NOT PRETTY SURE OF WHAT OU NEED.
IF YOU NEED TO EXTRACT BORDERS, THEN EXTRACT GEOMETRY IS YOUR COMMAND.
IF YOU NEED A 2D PROJECTION OF YOUR BORDERS, THEN YOU CAN DO IT IN A NEW SKETCH, AND PROJECT LINES.
IF THIS IS NOT WHAT YOU ARE LOOKING FOR PLEASE LET ME KNOW.
You could just machine it using planar mill/planar profile by selecting the outer edges and a floor plane.
When selecting the edges, you need to make sure that you specify the plane as 'User-Defined' and make the plane above the part. This will project the selected edges up to the specified plane and start the cut from there. The floor plane then defines the depth to cut to. See the attached part for an example.
Bear in mind that you'd have to allow stock on the profiling to cope with undercutting edges.
Otherwise, orient the view to the top view of your object then use Extract Curve - Specific Outline to get the outline of your model.
If the operation is cutting the yellow stripe around the part, there are two operations designed to do exactly this. If you have a solid, use solid_profile_3D. If you have curves, use profile_3D:
Go to Help > Manufacturing Tutorials > Open a Sample Part > cam_sample_mill_contour_setup_1.prt, and look at the program group SOLID_PROFILE_3D_PROCESS
Make sure that you are not over cutting the side faces of the part. When you look at the side faces - 1st image, they are not parallel to tool axis you have shown in 2nd image.
I hope you can understand what I have written here.
The first image that i sent is skewed somewhat, and doesnt give the best look at the relationship between side faces and the tool axis. The simulation shows clean tool path, with no over cutting of the side walls.
Thanks for your input.
Have you used 'compare' or 'show thickness by colour' option to check the stock ? If yes, then no problem. Also sometimes, we may not get clear idea if there is minor overcutting unless and until we check it with close tolerances.