Hello,
I am working on a couple of Lulzbot Taz Pros with the M175 v2 1.75mm machine head in a library makerspace setting.
Recently, we had one of our users start prints on both printers simultaneously, and for whatever reason, both prints detached from the build plate but the print also stuck to the nozzle and the filament that continued to be extruded was blocked from moving downwards. So instead of getting the usual “spaghetti” you’d get from a build plate detachment, the PLA all ballooned upwards, engulfing the hotend and basically encasing it. It was pretty gnarly, and somehow it happened on both printers at the same time. (Woe is me.)
To clean the PLA off, I (very carefully) removed the cooling fans, blower shroud, and extruder from the machine head mount, and then once I had good access to the hotend I used a heat gun to soften the PLA and clean most of it off. Then I reassembled everything.
On both printers, when I now try to load filament, the little feeder gears inside grip the filament like normal and start to pull it down, but the filament only moves about a centimeter down and then stops. Sometimes there is a little click (I think it’s the feeder gear slipping as it tries to push the filament lower and can’t).
I think that potentially there might be some PLA in the lower half of the extruder that was still in there when I stopped the print and then cooled, and is somehow not getting heated up enough to be soft to push through? But I really don’t know. Or, considering that the same thing is happening with both printers after I took the machine heads apart and reassembled them, could I have something not lined up or tightened to much or not enough? I followed the instructions here (OHAI: Open Hardware Assembly Instructions).
Any thoughts, or any suggestions for how to troubleshoot the cause of the filament loading to stop halfway through the extruder?
Thanks,
Phil
Update: I took the machine head apart again and removed the hotend from the extruder, then ran the extruder, and the filament goes through fine. So the clog appears to be in the hotend.
Any suggestions for cleaning/unclogging a mosquito hotend? I have never done a cold pull/atomic pull but from what I can tell you need at least some extrusion happening to perform those, am I correct? I have also read about people heating the hotend up with a heat gun and using a small alan wrench or drill bit to lear the clog. Any advice?
Thanks,
Phil
You can try heating the nozzle to the high end of the clogged filament’s range and then block the cooling fan. This will purposely cause heat creep and after a few minutes, attempt to push filament through the nozzle. If successful, unblock the cooling fan while continuing to push filament through. After a few minutes you can lower the nozzle temperature to about 100 degrees (plus or minus 10) and then pull the filament back (a cold pull).
Alternatively, heat the nozzle to the high end of the clogged filament’s range and block the cooling fan. Then use an allen wrench, drill bit, or a noclogger (2.85).
I also suggest having some cleaning filament around. Works great for cold pulls.
Thank you for the advice! Just to confirm: when doing the cold pull method you mentioned, would I do with this with hotend attached back to the extruder again? Or could I try pushing the filament just right through the hotend by hand to achieve the same thing? Here is its current state of assembly.
Thanks for the suggestions about the noclogger and the cleaning filament. I will make sure to have those tools/materials on hand in the future. (I’m quite a beginner at this.)
A cold pull using the method I described is usually done in lieu of disassembly.
I would be nervous about doing anything that involves force with the nozzle assembly unattached because you don’t want to damage the wiring. You would need something to hold the assembly as you heated it up (we are talking 200+ C, 400+ F) and that something may act as a heat sink which would be counter productive.
I can’t tell from the video if the nozzle is still attached to the heat block.
Good point, thanks. Yes, the nozzle is still attached to the heat block. I’ll reassemble and then give the fan blocking that you suggested a try. Hopefully that will cause enought heat to creep into the heat break that it will soften whatever is causing the blockage.
@b-morgan It worked, thank you! It really seems it was the heat break that was clogged, and it took removing/stopping the fan to get the heat up in there enough to soften the cog. I first had to push a 1.5mm allen wrench through once it was warm enough, and then I was able to do the cold pull as you described. Thanks again.