Simulating 2.5axis milling machine cut

I'm using SW2008 S.P. 2.1. I was using SW2005 prior to thisso I have limited experience with solid sweep cut.

I'm trying to make a retangular part that has a groove cut that isgenerated by a milling opration where the end mill slowly lowerinto the z-axis while the part is moved in the x-y plane along aradius path if one observe from the top (plan) view.

The trouble I am facing is keeping the tool upright (like what onecan expect on a 2.5 axis machine). I tried using "keep normalconstant" and it failed to generate the cut.

To avoid error, I can only choose "follow path. When doing thesolid cut, the tool follows the path the the point that it isnormal to the path. If I choose a direction vector that is parallelto the z-axis (unfortunately it will also be parallel to the y-zplane axis), the tool seem to maintain parallelism to the y-z planeand not to both x-z and y-z plane. So I still have a tilted tool.This would not be a problem if I am using a ball endmill as I canmake the break the sweep into straight and curve cut and fudge theproblem as long as my curve is tangent to the straight cut.

Unfortunately, I am trying to use an flat end mill with cornerraduis, so the bottom face of the cut sweep needs to be parallel tothe XY plane (or normal to z-axis).

Has anyone have any idea of creating this feature?

Thanks.SolidworksParts And Features