Circular fan duct for Prusa I3

I have been recently looking for a new fan duct for my Prusa i3 3d printer as I’ve found the stock one only pushes air in one direction. I was ideally looking for one that I could attach an inductive sensor to for one of my next attempts to improve the printer.

An inductive sensor detects metal, the plan was to attach it someone near the extruder and use it instead of the standard mechanical end stop switch that I previously had a problem with when the switch was missed and the extruder was pushed into the bed damaging various parts. The fun part is the printer’s firmware has an option for auto bed levelling, that effectively uses the sensor to detect the distance of extractor from the bed at various points on the bed and then creates a map, allowing the 3d printer to print on a unlevelled bed. I have found that levelling the bed with the mechanical screws on the bed to be very difficult to get correct and pretty frustrating so I am thinking this would make a good little project.

Back to the fan duct, I was able to find something similar to what I was after by mcleishn on titled “HICTOP fan nozzle cooler Filament”. I really liked the design however it lacked a mount for the inductive sensor and I was finding the duct difficult to print. So instead of making one from scratch I decided to make the following improvements to mcleishn’s design using tinkercad:

  • Added a mount for the inductive sensor to the side of the bracket
  • Added some extra support to the bracket to make the arm attaching the vent stronger
  • Made the top layer of the circular duct bigger to remove holes in prints
  • Added bits of plastic inside of the circular duct to improve air flow and to act as a support for the top to help prevent print problems.

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As you can see it came out pretty well. The finished designs are available on thingiverse here.

5 thoughts to “Circular fan duct for Prusa I3”

  1. Did you find it made a significant difference in cooling over the design you based it on. I had printed the design you based it on and found that the cooling was less effective than the orginal one-sided fan

    1. Hey Michael,

      On the original design I had a number of issue with included problems with the lack of a tight seal causing the air not to reach the prints as well as holes in the top of the print. My version has some internal supports to handle any print problems. Regarding the efficiency I have found that it does not blow air as powerfully, however it does blow air at whole area print area. It has actually improved my print quality.

      I have been toying with the idea of using two fans and feeding them both in together for extra air flow.

      Let me know if you do print my version, I’d be interested in you’re feedback.


  2. I know this is about a year old by now. I hope I’ll still get feedback. How do you attach the assembly to the extruder area?

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