Yes, an STL can be imported into Carbide Create Pro to make 3D toolpaths:
Which tool to use depends on what sort of work you wish to do and how you wish to approach it. Notable options include:
- Blender — for free-form 3D sculpting, but it has gained some facility for precision work, see “BlenderCAD” and “CADsketcher”
- FreeCAD — opensource 3D mechanical CAD program
- OpenSCAD — opensource programmatic 3D modeling tool
- Shapr3D — for folks w/ an iPad Pro and Apple Pencil
- Moment of Inspiration 3D — noted as being easy to use, and capable of both free-form 3D and precise mechanical CAD
- Alibre Atom3D — 3D mechanical CAD which is quite affordable
- Autodesk Fusion 360 — 3D mechanical CAD which has a number of different licensing options
- Solidworks
If you’d let us know what sort of work you wish to do, how you wish to approach it, and your budget we might be better able to advise.