1、Form of Projection 投影的形成投影的形成Types of Projection 投影法分类投影法分类Features of Orthographic Projection 正投影特性正投影特性Three-view of Component 物体的三视图物体的三视图Exercises 练习题练习题Principles of Orthographic Projection 正 投 影 法 原 理请点击相应标题显示其内容请点击相应标题显示其内容2Center of projectionPlane of projectionObjectLines of projectionProje
2、ctionForm of Projection 投影的形投影的形 成成Projection method : When the line of projection passes through the 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 ： 投影法是投射线通过物体，向选定的平面投射，投影法是投射线通过物体，向选定的平面投射，并在该面上得到图形的方法。并在该面上得到图形的方法。请
3、点击鼠标左键显示后面内容请点击鼠标左键显示后面内容3Types of Projection 投影法分类投影法分类Projection method投影法投影法Central projection method 中心投影法中心投影法( The central projection is mainly used for the pictorial drawings of buildings. 一般多用于建筑图样一般多用于建筑图样 ) Parallel projection method 平行投影法平行投影法( It is used in most engineering drawings.广泛用于
4、机械、电子、化工等行业的图样广泛用于机械、电子、化工等行业的图样 ) 请点击鼠标左键显示后面内容请点击鼠标左键显示后面内容43. Homophyly: When planar features or lines are inclined to the 类似性类似性 projection plane in general, the projection produces similar shapes of the original feature. The length of projected lines will be shorter than the real length.当图形或直线倾
5、斜于投影面时，图形的投影成类似形当图形或直线倾斜于投影面时，图形的投影成类似形 ,线线 段的投影段的投影 长长 度比度比 实长实长 短短 。 2. Accumulation: When planar features or lines are orthogonal to the 积聚性积聚性 projection plane, the projection accumulates to a line or a point.当图形或直线垂直于投影面时当图形或直线垂直于投影面时 ,其投影积聚成一直线或点。其投影积聚成一直线或点。 1. Authenticity: When planar featu
6、res or lines are in parallel with the 真实性真实性 projection plane, the projection shows the real shape or true length of the features being projected.当平面图形或直线平行于投影面时当平面图形或直线平行于投影面时 ,其投影反映实形或实长。其投影反映实形或实长。 Features of Orthographic Projection 正投影特性正投影特性请点击鼠标左键显示后面内容请点击鼠标左键显示后面内容51. Form of three-view draw
7、ings 三视图的形成三视图的形成Three-View of Component 物体的三视图物体的三视图请点击鼠标左键显示后面内容请点击鼠标左键显示后面内容Single orthographic projection单面正投影单面正投影A plan of an object is not always sufficient to describe it completely.仅有物体的一个投影不能确定它的空间形状。Additional orthographic views can be drawn to sufficiently describe an object. It is neces
8、sary to use multiple views in engineering drawings. 为了确定物体的空间形状为了确定物体的空间形状 , 需要增加投影面。故在工程图需要增加投影面。故在工程图样中多采用多面视图。样中多采用多面视图。 6These axes meet at a point which is called the origin.三三 投影轴垂直相交于原点投影轴垂直相交于原点 O. Y-axis Y轴 Three-View of Component 物体的三视图物体的三视图请点击鼠标左键显示后面内容请点击鼠标左键显示后面内容1) Set up three-view p
9、rojection system 建立三面投影体系建立三面投影体系The three projection planes are orthogonal from each other. Make up of one projection system.采用三个相互垂直的投影面采用三个相互垂直的投影面 ,构成投影体系。构成投影体系。 V-plane Vertical plane 正 (垂直 )平面H-plane Horizontal plane 水 平面W-plane Wall(Auxiliary vertical) plane 侧 (辅助垂直 )平面The intersection lines
10、 of the three projection planes are called the axes of projection.三投影面的交线为投影轴三投影面的交线为投影轴 X-axis X轴 Z-axis Z轴 7To draw three-view drawings on a drawing sheet将三投影面展成一个平面将三投影面展成一个平面The V-Plane is first fixed. V面不动面不动The H-Plane turns down 90. H面向下转面向下转 90,Y轴记为轴记为 YH ,The W-Plane turns right 90.W面向右转面向右
11、转 90,Y轴记为轴记为 YW 。The drawing produced on the profile projection plane (W-Plane).由左向右由左向右 观察将物体向观察将物体向 W面投影而得到的视图面投影而得到的视图 。 2) Draw three views 画三视图画三视图Front view主主 视图视图 ：Top view俯俯 视图视图 :The drawing produced on the frontal plane (V-Plane).由前向后由前向后 观察将物体向观察将物体向 V面投影而得到的视图；面投影而得到的视图；The drawing produ
12、ced on the horizontal projection plane (H-Plane)由上向下由上向下 观察将物体向观察将物体向 H面投影而得到的视图面投影而得到的视图 ；Llft view左左 视图视图 :请点击鼠标左键显示后面内容请点击鼠标左键显示后面内容Three-View of Component 物体的三视图物体的三视图82. View positions and rules for producing three-view drawings 三视图的位置关系和投影规律三视图的位置关系和投影规律1) Positions 位置关系位置关系 2) Rules 投影规律投影规律
13、45The height of the front view and the left-side view shouldbe aligned and is equal.主、侧视图主、侧视图 高平齐高平齐 ；The width of the top view and the left-side view shouldalso be aligned and is equal.俯、侧视图俯、侧视图 宽相等宽相等 。The length of the front view and the top view shouldbe aligned and is equal.主、俯视图主、俯视图 长对正长对正
14、；请点击鼠标左键显示后面内容请点击鼠标左键显示后面内容Three-View of Component 物体的三视图物体的三视图Front view 主视图主视图 Left-side view 侧视图侧视图 Length align长对正长对正 Height align高平齐高平齐 Width equality宽相等宽相等Top view 俯视图俯视图 9(图线有重合时的优先顺序图线有重合时的优先顺序 为：粗实线、虚线、细点为：粗实线、虚线、细点画线、双点画线、细实线画线、双点画线、细实线 )1) Define the scale, select the size of drawing shee
15、t.确定图幅和比例；确定图幅和比例； 2) Choose a direction for front view projection. 确定主视图的观察方向；确定主视图的观察方向； (使其主要表面平行或垂直于投影面使其主要表面平行或垂直于投影面 ,能表达更多的结构形状能表达更多的结构形状 ) 3)Draw the datum line, noticing that each view is in proper distance. 布置各视图的位置；布置各视图的位置；4) Project the object from three different directions and draw th
16、e corresponding views. 按照三等规律画其三视图；按照三等规律画其三视图； 5) Check and correct , erase all unnecessary lines. 校核有无错漏，擦去多余线条；校核有无错漏，擦去多余线条； 6) Draw deeply according to the demand.按标准图线加深视图。按标准图线加深视图。 (画出基准线、对称中心线、轴线）画出基准线、对称中心线、轴线） (加深顺序为：圆形、圆弧、水平线、垂直线、斜线加深顺序为：圆形、圆弧、水平线、垂直线、斜线)(可见轮廓线画粗实线，不可见轮廓线画虚线可见轮廓线画粗实线，不可见
17、轮廓线画虚线 )请点击鼠标左键显示后面内容请点击鼠标左键显示后面内容Three-View of Component 物体的三视图物体的三视图3. Steps for producing three-view drawings. 画物体三视图步骤画物体三视图步骤 10请点击鼠标左键显示后面内容请点击鼠标左键显示后面内容Plan or top viewFront viewLeft view1.Draw three views according to pictorial drawing. 根据立体图画出主、俯、左三个视图。根据立体图画出主、俯、左三个视图。 由于投影面的大小与视图无关。因此 ,在画三视图时,不必画出投影面的边框。
