Thursday, April 26, 2018

The Mother of All Print Cooling Fans Revisited: Printable Blower

The biggest problem with the remote print cooling setup I tried here was that the blowers can be a little hard to get or expensive to buy.  At the suggestion of someone on the RepRap forums, I decided to try my hand at designing a printed blower that would mimic the function if not the performance of the CPAP blower.

The heart of the blower is a hard disk drive motor which most people can pull out of an old drive for free.  If you don't have one, someone you know does.  At the makerspace, some of the members work in IT and often bring in boxes full of HDDs to be scrapped.  They're mostly after the aluminum chassis to be melted down for casting, and the magnets.  I like to grab the bearings from the head positioning lever, and I grabbed a few motors for just-in-case.  It looks like that was a good idea!

I made some measurements and created a model of the motor first, then the impeller, and finally the housing.  This isn't a final final design- more of a proof of concept.  I'll be updating the design to some final form to fit the CPAP hose, etc., in the near future.  I want to experiment with a straight-through type design where the exit port will be on the "bottom" of the housing (should be easier to print).

Printed blower with the cover in place, held on with a few pieces of aluminum tape for testing.  The blower is 68mm in diameter and 41 mm high.


Cover off showing the impeller, held on the motor with 3 screws.  The impeller is 60 mm in diameter, and rotates CCW.  As it spins, air drawn into the center of the impeller is flung outward by the vanes, and goes down into the base where it is directed out through the exit port.



HDD motor mounts in the base using 3 screws.


Base has posts to mount the motor, and wires are fed through a hole in the side.  The posts are probably not very aerodynamic, so I'll look for ways to change the design for a little better performance.  It might be better to take the wires out through the bottom surface for the same reason.



3D printed blower for remote print cooling in a 3D printer from Mark Rehorst on Vimeo.


Ebay is littered with cheap drivers for HDD motors.

Update:  I reworked the design, made it much more practical, and it moves a little more air, too.  It's still not as powerful as the CPAP blower, but I suspect that's mostly because of the motor speed.

The new design prints in 4 pieces, the 80mm diameter impeller, top bottom covers, and the 22 mm diameter exhaust tube.  I decided to make the tube a separate piece so that it would print in very high quality.  It also allows the possibility for different sized tubes to be mounted on the same blower.

The assembled blower.

All four pieces: the base and top covers, the exhaust tube, and the impeller.  No support material is needed for any of them.

All four pieces print without support material.  I printed the impeller in 100 um layers, and the other pieces at 200 um.  I used PETG for the impeller and ABS for the housing, but since none of it gets warm, you could really use just about any materials you like.

The bottom side of the base (left) has slots for routing the motor wires.


I added mounting holes on all six sides of the housing, and some slots on the bottom for routing motor wires in case you screw the bottom of the blower down to a flat surface.

The output tube is 22 mm in diameter to match the rubber end of the CPAP hose.

The exhaust tube fits into slots in the top and bottom covers.  There are also bosses to ensure that everything self aligns when you assemble it.  The top and bottom covers are held together with plastic anchor screws.

While the box fits together tightly, it's a 3D print, so there's no guarantee that it's air tight.  It's probably a good idea to run a strip of tape around the seam in the box where the top and bottom covers meet to reduce any losses that may occur via that route.

How does it work?  See for yourself:



You can download the CAD files or just export the STLs here.

Update  5/6/18:  I kept asking myself "why doesn't this thing move as much air as the CPAP blower?", so I did a couple basic tests.  Though I don't have a tachometer to measure the speed, setting them up side by side the answer was obvious.  The CPAP blower spins MUCH faster.  Another thing I noticed was that the clearance between the outer edge of the impeller and the housing in the CPAP blower was about 4 mm.  My printed housing was 83 mm in diameter and the impeller was 80 mm, so I designed and printed a 75 mm impeller to allow more clearance.  This impeller has 9 vanes instead of 12, which works nicely with the spacing of the 3 screw holes.

When I tested it again it didn't seem to move any more air.

That got me thinking- the CPAP motor is rated for 25W and when I'm running at full output, it's using about 12W to move the air (OK, some is moving the air and some is heating the motor).  The HDD motor is designed for low power- maybe 5 or 6W at 12V, so of course it isn't going to move the same amount of air as the 25W CPAP blower.  It's turning slower and it doesn't have the same power available to do the extra work needed to spin faster against the resistance of the air.

So, figuring that anyone who wants to use something like this for a print cooler for a 3D printer is probably going to have a 24V supply in the printer, I tried connecting it to a 24V power supply:

Printed blower with HDD motor running at 24V from Mark Rehorst on Vimeo.

Woohoo!  Look at that!

I decided to check the current:


Yup, about 1A which works out to about 24W.  The CPAP blower uses about 12W and it moves about the same amount of air.

I got out my handy-dandy IR thermometer and pointed it at the motor in the bottom of the case and it was reading about 60C after about 15 minutes of operation.  That's probably a bit excessive for a HDD motor and it probably won't last long at that temperature.  And you definitely shouldn't print the blower using PLA if you're going to run a HDD motor at that kind of power input.  Of course, in a normal 3D printer you don't need nearly that sort of air flow so it should be OK to run it for print cooling from a 24V supply.

I think this could be made to move air like the CPAP blower by using a BLDC motor used in RC cars and airplanes.  The CPAP uses a 4 pole motor rated for about 22k rpm and 25W.  That's about 2000 rpm/V.

In the RC world, they generally don't talk about voltage.  They think in terms of lithium battery cells connected in series.  Each cell produces 3.7V, so the closest thing to a 12V motor will be a "4S" (4 cells in series- 14.8V) motor.  So what we want is a 4S motor, preferably one that isn't rated for much more than 25W, which is similar to the CPAP motor spec.

The place to look for cheap brushless DC motors with similar ratings to the CPAP motor is RC hobby suppliers.  But you have to be careful when selecting an RC type motor is that they are often rated for huge amount of power in very small motors.  That means the winding resistance and inductance are. very low and they may take huge current (and run hot).  Those motors are usually kept cool by the prop-wash that is blowing over them whenever they operate.  The centrifugal compressor/blower I'm making copies the CPAP blower and puts the motor in the box with all the swirling air, so the motor should stay nice and cool.  Even at that, you don't want a motor that's going to suck too much current and you don't want it to burn up if you're running it from a 12V power supply.

If you're using this type of blower for a print cooler, it's never going to operate at full output, which means lower voltage motor should be OK even if you run the driver from a 12V supply.

A quick check at Hobbyking finds dozens of cheap brushless motors rated for 2000 rpm/V (2000kv in RC hobbyist lingo) or more, but only a few 4S rated motors.  If you use a lower voltage motor it will work OK, but if the driver ever fails it may burn up the motor.

Here's a promising motor for $7.42.  It's a 3100kv, 3S motor rated for 59W.  It should work fine from a 12V supply which will theoretically push it over 36k rpm, but again, we won't be running it nearly that fast for print cooling (PWM will keep the power and speed down) so it should work fine.  It's only 13mm in diameter and it weighs 10g!

UPDATE 4/1/20:


There's been a lot of interest in this post since the COVID-19 epidemic became a thing.  For anyone who is interested in trying something like this and doesn't know how to go about copying the curves in the blower impeller, I did a blog post that includes the technique I used here.

57 comments:

  1. Nice work on this Mark. I've really enjoyed following along with your work on this printer. I'm going to write an article about this for Hackaday.

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  2. Replies
    1. Here are the Fusion360 CAD files for the yellow one in the pictures: https://a360.co/2r9X5bO You can export as STL from that link (upper right corner). All three pieces will be in one STL file, but when you bring it into Slic3r, you can just split it into the 3 separate pieces then arrange them on the platen for printing. It doesn't print very well because of the overhangs on the bottom of the exhaust tube.

      I have redesigned the whole thing to be printed in 4 pieces including a separate piece for the exhaust tube. It is printing now and when it's finished I'll post pictures and links. The new design uses an 80 mm diameter impeller, so it should move more air. We'll see.

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    2. Hello, I am trying to Separate the file but am having trouble. I can get all the parts out of the casing but i cannot separate the top of the casing from the bottom of the casing. I was wondering if you could send me a separated stl file.

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    3. In PrusaSlicer, just drop the STL file on the platen, then select "split to objects" using the icon in the menu bar at the top of the window- it's a square icon with an "O" on it. That will separate the 3 pieces, then click on the auto-arrange icon in the menu bar (the icon to the right of the trash can) and they will be spaced out on the platen. Select the top cover by clicking on "printer blower.stl_2" on the right side of the window, then rotate that part 180 degrees along the X or Y axis.

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  3. Nice design , I may build this as I have plenty of old drives around. The other thing I considered was aquarium air pumps. The larger pumps might have just the right amount of air flow and the tubing is easy to route, maybe use brass or copper tubing for the nozzle output.

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    1. Thanks! There are different types of aquarium pumps- the AC powered ones that vibrate a bellows with flapper valves, and piston type that use a DC motor, brushed or brushless.

      The vibrating type are hard to control- they are either on or off unless you use some sort of VFD, but that gets expensive, and I suspect the pump is designed to be resonant at 60 or 120 Hz so even with a VFD you may not get much control of air flow. They also tend to make noise.

      The piston type about the same noise level, but the motor speed and so the air flow can be controlled by PWM. A lot of the cheaper piston type pumps are made for toys like squirt guns, so the brushed motors probably won't last long in a 3D printer. If you can find one with a brushless motor that has reasonable flow through a tube it could be pretty good.

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  4. Heiko WestermannMay 3, 2018 at 5:24 AM

    Great work! Did you try to copy the design of the CPAP or do you have some kind of information on how to design such fans? I don't know if its viable, but I think it would be nice further improve the design so it's either quieter or has more static pressure for more fancy shroud configurations. I recently replaced the hotend on my first crappy printer and now I'm dealing with lots of cooling errors with PLA due to the 'homebrew' shroud I am using. I found that most common shroud solutions are just bad or don't work with my 40mm radial fan so I would like to test some different solutions and I have an ESC and lots of harddrives flying around. My 12V radial fans also don't like do be PWM'ed so this solutions sounds like a great alternative.

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    1. I mostly copied it, but had to make allowances for the much larger diameter HDD motor. The impeller vane shape was literally copied from a photo of the CPAP impeller- I imported the jpg file, then traced over one of the vanes using spline curves.

      I have noticed that the clearance between the impeller and the sides of the housing seem larger in the CPAP blower (I left 1.5 mm in mine), so it might be possible to get more air by using a slightly smaller impeller.

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  5. These days, the hard drive motors are press-fit. Very hard to remove. I have a bunch of hard drives I can play with to see how to get the motor out without destroying it. Great idea!! Likewise CD/DVD disk drives could work. They run at 300 rpm.

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    1. You know, I didn't have any CDROM drive motors to look at (except the old, giant thing you can see laying on the table in the second video), but after looking modern ones on-line, they look like they may be a lot smaller than the HDD motor I used, which would make them better candidates for this sort of thing. Hmmmm. I'll have to see if I have an old CD/DVD drive laying around, or I can always grab one at the Makerspace.

      Actually, these motors run at whatever speed the driver pushes them to. I think the HDD motor is running close to 10k rpm at maximum speed.

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  6. looks great, but how is this different from a standard centrifugal fan?

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    1. Compare the impellers. This type typically moves more air, at higher pressure, with less noise, which is why it is used in CPAP machines.

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  7. Hey Mark! Great project, and thanks for posting updates! One question - how exactly did you manage to control the fan from your 3d printer? Unfortunately my 3D printer board (Melzi board) has a 2-pin socket for the cooling fan only, and I'm wondering how to find a PWM signal to drive the ESC

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    1. The driver I used is not an ESC. ESC's power up with the motor stopped for safety (you don't want a prop chopping up your hands when you connect the battery). I used a $13 driver from ebay that I linked in the original post. You can buy drivers for HDD motors for about $5 and some have PWM inputs.

      I simply connected the power input to the BLDC driver board to the print cooling fan connection on the SmoothieBoard. The print cooling fan output is a MOSFET that good for a few Amps, and it is PWM'd, so the firmware can control the fan speed. I use the pot connected to the driver board to limit the maximum fan speed.

      The driver board also has a PWM input, so it should be possible to drive it directly from one of the PWM pins of the controller's CPU.

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    2. Thanks for the reply! I am however a bit hesitant about the fan output of my board - and I'm afraid connecting it directly could kill the output. Do you think I could wire an external MOSFET to drive the motor controller? Or how can I find the PWM output from my board? The board in question is a Melzi clone - Anet A8 control board

      Thank you Mark!

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    3. The fan output's on printer controller boards are usually good for an amp or two, so if you connect one to the PWM input on the BLDC driver board, it's unlikely that you'd damage the controller board.

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  8. Are you planning to upload the white one on thingiverse or other direct download site? I have one or two HDD motors laying around.

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    1. I would have sworn that I included a link in the blog post, but looking back through it, I see that I didn't. I will update the post with a link to the Fusion360 files. Recheck the post...

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  9. Hi, great work you have done there!

    Since I am a noise freak and my main goal is to find a quieter solution than the "standard" 5015 12V blower fan I currently use for parts cooling, can you please tell me if this is actually quieter?

    I would be a shame to go over the trouble making one only to find out that it is louder than my current setup.

    PS. The 1-month wait for the motor driver is killing me, I could not find any faster alternative; any ideas of a simpler driver solution would be appreciated.

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    1. I don't have any decibel measurements of the noise level, but it's pretty darned quiet. In my experience, most of the noise in the cheap, small blowers and fans comes from the crappy bearings in the motors. HDD motors have some of the best bearings in existence. The fact that you can remotely locate the fan means you can put it behind the printer which will help reduce the noise level even more.

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  10. Can you please explain why an ESC will not do the trick? I am thinking of using a permanently 12V powered ESC (from the PSU), driven by PWM through a Servo port. Would that not work? I am asking because I can easily find one in a local store, whereas I must wait a month for the driver circuit from China.

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    1. ESC's for RC airplanes, cars, etc. have safety features built in to prevent the motor from running when you power up the ESC. That's to keep your quad copter from chopping up your fingers. The ESC requires a specific control signal ramping the speed up from zero. You might be able to make it work but I suspect it would require some custom firmware because 3D printer controllers don't usually drive ESCs.

      The cheapo driver board I linked doesn't have any of those safety features and has a PWM input so it can easily be driven by a 3D printer controller without any modifications to firmware.

      I know a month feels like a long time if you have to order it from China, but you'll survive. Your 3D printer will still be there. Maybe you can find a domestic source...

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    2. Yes, I see what you mean about the ESC operation logic, but it only applies when you intend to drive the motor through a normal 12V fan PWM output (which, indeed, is the easiest way to do it).

      Since I am too impatient to wait for the driver circuit, I already hooked the ESC up to the 12V supply from the PSU and a free servo port and modified Marlin, so that it sends the required (1000-2000ms) pulse to the servo port instead of sending the normal PWM to the default fan pin.

      Miraculously, it works! Sending M106-M107 commands actually makes the new turbo fan spin at the right speed :-)

      Regarding noise, I initially didn't notice that the fan was spinning in the wrong direction and I kind of freaked out (too much trouble for nothing). After fixing the wiring, it now seems to work fine and actually blows A LOT of air; I was hoping it would be a little quieter, though, since my feeling is that it is almost at the same levels as the previous 5015 fan I used.

      I have bought a few TPU tubes with different diameters today and plan to experiment with the air delivery to the nozzle during the weekend.

      I will keep you posted.

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    3. The blower moves a lot of air if you run it full-tilt. You can get greatly reduced sound and plenty of air flow by running it a little slower.

      Maybe you should post your modified Marlin so other can try it.

      Delete
  11. I'm really dumb with electronics, but this looks super interesting. So could I wire the two black/red power cables directly to the power supply, and then the third wire, the tachometer control wire, I could wire directly to and einsy/rambo? Would that work? Thanks :p

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  12. Also, there are 10,000rpm drives too.

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    1. If you are referring to the wires on the motor, no. This is a brushless DC motor that requires a specific type of driver to make it move. The motor is just 3 coils of wire and some magnets. The external electronic driver switches the current in the coils in sequence to make the rotor turn. Look up "brushless DC motor driver" to learn more.

      Small brushless fans have a driver built in, so just connecting them to DC power will make them run. HDD motors don't have a built in driver- there is normally a driver on the HDD circuit board.

      The speed of rotation depends almost entirely on the external driver and how fast it can energize the coils. A motor that comes out of a 7500 rpm disc drive will spin at whatever speed the driver tells it to, including well above 7500 rpm.

      Delete
    2. Thanks for the reply.

      So I found a driver with what looks like a 3 pin "PWM" section. I'm sort of curious, if I power the driver with the 24 volt PSU from the MK3, connect the hdd motor to the driver, could I then run a 3 wire connection from the einsy 3 pin fan controller to the 3 pin on the bldc driver? Would that even work? I'm just trying to see if there's anyway to have the einsy control the motor rpm during print.

      I was looking at this driver:
      https://images-na.ssl-images-amazon.com/images/I/81X5%2BQxNdmL._SL1500_.jpg

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    3. As nearly as I can tell, the 3 pin fan outputs on the Einsy Rambo board send 5V power to the fan and have a tachometer input that comes back from the fan to read the rotation speed. That is not the same thing as controlling the speed unless they are PWMing the drive voltage, in which case the tach output from the fan is probably useless.

      If the Rambo board can PWM the 5V power pins on the fan connector, you can use that as the PWM signal to regulate the speed of a BLDC motor like a HDD motor by connecting those pins from the Rambo to the PWM input on the BLDC driver.

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  13. It is a bit confusing, since the mk3 uses a 3 pin fan with tach, but when I read some threads they do mention pwm. I think maybe this is a bit too complicated for me, since I'm not very smart in terms of pcbs/electricity stuff.

    Is there such a thing as a driver that uses a tach signal instead of pwm?

    Sorry for my noobie questions haha

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    1. I don't think so. The tach pin is feedback from the fan motor to the controller so it can read the fan speed. It doesn't control the fan speed. The tach signal probably would not be reliable if you PWM the fan to control its speed because you're turning the power to the whole fan on and off which turn the power to the tach circuit on and off, too.

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  14. Dear Mark,

    thanks for your interesting blog.
    I just printed all four parts and they fit together nicely - but the HDD motor I got from an old Seagate drive seems to be to high as I can not get the enclosure to close when the motor and the fan are in place. Are there different types of HDD motors?

    Also, could you please provide the link to the model you used in the pictures (the one with the cable canals in the bottom enclosure, and the mounting holes all around), as the link you provided only leads to a probably older version without the cable routing canals and mounting holes.

    Thank you!
    Andreas

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    1. Yes, there are many different types of motors used in HDDs. My CAD file contains a model of the motor I used. You should check it to make sure it's the same as your motor, and make any changes necessary to the printed parts before you print.

      I'm sorry about the linked file- for some reason the timeline was pulled back when I last saved the file and all the mounting holes and wire channels were missing. It's fixed now.

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    2. Thanks for providing the updated F360 files!
      As for the HDD motor, I'll try to get ahold of one similar to yours so I won't have to tinker with the models ... ;-)

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    3. Dear Mark,

      printing and mounting the HDD motor went without a problem - the blower looks quite nice mechanically.
      Wiring it up seemed like a no-brainer, but I've been fighting for days getting the motor to turn...
      I'm using a motor driver like this: https://www.banggood.com/DC-12V-36V-15A-500W-Brushless-Motor-Controller-Hall-BLDC-Driver-Board-p-1311440.html
      and a 4-pin motor from an old WD HDD like his: https://www.mikrocontroller.net/attachment/197852/nidec.JPG

      As there are only 3 motor control pins (MA, MB, MC) on the controller board I thought connecting COM motor pin to GND on the controller could do the trick. But - you guess it - it does not.
      It does not even try to rotate, or wiggle, or move at all.

      Is the motor coil wiring not compatible with this type of controller?

      Thanks for your help!
      Andreas

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    4. I don't know why your HDD motor has 4 pins- maybe it is wired in a Y configuration which I have never seen in a HDD before. The controller is probably looking for input from a hall sensor and refusing to operate without it.

      I suggest you get a motor that has 3 pins and a controller that is sensorless like the one I linked.

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  15. Why do you have the exit port below the impeller? I thought the air is thrown off radially from the blades, so making it go down under the disk to escape seems to throw away some of the kinetic energy.

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    1. Being no expert on centrifugal blower design, I more or less copied the design of the blower that was in the CPAP machine, which looks like other CPAP blowers I have seen. I suspect it's done that way to maintain a uniform/constant load on the impeller and cool the motor that's usually in the same housing.

      Delete
  16. from what HDD exactly did you extract the motor for the design?
    Thank you
    Grethe

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    Replies
    1. I have no idea. Someone brought about 30 of them to be dismantled to the makerspace one day. They all use 3 phase BLDC motors, though the dimensions may vary a bit. You can always edit the linked CAD file to match the motor you have.

      Delete
  17. Can you comment on the benefit of the taper on the impeller blades?
    What if there was no taper (and the housing was also modified to match) - would it be louder or more more / less air or?

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    Replies
    1. I have no idea- I copied what was done in the CPAP blower. I believe the slope in the "roof" of the blower is intended to direct the air flow downward into the lower chamber. The impeller blades are probably shaped to match the sloping "roof".

      Delete
  18. Hey Mark, firstly I love this design for my purpose for use with the berd air system.

    I do Have one question though, as this is the only part left to order. Does the controller have to be "HDD BLDC" motor driver like the one you posted up further?

    Or can I use something like this >

    https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=5V-24V+MOTOR+DRIVER&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=5V-24V+HDD+MOTOR+DRIVER

    as I would like to utilize my 24v meanwell systems I have in place. I await your answer whether positive or negative.

    As always,
    Stay tuned and happy printing fellow Maker!
    SHENKOE out

    ReplyDelete
    Replies
    1. That looks like it ought to drive a brushless DC motor OK, but it doesn't appear to have a PWM input for speed control.

      Delete
    2. THANKS FOR YOUR REPLY, I READ IT A WHILE AGO, JUST NOW RESPONDING THOUGH.

      So i decided to just get the one you linked in the guide here. Will be setting this up in the upcoming week, if not this weekend.

      Will let you know how I fair if you would like the feedback.

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    3. I always like feedback! Good luck with it!

      Delete
  19. Hi!
    I have two questions/comments about your model
    1) Why the find are rotated backwards? AFAIK is make FORWARD position they will push more pressure into the output and also reduce noise
    2) From what i see the impeller is not in the same plane as the output. Basically it pushes the air into walls, and then the air leaks into the escape hole - output. Why not put it in the same plane as output hole, so it will not loose its kinetic energy bouncing on the walls?

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    1. 1) The fins are taking slow moving air at the center of the impeller and accelerating it and flinging it outward. If you rotate the impeller in the opposite direction the fast moving air at the edges of the impeller has to make an abrupt change in direction. I tried rotating the impeller the opposite way and it didn't move nearly as much air.

      2) That sounds like a good idea- try it out and let me know how it works! The moving air in the bottom of the housing keeps the motor running cool. You might have some trouble getting rid of motor heat if you take the air directly from the plane of the impeller. Also, these fans are designed to operate very quietly. You may be making a siren if you take the air from the impeller plane.

      Delete
  20. Hi Mark, Great work. I have used Ametek blowers (https://www.ametekdfs.com/dfsbrands/windjammer). Their turbines are not tapering. From manufacturing angle they are easier compared to the chines blowers.

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    1. Those are some big blowers! I bet they move a LOT of air.

      I've taken apart a few old CPAP machines, all with different blowers, and some have the type of impeller I copied and others have a closed top that would be much harder to print.

      It seems that there are a lot of ways to make a blower, and if you spin it at 30k rpm, it will move a lot of air.

      Delete
  21. Hi Mark,
    Great work, Can we generate 100 cm of water pressure from your latest model?
    What was the maximum pressure you were able to generate ? If you were not able to generate 100 cm of Water pressure what changes will be needed in your model?


    ReplyDelete
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    1. I have no idea how much pressure can be generated, or how to make it meet a specific target pressure. All I did was copy a CPAP blower and modify it to use an HDD motor.

      If you want to make a blower that provides 1m H2O of pressure, I suggest you do the exact same thing I did- find a commercial/industrial product that meets your specs and copy it.

      Delete
  22. On vane height: The vanes form the walls of chambers, As you move away from the center, the chamber gets wider (vanes get further apart) because the circumference gets bigger. The chamber walls (vanes) get shorter to compensate. You could instead make the vanes thicker instead of shorter, but this would produce choppier output. Of course, in reality a blower is there to change the pressure and velocity of the air as it moves outward, and that affects the profile too. Add in the uneven air flow, leakage over the vanes, and inlet and outlet effects and it takes specialized skill (that I don't have) to create a good design. Mark's mimetic approach is probably a good way to go.

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    1. Designing blowers like these is a dark art, for sure. I have a book on engineering turbo machines and it's no easy read. I've long ago forgotten how to do the math involved.

      Delete
  23. Mark - can I say I really love the attention to detail and innovation that you bring to your designs?

    With regards to the blower design, have you considered adding a stator (fixed guide vanes in the casing) to improve the conversion of centrifugal velocity into pressure? From memory, the efficiency of a blower like this is at a maximum when half of the work is done by the impeller, and the other half through the stator converting to pressure energy.

    Keep up the great work!

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    Replies
    1. Thanks!

      I haven't really been doing any development work on this since I first made the post two years ago. I don't print PLA much so don't really have much use for print cooling blowers. This post enjoyed a bried surge in popularity when people started trying to make low cost ventilators early in the COVID pandemic. Who nows, maybe someday I'll come back to it for another project...

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