Fan blades replacement

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I have two fans at home, one of them is quieter than the other. I assumed the reason was the shape and number of the blades, as the noisier one features a 3-blade rotor while the quieter one is a 5-blade one. 

A good design exercise that might bring some real-life benefit if proved successful. So I went on and created a model using Onshape, that had to be able to be printed in the Prusa MINI. I designed two parts, the hub, and the blade, that will join with a dovetail. 

While I did not do an exact copy of the quieter fan blades, I tried to stay as similar as possible. Which may not be good enough for the best results.

It was also a project to explore the viability of the 3D printed approach. So this is what I designed: 

To my amazement, 3D printing the blades really favored printing them all together, as the print time of each layer was so small if printing just one that the print needed to be slowed down. So printing five blades did only required around 3 times the print time of printing a single one.  In fact, the whole six pieces could be fitted into the print bed of the MINI. But in my case, I did want to use a different color for the hub, so I printed the hub and the blades separately. 



I used a supports-blocker for the supports not to creep into the sides of the dovetail to make sure it will slide gently in place. I added a 0.2 mm clearance into the designed which allowed and nice pressure fit of the components.


But although I was pleasantly surprised by the tight fit and the good looks of the parts, the final result was not a complete success. The fan still did its job of moving the air but not in a significantly quieter way as I was expecting, so I will not call this a success. 


On the plus side now I know how to fix a fan with broken blades :-)

I would love to hear from you in the comments below if you can shed some light on the matter of fan blades and noise. Maybe a different blade design, maybe some winglets, can make a difference ...

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