第2章正投影法原理

1、,Form of Projection 投影的形成Types of Projection 投影法分類Features of Orthographic Projection 正投影特性Three-view of Component 物體的三視圖Ex

2、ercises 練習題,Principles of Orthographic Projection 正 投 影 法 原 理,,請點擊相應標題顯示其內(nèi)容,Form of Projection 投影的形成,Projection method : When the line of projection passes through the

3、 object and the pre - established plane, there will be graphics produced on the plane. This method is called projection.,投影法： 投影法是投射線通過物體，向選定的平面投射， 并在該面上得到圖形的方法。,請點擊鼠標左鍵顯示后面內(nèi)容,,,,

4、Types of Projection 投影法分類,Projection method投影法,,Central projection method 中心投影法,( The central projection is mainly used for the pictorial drawings of buildings. 一般多用于建筑圖樣 ),Parallel projection method 平行投影法,( It

5、is used in most engineering drawings. 廣泛用于機械、電子、化工等行業(yè)的圖樣),請點擊鼠標左鍵顯示后面內(nèi)容,3. Homophyly: When planar features or lines are inclined to the 類似性 projection plane in general, the projection produ

6、ces similar shapes of the original feature. The length of projected lines will be shorter than the real length. 當圖形或直線傾斜于投影面時，圖形的投影

7、成類似形,線 段的投影長度比實長短。,2. Accumulation: When planar features or lines are orthogonal to the 積聚性 projection plane, the projection accumulates to a line

8、 or a point. 當圖形或直線垂直于投影面時,其投影積聚成一直線或點。,1. Authenticity: When planar features or lines are in parallel with the 真實性 projection plane, the projection shows the real shape

9、 or true length of the features being projected. 當平面圖形或直線平行于投影面時,其投影反映實形或?qū)嶉L。,,,,,,,,,,,,,,,,Features of Orthographic Projection 正投影特性,請點擊鼠標左鍵顯示后面內(nèi)容,,1. Form of three-view dr

10、awings 三視圖的形成,Three-View of Component 物體的三視圖,請點擊鼠標左鍵顯示后面內(nèi)容,Single orthographic projection單面正投影,How shall we do it? 如何解決？,A plan of an object is not always sufficient to describe it completely. 僅有物體的一個投影不能

11、確定 它的空間形狀。,Additional orthographic views can be drawn to sufficiently describe an object. It is necessary to use multiple views in engineering drawings. 為了確定物體的空間形狀, 需要增加投影面。故在工程圖樣中多采用多面視圖。,These axes meet a

12、t a point which is called the origin. 三投影軸垂直相交于原點O.,Y-axis→Y軸,,,,,,,,,Three-View of Component 物體的三視圖,請點擊鼠標左鍵顯示后面內(nèi)容,1) Set up three-view projection system 建立三面投影體系The three projection planes are orthogon

13、al from each other. Make up of one projection system.采用三個相互垂直的投影面,構(gòu)成投影體系。,,V-plane → Vertical plane 正(垂直)平面,H-plane → Horizontal plane 水平面,W-plane→ Wall(Auxiliary vertical) plane 側(cè)(輔助垂直)平面,The intersection lines o

14、f the three projection planes are called the axes of projection. 三投影面的交線為投影軸,,X-axis→X軸,Z-axis→Z軸,To draw three-view drawings on a drawing sheet將三投影面展成一個平面 The V-Plane is first fixed. V面不動

15、 The H-Plane turns down 90?. H面向下轉(zhuǎn)90?,Y軸記為YH , The W-Plane turns right 90?. W面向右轉(zhuǎn)90?,Y軸記為YW 。,The drawing produced on the profile projection plane (W-Plane).由左向右觀察將物體向W面投影而得到的視圖。,,2)

16、Draw three views 畫三視圖,Front view主視圖：,Top view俯視圖:,,The drawing produced on the frontal plane (V-Plane).由前向后觀察將物體向V面投影而得到的視圖；,The drawing produced on the horizontal projection plane (H-Plane)由上向下觀察將物體向H面投影而得到的視圖；,L

17、lft view左視圖:,,,,,,請點擊鼠標左鍵顯示后面內(nèi)容,Three-View of Component 物體的三視圖,,2. View positions and rules for producing three-view drawings 三視圖的位置關(guān)系和投影規(guī)律,1) Positions 位置關(guān)系,2) Rules 投影規(guī)律,,45°,The height of the fron

18、t view and the left-side view shouldbe aligned and is equal.主、側(cè)視圖高平齊；,The width of the top view and the left-side view shouldalso be aligned and is equal.俯、側(cè)視圖寬相等。,The length of the front view and the top view sho

19、uldbe aligned and is equal.主、俯視圖長對正；,,,請點擊鼠標左鍵顯示后面內(nèi)容,Three-View of Component 物體的三視圖,Front view 主視圖,Left-side view 側(cè)視圖,Length align 長對正,Height align高平齊,Width equality寬相等,,Top view 俯視圖,(圖線有重合時的優(yōu)先順序為：粗實線、虛線、細點畫線、雙

20、點畫線、細實線),1) Define the scale, select the size of drawing sheet.確定圖幅和比例；,2) Choose a direction for front view projection. 確定主視圖的觀察方向；,(使其主要表面平行或垂直于投影面,能表達更多的結(jié)構(gòu)形狀),3)Draw the datum line, noticing that each view is in prope

21、r distance. 布置各視圖的位置；,4) Project the object from three different directions and draw the corresponding views. 按照三等規(guī)律畫其三視圖；,5) Check and correct , erase all unnecessary lines. 校核有無錯漏，擦去多余線條；,6) Draw dee

22、ply according to the demand. 按標準圖線加深視圖。,(畫出基準線、對稱中心線、軸線）,(加深順序為：圓形、圓弧、水平線、垂直線、斜線),(可見輪廓線畫粗實線，不可見輪廓線畫虛線),,請點擊鼠標左鍵顯示后面內(nèi)容,Three-View of Component 物體的三視圖,3. Steps for producing three-view drawings. 畫物體三視圖步驟,,請點擊鼠標左鍵顯示后面內(nèi)

23、容,,,,,,,,,,,Plan or top　view,Front view,Left view,,,1.Draw three views according to pictorial drawing. 根據(jù)立體圖畫出主、俯、左三個視圖。,由于投影面的大小與視圖無關(guān)。因此,在畫三視圖時,不必畫出投影面的邊框。,Exercises 練習題,1. Find out the right three views

24、 for each pictorial drawing, and make out the right number in bracket.找出與立體圖相對應的三視圖，并在括號內(nèi)填寫相應編號。,2. Draw three views according to pictorial drawing ( the front view is looked from S).根據(jù)立體圖 (所給主視圖觀察方向S)，畫出相應的三視圖。,3

25、. Draw three views according to pictorial drawing ( the front view is looked from S).根據(jù)立體圖(所給主視圖觀察方向S)，畫出相應的三視圖。,請點擊相應題目顯示其內(nèi)容,本 小 節(jié) 結(jié) 束,謝謝您的認真學習！,退出,前一頁,S（Sight or center of projection投射中心）,,,,,,,Central projection：

26、When the lines of projection meet at a point, it is called central projection. 中心投影法: 投射線匯交于一點的投影法稱為中心投影法。,請點擊鼠標左鍵顯示后面內(nèi)容,Central projection method 中心投影法,Projection lines（投射線）,Object

27、 (物體),P Projection plane (投影面),Projection(投影),,Lines of projection will be parallel (投射線平行),,,,,,空間物體用大寫字母表示。,投影用小寫字母表示。,Parallel projection: When the lines of projection are parallel with

28、 each other, it is called parallel projection. 平行投影法 投射線互相平行的投影法稱為平行投影法。,請點擊鼠標左鍵顯示后面內(nèi)容,Parallel projection method 平行投影法,Object (物體),P Projection plane (投影面),Projection(投影),S,,(一般作為輔助圖樣),A

29、xonometric projection 軸測圖,Parallel Projection method 平行投影法,(光線S?P投影面),Oblique projection method斜投影法,,Orthogonal projection正投影圖,(作為正式的工程圖樣),Orthographic projection method 正投影法,(光線S?P投影面),p,,s,,s,請點擊鼠標左鍵顯示后面內(nèi)容

30、,90°,?90°,,,S,S,,,,,Orthogonal projection 正投影圖,正投影圖準確,真實,作圖簡單,但立體感不強。,Axonometric projection 軸測圖,軸測圖立體感強,但作圖較復雜,Priority of coinciding lines 圖線重合時的優(yōu)先順序,圖線有重合時的優(yōu)先順序為：粗實線、虛線、細點畫線、雙點畫線、細實線。,1. Find out the

31、right three views for each pictorial drawing, and make out the right number in each bracket. 找出與立體圖相對應的三視 圖，并在括號內(nèi)填寫相應編號。,請點擊解答顯示其內(nèi)容,1,2,3,4,5,6,7,8,9,10,11,12,,,,,,,,,,,,,2. Draw three views ac

32、cording to pictorial drawing ( the front view is looked from S). 根據(jù)立體圖 (所給主視圖觀察方向S)，畫出相應的三視圖。,請點擊解答顯示其內(nèi)容,3. Draw three views according to pictorial drawing ( the front view is looked from S). 根據(jù)