I am the proud owner of a mini and a TAZ 6. Mini worked great out of the box, but the TAZ 6 was a bit out of square and the Z-axis jammed and caused the printer to print out nylon completely encasing the hot end (below). I thought I would need to send it back, but I heated the hot end up and managed to free it from its nylon casing and was able to extrude filament. However the tip was covered in burned nylon and would fail on auto-leveling. I called Lulzbot and they suggested non-metallic scotch brite and I scrubbed and scrubbed, but the auto-leveling was still inconsistent. Then I hit on the solution, cut out a small circular piece of scotch brite and attach it to a dremel tool in place of one of the polishing pads and run in on low speed with the hot end heated up. Viola! works like champ. I have examined the tip under a magnifier and cannot see any scratching. Not sure if Lulzbot support would officially support this, but low speed and just touching it a couple times will clear off all the grime.
My printer does not have the auto level but I clean the tip by heating it up, turning it off then I hit the nozzle with a welders mini brass wire brush (about the size of a toothbrush) I am very careful not to hit the leads but this does make the tip very clean and shiny again.
After reading your experience with the non-metallic Scotch Brite, I got some at the grocery store (Scotch Brite Heavy Duty Scrub Sponge – sponge on one face, Scotch Brite stuff on the other), cut off a half-inch-wide strip from one end (so it was about four inches long), and tried manually scrubbing the nozzle tip on my TAZ 5 with it when it was hot (235 C), before starting a print.
My nozzle had been pretty crudded up, and the Scotch Brite cleaned off all the bits and bumps of stuff nicely. After each use I have to pick off the melted plastic (PETG in this case), and can re-use the same piece 2-3 times before it gets too messed-up. Then I cut off another section from the sponge for next time.
I’d been concerned about the Scotch Brite melting onto the nozzle, but it doesn’t seem to.
Great idea about the Scotch Brite, thanks!