Hi @Dkennison,
99% of the time in plastics the answer is “feed faster”, when melting occurs. Here’s an old post of mine where I used the single flute Amana 1/8" endmill to mill acrylic, at 16k RPM it took 54ipm to get a clean cut
So that was a chipload of 54/16000=0.0033"
Which is…above the max chipload I mentioned in the guideline table in the ebook, so while those guidelines were never meant to be a max value but rather a good starting point, in hindsight that specific 0.0025" recommended “max” was too low.
Over time I learned that acrylic craves high feedrate, and you can push things very far IF you reduce the depth of cut, because right after the feedrate problem there is the chip evacuation issue, and slotting deep in acrylic tends to be a recipe for packing chips and therefore…melting.