My first post here and I hope you guys can help me out.
The idea I get here is that you guys deal with stuff a bit over my work level in terms of tools you have and what you look for, I'm an in house technician working on just about anything that's needed, spanning from welding, fabrication, kitchen equipment, HVAC and I also do refrigeration, electrical, plumbing etc.
More recently, I started doing 3D printing and been working with that, so that's cool.
Anyways, onto what I need help with.
Dyson makes an air purifier called a DP04 (https://www.dyson.com/purifier...BwE&gclsrc=aw.ds), it's a simple design and was boasted to be the quietest unit out there and the company I work for bought a whole bunch of them and everything was wonderful, then one or 2 of them started making noise, this odd whistling sound occuring randomly that fades in and out.
Happens at different speeds but can take anywhere from 2 minutes to 2 hours before it starts to make this particular sound, we've now had about 12 of these do this and I've reached out to Dyson and worked with them for about a week or 2, emailing back and forth trying to solve it until they eventually just claimed it didn't exist becuase the unit they had on wasn't doing it.
I finally got OK to pull it apart and try to resolve it and my original theory was the bearings in the motor (https://www.ebay.com/itm/NIDEC...earing-/263960141817)
The motor is put together in such a way that changing the bearings wasn't easy like a regular motor, it's got a circuit board sitting on top of the stator where the stator windings are soldered onto, so to get the rotor out with the bearings, you have to unsolder it and so forth, the "end cap" on the motor is held in place with small notches being beaten in over it to keep it in place, so I don't think they ever imagined someone working on it, I tried 4 different bearings, eventually bought some that were $30.00 a piece but I couldn't get the motor back together properly and so the noise would be worse right off the bat, but it was a different sound, obviously from my misalignment.
I then started thinking about why the bearings would be going bad and figured the wheel might not be balanced, so I bought a little prop balancer since that seemed to be the right size for the fan wheel and I checked, it's very slightly out of balance but not drastically so. I tried 3D printing the wheel which came out surprisingly well but it also needs balancing but then I started wondering if it's even worth pursuing or if it's another problem, perhaps it's resonance or something like this.
I've attached some pictures to give an idea of what it looks like, I have plenty more pictures, hopefully you guys can help me figure out what to do with this, I'm kind of lost at the moment.