Yes, raft removal from Polymax can be challenging. You don't mention fans - 100% or Auto fan, and dual fans, might help. You have to somehow manage to get a toehold between the part and raft, either by twisting or digging with a chisel. Once you can get the edge of a good sharp scraper under there, put the part against a bench hook or other fixture so you can give the scraper a hard whack - often it will all pop off in one piece or something close to it.