been trying to engrave some clear acrylic to make an led sign for a friend, but its not been going as well as id like.

first tried a 1mm end mill, 22000rpm, 0.5mm DOC and 500mm/m. acrylic just melted and stick to the cutter and produced a poor finish.

I then tried a 4mm spot drill, 0.25mm DOC, 22000rpm and 300mm/m. started off very well with a perfect finish then after a while the acrylic melted and stick to the spot drill and gave a crap finish.

I then tried an 8mm spot drill, 0.25mm DOC, 22000rpm 300mm/m. went ok for about 30 seconds then acrylic melted and stick to the spot drill.

so decided 4mm spot drill was giving best results and played around with a few different feed rates, I can get good results but then every time after a few mins of cutting the acrylic melts and sticks to the end and causes a shit finish.

anyone got any tips?