IGES (.igs, .iges) is a common ASCII-based CAD format and most of the modern CAD programs support it and can export their CAD drawings to it, which means it should be pretty easy to achieve dwg to iges conversion. Especially considering the fact that both DWG and IGES formats are well-supported in various CAD / 3D modeling tools.
Open DWG file Open IGES fileA CAD viewer program with conversion capabilities
A CAD and Gerber conversion software
A set of 3D modeling tools
A 3D modelling software
3D CAD/CAM tool for product development
Creo Parametric (formerly known as Pro/ENGINEER) is a complete 3D CAD software solution by PTC
A CAD converter with huge format support
A dedicated 2D/3D CAD software
A 3D CAD translation software
A suite of CAD applications