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PLA gets stuck every time, but PET is ok  

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a14219
(@a14219)
New Member
PLA gets stuck every time, but PET is ok

Hi there,

I've been struggling to get this working and I really don't know where the problem could be. My Prusa i3 MK3S has been working flawlessly for about a year now. I printed mostly PETG and sometimes PLA. Now I need to print more PLA and every time I try, the nozzle gets stuck after a while.

 

Nozzle stuck

 

I only use Prusament PLA and usually print it at 220 ºC. I tried raising temperature up to 235 ºC and it helped a little bit, but it gets stuck nevertheless after printing for a while.
The filament stuck in the hot end looks like this:

 

Filament

 

And there is a little clog falling down when loading new filament.

 

Clog

 

I'm using mostly Ultimaker Cura to slice my prints. Will try Prusa Slic3r in case this is a software problem.

Does anyone know what could it be? I never have problems printing PETG, this only happens with PLA.

 

Thank you.

Best Answer by JoanTabb:

are you printing in an enclosure?

Is the ambient temperature high?

it looks like your filament is softening above the cold end PTFE

 

if you are using an enclosure  or the temperature is high.    open the enclosure door or cool the temperature down!

Posted : 14/07/2020 8:05 am
JoanTabb
(@joantabb)
Moderator
RE: PLA gets stuck every time, but PET is ok

are you printing in an enclosure?

Is the ambient temperature high?

it looks like your filament is softening above the cold end PTFE

 

if you are using an enclosure  or the temperature is high.    open the enclosure door or cool the temperature down!

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 14/07/2020 10:48 am
a14219
(@a14219)
New Member
Topic starter answered:
RE: PLA gets stuck every time, but PET is ok
Posted by: @joantabb

are you printing in an enclosure?

Is the ambient temperature high?

it looks like your filament is softening above the cold end PTFE

 

if you are using an enclosure  or the temperature is high.    open the enclosure door or cool the temperature down!

Yes, I'm using an enclosure. The ambient temperature is between 20 and 21 ºC all the time.

I will definitely try without enclosure, thank you very much.

Posted : 14/07/2020 10:58 am
Neophyl
(@neophyl)
Famed Member
RE: PLA gets stuck every time, but PET is ok

Joans advice is probably the trick but one other thing is,  have you done a few cold pulls before switching from petg to pla ?  If there is any petg residue left in there it could be causing a partial clog  for the pla making it harder to extrude which would exacerbate any other problems.  Its always a good idea to do a cold pull or 3 when switching from a higher temperature filament to a lower one.

Posted : 14/07/2020 11:59 am
a14219
(@a14219)
New Member
Topic starter answered:
RE: PLA gets stuck every time, but PET is ok
Posted by: @neophyl

have you done a few cold pulls before switching from petg to pla ?

Yes I already did that.

Thank you very much for your help, it's been printing all night so far without any problem. I never thought PLA would soften at such a low temperature! It's usually 40 ºC in the enclosure.

😊

 

Posted : 15/07/2020 5:53 am
Andrew
(@andrew-5)
Estimable Member
RE: PLA gets stuck every time, but PET is ok

It's not the 40deg in the enclosure softening the PLA it's heat creep and heat transfer from the extruder that is doing it. The problem is that when the PLA is starting at 40deg it has a fair head start on PLA that is at say 28deg. Leaving the door open will let the PLA stay "cooler" for longer.

Andrew

Posted : 19/07/2020 4:55 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: PLA gets stuck every time, but PET is ok

@a14219

As andrewld mentioned, the extruder motor heats the drive pulley and thus softens the PLA. For this reason, I cool my extruder motor (40x40 Noktua fan) and can keep the temperatures in the area of the gearbox and the drive pulley stable. The same solution on the MMU2 idlermotor.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 19/07/2020 5:04 pm
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