Confusing nozzle blockage with PLA
Hello everyone,
i'm kind of confused by my recent situation, i bought some PLA from dasFilament and already printed ~130h with the white PLA without any issues but when i changed to the blue PLA the extrusion would stop mid print with the extruder gears skipping. This would happen after about 45m to 1h, so when it happened i unloaded the filament, cut the tip off and loaded it back in, to my surprise the extrusion would be flawless again and the print was able to continue again for 45m to 1h after which the clogging occurred again. Then i unloaded the filament, aborted the print and loaded the white PLA and printed again with the same gcode. This time everything just worked for the entire print. Then i swapped back to the blue PLA and ran the same gcode, and the nozzle clogged again. I then disassembled my extruder and cleaned the hotend, there was no obvious contamination in the heatbreak or nozzle so i put everything back together and printed the same gcode with white PLA which again worked, then i changed back to blue and it clogged again. I tried changing the extruder pretension, increasing it delayed the clogging to some later point, but didn't solve it. I noticed that when the nozzle seems clogged and i unload the filament and try to load it back immediately it will not work, but when i cut off the tip it works. So the tip is somehow causing the clogg but it cannot make any sense of this since the tips of both white and blue PLA look very similar after unloading.
I really cant figure out what might cause this problem, except for the filament just being bad, but i cant really imagine this being the case.
I appreciate any help on this 🙂
Best Answer by th3royal:
So i solved this problem after a very long time trouble shooting this issue. It was, as seems kinda obvious in hindsight, a heat creep issue. For some reason the blue PLA has a significant lower melting temperature than the white PLA causing is to soften in the lower part of the PTFE tube. With the many retractions in the print this would eventually cause the filament to get stuck in the PTFE tube. When unloading the Filament after a jam, the tip would be slightly larger in diameter, thus not being able to fit well through the PFTE tube and causing a lot of friction.
So how did i solve this ?
First i went through all the steps to clear a blocked nozzle: https://help.prusa3d.com/article/clogged-nozzle-hotend-mk3-5-s-mk3s-mk2-5s_2008
After that did not solve the problem i lowered the nozzle temperature to 205 C, which is the lowest recommended by the manufacturer. Additionally i applied some thermal paste between heatbreak and heatskink, like shown in this Prusa guide https://help.prusa3d.com/article/extrusion-stopped-mid-print-heat-creep_1948
"Add the thermal paste to the heatbreak
Especially if you were taking the hotend apart in order to clean it, before putting the hotend back together, don't forget to apply some thermal paste on the heatbreak thread that is in contact with the heatsink (the same kind of thermal paste used for computer processors). You can get the paste from our eshop, or similar high quality generic thermal paste. Here’s what your heatbreak should look like with enough thermal paste. Refer to this guide (for MK3S/MK2.5S/MMU2S. For MK3/MK2.5, there is a separate guide) for more information about how to dismantle the extruder and the hotend."
After that i was able to successfully print this filament, i hope this is helpfull for anyone with a similar issue.
Check the diameter of the filament in a few places, Run some through your fingers and feel for rough spots and slight changes.
Cheerio,
RE: Confusing nozzle blockage with PLA
I didnt notice any inconsistencies with the filament, checked like 2m of the filament with a caliper and didnt find anything above 1.75mm or below 1.74mm.
Good. Check again around a stopping point.
Cheerio,
RE: Confusing nozzle blockage with PLA
So i solved this problem after a very long time trouble shooting this issue. It was, as seems kinda obvious in hindsight, a heat creep issue. For some reason the blue PLA has a significant lower melting temperature than the white PLA causing is to soften in the lower part of the PTFE tube. With the many retractions in the print this would eventually cause the filament to get stuck in the PTFE tube. When unloading the Filament after a jam, the tip would be slightly larger in diameter, thus not being able to fit well through the PFTE tube and causing a lot of friction.
So how did i solve this ?
First i went through all the steps to clear a blocked nozzle: https://help.prusa3d.com/article/clogged-nozzle-hotend-mk3-5-s-mk3s-mk2-5s_2008
After that did not solve the problem i lowered the nozzle temperature to 205 C, which is the lowest recommended by the manufacturer. Additionally i applied some thermal paste between heatbreak and heatskink, like shown in this Prusa guide https://help.prusa3d.com/article/extrusion-stopped-mid-print-heat-creep_1948
"Add the thermal paste to the heatbreak
Especially if you were taking the hotend apart in order to clean it, before putting the hotend back together, don't forget to apply some thermal paste on the heatbreak thread that is in contact with the heatsink (the same kind of thermal paste used for computer processors). You can get the paste from our eshop, or similar high quality generic thermal paste. Here’s what your heatbreak should look like with enough thermal paste. Refer to this guide (for MK3S/MK2.5S/MMU2S. For MK3/MK2.5, there is a separate guide) for more information about how to dismantle the extruder and the hotend."
After that i was able to successfully print this filament, i hope this is helpfull for anyone with a similar issue.