I just tried the sample of Polymaker Polysmooth that came with the Polymaker sample selection.
This is a very flexible filament - so flexible that when it fed in, it apparently bent at the top of the cold-end and went sideways into the cooling fan! I heard the screech and thought the bearings had gone. However when I pulled the filament out - it was like a clown or magic trick, it kept coming out, and coming out... and the fan stated up again.
So - it appears there is not enough 'guide' for this type of filament to enter the hot-end reliably with the current design - the gripper gear pulls it in, but it bends at the cold end.
I tried boosting the temp to the 230deg called for with only a little better results - got a dribble out of the nozzle before the fan screeched again.
Anybody else have any better luck? Do I need to boost the hot-end temperature way over spec?
Thanks in advance.