Just to make things a little more interesting: I’m having the exact same problem as the original poster on my Taz 6. Sitting not more than three feet away is my Lulzbot Mini which prints like a dream. I can swap the filaments between the two machines and fail on the Taz 6 but success on the Mini. Small prints on the Taz 6 are fine, but when you print big it will print a few layers perfectly and then clog up and stop printing. The printer was fine until recently. All fans are functioning as expected.
I’m in New Hampshire and the room is around 65-67 F. The two printers even sit on the same workbench. I’m using the same version of Cura to print.
What size filament are you using? If not 1.75mm, do you have some that you can try?
In my case, I believe it has a lot to do with the friction of the particular filament I was using. I have since made a couple of prints and they have gone well. First was with a short print with a different 2.85mm filament that had a smoother finish and it was noticeably easier to push/pull this in the PTFE guide tube. This printed fine. Second print was with a 1.75mm filament (~10 hour print) and it printed just fine without any additional fan or cooling.
Prior to both prints, I noticed that there was a lot of backlash on the herringbone gears on the extruder and adjusted the stepper to remove this. The mounting screws on the stepper were quite loose.
I also made a small bracket to hold the PTFE tube in place to minimize any more wear on the idler block that I mentioned in a previous post.
I also have a lot of wear on the part of the idler block that guides the filament. I am wondering if the filament moving too far off the hobbed bolt could be causing some of the grinding issues.
I tried to address this by capturing the PTFE tube using a bracket above the extruder. I haven’t done much 2.85mm prints since the change so can’t tell if it fixed the issue.
Good to know that you are printing without the PTFE tube. I’ve wondered if that would work well. Did you move the spool above the printer?