You could also give a try to 3DReshaper. It offers perfect tools to clean and/or filter the cloud automatically before creating an accurate 3D mesh.
It is very easy to get the level of precision that you need in the mesh thanks to the meshing in 2 steps.
Once you have a mesh, you could either export this mesh in *.stp or convert it to a CAD model (through the CAD menu). Once you have a CAD model, you can export it in IGES or STEP format.
You can download a free trial version of 3DReshaper from here: http://www.3dreshaper.com/en/software-en/download-software/current-release-software
Contact the support while you test so you can be guided!