The tool should never dig in to the part.
If you are seeing excess material removal with the IPW, can you please provide a picture, and indicate the part and blank, and where you think the tool is digging in?
Please check you 'Cutting Parameters' for
1) Island Clean Up
2) Wall Clean Up
Sometimes if you don't do this, cutter may dig into uncleaned portion while retract/transfer moves.
I don't think those options are still available on NX 10.
I am migrating to NX 10 from NX 7.5, and i can't find those options anymore
What is the Visualization Preferences set at in your model?
I set mine to Ultra Fine.
Is there a large geometry in/out tolerance?
Is there a large boundry in/out tolerance?
There could be a XYZ discrepency with your tool parameter and tool pattern.
Do you have the Allow under cutting turned on?
Do you have a Milling tool Z Offset in the regestar?
You could have a tool in the operation and a deferent tool selected with the Library reference