I have been playing with creasing wheels for a while now on our Zund. I wish I could tell you exactly what's what... but I am not having great results myself! For one, Zund has 18 different wheels for different types of cardboard/paper/plastics. And two, you need paper/cardboard that's fabricated specifically for folding. And you need to know the direction of the grain of said paper/cardboard.
In short, creasing is a trade in itself! Check with your supplier, they might have specs for the paper you are using. Or they might be able to steer you in the right direction.
I found this document, maybe it will be as helpful to you as it was for me.
http://www.aadieinc.com/newsletters/ABC Crease Fold Force.pdf
Good luck!