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Brushless DC motor spindle

Discussion in 'CNC Mills/Routers' started by The Dude, Jan 7, 2014.

  1. The Dude

    The Dude Veteran
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    I've seen these airplane motors that are brushless DC motors capable of 120,000 rpm. Is that going to work for a cnc machine? I mean the torque is not huge but compared to a dremel it seems close or even better but at a much lighter weight and lower cost($30 vs $80). When I saw the high rpms I thought it would be good for some other applications. I also don't really understand how to buy a collet for one of these. It's just a 3mm shaft with nothing to put a bit into so you have to buy this extra piece.
     
  2. GorillaBob

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    If I remember right, one of the PhlatBoyz used a brushless motor on his PhlatPrinter III. For a router, you would want a motor with good torque and not as high of RPMs. The higher Kv motors tend to not handle jobs requiring high torque. I may be wrong and someone will pitch in. I'll go see if I can find the thread with the motor. I think the guy built his own collete adapter that adapted from the motor to a collet that would hold the bits.
     
  3. Mark Carew

    Mark Carew OpenBuilds Team
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  4. Robert Hummel

    Robert Hummel Custom Builder
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    I have used a 900kv out runner that comes with a 8mm shaft, model is 5045 I then pressed and assembled the motor on to the er11 collet also 8mm
    It lasted a good time and was able to mill 3/8 aluminum plate. Prob would have lasted a lot longer but I pushed it hard. Wood and HDPE it had no problems

     
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  5. The Dude

    The Dude Veteran
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    hmmm, I see both of those links don't work. So what do you need to buy to attach to the motor that holds the collet?

    I was thinking of getting this instead of a dremel/colt/handheld rotary tool... and then using it to make the parts for the OX... and then putting my heavy duty router on the OX... and then reuse this motor for polishing/engraving/drilling teeth/whatever takes 120,000 RPM, hehe.
     
  6. Robert Hummel

    Robert Hummel Custom Builder
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    List of parts
    ER11 collet 100mm x 8mm
    http://bit.ly/1iQAMPy
    Out runner 5045 "has 8mm shaft
    http://bit.ly/1eFruAO
    80 amp ESC
    Then to control it u need a 555 timer circuit
    image.jpg
    So all you do is disassemble the 5045 watch your fingers trust me lol
    Then put it back together using the collet instead of the shaft that came with. I used a hck saw to cut the retainer clip slots.
    Be sure not to press the motor back together to tight as it will wear the bearings faster.
    To calculate your rpm it is supply volts multiplied by your KV
    I recommend 10 amp power supply at 12vdc
    900KV would give you 10,800 RPM max and that's more then enough for anything you would want to mill with it
    I got all my parts from eBay and total cost was $89 for motor and 100amp ESC combo and $26 for the collet/nut and 1/8 insert
     
    #6 Robert Hummel, Jan 7, 2014
    Last edited: Jan 7, 2014
  7. The Dude

    The Dude Veteran
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    Wow! That's what I needed to know! And now that I know, I have more questions, haha. It says the runout of the collet is 0.015MM (0.0006") Run-Out Tolerance... so is that what you get after you put it into this motor? DO I need special tools to "press and assemble" the shaft onto the motor?

    You said you burned the motor up? Any ideas how to make it last longer? Can it be rebuilt or does it have to be replaced? Maybe if you had a fan on it? A heat sink?
     
    #7 The Dude, Jan 8, 2014
    Last edited: Jan 8, 2014
  8. JustinTime

    JustinTime Master
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    I too will not recommend the 120,000 rpm motor. The bit you will be using may melt, if it's metal you cut, or burn the wood, if wood is what you cut. Unless you go with an insane high ipm (inch/mim). I use a 12vdc power supply and I cranked it up to max, which is 14.5v.

    To not burn the motor just don't load it to much. Cut shallower cuts and use lower ipm. If the motor gets hot you are overloading it, if the motor runs just warm to the touch it will last a long while. I have mine over a year and it's just like new.

    BTW, I wouldn't bother to build the motor controller mentioned above. On e-bay you can buy a servo tester for two bucks, shipped, or so. That's what I'm using.

    http://www.phlatforum.com/xenforo/threads/yorams-mods.2389/
    http://www.phlatforum.com/xenforo/threads/led-ring.3129/
     
    #8 JustinTime, Jan 8, 2014
    Last edited: Jan 8, 2014
  9. Robert Hummel

    Robert Hummel Custom Builder
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    I didn't really care about run out so I can't really say, just anything was better then a rotary tool :)
    I used my drill press with the chuck holding the old shaft as a push pin.
    The reason I burned it up was not heat related rather aggressive ipm in 3/8 aluminum plate is what ended its life.
    I had another idea now that I have a mill but have no need for 1 as I have a 1.5 and 2.2 kW spindle now.

    Here is a pic and the idea is to use abec7 608 bearings to take more aggressive feeds and extend its life
    image.jpg
     
  10. Nick Lancaster

    Nick Lancaster Journeyman
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    Instead of diret coupling you could gear down the RPM. would still have to build a holder for the collet shaft and bearings.

    Also I found this little jem that would let you control the motor speed in 100rpm increments from mach3 or LinuxCNC.

    http://www.logicnc.com/
     
    #10 Nick Lancaster, Jan 8, 2014
    Last edited: Jan 8, 2014
  11. The Dude

    The Dude Veteran
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    So basically I can construct a variable speed, extremely high precision handheld rotary tool that can be turned on and controlled from LinuxCNC or Mach3 for about $100? Sounds like a deal!

    OK so I do have a drill press... I could run the motor slow in aluminum.... and then later on rebuild it like above... or would it be easier to just build it like above photo? Are those off-the-shelf parts? How did you couple the router shaft to the motor shaft? Or is this one big shaft that came attached to the collet?
     
  12. Nick Lancaster

    Nick Lancaster Journeyman
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    The picture just above my post would need custom fabricated parts. The video above using one that you only have to press out the 8mm shaft and then press in the collet shaft.
     
  13. The Dude

    The Dude Veteran
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    Hey is this the same spindle as shown here http://www.raynerd.co.uk/?p=1562
    It looks like this would be something you could later on convert to into a lathe that attaches to the OX to make a CNC lathe...
     
  14. Nick Lancaster

    Nick Lancaster Journeyman
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    Sure looks like it. brilliant, i want one now.

    It would not have enough torque for a lathe. And as far as using it for a 4th axis it has no step and hold features it is purely rotary.
     
  15. Robert Hummel

    Robert Hummel Custom Builder
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    Yes that is the same concept and yes it is possible rebuild it.
    All that holds the er shaft and motor together is the press fit and set screws in the body of the outrunner
    Awww brings back memories haha
    I have all the parts on hand except the motor maybe in the future I will build it again for kicks lol
     
  16. The Dude

    The Dude Veteran
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    Could I use some kind of pillow-block bearing holders with 608 bearings as an off-the-shelf shaft support? I saw them on ebay here http://www.ebay.com/itm/2PCS-8mm-Di...=BI_Heavy_Equipment_Parts&hash=item19e2a38050

    Maybe that would accomplish the same thing as the custom parts above? It might be a little tricky but I think I could get a shaft+motor and then use that to make a spindle mount that holds 3 pillow-block bearings and has a motor attachment. The only problem I can foresee is if the cnc machine wants to go down it would apply force to the motor in the z direction and push the shaft out the back of the motor or something like that.
     
  17. JustinTime

    JustinTime Master
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    Not if you put a bearing just above the collet, as can be seen in the video above, and the bearing is supported in a bracket or pillow block or what ever. Mine is (you can't see it in the links above, it is between the second and third MDF layer) and I never have problem with the shaft getting pushed out of the motor.
     
  18. The Dude

    The Dude Veteran
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    I'm going to make a vacuum cleaner dust remover that goes around the collet, I could add a suction tube to create airflow around the motor. Until then I have little 12V fans from PCs. It may also be possible to add a thermal shutoff switch... I just disassembled a laserjet, maybe there's one in there ;)
     
    #18 The Dude, Jan 9, 2014
    Last edited: Jan 9, 2014
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  19. The Dude

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    So mount the lowest bearing such that it's race contacts the collet holder flange? Maybe use a washer? Does it need to be some kind of thrust bearing or will 608's work just as well? Man I wish I could make the bearing press fit holder, lol.
     
  20. JustinTime

    JustinTime Master
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    When I ran my motor at 24V I had lots of heating issues. Now I run it at 14.5V and I have no heating issues, none. I run the motor for three hours strait and it's just hand warm.

    BTW, the ribs on the front/back of the housing act like a fan too, at a very low efficiency, but still enough to make some kind of airflow.
     
  21. JustinTime

    JustinTime Master
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    Correct
    I don't use any special bearings. Just 8mm id bearings. I wanted to buy better quality bearings and ordered them and paid them but the seller was out of stock and sent me lower (cheaper) ones. I complained and got my money back and got to keep the bearings too. They work just fine with no problem whats so ever.
     
  22. The Dude

    The Dude Veteran
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    Thanks everyone. I think I have a plan now.
    1. Get the motor+collet-shank
    2. Install shank in motor
    3. Fabricate custom bearing holder
    4. Reassemble
    5. Check and replace bearings annually($0.50ea), replace motor as needed($40).

    This looks like great long-term inexpensive solution for spindles on CNC. After I get the OX running and my $200 router burns out, I'll just put a heavier motor on my old spindle ;).
     
  23. Nick Lancaster

    Nick Lancaster Journeyman
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    Just attach a little fan to the stub of the shaft sticking out of the motor.

    Sort of like this.

     
  24. Robert Hummel

    Robert Hummel Custom Builder
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    The motor only gets warm to the touch at 12-14vdc and air flows through the motor due to the housing design.
    I would say from experience the main thing to worrie about is dust and chips getting into the windings
     
  25. Mark Carew

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    Robert Hummel likes this.
  26. matt_o_70

    matt_o_70 Journeyman
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  27. Robert Hummel

    Robert Hummel Custom Builder
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  28. Mark Carew

    Mark Carew OpenBuilds Team
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    Let's make one! cnc of course :)
     
  29. The Dude

    The Dude Veteran
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    I'm up for doing a lathe. Preferably one that bolts onto the routy or OX and can make screws as well as 3D sculptures like faces of michaelangelo, etc.
     
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  30. Public Do Omens

    Guest Builder

    Lathe is a nice idea.

    I had a friend whom wanted a totem pole made with 3 axis CNC i am building.
    I will tackle it meter at a time. My CNC will be open on the X - Axis so extra long parts can fit.
    Reference marks are used to align the work segments.

    Divide & Conquer

    Check out http://www.openbuilds.com/members/cnc-mogul.507/
    Nice image he has for his avatar.
     

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