1、Unit 5 Engineering DrawingContentslNew Words&Expressions lText&TranslationlComplex Sentence AnalysislKey to ExercisesNew Words&Expressionslcoordinate system 坐标系lCartesian k:tizin adj.笛卡尔的 lkeep track of 跟踪定位于 lWorld Coordinate System(WCS)世界坐标系 lUser Coordinate System(UCS)用户坐标系 laxis ksis n.轴lperpend
2、icularly p:pndikjulli adv.垂直地lprojection prdekn n.投影New Words&Expressionslorthographic projection 正交投影lauxiliary:gziljri adj.辅助的，补助的ldatum plane 基准面lorientation :rientein n.定位,校准lrevolve rivlv v.旋转lplanar plein adj.平面的，二维的lexploded drawing 爆炸图,分解图lpictorial pikt:ril adj.图示的New Words&Expressionslpart
3、ial view 局部视图lsymmetrical simetrikl adj.对称的 lconfiguration kn,figjurein n.构造，配置lmate meit v.配合，连接 lalign lain v.配直，校直，调准 lassembly constrain 装配约束 lthird-angle projection 第三角投影法lquadrant kwdrnt n.象限,四分仪lprofile plane 侧面ldashed line 虚线，短画线Text&Translationl1.Coordinate SystemlThe basic of all input Aut
4、oCAD is the Cartesian coordinate system,and the various methods of input(absolute or relative)rely on this system.In addition,AutoCAD has two internal coordinate systems to help you keep track of where you are in a drawing:the World Coordinate System(WCS)and the User Coordinate System(UCS).Text&Tran
5、slationlThe fixed Cartesian coordinate system locates all points on an AutoCAD drawing by defining a series of positive and negative axes to locate positions in space.Fig.5-1(a)illustrates the axis for two-dimension(2D)drawing.There is a permanent origin point(0,0)which is referenced,an x axis runni
6、ng horizontally in a positive and negative direction from the origin,and a y axis traveling perpendicularly in a vertical direction.1 When a point is located,it is based on the origin point unless you are working in the three dimensions,in which case,you will have a third axis,called the z axis(Fig.
7、5-1 b).Text&TranslationFig.5-1 The coordinate systemText&Translationl2.Types of Views lThere are many view types which may be shown,as illustrated in Fig.5-2.Text&TranslationFig.5-2 Types of viewsText&Translationl（1）Projection.An orthographic projection of an object as seen from the front,top,right
8、side,etc.l（2）Auxiliary.Any view created by projecting 90 to an inclined surface,datum plane,or along an axis.l（3）General.Any view which is oriented by the user and is not dependent upon any other view for its orientation.l（4）Detailed.Any view which is derived by taking a portion of an existing view
9、and scaling it for dimensioning and clarification purposes.l（5）Revolved.A planar,area cross-section was revolved 90 about the cutting plane line and offset alone,its length.l（6）Full View.Show the entire model.Text&Translationl（7）Half View.Show only the portion of the model on one side of a datum pla
10、ne.l（8）Broken View.Used on large objects to remove a section between two points and move the remaining sections close together.l（9）Section.Display a cross-section for a particular view.l（10）Exploded Drawing.The exploded drawing is a type of pictorial drawing designed to show several parts in their p
11、roper location prior to assembly，see Fig.5-3.Although the exploded view is not used as the working drawing for the machinist,it has an important place in mechanical technology.Exploded views appear extensively in manuals and handbooks that are used for repair and assembly of machines and other mecha
12、nisms.Text&TranslationFig.5-3 Exploded Drawing Text&Translationl（11）Partial view.When a symmetrical object is drafted,two views are sufficient to represent it（typically,one view is omitted）.A partial view can be used to substitute one of the two views.2Sectional and auxiliary views are also commonly
13、 used to present part detail.Sectional views are extremely useful in displaying the detailed design of a complicated internal configuration.If the section is symmetrical around a centerline,only the upper half needs to be shown.The lower half is typically shown only in outline.Casting designers ofte
14、n employ sectional views to explode detail.When a major surface is inclined to three projection planes,only a distorted picture can be seen.An auxiliary plane that is parallel to the major surface can be used to display an undistorted view.Text&TranslationlStudy this diagram describing mate,align,or
15、ient and insert assembly constrains,see Fig.5-4.Text&TranslationFig.5-4 Constrain for assembly the BRACKET and BUSHING partsText&Translationl3.Multiview DrawinglEngineering drawing is an abstract universal language used to represent a designers idea to others.It is the most accepted medium of commun
16、ication in all phases of industrial and engineering work.Text&TranslationlIn todays modern manufacturing industry,several types of drawing are acceptable.However,the standard is the multiview drawing，see Fig.5-5.A multiview drawing usually contains two or three views(Front,Top,and Side).Each view is
17、 an orthographic projection of a plane.In the United States and Canada,the third-angle projection is the system used,see Fig.5-6.In the figure,the four quadrants of the x-z plane(called the,and angles)are illustrated.3For the third-angle projection,we always place the object in the third quadrant an
18、d project the object in three planes.This is done by projecting the object onto the frontal,horizontal,and profile planes.The projection on the frontal plane(x-z)is fixed and the image is called the front view.With the projected image,the horizontal plane(x-y)is rotated 90 clockwise on the x axis,th
19、e result is a top view of the object.The profile plane(c-z)is rotated 90 clockwise about the z axis to obtain a right-hand side view.Hidden lines are shown by using dashed lines on the drawing.Text&TranslationFig.5-5 Multiview drawing of a bracketText&TranslationFig.5-6 Third-angle projectionText&Tr
20、anslationl1.坐标系坐标系l笛卡尔坐标系是输入AutoCAD的全部基础，各种输入方法（如绝对坐标，相对坐标）都依赖于这个系统。此外，AutoCAD有两个内部坐标系：世界坐标系（WCS）和用户坐标系（UCS），来帮助你确定所在绘图区中的位置。l通过定义一系列空间固定位置的正负轴，固定的笛卡尔坐标系可以对AutoCAD图面上的所有点进行定位。如图5-1(a)所示为用于二维绘图的坐标轴。有一个固定的参考原点（0，0），x轴从原点出发沿水平方向正负延伸，y轴从原点出发沿垂直方向上下延伸。根据原点（0，0）对其他任意一个点定位，但是在三维空间中绘图时，应该具有第三根轴，该轴叫y轴。如图5-1(
21、b)示。Text&Translation图5-1 坐标系Text&Translationl2.视图类型视图类型l有许多可以来表达的视图类型，如图5-2所示。Text&Translation图5-2 视图类型Text&Translationl（1）投影视图。从前面、顶面、右侧面等观察物体的正交投影图。l（2）辅助视图。向斜面、参考面或沿一个轴线做90投影所产生的视图。l（3）总图。由用户自行决定方位的视图，它不依赖于其方位的视图。l（4）局部放大图。为了标注尺寸和看清图形而从已知视图中取出一部分并将其放大的一种视图。l（5）旋转视图。二维平面中，横截面绕剖切线旋转90后移出一定距离的视图。l（6
22、）全视图。显示整个模型的视图。Text&Translationl（7）半视图。只显示在参考面一侧的部分视图。l（8）折断视图。为了表达大的物体，移去（中间）两点间的截面并将留下的部分移动到截面视图。l（9）剖面图。用于显示一个特定视图的横截面。l（10）分解图。分解图是在装配前显示每个零件位置关系的一种示意图，如图5-3所示。尽管机械工程师不把分解图用作工作图，但它在机械技术上占有重要位置。分解图广泛出现在维修、机器及其他机构装配的说明书和手册中。l机器部件装配的分解视图：Text&Translation 图5-3 分解视图Text&Translationl（11）局部视图。当画一个对称结构的
23、物体时，两个视图便足以表达（习惯上一个视图被省略）。局部视图可用于代替两个图之一。剖面图和辅助视图通常用于表达零件的局部细节。剖面图在用于显示一个复杂内部结构的细节设计时尤其有用。如果截面沿着中心线对称，只有上半部需要表达。下半部通常只用轮廓线显示出来。铸件设计师们利用剖面图来分解局部。当一个主要面倾斜于三个投影面时，只能看到歪曲了的图形，一个平行于主要面的辅助平面，可以来显示物体未被歪曲的视图。l研究如图5-4所示描述匹配、对齐、定位以及插入等装配约束。Text&Translation 图5-4 装配支架与轴衬零件时的约束Text&Translationl3.多视图多视图l工程图是用来向别人
24、表达设计者思想的一种抽象的通用语言。它是工业和工程中各个方面交流沟通的媒体。l在现代制造业中，有几种图纸类型是可以接受的。然而，标准的图形是视图图纸，如图5-5所示。一张多视图图纸通常包含有两个或三个视图（前、俯和侧视图）。每个视图是一个面的正交投影。在美国和加拿大，使用的系统是第三角投影，如图5-6所示。在图中显示了x-z平面的四个象限（分别称为I和N角）。对于第三角投影来讲，总是将物体放在第三象限，同时将物体投影到三个面上。这是通过将物体投影到正面、水平面和侧面上来实现的。物体在前平面（x-z平面）上的投影是固定的，其图像称为前视图。水平面（x-y平面）上的投影图沿x轴顺时针转90,得到物
25、体的俯视图。侧面（y-z平面）上的投影图绕z轴顺时针转90，得到右视图。被遮隐的线在视图中用虚线表示。Text&Translation图5-5 支架的多视图Text&Translation图5-6 第三角视图 Complex Sentence Analysisl1 When a point is located,it is based on the origin point unless you are working in the three dimensions,in which case,you will have a third axis,called the z axis.根据原点（
26、0，0）对其他任意一个点定位，但是在三维空间中绘图时，应该具有第三根轴，该轴称为z轴。lunless:引导让步状语从句l in.case 在情况下，which指代you are working in the three dimensionsComplex Sentence Analysisl2 Sectional and auxiliary views are also commonly used to present part detail.剖面图和辅助视图同样经常被用来表示零件视图。lbe used to do:被用来做，注意区分该短语与be used to doing 的区别，be us
27、ed to doing表示习惯做某事Complex Sentence Analysisl 3 For the third-angle projection,we always place the object in the third quadrant and project the object in three planes.对于第三角投影来讲，总是将物体放在第三象限，同时将物体投影到三个面上。Key to Exercisesl.Translate the following phrases into Chinese or English.l1.工程制图l2.coordinate syst
28、em l3.世界坐标系 l4.User Coordinate System(UCS)l5.正交投影l6.datum plane l7.分解图l8.partial viewl9.第三角投影法l10.profile plane Key to Exercisesl.Mark the following statements with True(T)or False(F)according to the text.l1.Tl2.Fl3.Fl4.Tl5.FKey to Exercisesl.Fill in the blanks with the suitable words or phrases giv
29、en below.l1.draftedl2.sufficientl3.auxiliaryl4.extremelyl5.internal configurationl6.is parallel toKey to Exercisesl.Translate the Chinese parts given in the brackets into English.l1.the Cartesian coordinate systeml2.by defining a series of positive and negative axes to locate positions in spacel3.you are working in the three dimensionsl4.for dimensioning and clarification purposesl5.all phases of industrial and engineering worklThe end!
