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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
    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)

  12. #12

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    Re: Building my first CNC - final questions

    Thank you.

  13. #13
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    Re: Building my first CNC - final questions

    1000x1000? How much will the gantry weigh? What speed do you want to move at? These questions are more important at the beginning than what software/controller/stepper voltage will be used.

    I would bet that such a large machine will need you to increase the motor size to accommodate the inertial of the gantry and head.

    Just my $0.02

  14. #14
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    Re: Building my first CNC - final questions

    Quote Originally Posted by nejc1337 View Post
    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/3233...chweb201603_52

    DRIVERS: https://www.ebay.com/itm/Digital-DM5...AAAOSw~CVdExKj

    MOTORS: https://www.ebay.com/itm/EU-Free-Shi...oAAOSwBmhdchUr

    I'm using one of these type boards as Ger mentioned earlier. £5 ebay special.
    https://www.ebay.co.uk/itm/USB-Inter...oAAOSwufFcg3w1
    Using Mach3 on P Port
    An old Dell with WinXP service pack 3.

    The damn thing is faultless. (well unless I program the G-code stupidly )

    I'd like to eventually go to a UC400eth but don't really need to tbf.

  15. #15

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    Re: Building my first CNC - final questions

    What do you think about these motors with 1,8 mH: 57CM23 version: https://www.aliexpress.com/item/3299...chweb201603_52

    And pair them with DM542T drivers, should it be okay?

    And also, how do I know how powerful (Watts) power supply I need (I would buy 48 V power supply)?
    Thanks.

    EDIT: I didn't even see the last 2 answers.

    Thank you, @dazp1976, I will probably just buy this one.

    @maxspongebob, I must admit, I haven't really thought about this. So you think these kind of motors would not be enough? The router itself will be built from MDF and in the size of 1000x1000mm.

  16. #16
    Community Moderator ger21's Avatar
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    Re: Building my first CNC - final questions

    How are you deiving it? Screws?
    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)

  17. #17

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    Re: Building my first CNC - final questions

    Yes, SFU1605 ballscrews (5 mm pitch) and SBR20 linear rails.

  18. #18
    Community Moderator ger21's Avatar
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    Re: Building my first CNC - final questions

    Then you definitely want the lowest inductance, and highest possible voltage.
    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)

  19. #19
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    Re: Building my first CNC - final questions

    It's probably a good idea to do some of the math that will define the limit of motion of the machine before you shell out the $ for parts.

    For instance, with a 1605 ballscrew, you are probably looking at a limit of 1000 RPM on the screw. My experience is that you can drive a long screw faster, but a cheap screw will probably start to flap at higher speed. So, that puts you at around 12 seconds to get from one end of the table to the other. If you want to go faster, you could use a 1610 screw, but the torque requirement would double.

  20. #20

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    Re: Building my first CNC - final questions

    I get it, thanks. I don't have any clue of what the torque should be because it's my firat time doing this. It's important to point out that most of the work will be done on a smaller scale, say 400x400mm so I think I shouldn't care so much for the slow speeds from one end to another.

    Also, can anyone please reply to this question from before:

    What do you think about these motors with 1,8 mH: 57CM23 version: https://www.aliexpress.com/item/3299...chweb201603_52

    And pair them with DM542T drivers, should it be okay?

    And also, how do I know how powerful (Watts) power supply I need (I would buy 48 V power supply)?


    Thanks.

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