"sandman"
Probably too much speed and the teeth aren't course enough.
Cutting stuff like that calls for chip removal and cooling. Add a
powerful blast of concentrated air at the point of the saw cut.

Interesting. I tried a cutting wheel about 1/16" thick and 1" dia. at about
10,000 rpm. Slowing it down didn't help. Then I tried a diamond-coated
wheel, a bit more than 0.12" thick, which fits the steel plate that goes
into this groove perfectly. That went better but I still get melted Lexan.

I guess I need one of those itsy-bitsy circular saw blades, and I know
exactly where to get one!

I suppose my vacuum cleaner will do for a powerful blast of air. :-)

Thanks, sandman!