今天我们学习《机械制图》——机件的常用表达方法第二部分的内容。今天的主要内容是剖视图。Today we study "Mechanical Drawing" - the second part of the common methods of expression of machine parts. Today's main content is the sectional view.
No.1 剖视图的概念和基本画法
一.剖视图的概念和基本画法
1.剖视图主要用于表达机件内部的结构形状。当机件的视图中需表达内部结构形状的细虚线过多，甚至细虚线与细虚线，细虚线与粗实线重叠，影响到清晰读图和标注尺寸时，常常用剖视图表达。为了清楚的表达机件的内部形状，假想用剖切面剖开物体，将处在观察者和剖切面之间的部分移去，而将其余部分向投影面投射所得的图形，称为剖视图，可简称剖视。
2.画剖视图的步骤：
（1）确定剖切面的位置
（2）画剖视图
（3）画剖面符号或剖面线
（4）画剖切符号，剖切线和标注剖视图的名称
I. The concept and basic drawing method of section view
1. The sectional view is mainly used to express the internal structure shape of the machine part. When the view of the machine needs to express the internal structure of the shape of the thin dotted line too much, or even thin dotted line and thin dotted line, thin dotted line and thick solid line overlap, affecting the clear reading and marking dimensions, often expressed in section view. In order to clearly express the internal shape of the machine part, suppose the object is cut open with a section, the part between the observer and the section will be removed, and the rest of the projection to the projection surface of the resulting figure, called the section view, can be referred to as the section view.
2. Steps of drawing a sectional view.
(1) determine the location of the section surface
(2) Draw the section view
(3) Draw section symbols or section lines
(4) Draw section symbols, section lines and label the name of the section view
No.2剖视图的分类
二.剖视图的分类
按照剖切面剖开物体范围的不同情况，剖视图分为全剖视图，半剖视图和局部剖视图。
1.全剖视图：用剖切平面完全地剖开物体所得的剖视图，称为全剖视图。
注：对于机件的肋，轮辐及薄壁等，如按纵向剖切，这些结构通常按不剖绘制，即不画剖面符号，而用粗实线将它与邻接部分分开。
2.半剖视图：当物体具有对称平面时，向垂直于对称平面的投影面上投射所得的图形，可以对称中心为界，一半画成剖视图，另一半画成视图，这种视图称为半剖视图。
注：在半剖视图中，半个外形视图和半个剖视图的分界线应画成细点画线，不能画出粗实线。由于图线对称，零件的内部形状已在半个剖视图中表示清楚，所以在表达外部形状的半个视图中，细虚线应省略不画。但是，如果机件的某些内部形状在半剖视图中没有表达清楚，则在表达外部形状的半个视图中，应该用细虚线画出。
3.局部剖视图：用剖切平面局部地剖开物体所得的剖视图，称为局部剖视图。
注：当单一剖切平面的剖切位置明显时，可以省略局部剖视图的标注。局部剖视图用波浪线分界，波浪线不应与图样上其他图线重合；当被剖切结构为回转体时，允许用这个结构的轴线作为局部剖视和视图的分界线。
II. Classification of sectional views
According to the different cases of the range of the cut surface cut objects, the sectional view is divided into full sectional view, half sectional view and partial sectional view.
1. Full sectional view: the sectional view obtained by completely dissecting the object with a sectional plane is called full sectional view.
Note: For the ribs, spokes and thin walls of machine parts, such as longitudinal section, these structures are usually drawn without sectioning, i.e. without drawing the section symbols, but using thick solid lines to separate it from the neighboring parts.
2. Semi-sectional view: When the object has a plane of symmetry, the figure projected on the projection plane perpendicular to the plane of symmetry can be bounded by the center of symmetry, half of which is drawn as a section view, and the other half is drawn as a view, this view is called a semi-sectional view.
Note: In the semi-sectional view, half of the profile view and half of the section view of the dividing line should be drawn as a thin dotted line, can not draw a thick solid line. Due to the symmetry of the drawing line, the internal shape of the part has been clearly expressed in the half section view, so in the expression of the external shape of the half view, the fine dotted line should be omitted not to draw. However, if some internal shape of the machine part is not clearly expressed in the half section view, then in the half view expressing the external shape, should be drawn with a thin dotted line.
3. Partial section view: the section view obtained by partially dissecting the object with a section plane is called partial section view.
Note: When the section position of a single section plane is obvious, you can omit the labeling of the partial section view. The local section view is divided by wavy lines, and the wavy lines should not overlap with other lines on the drawing; when the structure to be cut is a rotary body, the axis of the structure is allowed to be used as the dividing line between the local section view and the view.
No.3剖切面的分类和剖切方法
三.剖切面的分类和剖切方法
一般用平面剖切机件，也可用柱面剖切机件
单一剖切面：
1.用平行于某一基本投影面的平面剖切
2.用柱面剖切：采用柱面剖切机件时，剖视图应按展开绘制。
3.用不平行于任何基本投影面的剖切平面剖切：用不平行于任何基本投影面的剖切平面剖切，习惯上称为斜剖
采用斜剖视图时，按投影关系配置在与剖切符号相对应的位置；也可将剖视图平移至图纸的适当位置；在不引起误解时，还允许将图线旋转，但旋转后的图名应在“x-x”后（也可在前）加旋转方向的符号。
III. Classification of cutting surface and cutting method
Generally use plane cutting machine, also can use column surface cutting machine
Single section.
1. Cut with a plane parallel to a basic projection plane
2. Cut by column surface: when using column surface to cut the machine, the section view should be drawn according to the expansion.
3. Cut with a section plane not parallel to any basic projection plane: cut with a section plane not parallel to any basic projection plane, customarily called oblique section
When the oblique section view is used, it is configured in the position corresponding to the section symbol according to the projection relationship; the section view can also be panned to the appropriate position of the drawing; when it does not cause misunderstanding, it is also allowed to rotate the drawing line, but the name of the rotated drawing should be after "x-x" (also in front) plus the symbol of the direction of rotation.
参考资料：文字：百度；图片：微博；翻译：百度翻译
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