1. First open the CAD software, and then open a large file. Enter "PU" in the command box below, which means cleaning, as shown in the figure below.

2. Secondly, on the page that appears, you need to check "Confirm each item to be cleaned" and "Clean nested items", as shown in the following figure.

3. Then, after the inspection, click the "Clean All" button at the bottom of the page, as shown in the figure below.

4. After the last click, the information about whether to clean up will pop up. Just click the "Yes to All" button, which will reduce the file space and make it not too big, as shown in the figure below.