40mm Supportless, Directed Cooling Fan Duct for MendelMax & Prusa

by AeroMonkeyDork, published

40mm Supportless, Directed Cooling Fan Duct for MendelMax & Prusa by AeroMonkeyDork Mar 18, 2013
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This duct takes the good 40mm Fan Duct V3 from Ultibots and optimizes it to not require printing supports, and to evenly distribute the cooling flow across the width of the gap. It also gives more directed flow toward the printed parts at the end of the print nozzle.


Print without support. I printed mine at 0.20 mm on a 0.35 nozzle. 3 perimeters and 3 solid top & bottom layers.

The fan mount is taken straight from http://www.thingiverse.com/thing:34387.

The fan mount is also the belt clamps.

18 March 2013 - Note: I have sized the holes that mount to the fan to be tapped for an M3 bolt so it does not need a nut. These holes have a 2.5 mm diameter, so if you want to use a nut to hold your fan on, just drill them to the diameter you need.

04 June 2013 - Added v2 stl that makes the exit slots 5 mm longer by request. The width of the slots was reduced slightly to keep the total exit area the same. I have not tried printing this version, so let me know if this version works!

30 June 2013 - Added the stp files of each version (I used the 203 version of the step exporter in Alibre, as opposed to the 214 version. I don't know the difference)

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Many thanks for this! I just used the main body but with a custom mount it's spot on for my Prusa i3 clone, I printed it in Nylon as I wanted something that would deal better with proximity to and occasional light contact with the hot end.

Thank you AeroMonkeyDork, this printed well.

The fan_mount.stl doesn't fit a 40mm fan. It's actually 46mm in width and the holes are 36mm apart (measured from the center of each hole) and on my fan it's 32mm.

As far as I can see, the fan should be mounted to the fan duct. The "fan_mount.stl" is for mounting the duct to the carriage, and not for the fan itself. Hope this helps.

Hey Gemini64, I just uploaded them. Let me know if you're able to open them. (If not I can export them as STEP 214 & I don't know what the difference is between that and the STEP 203 that I used.)

Very sorry for answering 5 months late, I don't understand why I can't get email notifications of comments posted on Thingiverse. Both STEP files were fine.

I'm not exactly sure myself of the fine nuances between AP203 and AP214. :-)


Hello AeroMonkeyDork, could you upload a STEP version of your file? That way those of us who use a different CAD program than Alibre can import a solid file rather than try to modify the STL.


I can change the dimensions on the slot. I'll upload a model when I get a chance.

This design works great, except for one minor issue. When using the J-head on my setup, the cooling is directed more towards the front rather than evenly across the nozzle. The uneven distribution of airflow does impact print quality, particularly with small layer heights. How difficult would it be to move the nozzle holes back 5mm (or lengthen them back 10mm) for even coverage using this hotend?