Verbatim PLA Was Great, Now Clogs

We’ve had great success printing several rolls of Verbatim PLA with our Dual Extruder V2 on our Taz 5, at 205C with a 60C bed. Until now. Suddenly we are experiencing jams that can’t be effectively cleared even with cold pulls. We swapped in a new nozzle, it printed for a while, and then it also clogged.

On the most recent cold pull, there was a very distinct brown flaky film on the end of the plug we pulled out:

We also saw this film on other cold pulls, and inside of the hopelessly-clogged nozzle we pulled off (which is the one in the photo, if you look closely you can see the brown inside).

We then discovered that the roll we are printing with is a different lot number than all of the other ones we’ve had so much success with, so we are switching back to one of those and trying again. We’ll see how it goes. In the mean time, does anyone have any idea what that brown film might be? It will flake right off if you scrape it with an Exacto knife. It looks very much like rust, but I can’t imagine that’s what it is, I don’t know where that would come from. By the way, this roll had been vacuum sealed with desiccant until just a few days ago.

That nozzle got hot. I mean, “Holy shit what were you printing???” hot. You can see the brass discolored and oxidiezed a bit on the side in contact with the heatblock normally, and there appears to be burnt on residue of something inside the barrel. The rust colored bits might actually be copper powder flaking off from inside the nozzle from the heat. Were you guys printing polycarbonate with this one at some point recently? It almost looks like someone took the nozzle up to 300c without cleaning it first, burnt on a bunch of old filliament, then left it at that temperature empty with no filliament to absorb the heat and air in the nozzle tip for a few hours.

Maybe it’s debris in the filliament, or a bad batch, but the nozzle itself doesn’t look happy to me either.

I am 100% certain that the nozzle has not been overheated. I think we took it up to 240 during attempts to clear it, but when printing it was at 205. We checked it with a Fluke contact probe.

What we are looking at now is whether we are trying to feed it too fast. We had been using Cura, but switched to Simplify 3D. The default printing speed for PLA in Simplify is about twice as fast as that in Cura. We’re going to bump that back down and see if we stop having clogging issues.

BTW the new roll from the old lot number clogged almost right away. Prior to that we had had 100% success with several rolls of this filament, all using Cura.