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Road to a fanless printhead 2 - brushless DIY blower

In continuation of my previous DIY blower post, I have some progress to report.

So there I was thinking which brushless motor to get for my DIY blower, and couldn't really find anything suitable (partly because of my total lack of knowledge about brushless motors and controllers). And then it struck me. Why buy a motor and controller, and then mess with programming and interfacing it with the printer's electronics when there are people who did all that messy work for me. There is a component all we DIYers have in abundance - DC fans! They are brushless, have integrated controllers and are PWM controlled. Now, to power a blower like this one would need a really powerful fan.

Luckily for me (in this particular case), the water-cooler in my workstation PC broke down recently and it came with 2 really powerful 120mm fans. Well, it was time for some fan surgery. :)

[this won't hurt a bit...]

First off, I needed some way to extract the motor, so I kinda ripped one apart completely, and then I realized I would have trouble attaching the impeller to the tiny shaft (yes, I know, tiny shaft, very funny), and even more trouble keeping it centered. So fan no.1 was a bust.

Now I approached fan no.2 with a bit more care. First I snapped away all the blades (very sharp and nasty when broken!) and removed the little clip in the back which holds the rotor in place (being careful not to lose it). 

I could now remove the rotor, but it still had what you could call stumps left from where I amputated removed the fan blades. Using a hobby knife I got rid of those as best as I could. To finish the job, I placed it in my trusty drill press and set it to rotate at high speed while holding a piece of sandpaper to it. (Kind of an impromptu lathe, if you will.)

Excuse the lack of photos at this step, I forgot to take them at the time and it was too late afterwards!

Then I returned the rotor back to its place and attached it with the small clip. I also got rid of the fan's frame by cutting the 4 legs connecting the motor to the frame.

It was time for some careful measurement and drawing. What I got in the end looked something like this:

The design I came up with was very basic, because I wanted to try it out as soon as I could. Here's what it looks like:

The impeller in the picture is mirrored though, in the end I opted for a backwards curved one, because it produces more pressure and is quieter.

Note that the goal here is to push air down a substantial length of silicone tubing which has an inner diameter of only 8mm, so pressure is essential.

This design also features the world's most horrible approximation of an involute curve, because I have absolutely no clue how to construct one in AutoCAD (at least not in a fast way).

With the design done, I fired up the printer and this is what came out in the end:

I left the temperature too high while printing the impeller so it came out a bit shoddy, but it works. The tape is here to seal the air from escaping where the parts connect. The impeller is attached to the rotor with extra heavy duty double sided tape. I've used it before for things that rotate fast and it holds forever, but it's still removable with a bit of force if you need to change things.

So there you have it, a DIY brushless blower. But the million dollar question is...

Why yes, it does! Thank you for asking. And compared to the DC motor I used before, this is like a gazillion times more quiet.

I know the old "video or it didn't happen" so here's a crappy video I managed to record (it's 4 AM here, so that's the best you get for now).

For reference, the scale in the video is 40cm long.

Quite some airflow through an 8mm openining, huh? I must determine the correct length of tubing I need for the printhead and test with that too, although for now I can confirm that it indeed pushes air even through the much too long piece of tubing I have now.

Now imagine how cool this would be with a properly designed impeller and casing?

More tests and videos to come as soon as I find some time.

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