3D models saved in the Dassault Systems Universal 3D XML format (.3dxml) can be converted to IGES ASCII CAD files (.igs) using the Export or Save as.. function in CATIA CAD software, or any other dedicated 3D modeling software or converter with the support of .3dxml files. Considering 3DXML is a proprietary format, the options for 3dxml to igs conversion will be somewhat limited.
Open 3DXML file Open IGS fileA CAD converter with huge format support
A CAD visualizaton, analyzation and translating system