I have the Chameleon working and swapping filament fairly reliably. But... on the second or third layer the hotend inevitably clogs. When I disassemble it and have a look, I find a ball of PLA "lint" in the neck of the heat break - - basically the result of the filament stringing when retracting and then getting wadded up. I can just remove the lint with tweezers and that clears it - there's no clogging in the nozzle or below the neck of the heat break.
I know Bill and probably others have spent a lot of time tweaking to avoid these types of problems, so I'm hoping to get pointed in the right direction for things to try.
For reference I'm using a V6/Volcano so the heat block is longer than other hotends. So I've tweaked the unload gcode to increase the distance the filament is "plunged" but that hasn't helped. I'm extruding at 205 degrees. Using a BMG clone as a Bowden.
Ah... I'm sorry... confused messages. Yes... the strings need to be cleared up... and that's controlled with temperature. Take a look at FAQ #10 and see if that doesn't help you. https://www.3dchameleon.com/faq Bill
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.
Is there a PTFE liner in that hotend? If not, you'll want to very quickly retract it out of the metal portion and back into the PTFE Bowden tube. That section, you'll want to use a 1.8mm ID section of tube to constrict it down as you allow it to cool. Also, don't let is stop in there until it's cool... because as soon as you remove it, it'll swell. It needs to be constricted to the 1.8mm until it drops below the glass transition temperature... usually for PLA, that's about 55-65 degrees.
Never allow it to cool in the metal portion... it will most definitely swell and jam.