Wow, thanks to everyone for the replies. I can't work on that machine today but will get back to it tomorrow. We are in an academic setting and the technician who set up and maintained our machine moved across the country a couple of months ago. We are trying to get a handle on maintenance and running this particular job at the same time.
Brady, thanks for the suggestion of feed and rotation with ramping. I've never run ramps before and will be looking at your article which seems quite helpful. I tried the speeds that I did based upon other recommendations and slowed it down as it became clear that we were not getting what we should.

From the bill of purchase and looking at the machine itself, we are running a PRS Standard shopbot with a 4x8 bed. The spindle says that it is HSD brand and 4 hp. As far as I can tell it maxes out at 18k rpm. I know someone who cuts acrylic with 24k at 100 inches per minute and gets excellent results, but that totally different setup with a mastercam etc.

Yes, the goal is to cut acrylic in the manner that the original post says. I had a few minutes at the end of the work week to test out this tapered bit so decided to cut out a couple of words - it seemed like a good test.
Does anyone know of a standard cut test?
The vendor of the acrylic mirror recommended the mounting to sintra to protect the mirror backing. Due to it's softer material makeup, the sintra has been fine to cut on the tablesaw ,but it appears this may be a drawback with the cnc. I can say that it appears to not be causing a problem. We may consider mounting to another plain sheet of acrylic to standardize moving forward.


It's unfortunate to find out that the ball nose is not a good tapered bit for this purpose. We've got another one coming at a 3deg angle from woodline that they custom made.
Is this the kind of endmill bit that you were thinking of:
http://preview.tinyurl.com/o2hthan

For tapered bits, Amana send us to Woodline and Onsrud recommended a similar ball nose.
Thanks,
Peter