STL format is used mainly in 3D printers and is well supported in 3D modeling / CAD software so modeled parts can be exported for the 3D printing. Your best bet for CATDRAWING to STL conversion would be to use CATIA from which .catdrawing files originate. But perhaps some 3D/CAD conversion utilities can be of use here.
Convert CATIA drawing file to Stereolithography CAD file.
We found 3 software records in the database related to .catdrawing to .stl file format conversion.
Microsoft Windows software - convert catdrawing to stl on Windows
A CAD converter with huge format support
Convert from catdrawing file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned catdrawing to stl. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A 3D CAD translation softwate
A PLM/CAD/CAM/CAE software suite