With splitting scheme 36 Chapter 6 Implementation and examples 38 Chapter 7 Conclusions 42 References 43 List of figures Figure 1-1. Flowchart showing the overview of our approach 13 Figure 2-1. Parting range of a point on the surface 15 Figure 3-1. Point set A after rotating step and a horizontal line L lying on two lowest points 19 Figure 3-2. Parting range determined from two extreme vectors 19 Figure 4-1. Determination of concave points 24 Figure 4-2. Concave point sets of a contour 24 Figure 4-3. One of the solutions in dividing a non-mouldable object 25 Figure 4-4a. A sphere with two holes 27 Figure 4-4b. Concave point sets of (4-4a) 28 Figure 4-4c. Showing only the concave point set S viewing in y direction 28 Figure 4-4d. Set R computed from (4-4c) 29 Figure 4-5. Combination of two concave point sets in the same slice 29 Figure 4-6. Concave region C blocks the combination of region A and region B 29 Figure 5-1. Data structure of facets 35 Figure 5-2. The teeth-shaped borders of pieces 37 Figure 5-3. Data structure for splitting a triangle facet 37 Figure 6-1. Examples of the output result: divided into two pieces 39 Figure 6-2. Examples of the output result: divided into three pieces 40 Figure 6-3. Examples of the output result: divided into four pieces 40 List of tables Table 1. Time taken for each model 41569548 bytesapplication/pdfen-US脫模方向可脫模性脫模範圍parting directionmouldabilityparting rangethesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/61348/1/ntu-94-R91522609-1.pdf