@Lewis Shattuck I customized an extruder plate from Thingiverse and added a threaded hole at the top, but I was never able to get the Maker extruder to pick up the filament. I ended up replacing the extruder and hot end with a Bowden setup and it worked much better.

The PTFE liner goes through the heatsink but stops at the heat break. I'm using the 85mm 1.8 PTFE tube that came with the Chameleon. But there's no problem retracting the filament from the hotend. During a tool change the filament is retracted correctly and the other filament loads correctly. But it no longer gets to the nozzle because of the lint ball, so there's no extrusion. Even in this clogged state I can retract and reload the filament repeatedly with no problems, there's just no plastic coming out of the nozzle. So it seems like it's not a problem with the shape of the tip of the filament, just that there's a lot of stringing at the front of the filament which then bunches up into a stringy ball that blocks the heat break.

@Bill Thanks Bill, that's a huge help. I'll give a BMG style extruder a shot.

@Bill Thanks Bill, that's a huge help. I'll give a BMG style extruder a shot.

@Bill I'm not great with editing existing STLs (or don't have the right tool) so I'm going to model a new one from scratch. Can you tell me the specs for the screw threads? Thanks, Marc

@Bill Thanks, I'll give that a try.