It appears that Autodesk 3D scene files (.a3s) can be converted or exported to formats for 3D printing (.stl) with Autodesk software only. Sadly, we do not know about any other 3rd party tools that could capable of this conversion.
Convert Autodesk 3D scene file to Stereolithography CAD file.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert a3s to stl on Windows
A popular 3D animation software, 3ds Max (previously known as 3D Studio Max) is used by professional to create stunning 3D content. It contains modeling capabilities, flexible plug-in architecture, scripting language, etc. It is mostly used by computer game developers. It is also used to create movie visual effects. 3ds Max is only for Microsoft Windows.
Convert from a3s file
to stl file
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.