The free Version of Amapi3D 6.1 has an "iges" file format export (practical for primitives like helix and so one)
You can find Amapi3D 6.1 here
http://forums.polyloop.net/forumdisplay.php?f=83 (just register on the forum and post one message :)

But Moi seems reload the file in format iges, but nothing is visible ?
Here a sphere & a cube
maybe the header of the Iges Amapifile is not classical?
(Amapi reload his Iges file :)

Ps Nurbs in Amapi 6.1 are not "real" nurbs
It's different for up version