ClickFile
menu Export.At the Command prompt, enter
export.
In the Export Data dialog box, enter a file name.
Under Files of Type, select Lithography (*.stl). Click
Save.
Select one or more solid objects. All objects must be entirely
within the positive XYZ octant of the world coordinate system
(WCS). That is, their X, Y, and Z coordinates must be
greater than zero.
The file
extension .stl is automatically appended to
the file name.