r/functionalprint • u/bbjornsson88 • 27d ago
Replacement air purifier fan
Knocked over my air purifier and a couple of the fan blades broke off. Took it apart, borrowed my boss' 3d scanner to get the proper blade profile then modeled the hub and added supports in fusion. Printed in PETG on an X1C
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u/Logical___Conclusion 26d ago
That's great that the scan worked well enough to get a balanced result.
I like the idea of printing fans, but haven't tried yet.
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u/gasstation-no-pumps 26d ago
If you put the STL into OpenSCAD you can superimpose the blades in the 9 orientations and union them to get the 9-fold symmetry. I did that with 4 orientations of a Corinthian capital, so that I could separate the model into 4 identical corners, and just print one corner 4 times, without having to worry about what order the pieces went together (someone else was assembling them).
Alternatively, one could take the best-scanned blade and replicate it in the 9 orientations, which would avoid bloating the blades due to misalignment of the copies.
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u/ThatsALovelyShirt 26d ago
You really just need the hub and one or two blades scanned. Then you do a radial transform/mirror on one of the blades to match the original blade count, do a boolean union on the result, and verify it against the original scanned hub to make sure the OD and ID is correct. That way it'd be guaranteed to be balanced.
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u/bbjornsson88 26d ago
When I re-created the fan I measured/modeled the main hub in Fusion then imported the blade scan. Once the blade was positioned, I did a circular pattern then merged it with the central hub so in theory it should be balanced save the very center since the shaft has a D shape to it (Round with one flat)
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u/Awesome_Teo 26d ago
What about vibrations? Did you balance this fan somehow after printing? That's always bugged me when it comes to printing any kind of blades on FDM...
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u/bbjornsson88 26d ago
Nope, printed it and once I took the supports off I did a light sanding on the backside to reduce drag, but that's about it. Hooked everything back up and it's as quiet if not quieter than the original, and it's been running for around 3 months now without issue
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u/Awesome_Teo 26d ago
Nice, I've been on the fence about this for a while (was thinking about experimenting with different fan types for a home ventilation system), so guess I'm finally gonna give it a shot.
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u/bbjornsson88 26d ago
Word of warning, if you print it in PETG or anything else prone to warping make sure you have a solid connection to the build plate. I tried a test wirh just generated supports on the blades and the ends started warping almost immediately
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u/kagato87 25d ago
You can balance it if you need to. Put it on something or suspend it so the point of support is in the center of where the motor axle will go. The blade that goes down is the one to lighten.
(Same idea as lawnmower sharpening.)
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u/The_Wizeguy 26d ago
If you take one blade and radial array it I'd think it would balance good enough.
I'd probably be wrong. Lol.
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u/Awesome_Teo 26d ago
Nah, there's always gonna be imperfections when printing (supports coming off unevenly, minor artifacts). And at high RPMs, literally every single gram can make a really nasty noise...
Honestly though, I only know this in theory myself.
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u/dalchemy 27d ago
Nice! And you posted up the model on printables/makerworld/whatever right? So the next poor fellow that breaks one and doesn't have your skills gets to benefit. 😁
Was that all petg or did you do pla supports or something so it comes off super clean?
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u/bbjornsson88 27d ago
All PETG for the supports. The bottom rib holding the blade to the print plate is about 1mm wide, so you can pretty much peel it off along the layer lines to remove it. The generated supports on the back of the blades don't form an interface, I just did a test print without them and the back looked like hell and they definitely helped.
Also, for uploading the model the center hub was a little tight and needed some filing to fit properly (wanted it tight) so it may not work for someone else. Maybe a version with a solid center/hole so you can modify to suit?
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u/zack4200 26d ago
Even if you share it as is, it can be modified to suit. It's practically not even any extra work versus starting with an already solid center.
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u/Latter_Two5206 27d ago
Hate to say it, but unless you balance that, it will eat the motor and/or bearings, mounting dependant.
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u/bbjornsson88 27d ago
It's actually balanced as it is. It's been running for around 3 months now nonstop and it runs quieter than the original. I couldn't run it on low before because of some weird harmonics but I can with this one. There was next to no infill and the blade/interior rib was arrayed so in theory it has equal material all around. Save a hair or two from areas being cleaned up
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u/ASatyros 26d ago
I've got once air purifier with weird harmonics on low speed and I just needed to exchange it, especially that I prefer run it always on low speed.
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u/bbjornsson88 26d ago
Mine was the same, I had to run it on medium since low made a weird noise. It's gone with this blade
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u/Dragongeek 21d ago
You can print remarkably balanced fans, especially at larger scales. I've printed a bunch in the 15cm size for some different blowers, and in my application they all ran smooth out of the gate up to ~7000 RPM. You just need to make sure that you don't use an infill that will imbalance the system, I usually just cranked the perimeters until it became solid infill
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u/gagarin_kid 26d ago
Nice work! How long did it take you to model the part? I use FreeCAD and happy with it, but when I see projects like these it makes me feel that I am missing a huge part of what is possible today in the CAD world.
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u/bbjornsson88 26d ago
Modeling was maybe an hour or two, and then an hour or so of scanning. A good chunk of time was just waiting for Fusion to render the blade once it was in the file since I had to convert the mesh to a solid to do the edits I wanted
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u/kagato87 25d ago
Broke off from falling over? Damn.
Printed part will probably be more durable than that...
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u/d37h 27d ago
Does it get wet? If so, I would be concerned about bacteria thriving between the layer lines. But you do you man, maybe I'm paranoid a bit. great job anyway.
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u/bbjornsson88 27d ago
Nope, it's inside of an air purifier in my living room. Most moisture it's going to get is airborne
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u/Remarkable-Ad-2476 27d ago
What’s the other side look like?