Acrylic Inlay - How do you do it with VCarve?

[vcarvepost]

Dear VCarve-friends,
this is my first real post in this great forum and so first of all I want to say "hello" to everybody and in advance a big thank for your help and comments on my way to become an expert in VCarve.
I hope my school english is not rusted too much, so everybody understand where my problem is. Otherwise, please feel free to talk about the incomprehensible passages.
So, here is my problem:

I created an object with an acrylic inlay. So far no problem, but when I cut it out, my solid carbide end mills are close to break due to a real ´hard´ toolpath.
I just can say ´hard` to it, because I don´t know why my new 3mm single flute solid carbide end mill (with polished flute, made by VHF or Kemmer Präzision) broke without any traceable reason.
My CNC has a high frequency spindle, so it needs more rpm than stronger three-phase spindles. I tried several combinations of speed and feed rates, but the problem did not go away.

My research is: 3 - 6mm single flute, 18.000 - 24.000 rpm @ 16 - 20 mm/sec (~0,96 - 1,2m /min), maximum infeed (is this the right english word?) / cutting depth per round is 1 - 1,5mm . The end mill is cooled with compressed air.
I do not know, whether it is Plexiglas XT or GS (XT is extruded, GS is casted). Maybe, it is XT and so out of that the reason for the problems?!

Summary:
The flute just breaks / makes unnormal noises (6mm) when it starts running the toolpath (program start / restart / deeper level / next toolpath). After a few mm in the material everything works quite good. But, whenever the flute completed a pass and reenters into the material, noises / crashes appear again.
The toolpath was created without tabs, ramps etc. In the meantime, I tried to use a flat ramp (just 5°), conventional and climb milling, but all this did not help.

What kind of ramps / features do you use in VCarve / Aspire for cutting pockets and profiles in acrlyc?

Thanks for your reply.

[Xxray]

I cut thick plexi all the time using these or similar
http://www.amazon.com/gp/product/B007QRBDH4

With slow feed [50 ipm] and low RPM's.