I am using CREO 2.0 for a valve train analysis. I want to determine how much spring I need to return the valve, hopefully to keep the follower on the cam. So I place a trial return force on the valve and allow lift-off. Looking at a previous thread answered by Kas back in 2011, I place limits on the valve travel and allow cam lift-off, but my roller-follower never returns to the cam. I have tried using the exact limits as shown by the cam, or increasing those limits slightly --- still no luck. I have 3 cams in the train, but am allowing lift-off on only the main cam and roller-follower. The power of this tool is tremendous; if only I could figure out how to use it! Any help would be greatly appreciated. "rework"