Help with minimizing run times

[mrwoodworks]

I have taken on the project to reproduce a rather large crown molding for an exterior application. Plan on using solid PVC material (like Azek) to mill.
Will use 1" material for base and then stack/glue material where needed on the thicker areas.
I have a tried a couple of methods of machining simulations and am unsure which is the best. If I input the piece as a whole and have a part size that is 3" thick, I will have to override my machines safety bit parameters. In other words I will have to override the length of the cutter used to mill the lower "crown" section, in order to not spend time cutting air. Not necessarily the best move...overriding machine safety standards. Instead of doing that, I thought of machining this as two seperate programs, but actually using the same piece. One program would run the lower crown and one could run the upper ogee. The lower crown would be on a part piece that is 1.25 thick and the upper ogee would run on a 3" thick part.
That helped. Also, I could use a 1/4" bullnose on most of the piece and have a very acceptable finish. However, there would be one small section that I would need to run an 1/8" ball nose. I wanted to use the molding tool to run this is as it would be faster than the modeling tool. Is there a way to create a vector boundary in the molding tool? and run only within the boundary? I'm pretty sure that I've done that in two rail sweep, and was hoping I could do it in the molding tool so that I would not have to fiddle with cutting, pasting, and overlapping profiles.
Thanks for any input you may have.

[dealguy11]

1. I would run this entire part using the moulding toolpath, not a carving path. You'll get a better finish and it should run faster
2. If you're doing this in Azek, which is pretty soft, with a 1/4" bit, and you're gluing up the rough shape, then why not just do the final cut in 2 passes - 1 moulding path for the 1/4" bit, and 1 moulding path for the 1/8" bit? Then you'll get no air cutting, assuming your machine can deal with it. In other words, no roughing pass

[mrwoodworks]

Roughing path times are not a lot. The difference however, from 1/4 and 1/8 ballnose is significant. I really only need the 1/8 ballnose in one valley of the profile about 1/2" wide. I was hoping I could make a vector boundary and make it work with the molding tool, but looks like I'm going to have to do some cutting, pasting, and overlaying of profiles to make it work.
Thanks for responding.

[dealguy11]

I agree you wouldn't do the entire thing with the 1/8" bit. Cutting the overall profile into a couple of smaller pieces for the 1/8" bit shouldn't be a big deal. Best to do the the whole thing with the 1/4" bit, then just go back in the couple of areas needed with the 1/8" bit, sort of like rest machining but with moulding toolpaths. If you were going to use the 1/8" bit you were going to have to do cutting and pasting regardless.