Hi Andras,

Generally if you construct your object with many surfaces, it will be difficult to eliminate creases where they touch each other.

Here are a couple of posts where I try to explain how/why this happens:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1398.18
http://moi3d.com/forum/index.php?webtag=MOI&msg=1398.19

That's the kind of thing that you are running into here.

In the future I do plan on adding in some additional functions to try and make adjacent surfaces smooth to one another, but it is a difficult problem and will probably take some time before it is possible to do this in MoI.

Right now the best way to ensure smoothness between different pieces is to use Fillet or Blend to construct a smooth fitting piece. Other construction commands like Sweep, Loft, or Network won't do any special work right now to ensure adjacent smoothness.

Another method is to try and use larger surfaces to build a smooth piece instead of having it split up into smaller regions.

If you want to post your .3dm model file, I might be able to give you some better suggestions on how to improve it.

- Michael