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At the moment, I am thinking about print fans that cool the plastic when printing. I am not asking about the design of the fanducts, which might be a whole book on its own. I would like to know how to find out the best application of print cooling for a given PLA filament, - that is fan speeds and setup in a slicer of your choice (to learn what the different options are).

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Everybody's combination of fan hardware and print settings is different. Unless someone else has the exact same printer and slicer profiles as you, there's no way to really say anything like "use X% for PLA" or whatever. For practical purposes, you just empirically figure it out with test prints based on a few simple rules of thumb:

  • Use lots of cooling for PLA, moderate cooling for PETG, and minimal cooling for ABS. (Note that sometimes ABS does benefit from gentle airflow, and PLA shouldn't necessarily always just be blasted at max power.)
  • Use less cooling on big prints where each layer takes a long time, more cooling on small prints where each layer is very quick.
  • Axial / box fan? You'll probably want to run it at full power. Radial / squirrel cage blower? You may want to run lower power.
  • Overhangs curling up or sagging? More airflow may be needed. (Lower layer heights also help enormously.)
  • Hot end temp sagging when the fan kicks on? Try less airflow. (Or insulate your hot block better.)
  • Weak layer bonding? Try less airflow. (Or raise your hot end temp.)
  • Small, fast prints getting mushy or corners "pulling in"? You need more airflow. (Or lower heatbed temps.)
  • Print warping / corners lifting off the bed? Try less airflow, particularly on the lowest few layers. (Or higher heatbed temps, or a better adhesion layer, or less nozzle/bed gap for the first layer, or any other approach.)
  • Fan too noisy? Try less airflow. (Or get a better fan.)
  • Filament stringing during travel moves? Try less airflow pointed directly at the nozzle. (Or tune your retraction settings better, or get the moisture out of your filament, or lower hot end temp.)
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    $\begingroup$ Outstanding answer, this was exactly the compilation of knowledge I wished for. $\endgroup$
    – kamuro
    Commented Jul 12, 2016 at 21:23
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I use side-wind to cool down model as simple as possible. It's just a 12cm in diam fan which is driven from arduino (the same contacts as the fan next to the nozzle). No duct, no other stuff. The only thing I consider in terms of making things better is to set up 2 fans which could coll down model from both sides.

The issue is that when model is more complex then cool air is not reaching out oll these crannies and then on some corners I see the difference. Because of this issue I have to orient model facing to the fan in the way which will decrease such effect and I'm usually happy with results. If you are able to imagine how the airflow behaves then you can achieve perfection :)

Of course fan is driven but to be honest I usually use 100% of its blowing power except with first layer which I usually don't blow at all.

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  • $\begingroup$ I am pretty fine with the fanduct, it's a so far pretty proven design that can be found here: thingiverse.com/thing:953811 But I'm glad to hear that your implementation of the part cooling is simple and still works. Thanks for that input. Now I'm still waiting for someone to explain what is ideal and why ;) $\endgroup$
    – kamuro
    Commented Jul 12, 2016 at 10:28
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    $\begingroup$ Sure sure, I'd also like to see other's solutions. Of course I also got that kinda fan as you have (a bit simpler one) but I still use side-wind because for smal details there is no enough time to cool down printing area especially when nozzle immediatelly jumps to next position (where there is no cooling flow) and then quickly gets back. This is where side-wind works for me. $\endgroup$
    – darth pixel
    Commented Jul 12, 2016 at 10:58
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I use PLA and both my fans stopped working. I am not techy and couldn't figure out how to fix them so I set up a house fan that blew directly at the motor keeping it cool and it works as good if not better than the fans that came with the 3d printer. You cannot let your motors over heat because your filament will get curled up insize the nozzle.So try that before buying 3d printer fans.

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    $\begingroup$ Hi, Jeanie, and welcome! I think what Kamuro is referring to is how to control fans for cooling the model during different parts of the print process. Motor cooling is also required in some cases, but I suspect that might not be the issue here. However, in your case, could perhaps the fan cooling the motor also indirectly cool the print? :-) $\endgroup$
    – Tormod Haugene
    Commented Jul 21, 2016 at 19:44
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    $\begingroup$ yes it cools the print too which seems to work perfectly :-) $\endgroup$
    – Jeanie
    Commented Jul 21, 2016 at 20:20
  • $\begingroup$ How does letting motors overheat make the filament curl up? $\endgroup$
    – Tom van der Zanden
    Commented Jul 22, 2016 at 12:03

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