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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > Building my first CNC - final questions
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  1. #1

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    Building my first CNC - final questions

    Hello.

    I am building my first CNC router about 1000x1000mm big. I have some questions regarding electronic components since I do not have much background about this.

    1. I was looking at kits containing Nema23 3Nm(425oz.in.) stepper motors, DM542 drivers and 35 V power supply. I was reading about voltage these motors require and apparently, it depends on motor phase inductanse (in mH), with the formula 32*sqrt(mH). So my question is, if I buy the motors with 3,8 mH, this would require 62 V to reach max torque of 3Nm - will the driver limitation of 50 V do any harm or will it relatively decrease max torque, so it being (50/62)*3Nm=2,4Nm? Or will power supply of 35 V further decrease max torque to (35/62)*3Nm=1,7Nm? Do I understand this correctly at all? So would choosing motors with inductanse of 2,3 mH and power supply of 48 V enable me to reach max torque?

    2. I would like to use Mach3 and am looking for a compatible breakout-board. From what I've read, the ethernet connection is the most stable, do I just need a network card with LAN plug and I can use that?

    3. Do you recommend any specific combinations of motors and drivers from?

    Thank you very much for your help.

  2. #2
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    Re: Building my first CNC - final questions

    Hello Nej -The motor supplier will have a voltage torque speed chart to answer your main question. But the difference at the higher voltages is not much at low speed more at high speed. but the chart will tell you exactly. M3 is old tech and at a dead end. I suggest you look at more up to date machine controllers. there are a lot out there. I use UCCNC...Peter

  3. #3

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    Re: Building my first CNC - final questions

    Thank you.

    So there is no problem with using the motors with 6,8 mH and then having the 35 V power supply? Okay, thank you about the M3.

    What about the drivers, are the DM542 okay?

    If anyone is willing to explain the things from my 1st question in detail, I would really appreciate it, but thanks everyone anyway.

  4. #4
    Community Moderator ger21's Avatar
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    Re: Building my first CNC - final questions

    Steppers are rated for their holding torque, when they are not spinning. This will be the same regardless of voltage.

    Once a stepper starts spinning, the torque will decrease as rpm's increase. The higher the voltage, the slower the torque decreases.
    This basically works out to be that speed is proportional to voltage. The machine will be almost twice as fast at 62V as it will be at 36V.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  5. #5
    Community Moderator ger21's Avatar
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    Re: Building my first CNC - final questions

    2. I would like to use Mach3 and am looking for a compatible breakout-board. From what I've read, the ethernet connection is the most stable, do I just need a network card with LAN plug and I can use that?
    You need a LAN port on the PC, and a Mach3 compatible ethernet motion controller. The most popular is the Ethernet Smoothstepper.
    I'd also recommend UCCNC, though, as Mach3 is obsolete at this point in time. Development stopped on it over 5 years ago.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  6. #6

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    Re: Building my first CNC - final questions

    Thanks, guys!

    @ger21, 1st answer: Ok, I understand that. But nothing "bad" can happen if I use 36 V instead of 62 V, right? And, if I understand correctly, it is then best to look for motors with lower inductance to efficiently use lower voltage?

    @ger21, 2nd answer: Okay, but from what I saw, even the cheapest controllers for use with UCCNC are a lot more expensive than some cheap Mach3 breakoutboards. I could use my old PC and connect everything through parallel port and use Mach3. I plan to use the CNC for hobby purposes mostly, so I can't afford to buy controllers for 200 $ or so.



    Do you see any problem in using this combination for my CNC:

    BOARD: https://www.aliexpress.com/item/32334451366.html?spm=a2g0o.productlist.0.0.113b609 3iLKqee&s=p&algo_pvid=677a7805-a9fd-44be-b577-c25ccf38c0c1&algo_expid=677a7805-a9fd-44be-b577-c25ccf38c0c1-5&btsid=11406f9c-a229-4c27-89b2-fcfc4846a0c7&ws_ab_test=searchweb0_0,searchweb2016 02_7,searchweb201603_52

    DRIVERS: https://www.ebay.com/itm/Digital-DM542T-Stepper-Motor-Controller-Driver-200-KHz-For-Nema-42-57-86-TTL-DSP/183992711963?epid=4031259382&hash=item2ad6d1fb1b:g :u6AAAOSw~CVdExKj

    MOTORS: https://www.ebay.com/itm/EU-Free-Ship-LONGS-Nema23-Stepper-Motor-23HS8630B-Dual-Shaft-270oz-in-3-0A-76mm/153421291329?hash=item23b89f1f41:g:4joAAOSwBmhdchU r

  7. #7
    Community Moderator ger21's Avatar
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    Re: Building my first CNC - final questions

    1st answer: Ok, I understand that. But nothing "bad" can happen if I use 36 V instead of 62 V, right? And, if I understand correctly, it is then best to look for motors with lower inductance to efficiently use lower voltage?
    It won't hurt anything but the performance. Usually, the inexpensive kits give poor performance.


    Okay, but from what I saw, even the cheapest controllers for use with UCCNC are a lot more expensive than some cheap Mach3 breakoutboards.
    Most if not all of the cheap chinese controllers do not support all of Mach3's functionality. But if that's all you can afford...
    Are you planning on buying a Mach3 license, which is $175?
    A CNC Drive controller and UCCNC license is cheaper than a Mach3 license and cheap chinese controller, and works much better.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  8. #8

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    Re: Building my first CNC - final questions

    I understand. So it IS better to look for lower inductance motors in my case when the drivers (DM542) don't support voltages over 50 V?

    Ah, okay, I get it, in that case I am leaning towards UCCNC as well. Is UC100 controller okay? But then I need a breakout board as well? Does it matter which one?
    Or maybe this: https://www.ebay.com/itm/4-Axis-CNC-...wAAOSwgA1bvcBL
    And then I don't need an additional breakout board?

    Thanks again.

  9. #9
    Community Moderator ger21's Avatar
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    Re: Building my first CNC - final questions

    It's always better to use low inductance motors.

    Yes, the UC100 is much better than any chinese controller. But the UC400ETH is better, if you can afford it.
    I would not recommend any chinese controller.

    These cheap breakout boards are popular.
    https://www.ebay.com/itm/5-Axis-CNC-...IAAOSwjiFZY9t9
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  10. #10

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    Re: Building my first CNC - final questions

    Thank you. What about that UC300 from the link I posted? Is it okay? And then I do not need a breakout board or do I?
    Thanks.

  11. #11
    Hi nejc1337 , if you are planning to get the whole kit, maybe you can conntact with us. This kit is 3Nm OPEN loop stepper motor, with MA450A driver. Recommended voltage is 36VDC. (This is the most common voltage for nema23 motors).
    https://www.fasttobuy.com/new-diy-cn...nc_p34871.html

    If you think about higher voltage, you may need to change to nema34 stepper kits, or Closed loop stepper kits. Compared with the open loop kit, closed loop kit costs a little more, but the torque is higher. Say the 3Nm open loop stepper, the torque can only reach 40% (1.2Nm) torque at speed 500rpm, while the 3Nm closed loop motor can reach 80% (2.4Nm) at same speed.

    I would be glad to help if you need other information. Thanks

  12. #12
    Community Moderator ger21's Avatar
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    Re: Building my first CNC - final questions

    Yes, I use a UC300ETH, and it is much better than a UC100, as it has more features, and more ports.
    But it requires multiple breakout boards, as it has 5 separate ports. I use the UB1 breakout board, but it costs more than the UC300ETH.

    The UC400ETH is a good middle ground, and only costs a little more than the UC100.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

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