How To Use CAD?

China PTJ Hardware Shop
7 min readNov 7, 2022


How to use CAD?What Is CAD? How to use CAD?

CAD stands for Computer Aided Design. It is the most popular auxiliary drawing software system in China, which is widely used in civil architecture, decoration, urban planning, garden design, electronic circuit, mechanical design, clothing, shoes and hats, aerospace, light industry and chemical industry and many other fields.

How To Use CAD?

As for the meaning of CAD, in the application of renderings, the role of CAD mainly lies in accurate drawing. First, the plane reference, because in many garden landscape renderings, it is impossible to use 3D to draw accurate terrain. The general approach is to import the CAD drawing into 3DMAX as a reference; The second is to draw complex graphics. In the process of making renderings, if you encounter more complex graphics or require accurate graphics that are difficult to complete in 3D, you should use CAD to help; Third, the use of some model libraries. What does CAD mean? A large number of professional application modules and software of CAD decide that it is fast and convenient in a certain field and aspect, and it is wrong not to treat it objectively.

In addition, it is difficult for workers to construct according to the renderings, because the renderings only make visible parts, and the invisible parts are not made; The exact size of the drawn model cannot be measured. Therefore, many customers will require a construction drawing, including plan, elevation, section, ceiling, circuit diagram, lamp bitmap, local detail drawing, etc. This requires us to have a strong ability to read and draw drawings. If we can’t even understand the basic plane, elevation and section drawings, we can’t make accurate renderings according to the drawings, let alone draw construction drawings according to the finished renderings.

I took the time to summarize and share some skills that I thought were dry goods. If you are a student or a junior soldier or a junior leader in the design institute, it may be of great benefit to read this summary of traditional drawing tool CAD… Of course, I hope this is a good introduction, and I hope you can leave your own experience in the message area.

To what extent is CAD proficiency? I think it can be called proficiency to finish the painting accurately in the shortest time. The “shortest time” is because CAD relies on both hands and brains. Two hands operate, and commands are king. What’s more, we often encounter unknown commands that hinder your drawing, as well as bugs… crashes… crashes… even if you are skilled, there is still room for most people to improve efficiency.

At the beginning, you should be clear about what you want to draw, be familiar with the commands or plug-ins you can deploy, and understand that the way to solve BUGs is an important way to improve efficiency, reduce overtime, and cherish life.

1、 What should I do first when I get a CAD drawing?

First copy and backup one, then thin it! Simplification is an important prerequisite to speed up the follow-up work. After all, the computer’s data processing capacity is limited

Use the command “PU” in CAD to clean up empty layers, unnecessary styles, etc;

Then adjust the view — 3D view — left/right view to check whether all figures are on the same face. If not, select “Z axis coordinate to 0” (you can directly select the figure to modify the Z coordinate to 0, and here it is recommended to use a plug-in to return to 0, because only the modification of characteristics is often useless, and you can get it by replying “Z coordinate to 0 plug-in” to the contribution official account iedaycn). Returning to 0 Z coordinate can reduce data information, The more important thing is to ensure that your drawings are on the same plane. Otherwise, the lines or surfaces you draw will not be on the same plane, either high or low. As a result, the cover cannot be filled in CAD, and the height of the imported Sketchup model will be different.
Then use the quick selection tool (shortcut key: qselect) to select useless miscellaneous lines, characters, fills, etc., and delete them. If it is a CAD with a large amount of data, this operation can greatly optimize the drawing.

If there are too many messy layers, you can also extract useful layers and put them into a new CAD drawing. You can select the required layers by using the isolated (command: layiso, or the shortcut tool called out in the following figure),

Then paste in situ (shortcut: Alt+E+D, or select Edit — Paste to Original Coordinates on the toolbar) to enter the new CAD drawing. If you can’t see it after pasting, you can use the command “Z” and then enter “A” to adjust the view frame, and then use the command “RE” to regenerate the drawing.

If the new CAD drawing is used to import Sketchup for model building, it is recommended to add a fixed frame to the original CAD drawing and then copy it, and then Ctrl+V — enter 0, 0 coordinates in the new CAD drawing to unify the drawing to the original coordinate point, so that it can be aligned in SU at that time.

Note: The copy and paste of CAD drawings must be carried out in the same CAD version. For example, if CAD2008 and CAD2017 are opened on my computer at the same time, the original drawings I opened with CAD2008 cannot be directly pasted into the drawings opened with CAD2017.

2、 The basic processing is almost complete. Now let’s start to draw the part myself

Eh? It is found that the existing CAD is incomplete and needs to trace the content on the picture. Come on, select Insert Raster Image in the toolbar, and then use the AL command to scale and align (there are many other ways to scale and align, depending on personal habits). The specific operation method can be seen in an article I published in 2015: Method of Scaling Drawings or Pictures in CAD (AL Command Version).

When zooming and aligning or there is a lot of drawing content, you also need to adjust the layer order (command: dr). You can also select the layer order through Tools — Drawing Order — Front and Back, because sometimes the functions of the toolbar will become invalid, and the shortcut keys are relatively common.

If the graph obtained is oblique, not just north and south, in order to facilitate drawing and plotting, we usually need to use the UCS command to rotate the coordinate system. Command: UCS — select X axis and Y axis — enter the command plan — enter to switch the view to plan view of UCS

When filling, you often encounter a situation where you cannot fill in. You can zoom out the view and try again, or go back to the steps mentioned earlier to check whether the graphics are coplanar. If you can’t, you can redraw the sidelines.

If it still fails, in addition to considering system variables, check the options: command OP — — Display — — check Apply entity filling
The angle of the drawing is not quite right. I want to rotate it, but I can’t determine the angle. What should I do? Enter the rotation command RO, click the object to be rotated — select the rotation base point — and then enter the command R to specify a reference angle for rotation
There are filler blocks but no edges. How to generate edges through filler blocks?

This is called rebuild hatch boundary. (Command: www, this command needs plug-ins to be available, and you can get it by replying “Rebuild hatch boundary plug-in” to the contribution official account iedaycn)
How to count the area when there are filler blocks on the sidelines?

If there is only one filling that is easy to calculate, the properties dialog box (command: ch or ctrl+1 or mo) will pop up directly, and you can view the area directly. However, most of the time, there are a lot of graphs that need area statistics. When there are many graphs, the area directly displayed is not comprehensive. At this time, we can use an area statistics plug-in. (Command: mparea, this command needs plug-ins to be available, which can be obtained by replying to “area statistics plug-in” to the contribution official account iedaycn)

Xiangyuan/Tianzheng can also be used for statistics.

Xiangyuan statistical method: Tools — Calculate — Calculate the area. Follow the prompts later;

You can search the Tianzheng statistical method to see other introductions.
The default saved CAD file is a lower version: enter OP in the drawing interface — click the Open and Save tab — select a lower version in the File Save Save As field

Thick line to wireframe function: single thick PL line to thin PL box (command: ch_plk, this command needs plug-in to be available, which can be obtained by replying “thick line to wireframe plug-in” to the contribution official account iedaycn)

Merging two polylines: command join, line to polyline: command PE
When outputting drawings, there are often educational watermark words around the drawings. If you want to remove the plug-in that can be loaded with educational watermark (this function is available only when the plug-in is needed, and can be obtained by replying “educational watermark plug-in” to the contribution official account iedaycn)

How to use all the plug-ins mentioned above?

On the toolbar, select Tools — Load Application — Select the plug-in to load — Load. The plug-in must be reloaded every time it is opened. If you do not remember the plug-in command, you can open the plug-in in Notepad to view its functions and commands.