How to get conformal mesh using Netgen with OCC from STEP

Hi,

I am working on a VS project where I am importing STEP or IGES, and using Netgen (ver. 4.9.11) to mesh them to get tetrahedrons. When I mesh a single solid, it work well, but for multiple solids, it gives a problem for me. The mesh from multiple solids is not conformal. In other words, those points on a shared surface are not matched. If I use CGS format, Netgen gives conformal mesh, but if I use STEP or IGES, Netgen gives non-conformal mesh. The following is an example of CGS format which gives conformal mesh.

algebraic3d
solid cube1 = orthobrick (0, 0, 0; 3, 3, 1);
solid cube2 = orthobrick (1, 1, 1; 2, 2, 2);
tlo cube1 -col=[1,0,0];
tlo cube2 -col=[0,0,1];

How can I get a conformal mesh using STEP or IGES?
Is there any special thing on STEP or IGES to get conformal mesh?

Thanks in advance.
Junho