This is because in the process of drawing, it is necessary to establish various "blocks", "layers" and styles. With the modification of drawings, CAD files become larger and larger. The following are specific solutions:

1. First, open the CAD software and enter the shortcut key "PU" at the command line.

2. In the pop-up dialog box, check the two options shown in the box below.

3. Next, click Clear All.

4. If a dialog box pops up to confirm the cleaning, click Yes to All to streamline the file successfully.