This is Resurf it convert OBJ to Iges, but you have only one Setting.

Step 1: load your OBJ mesh into software;

Step 2: click menu 'Surface> Blend mesh to NURBS' , the software will create NURBS surfaces from your OBJ mesh automatically. The NURBS surfaces are water-tight and exact G1 transition.

Step 3: save the NURBS surfaces as .igs file. Since the surfaces are water-tight, they can be sewed as solid without changing any geometry by other software.


http://www.resurf3d.com/Objmesh2solid.htm