It's a step back in time for me but we always milled these features with planar profile. After the tool reaches the top of the tapered feature, 3+2 contouring gets the rest. We had NX 4 back then and our choice was to set the under side of the mandrel as the boundary plane and top edge of taper as floor plane. The boundary geometry = the top edges of the undercut where it meets the mandrel. First DOC was cutter thickness. Other DOC's to suit. Be sure to give plenty of engage retract clearance so the cutter doesn't gouge the mandrel on the way down and up because it may not check for this.
Not very sophisticated but it gets the job done very quickly which is important in your industry.
Which version of NX are you using ? I think NX9 has direct option (Groove Milling) to mill this with T cutter where you can define steps - depth and side
In NX9/10 you can produce this with groove milling. But it works with features. It works fine. But as I see this, I don't think, that this will be recogniced as a linear groove.
Sorry, I can't open the step-file, something must be wrong.
Actually, that's a ParaSolids File.
I think that FBM would have difficulty recognizing this as a feature. This type of component has many shapes and forms under the mandrel, almost all of which are contoured to some degree. A small %age of parts would get picked up by FBM. Typically we used to use API for these. Depth was controlled by expressions created in the design phase.
Groove Milliing and Radial Groove Milling have the cutting strategy you want, but today they are limited to linear and circular grooves.
Until groove milling is expanded, I would use planar profile or solid profile.
If the Z under the ledge is critical, you also have the option to use a tracking point on the top of the t-cutter.
This is possible using Planar Mill with cut pattern set to profile. set additional passes to however many you want and step over as necessary then set cut levels accordingly.
I set the profile to the inner edge of the groove.
I would prefer to use the new grooving options for this sort of work as they look good but are limited at the moment, I have raised enhancement request to add external radial grooving to complement the new internal radial grooving.
Hope this is of some help.