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Brushless DC motor spindle

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

  1. cletero

    cletero New
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    After a few days of search I found this page which talks some about this type of motor (although used for a different application) and shows some connection diagrams, so I share it here in case somebody else comes by and may find it helpfull:

    The Recumbent Bicycle and Human Powered Vehicle Information Center

    It shows the following wiring diagram, I'll also put it here for future reference.
    Of course, the batteries and charge would be replaced by a power supply in our case and the throttle would be the servo tester knob, also, as far as I know, some servo testers include the BEC, am I right?

    batteryschematic.gif
     
  2. cletero

    cletero New
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    jajaja yeah! I meant the ESC, but I'm also not sure if it includes the BEC, or at least that's what the description says.

    Just to be sure... this is a BEC, right? This one is up to 26V, so it should work with both my options:

    Receiver Power Supply 5V/3A Brushless ESC External Type BEC UBEC Support 2-6S T1 | eBay

    Thanks!!
     
  3. Gavin Milne

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    I'll write a longer reply soon, but I'm using the spindle designed by Robert Hummer (above) and a generic ESC controller. I take a PWM signal from my controller (a Pi CNC from Protoneer) into custom made shield for an Arduino that has a low-pass filter on-board and then outputs direct to the ESC (through the white signal wire).

    So my ESC has two power cables and the one signal wire. Works perfectly. The electronics are extremely basic, as is the code for the Arduino. Happy to share if this is what you need.
     
  4. cletero

    cletero New
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    Hi! by all means, share, yes hehehe... not sure I understand all of it but I'm in a learning process.

    Thanks!!
     
  5. Gavin Milne

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  6. Sonny Lowe

    Sonny Lowe Journeyman
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    Wow, interesting stuff, thanks for all the info so far, I'll be mulling this over in preparation of my next project :)
     
  7. Gary Caruso

    Gary Caruso OpenBuilds Volunteer
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  8. cletero

    cletero New
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    Thanks, didn't see that!! I'll search for another one.

    Good thing I hadn't bought it as I have this project somewhat stopped as I'm researching some way of adding a closed loop speed control.
     
  9. Gary Caruso

    Gary Caruso OpenBuilds Volunteer
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  10. cletero

    cletero New
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    Yeap, that sounds great! However, I have trouble finding them... on eBay most (in fact, all the ones I found) sensored brushless motors seem to be in-runners, not out runners, but most of all, to high kv
    Will keep searching for them on rc stores and the like.... :thumbsup:

    In fact, more than speed regulation, what I need is constant speed... if I had a motor that maintains 10 000 to 12 000 rpm constantly, even when the tool starts cutting, I could use different pulleys to achieve the required final speed. What many people report when using this motors is a 10-20% speed reduction when the tool goes from "cutting air" to cutting the material, which seems a bit too much for my taste.
     
  11. cletero

    cletero New
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    I believe you mean something like this guy used:
    I had heard about it but still, results are not convincing me, it's a bit like the response is a bit slow so there's still quite a bit of speed variation. Although probably due to the motor being low power. Any thoughts?

    By the way, for reference, the guy builds a pretty nice (although small for my taste ;) ) spindle with a foredom handpiece, you can see the first of three parts video here:
     
  12. Gary Caruso

    Gary Caruso OpenBuilds Volunteer
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    the link i posted has large sensored outrunner :)
     
  13. cletero

    cletero New
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  14. lovelacetom

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    What is motor?
    What is DC motor?
    What is BLDC?

    RC motor is AC motor, dont mislead...
     
  15. Gary Caruso

    Gary Caruso OpenBuilds Volunteer
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    Who is trying to mislead?
    To say "rc motor is ac motor" is misleading
     
  16. Toysrfun

    Toysrfun New
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    A 1900kv 1/5 scale motor would have a max rpm around 24,000 and plenty of torque. Bearings can be easily upgraded if runout is concern. Cheap motors have abec1 and good motors will have abec5 or better. $5-$15 bearing upgrade. Don’t use an out runner. Lower kv is more torque. 800kv would be prime but with 1/5 any in that range should produce plenty of torque for a small project. They come with 8mm shafts and you can purchase 8mm er11 or er16 collet ends for $8. If using an 1/8 style motor you’d need a high quality with an 8mm shaft and those are expensive but water coolers are readily available for $20. If using 1/5 with a 56mm smooth body you can also find water coolers for those. Nice thing is that they are compact and powerful I have one rated at 380 amps and would work great for a swivel 5 axis head for doing detail characters as well pcb boards. If you have them laying around it’s worth doing but if you have to buy everything spindles have come down in price. Finding quality ones can be tricky. Considering Hobby grade Rc motors are typically built well and those companies rely on reputations you can’t ussually go wrong with some mid line brand names. One I have here is a $200 motor but I don’t have any other current use for it and it’s for a 3D printer with a 5 axis adapter for milling D&D characters and various other “micro” parts where a large spindle is only going to get in my way and over weight my gantry. Using high speed servos and very light cutting you can get through a part much faster than slow deep cuts that wear on the motor. Keep in mind these motors use deep groove bearings. This is something I plan to upgrade having a full machine shop I will be adding a thrust and ac bearing to it with custom bearing end plates. Keep in mind your intentions and that should dictate what you use.



     
  17. David the swarfer

    David the swarfer OpenBuilds Team
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    120000rpm is great for tiny diamond burrs when grinding teeth like a dentist, not much use for cutting foam, wood and plastics.

    you want something around 35000rpm, the helicopter brushless motors of around 3000kv on 12v do this just fine.
    however!
    you cannot use the motor bearings to hold the collet (they cannot take the cutting loads), you have to construct a tube with bearings rated for the speed in it, AND the bearings have to be a mix of angular contact and axial bearing to take both the side loads (milling a slot) and the end loads (plunging down)
    and it all needs to be very accurate and balanced. the higher the speed the more critical it is.

    A much simpler way to get going is just a Dremel 3000. This will allow you to cut out your Ox plates and step up to the Bosch router.
     
  18. Jason Moore

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    What rpm could you get?
     
  19. JustinTime

    JustinTime Veteran
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    KV (900 in his case) x Voltage. That will be the idle RPM.
     

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