Hi dojn, it would definitely help if you could also post the 3DM model file with your curves in it.

But from what I can tell, it looks like you are seeing the effect there of sweep trying to keep the profile perpendicular to the rail curve, and when you have a wide shape that is going around a bend with a tighter radius than the width, it creates a kind of bunching effect.

Here is a bit of a simplified example to show you what I mean:

Imagine you have a top view on a curve that is being swept around a rail, like this:




Because the rail has a tight enough bend in it, as things move along the rail there will be a kind of bunching effect where the pieces cross over each other because they are too large for that tight of a bend like this:



I believe that's what you have run into in your case.


If I understand the shape that you are trying to make, I'd suggest making it out of 2 separate pieces and then filleting them to make them smoothly connected.

Please see these previous posts for an example:

http://moi3d.com/forum/index.php?webtag=MOI&msg=2164.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=2164.4


- Michael