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I was wondering if adding (an) extra fan(s) (not connected to the printer, but blowing on the print area) could improve the quality of PLA based prints(printing at 210 C). The printer already has a built in fan with a fan shroud that directs air to the hotend, but is it beneficial to add an extra fan in order to get better results on overhangs, fine details, etc, or does extra cooling negatively/not affect print quality?

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    $\begingroup$ Adding extra fans to cool the print down faster during printen will most certainly cause more problems than it will solve. If the print cools down rapidly, the chance of it warping and/or falling off the bed is more likely. Also aiming a fan directly at the print will add more stress on the hotend because something (the fan) keeps cooling it down, making it work harder than needed. $\endgroup$ – Granny Feb 13 '18 at 13:10
  • $\begingroup$ Thanks for the comment. Just for clarification, did you mean "aiming the fan directly at the hotend" will result in more stress on the hotend, instead of "aiming the fan directly at the print"? $\endgroup$ – zack1544 Feb 14 '18 at 6:30
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    $\begingroup$ Well if you are blowing colder air at the hotend the hotend will struggle more to reach the desired temp. Just like when your fan shroud is blowing on your heatblock or hotend causing it to drop in temp. Aiming it at the print itself can cause it to warp. $\endgroup$ – Granny Feb 14 '18 at 7:30
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The printer already has a built in fan with a fan shroud that directs air to the hotend

Unless your printer is defective, it may look like so, but the airflow should really be directed towards the print, not the hot-end. Cooling the hot-end will at best just waste energy, requiring extra heat to keep it hot, at worst affect your print quality negatively.

is it beneficial to add an extra fan in order to get better results on overhangs?

The issue with external fans, not connected to the printer, is that you can't properly direct their ariflow, so:

  • you will direct some of it on the hot-end itself (see above on why that's not good)
  • you will potentially cool your print unevenly, which - depending from how much, how fast, and what type of filament you are using - may warp your prints

That said, depending from a number of factors, including your ability to position the fans appropriately, you may gain some benefit from them (I saw people doing this to help with PETG stringing), but I would recommend instead to upgrade the part fan of your printer (e.g.: larger diameter, higher RPM) and your duct (better focus on the extruded filament), as these upgrades will have no drawbacks and will perform consistently on each part of the print.

For most common printer, there are printable mods that allow to do both, often available off thingiverse or on dedicated user community forums.

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  • $\begingroup$ Thanks for the insightful and detailed answer. Maybe the fan shroud is the cause of the under-extrusion my printer has been experiencing lately? Or it could just mean that I need to replace the nozzle (or worst case, the hotend). $\endgroup$ – zack1544 Feb 14 '18 at 6:25
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    $\begingroup$ @zack1544 - everything is possible depending from.a myriad of factors, but if your printer is undersextruding, I would start investigating the nozzle, I would say the possibility for the fan to cause underextrusion are limited. $\endgroup$ – mac Feb 14 '18 at 7:47
  • $\begingroup$ @mac The Tronxy X5S hot end duct is notorious for blowing directly onto the base of the nozzle, rather than the part - to the point where the extruder would begin skipping because the temperature at the nozzle had drop significantly, even when the heater block itself is still at set point temperature. $\endgroup$ – towe Apr 11 '19 at 12:11
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Fan blow at hot end is necessary because hotend needs cooling.

For PLA it will yield better result with a seperate controllable fan direct airflow across the print head, but just like everything with 3D printing, you will need to test out every possible configuration to get the best for your setup.

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