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Using CPAP blower fan as parts cooler

Discussion in '3D printers' started by Troy Proffitt, Jan 9, 2020.

  1. Troy Proffitt

    Troy Proffitt Well-Known
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    Recently, I have been researching how to enclose my printer since I am starting to print more ABS than PLA and wanted to figure out a way to pump external cold air into the enclosure. I bought an aquarium air pump and some tubing and quickly realized that the airflow was totally inadequate for the use I intended. At Christmas this year I was given an old CPAP machine. When I took it apart, I discovered a 3 phase 12v centrifugal fan that was quiet and powerful.

    [​IMG]

    I went onto amazon and found a 3 phase controller that would work well with the fan:
    https://www.amazon.com/dp/B078T8YPG...olid=2S7TX22N5DB6M&psc=1&ref_=lv_ov_lig_dp_it



    The controller includes a potentiometer and a switch that will reverse the direction. I quickly discovered that I could almost run the fan at its slowest setting and still provide plenty of air pressure.

    [​IMG]

    Very easy to hook up, but I was worried about that the Duet controller couldn't provide the amps needed to run this, so I ended up purchasing a DC-DC relay so I could use the power source that came with the CPAP machine (12v 5 amp). Relay can be found here:

    https://www.amazon.com/gp/product/B07JP6CP8X/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

    [​IMG]

    To protect the electronics and fan, I just went to Home Depot and picked up a $7 junction box.

    Lastly, I designed a fan mount for my printer carriage:

    [​IMG]

    I am using the CPAP tubing that came with the machine and it's a bit short, but I was able to get it to work. I'll probably buy a longer one since they don't cost very much, and the fan is plenty powerful.

    After 9 revisions to the model, I finally ended up with something that would work! I'm still testing everything out, but it looks good so far:

    [​IMG]
    [​IMG]

    I'll try to get a video of it in action later tonight.
     
  2. Troy Proffitt

    Troy Proffitt Well-Known
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    Here is the video! Works great..
     
  3. Some Dude

    Some Dude New
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    Hi Troy - great post. Question for you if you have time. I actually am using this information for a similar project. I have a couple CPAPs that have gone bad and I just want to bypass all the logic boards and just push constant pressure out of my fan using a controller. I think I can pretty much just use what you had above verbatim, and just strip out all the electronics and use the existing CPAP housing. My main question is this... I'm not much of an electrical person. What is the point of the relay? What happens if I don't use it? Thanks for your post and possible help!
     
  4. Christian James

    Christian James Journeyman
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    Cold air is bad news for ABS or are you just trying to cool the electronics?
     
  5. Troy Proffitt

    Troy Proffitt Well-Known
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    The reason I used a relay is because I was worried that the 3d printer contoller couldn't provide the amperage needed to safely control the CPAP fan. A relay uses a voltage "signal" (in my case, the 12v power from my controller) and then opens a circuit to a much higher amperage 12v power source (the original CPAP power brick). If your 12v power source is sufficient to power the blower, there is no reason to use the relay.
     
  6. Troy Proffitt

    Troy Proffitt Well-Known
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    On ABS prints, I don't use the parts cooler at all so it will be turned off.
     
  7. Christian James

    Christian James Journeyman
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    I didn't really mean the filament cooler beside the nozzle - what I'm referring to is the printing environment.
    ABS needs a warm environment to prevent de-lamination of the print. The heated build plate, typically 100C+ for ABS, keeps the bottom of the print heated whereas if the upper layers are cold,stresses become too great and the print cracks (de-laminates). Building a cabinet is a good idea though.
     
  8. Some Dude

    Some Dude New
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    Gotcha. Makes sense. Thanks again for the help. i just got that 3-phase controller in the mail a few minutes ago. Gonna try it out now!!
     
  9. Vasiliy Pupkin

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    Since mainboard uses PWM to regulate part cooling fan speed, how do you make sure that your relay can switch with the required frequency (frequency of PWM)? As far as I'm aware it cannot. So did it work finally?
     
  10. Troy Proffitt

    Troy Proffitt Well-Known
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    Yes, I was able to get it to turn on, but never could consistently change the speed of the fan via the software. I could still adjust using the dial on the PWM controller. Turning on/off via GCODE worked fairly well.
     
  11. JB Lizard

    JB Lizard New
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    Excellent build. I was just trying to confirm if you can just run the original power supply thru that motor controller directly with no control voltage or relay? I just need precise speed control for a CPAP 3 phase DC blower. I'm using it for a for a mini foundry project. The original power supply I have is 12V DC 6.67A
     
  12. Dgodrummer

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    hi Troy - thank you for this post/links! They are very helpful.
    I am a woodworker, making a positive pressure mask using a similar CPAP blower. I'm powering it with a 18v Ridgid tool battery, followed by a small adjustable voltage regulator to drop voltage to 12v. I just ordered the 3 phase controller you linked. I have a Carbon x1 printer to make the box to house the components which I am designing in fusion 360.

    Can you would explain where to connect 3 wires from blower to the controller: I have Yellow, Purple and Brown wires from blower to 3 phase controller power inputs: C/B/A/ - DC/ +DC connector. AND also where to connect the 2 power wires (red/black) from the voltage regulator to 3 phase controller. Assuming, but not quite sure, that the DC -/+ connectors are power inputs?

    Any help is sure appreciated.
     

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