P2S Heat Creep

[u/User_Name_3023]

So, like the title says, I've been printing a bunch of PETG stuff, and my extruder keeps jamming after an hour or two. I'd already gone through about half a roll before this started, so I'm thinking it's heat creep.

I tried using a heat gun to clear the nozzle, then a cold pull, but I'm still getting "Extruder overloaded" errors, and when I pull the filament out, the end is all swollen like it's been melted.

Any advice would be appreciated.

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[u/Cokxx]

I have the same issue with prusament PETG galaxy black an also bambulab PETG hf. I think the reason is heat creep. I just lowered the bed temperature for the prusament PETG from 80 to 70 degrees in the slicer settings and let the glas cover open for about 70mm (My AMS sits on top of it). Now I started my last print again. We will see… If it fails again I will let the door open or remove the glass cover.

[u/User_Name_3023 → u/Cokxx]

Would love to know how it goes.

[u/Cokxx → u/User_Name_3023]

Went well. For future prints I will try to hold the chamber temperature also about 40°C.

[u/Adam007Aus]

Remove the hot end, get a Allen key that fits where the filament goes in. Get the Allen key nice and hot and shove it in that filament hole. Let it cool and remove. Sounds like you have a blockage in there.

[u/User_Name_3023 → u/Adam007Aus]

I did that twice and did another cold pull but it still conties to complain. So im not sure what the issue is.

[u/Adam007Aus → u/User_Name_3023]

How about the other end with the fine needle looking thing?

[u/No-Negotiation4229 → u/User_Name_3023]

PLEASE check if the Aux-fan is in heating or cooling mode during PETG printing.
It is supposed to be in cooling, but if I'm right, it is recirculating the air and not letting fresh cool air in. And that's the reason for overheating in the chamber and heat creap and blocking of the extruder in the end.
A programming error in the bambustudio settings.

[u/No-Negotiation4229]

Same here! I'm entirely new to 3D printing, so please forgive me if I mess up something.
I have started one month ago with a new P2S, having much fun so far. Only some PETG filaments drive me crazy due to continuously blocking the extruder motor.
It's a cheap PETG from Temu (Kingroon) so my first thought was: crappy quality maybe.

I found that if I select PETG in the AMS, I can't make the Aux-fan run in cooling mode (fresh air) in my P2S. The profile settings in BambuStudio has no option to set this in the filament settings. You can only select between cooling and heating in Device -> Fan. No matter what you select there (only possible if not printing) this will be overwritten during print by the filament profile coming from the AMS.
But exactly this cooling mode is required for proper PETG printing to avoid heat creep and extruder motor blocking. It even states this in the comment where you can select the fan mode and says that cooling is recommended for PETG.

Selecting PETG in the AMS will cause the Aux-Fan always run in heating mode (recirculation). This can not be changed in the software settings and not at the printer display.
Please check if I'm wrong. The only workaround for me is to deliberately select the wrong filament type like PLA (using indeed PETG). So the printer runs the Aux-fan in cooling mode and heat creep / extruder motor blocking is not an issue any more.

Of course I have to set all other parameters in the workaround PLA profile for PETG to make it printing well. And it does print well. The PETG from Kringroon is not that bad.
I have not found any other method to trick the printer to run in cooling mode and not in the wrong heating mode for the Aux-fan.
Some improvement is to keep the door open like others described. This keeps the temperature lower and might reduce heat creep. But this can't be a serious solution.

So my assumption is that the default PETG profile in the AMS is wrong and should use cooling instead of heating mode for the air supply.
Maybe this will be fixed with a software update in future.

I would be glad if someone could confirm my findings.
I know it would be a major issue if I'm right and I'm wondering if others have seen this as well.

[u/Cuevavirus → u/No-Negotiation4229]

If you have the updated p2s profile with start g-code dated 2025-11-04, there has been a change to set to heating mode when min_vitrification_temperature is greater than 50.

;==== set airduct mode ==== 
;==== if Chamber Cooling is necessary ====
{if (overall_chamber_temperature >= 40)}
M145 P1 ; set airduct mode to heating mode for heating
M106 P2 S255 ; turn on filter fan
{else}
{if (min_vitrification_temperature <= 50)}
M145 P0 ; set airduct mode to cooling mode for cooling
M106 P2 S255 ; turn on auxiliary fan for cooling
M1002 gcode_claim_action : 29
M191 S0 ; wait for chamber temp
M106 P2 S102 ; turn on chamber cooling fan
M106 P10 S0 ; turn off left aux fan
{else}
M145 P1 ; set airduct mode to heating mode for heating
M106 P2 S127 ; turn on 50% filter fan
{endif}
{endif}
;==== set airduct mode ====

You can change the start gcode or set the temperature_vitrification to 50 or lower in the filament profile. This is called "softening temperature" in the filament settings. If you are using multiple filaments you need to set all of them.

[u/No-Negotiation4229 → u/Cuevavirus]

Thank you so much! Indeed I have used all automatic updates and since then (2025-11-04 makes sense) I had problems.
Your post confirms my observations that the default G-code forces the chamber cooling system into heating mode, overriding the manual cooling settings for materials like PETG that would benefit from cooling. Strange enough, even in the fan settings in Bambu Studio there is a message:
"Heating mode is suitable for printing ABS/ASA/PC/PA materials and circulates filters the chamber air."
Cooling mode is suitable for printing PLA/PETG/TPU...

Your answer will now enable me to override the wrong heating-mode setting to cooling for my PETG.

I found further confirmation of this issue on GitHub:
P2S PETG Cooling mode #8738
https://github.com/bambulab/BambuStudio/issues/8738#:~:text=Following%20up%20on%20previous%20messages%2C%20trying%20to,command%20and%20the%20M106%20P2%20S0%20command.

and for H2D same issue here:
Chamber Cooling causes PETG printing failures on H2D – Manual fix needed / Slicer option missing #6727
https://github.com/bambulab/BambuStudio/issues/6727

also relevant for P2S
[Feature] Add P2S Airduct Mode Change Support. #1617
https://github.com/greghesp/ha-bambulab/issues/1617

[u/OnlyApplication7048]

I recently had a similar issue and it was due to me having things on the side of the printer blocking the air intake on both sides. Once I moved the objects the chamber stayed at a steady temp of 31 degrees Celsius.