MeshLab is free open source softwere used for mesh processing.
It is great tool for file format conversion.
It can import and export below file formats.
IMPORT: ply, stl, off, obj, 3ds, collada, ptx, v3d, pts, apts, xyz, gts, tri, asc, x3d, x3dv, vrml, aln
EXPORT: ply, stl, off, obj, 3ds, collada, vrml, dxf, gts, u3d, idtf, x3d
Most stl files contains geometry errors due to conversion process.
Netfabb basic is used for viewing and repairing stl files.
In free version you can repair, scale and split your stl files.
3D Design Softwares
For creating 3D files for 3D printing you can use any below listed sofware.
- Google Sketchup
- 123D Design
- Autodesk Inventor