Filament Jammed

This week I was printing perfect. This morning I changed my PLA spool to a new one from other company.
The filament keeps jamming in the extruder after 30min-2h of starting the print. It already did 4 times. I reduced the retraction and modified temperatures to no avail.
If I open the door of the extruder I can see the filament has become twisted and stuck at the entrance of the hotend. If I cut the filament just before the twist y can easily extract the filament in the hotend with pliers.
The nozzle is not clogged, if I push filament it goes easy and I can see the fused material exiting the nozzle.
These pictures show what I see when I open the print head door and when I pull a bit the filament (you can better see the ‘knot’).

This looks like you’ve got some heat creep happening, the PTFE tube in your hotend could be damaged.

Have you tried replacing the hotend? A spare came with the machine, and it’s easy to replace. I’d try if that works first.


I think I solved it. After 5-6 frustrating failures (always the same symptoms) using different parameters, I found the right conditions. Now it’s almost 24 hours at work.
What solved the problem was to lower the temperature of the print head to 200 ºC.
It appears that the heat from the nozzle block softened the filament prior to entry into the block. Although the filament specifications indicate a working temperature of 195-220, at 205 ºC the problem already appeared. Probably the fact of being in the enclosure and with a high temperature of the bed (60 ºC) was producing temperature conditions higher than expected.
This was with the original SM2 printhead. I think the biggest ventilation in the new version is to avoid this problem.


I’ve just encountered the same problem. I believe in my case the failure was due to excessive heat build-up in the enclosure. I intentionally had my enclosure sealed up to prevent warping of a fairly large model I was printing with PPLA, but after a couple of filament jams every few hours, I left the enclosure open and have been printing without issue for the past 12+ hours.

I do not suggest adjusting nozzle temperature - if the nozzle temp is correct in terms of filament deposition / stringing / etc. it’s probably better to focus on reducing the temperature in the enclosure (or room).

Out of interest: Do you have the new or the old printhead?
I see several such problems on facebook and here, but this is pretty new to me. I’m wondering if this is just happenstance, or if the new printhead is not cooling the heatsink enough.
Regardless if it is related to the new design or not, I guess the ultimate solution would probably be to increase heatsink cooling - it might be enough to just unscrew the cover of the printhead on the right side, or even on both sides. If not, I guess the fan design needs to be reviewed. When I dismanteled my old printhead once, I was a bit underwhelmed how they guide the air across the heatsink only in a very narrow area and suspected that this might not be enough, but since I yet never had problems and did not see others having any, I kept quiet… I only printed at 230° max, never yet going to ABS temps or so…

I agree. I was thinking the same as you.

I was using a colorFabb PLA / PHA filament that has an indication between 195 and 220 ºC. At 205 ºC the problem already appeared, so the working margin is very small. I also thought of trying with the enclosure open, but it was a 24-hour print, and the enclosure helps to eliminate noise at night (another solution with the same noise problem would have been to turn on the enclosure fan).

The area of ​​the extruder gearwheel should not get so hot because then the filament softens and can bend before entering the lower block as seen in the photos in my first post.

I have the old version of the print head. I don’t know if the new version of the module will improve the situation. It’s hard to tell from the data that Snapmaker gives. They usually say ‘better’, ‘faster’, ‘improved’ but unfortunately they do not provide a technical specifications sheet that users can objectively evaluate.

Oh wow, that sounds awful. Still, I’ve done a few long-going prints with PLA at such temps and did not see that problem - so are you sure your heat sink cooling fan is OK? Is it actually spinning? Or do you think it is just the PLA brand?

Last weeks I was printing with PLA+ from GST3D and had no problems. When working both brands gave me similar surface quality (although the cost is very different). So, the filament is a factor for sure. With the GST3D I was slicing with Luban but with colorFabb I sliced with Cura. I will check the g-code for differences and the fan itself to assure it is working.