2012第3讲－表达机件的常用方法-2

1、1机械图样的五种基本表示法 Five basic methods for mechanical part drawing： 视图 Views 2.剖视图 Sectional Views （剖切平面的种类 Types of cutting plane ）3. 断面图Cross-Sections 4. 局部放大图Local Enlarged Views 简化画法 Conventional drawing 介绍第三角画法 Third-angle projection第 三 讲表达机件的常用方法-IIFundamental methods for representation of mechanica

2、l parts技术制图国家标准GB/T 4458.12002 规定全剖、半剖、局部剖2用局部视图替换左视图。Replace the left side view by a local sectional view.343.1 剖切平面的种类及适用条件1.单一剖切平面Single cutting plane全剖 Full section半剖 Half section局部剖 Broken-out section斜剖视 Inclined section5 两相交的剖切平面（旋转剖）Intersecting cutting plane (Aligned section)AAAAAAA 当机件的内部结构

3、形状用一个剖切平面剖切不能表达完全，且机件又具有回转轴时。As the interior structure of one part which revolves about an axis cant be represented completely by one cutting plane section .方法： 用几个相交的剖切平面将机件剖开，先将与倾斜剖切平面接触的结构要素及相关部分转正，再进行投影。Cutting the part with two intersecting planes and rotating the aligned section view of the pa

4、rt about an axis ,then projecting it.此处无交线 No intersecting line旋转剖视图 aligned sectional view为避免实体化的感觉，肋板的纵向剖切不画剖面线。To avoid the impression of solidity, a section not showing the ribs section-lined is preferred纵向剖切到的肋板的真实投影可能会给读图人以误解。 A true-projection sectional view of a part, would be misleading whe

5、n the cutting plane passed longitudinally through the center of the rib.7 几个平行的剖切平面 Parallel cutting planes （阶梯剖offset section ） 当机件上的孔槽及空腔等内部结构不在同一平面内时。 Offset sections are used for complex parts that have a number of important features that cannot be sectioned using a straight cutting plane.AA AAA

6、A8 几个平行的剖切平面 （阶梯剖offset section ） 注意问题： 两剖切平面的转折处不应与图上的轮廓线重合，在剖视图上不应在转折处画线。The change of plane that occurs when the cutting plane is bent 90 degrees is not represented with lines in the section view. 在剖视图内不能出现不完整的要素。只有当两个要素有公共对称中心线或轴线时，可以此为界各画一半。 There shouldnt be incomplete feature on the section e

7、xcept when two features have a common center-line of symmetry or axis ( Half of each feature can be drawn with the center-line as a dividing line.)AAAAAAAA AAAA阶梯剖切平面Offset sectionAAAAAA阶梯剖视图 Offset sectional view11一. 重合断面 Revolved cross-section 断面图置于图形之内。The cross section is revolved in place and c

8、oincides with the relevant vies.用细实线绘制轮廓，加剖面符号。Contour by thin solid line and filled with section lines断面形状对称,省略标注。Label is omitted to symmetrical cross-section3.2断面图 Cross-section (called cuts for short)表达机件断面形状的方法。Used to indicate the cross sectional shape of an object.断面形状不对称：标注剖切平面位置及投影方向，不注名称。W

9、hen the cross-section is nonsymmetrical, an arrowed cutting plane symbol without name is used to label.12二. 移出断面Removed cross-section 断面图置于图形之外。The cross-section be removed to outside of the drawing.用粗实线绘制轮廓，加剖面符号。Contour by thick solid line and filled with section lines.轴上有回转面的孔、坑：断面封口。Close contou

10、r for revolutionary hole, groove点划线应垂直于轮廓线轴上非回转面的孔、坑、槽：断面开口。Open contour for non-revolutionary hole, groove or slot.1313AAA-AB-BBB当断面移出置于剖切平面的延长线上，如图形不对称，需用箭头标明投影方向The removed cross-section may be aligned with the cutting symbol and the letters may be omitted. 当断面移出不位于剖切平面的延长线上，需进行标注； If the removed

11、 cross-section may be placed in any free space on the drawing. Like A-A. In this case, the location of the cutting plane is indicated on the relevant views by the lettered cutting symbol, the direction of the projection is indicated by the arrow. 如果图形对称，可省略投影方向箭头。 When the cut is symmetric, the arro

12、ws may be omitted.如果图形对称，则无需标注； When the cut is symmetric, it may be placed on a cutting line extended and no identification is required.14A-A152:12:1 用细实线圈出被放大部位。有多处放大，需用罗马数字标明， 并在局部放大图上方标明相应的罗马数字及所用比例（相对实物） 局部放大图可画成视图、剖视图或断面图，视需要而定。3.3 局部放大图Local enlarged views当机件上部分结构的图形过小时，可以采用局部放大的比例画出。163.3 规定

13、和简化画法Conventional Representations一、肋板的画法Ribs 对于机件的肋板，如按纵向剖切，肋板不画剖面符号，而用粗实线将它与其邻接部分分开。横向剖切肋板则画出剖面线。Rib should be separated by thick solid lines but not section-lined if the cutting plane cuts along the center plane of the rib ,while section-lined if the cutting plane passes crosswise through the plat

14、e.A AAABBBBBB正确Correct错误Incorrect17二、均匀分布的肋板及孔的画法 Ribs and holes distributed uniformly肋不对称画成对称 Ribs appear as symmetrical孔未剖到画成剖到Hole appear as sectionedBBBB 若干直径相同且成规律分布的孔，可以仅画出一个或几个，其余只需用细点画线表示其中心位置。Holes with same size positioned regularly can be represented by one complete sample and the rest by

15、 center lines on their positionsAAAA18实长True length实长True length三、断开的画法 Breaks 轴、杆类较长的机件，当沿长度方向形状相同或按一定规律变化时，允许断开画出。The conventional representation of breaks is used to shorten a relatively ling piece so that it can be shown to a larger scale .标注尺寸时，仍注实长。Dimension shows the true length.拉杆轴套断开画法阶梯轴断开

16、画法19四、对称图形的画法Views of symmetrical parts 在不致引起误解时，可只画一半或四分之一。并在对称中心线的两端画出两条与其垂直的平行细实线。Symmetrical parts may be drawn as one half or a quarter of the whole , provided that no misunderstanding.对称省略图标记（symbol for symmetrical omitting）二分之一表示整体四分之一表示整体20五、机件上小平面的画法Small plane on the part 当回转体机件上的平面在图形中不能充

17、分表达时，可用相交的两条细实线表示。Small plane indicated by two diagonally drawn thin solid lines21小 结 本章所介绍的各种视图、剖视图的画法及标注方法，均系国标规定，必须很好掌握，才能画出合格的工程图纸。 简化及规定画法只介绍了常用的几种，这部分内容较多，需要时可查阅有关标准。22作业： P63 5 按规定补全主、左视图（注意剖面线的间隔和方向，各视图保持一致）6 三视图（可取适当剖视，不注尺寸）23侧视图（右）Right Side主视图Front俯视图 Top第一角投影First-Angle Projection水平投影面 Horizontal Plane正投影面 Front Plane侧投影面Right Side Plane附录：第三角投影简介Third-Angle Projection24俯视图主视图侧视图（右）展开折线水平投影面正投影面侧投影面第三角投影 Third-Angle projection25第三分角的三视图 Three Primary Views 主俯右26正面观察-主视图顶面观察-俯视图右面观察-右视图第三分角的六视图 Six Primary Views by third-angle 28六个投影面的展开 Open the