Is it normal for the print fan not to run - it works...
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Is it normal for the print fan not to run - it works...  

Active Member
Is it normal for the print fan not to run - it works...

I was doing a print today, and noticed the print fan was not functioning.  I was alarmed at first, but when I went into 'tune' it showed it at 0.  I can change it, and the fan starts up just fine.

Is there a reason it's at 0?  

Posted : 21/03/2023 12:24 am
RE: Is it normal for the print fan not to run - it works...

What filament are you using?
PLA usually has fan from layer two up,
for PETG the fan usually comes on, at layer 4
regards Joan

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 : 21/03/2023 1:19 am
Reputable Member
RE: Is it normal for the print fan not to run - it works...

In Prusa Slicer, turn on EXPERT mode and then go to FILAMENT SETTINGS..  then look at the COOLING section.

You will see all kinds of settings for the fan. Every type of filament (PLA, PETG, etc) will have different settings. PLA requires more cooling than PETG and so you might see it off for the first few layers, but on for others.. some PETG profiles might not use the fan much.. but this is where you can tune your filament for the model you are printing.. For instance.. if you are doing an overhang and using PETG, you might want to drop the nozzle temp and turn on more cooling .. But this is where the fan gets controlled and so looking in here should tell you why you didn't see your fan on.


Posted : 21/03/2023 1:45 am
Active Member
Topic starter answered:
RE: Is it normal for the print fan not to run - it works...

PLA.  I just assumed it would be running.  

Posted : 21/03/2023 2:22 am
Illustrious Member

To check if the part fan works, you can run following gcode in Pronterface or Octoprint console:

M106 S255

This should make the fan spin at full speed.

Otherwise, as mentioned above, check the slicer settings (expermode).



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Posted : 21/03/2023 9:56 am
Estimable Member
Posted by: @jlainton

PLA.  I just assumed it would be running.  

To increase adhesion to the bed, the fan is off by default on the first layer, on all materials. For PLA, the default is the fan is turned on during layer 2 and up. And it doesn't turn on at full speed by default either. It ramps up, only reaching full speed at layer 4 (by default).

Perhaps try printing something small with defaults (or one of the files on the included USB) and watching how the printer works? For PLA, what I've observed:

  • No fan on 1st layer
  • Print head moves slowly on 1st layer
  • Fan turns on at 2nd layer, but is running slow
  • Print head speeds up on 2nd layer
  • Fan and print head both speed up yet again on 3rd layer

When watching your printer, you'll know when the printer is done with the 1st layer because it moves to the skirt (unless you disabled the skirt) and prints a 2nd layer on it. As soon as it moves to the skirt for the 2nd layer, the fan starts running (slowly).

According to the below help article from Prusa, the fan doesn't reach full speed until the 4th layer, but I haven't personally noticed a speed difference from just watching and listening to the printer when it starts the 4th layer. However, the changes from layer 1 to layer 2, and from 2 to 3, are easily visible to the naked eye and ear, at least to me.

All that said...if you're printing PLA, and the fan isn't running by layer 2, and you haven't changed cooling settings in PrusaSlicer, then something is wrong. Otherwise, if it was printing first layer when you saw the fan wasn't running, but it runs on layer 2 and up, then all is as it should be.

Posted : 22/03/2023 1:48 pm