Manual:Traditional 2D drafting/zh-cn

可能你对 FreeCAD 感兴趣，因为你有技术绘图经验，例如使用过 AutoCAD 等软件. 你了解设计，或者你更喜欢在实际制造它们之前先绘制出来. 无论哪种情况，FreeCAD 都具有更传统的工作台： Draft Workbench，包含大多数 2D CAD 应用程序中都有的工具.

Draft 工作台虽然继承了传统 2D CAD 的工作方式，但并不局限于 2D 领域. Draft 工作台的所有工具都可以在整个 3D 空间中工作. 许多 Draft 工具，例如， Move 和 Rotate在 FreeCAD 中使用广泛，因为比起手动更改位置参数，Move 和 Rotate 更直观.

在 Draft 工作台提供的工具中，你会发现传统的绘图工具，像 Line， Circle, or  Wire (polyline), modification tools like  Move,  Rotate or  Offset, a working plane/grid system，修改工具之类，像 Move,  Rotate or  Offset, a working plane/grid system，让你精确定义正在工作的平面，以及一个完整的 snapping system ，使得相对于彼此绘制和定位元素非常容易.

为了展示 Draft 的工作流程和能力范围，我们做一个简单的练习，结果将是这个小图，一个只包含厨房顶部的小房子的平面图（一个非常荒谬的平面图，但我们可以在这里做我们想做的事，不是够了吗？）：




 * 切换到 Draft 工作台
 * 与所有技术绘图应用程序一样，正确设置环境是明智的，它将为你节省大量时间. 在菜单 Edit -> Preferences -> Draft 根据自己的喜好配置grid and working plane, Text 和 Dimension. 但是，在本练习中，我们将这些设置保留默认值.




 * 你可能需要注意一个选项，它很霸道："Fill objects with faces whenever possible" 选项. 如果选中这个选项，默认情况下 FreeCAD 将用面来填充诸如矩形或圆形这类的闭合对象，这样可能就难以捕捉到底层对象了. 你可以立即关闭此选项，或者稍后关闭每个单独对象的 "Make Face" 属性，以防止它们创建面.


 * Draft 工作台还有两个特殊的工具栏. 一个具是 visual settings，可以更改当前工作平面，打开/关闭 construction mode，设置要用于新对象的线条颜色、面的颜色、线宽和文本大小. 另一个是snap locations，可以打开/关闭网格并设置/取消设置单个 Snap locations.




 * 打开所有捕捉按钮是会带来方便，但也会使绘图变慢，因为移动鼠标光标时需要进行更多的计算. 通常只保留实际使用的那些就好了.


 * 我们先打开 construction mode，这样可以绘制一些引导线，在其基础上绘制最终的几何图形.
 * 愿意的话，将 working plane 设置为 XY. 这样无论当前视图如何，工作平面都不会改变. 如果没有设置，工作平面将自动适应当前视图，只要想在 XY（地面）平面上绘图，都应该小心注意保持在顶视图.
 * 然后，选择 [[Image:Draft_Rectangle.png|16px]] Rectangle 工具并绘制一个矩形，从点（0,0,0）开始，2 米乘 2 米（将 Z 保持为零）. 请注意，大多数 Draft 命令都完全可以使用双字母快捷键从键盘执行，而无需鼠标. 我们的第一个 2x2m 的矩形可以这样完成：re 0 Enter 0 Enter 0 Enter 2m Enter 2m Enter 0 Enter.
 * 将矩形向内复制 15cm，使用 [[Image:Draft_Offset.png|16px]] Offset 工具，打开复制模式，并给出距离 15cm.




 * 接下来，绘制几条垂直的线来定义门窗的位置，使用 [[Image:Draft_Line.png|16px]] Line 工具. 这些线与两个矩形的交叉点为我们提供帮助，来捕捉墙壁的位置. 从点（15cm，1m，0）到点（15cm，3m，0）绘制第一条线.
 * 使用 [[Image:Draft_Move.png|16px]] Move 工具，打开 Copy 模式,将这条线复制 5 次. 同时打开 Relative 模式，定义相对距离的移动，这比计算每条线的确切位置更容易. 给每个新副本任意起始点，例如，可以保留在（0,0,0），指定相对终点如下：
 * line001: x: 10cm
 * line002: x: 120cm
 * line003: x: -55cm, y: -2m
 * line004: x: 80cm
 * line005: x: 15cm




 * 这就是我们现在所需要的，所以我们可以关闭构造模式. 检查一下所有构造几何体是否已放入 "Construction" 组中，这样可以轻松地将其全部隐藏起来，甚至可以在以后完全删除它.
 * 现在用 [[Image:Draft_Wire.png|16px]] Wire 工具绘制两面墙壁. 确保 [[Image:Snap_Intersection.png|16px]] intersection snap 已打开，因为我们需要捕捉到线条和矩形的交叉点. 绘制如下两条线，单击圈出轮廓的所有点. 要使它们闭合，请再次单击第一个点，或触发 Close 按钮.




 * 可以选择两个墙，将它们的 Pattern 属性设置为 Simple，并将它们的 Pattern size 设置为合适的值，比如 0.005，这样便将它们的默认灰色改为了漂亮的阴影图案.




 * 现在，可以右键单击 Construction 组并选择 Hide Selection 来隐藏构造几何体.
 * 我们现在画窗户和门. 确保[[Image:Snap_Midpoint.png|16px]] midpoint snap 已打开，如下所示，绘制六条线：




 * 现在将更改门线，创建一个打开的门的符号. 首先使用 [[Image:Draft_Rotate.png|16px]] Rotate 工具. 单击线的端点作为旋转中心，将其起始角度设置为 0 ，结束角度为 -90'.
 * 然后用 [[Image:Draft_Arc.png|16px]] Arc 工具创建开门的弧线. 选中与上一步中使用的旋转中心相同的点作为中心，单击该线的另一个点以给出半径，然后选择起点和终点，如下所示.




 * 现在开始摆放一些家具. 首先，从左上角绘制一个矩形，放好一个厨房台面，给出 170cm 的宽度和 -60cm 的高度. 在下图中，矩形的 Transparency 属性设置为 80％，让它看起来像个漂亮的家具.
 * 然后，添加一个水槽和一个灶台. 手工绘制这些符号可能非常繁琐，通常很容易在互联网上找到它们，例如在http://www.cad-blocks.net. 在页面底部的 Downloads，为方便起见，我们从这个项目中提取了一个水槽和一个灶台，并将它们保存为 DXF 文件. 你可以访问下面的链接来下载这两个文件，右键单击 Raw 按钮，然后 另存为.
 * 将 DXF 文件插入打开的 FreeCAD 文档有两种方法，可以选择 File -> Import 菜单选项，也可以将 DXF 文件从文件浏览器拖放到 FreeCAD 窗口中来完成. DXF 文件的内容可能不会出现在当前视图的中心，具体取决于它们在DXF 文件中的位置. 可以使用菜单 View -> Standard views -> Fit all 适当缩放，看到导入的对象. 插入两个 DXF 文件，将它们移动到厨房台面上的适当位置.




 * We can now place a couple of dimensions using the [[Image:Draft_Dimension.png|16px]] Dimension tool. Dimensions are drawn by clicking 3 points: the start point, an end point, and a third point to place the dimension line. To make horizontal or vertical dimensions, even if the two first points are not aligned, press Shift while clicking the second point.
 * You can change the position of a dimension text by double-clicking the dimension in the tree view. A control point will allow you to move the text graphically. In our exercise, the "0.15" texts have been moved away for better clarity.
 * You can change the contents of the dimension text by editing their Override property. In our example, the texts of the door and window dimensions have been edited to indicate their heights:




 * Let's add some description texts using the [[Image:Draft_Text.png|16px]] Text tool. Click a point to position the text, then enter the lines of text, pressing Enter after each line. To finish, press Enter twice.
 * The indication lines (also called "leaders") that link the texts to the item they are describing are simply done with the Wire tool. Draw wires, starting from the text position, to the place being described. Once that is done, you can add a bullet or arrow at the end of the wires by setting their End Arrow property to True




 * Our drawing is now complete! Since there are quite a number of objects there, it would be wise do some cleaning and restructure everything into nice groups, to make the file easier to understand for other people:




 * We can now print our work by placing it on a Drawing sheet, which we will show later in this manual, or directly export our drawing to other CAD applications, by exporting it to a DXF file. Simply select our "Floor plan" group, select menu File -> Export, and select the Autodesk DXF format. The file can then be opened in any other 2D CAD application such as LibreCAD. You might notice some differences, depending on the configurations of each application.




 * The most important thing about the Draft Workbench, however, is that the geometry you create with it can be used as a base or easily extruded into 3D objects, simply by using the [[Image:Part_Extrude.png|16px]] Part_Extrude tool from the Part Workbench, or, to stay in Draft, the [[Image:Draft_Trimex.png|16px]] Trimex (Trim/Extend/Extrude) tool, which under the hood performs a Part Extrusion, but does it "the Draft way", that is, allows you to indicate and snap the extrusion length graphically. Experiment extruding our walls as shown below.
 * By pressing the [[Image:Draft_SelectPlane.png|16px]] working plane button after selecting a face of an object, you are also able to place the working plane anywhere, and therefore draw Draft objects in different planes, for example on top of the walls. These can then be extruded to form other 3D solids. Experiment setting the working plane on one of the top faces of the walls, then draw some rectangles up there.




 * All kinds of openings can also be done as easily by drawing Draft objects on the faces of walls, then extruding them, then using the boolean tools from the Part Workbench to subtract them from another solid, as we saw in the previous chapter.

Fundamentally, what the Draft Workbench does is provide graphical ways to create basic Part operations. While in Part you will usually position objects by setting their placement parameter, in Draft you can do it on-screen. There are times when one is better, other times when the other is preferable. Don't forget, you can create custom toolbars in one of these workbenches, add the tools from the other, and get the best of both worlds.

Downloads


 * The file created during this exercise: https://github.com/yorikvanhavre/FreeCAD-manual/blob/master/files/cabin.FCStd
 * The sink DXF file: https://github.com/yorikvanhavre/FreeCAD-manual/blob/master/files/sink.dxf
 * The cookertop DXF file: https://github.com/yorikvanhavre/FreeCAD-manual/blob/master/files/cooktop.dxf
 * The final DXF file produced during this exercise: https://github.com/yorikvanhavre/FreeCAD-manual/blob/master/files/cabin.dxf

Read more


 * The Draft Workbench
 * Snapping
 * The Draft working plane