Lovely shiney glitter can't beat it.!!!

Micheal try not to plung on entry to material, always spiral or ramp if possible. If you listen you can hear it snatching at the material on entry this will kill the cutter quickly and also knocks hell out the machine and spindle.
If you can only plunge then what I do is make the first path a slow peck drill with the same cutter at the entry point to just less than the finish depth.! this is far less stressful on both machine and cutter.

Another thing I noticed was that it sounds like your using the same size cutter has the raduis in the corners.? I guess you probably drew a square and the corners where just rounded but this also kills cutters due to the fact for a split second it's cutting on 2 sides and again snatchs, Both blunting cutter edge and leaving a poor finish in the corner.?
Seen has you can never have square corners with round cutter it's far Better to radius your corners and either use a slightly smaller cutter or make the radius slightly larger than cutter.