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  1. #25
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    Re: Any pics of cnc control cabinets?

    Sounds like I need to stop and get a better understanding of proper grounding. There seems to be some mixed opinions on whether or not to tie earth ground to dc common. I always assumed everything should be grounded to the same ground. Currently my dc components are grounded to the small enclosure I have, as well as the a.c. ground and it hasn't caused any issues, but maybe not the proper way to do it? Just wamt to make sure i have this right before spending time on the new cabinet

  2. #26
    ericks
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    Re: Any pics of cnc control cabinets?

    Hi, i connect the mains earth to anywhere where it is required/where there is an indicated earth connection. But i do not tie/connect the neg of any SMPSU to earth

  3. #27
    Super Moderator Al_The_Man's Avatar
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    Re: Any pics of cnc control cabinets?

    Quote Originally Posted by QuinnSjoblom View Post
    Sounds like I need to stop and get a better understanding of proper grounding.
    There are two schools of thought out there, some that say you should never ground any of the DC supply commons, the other is to earth reference all supplies, I have always followed the latter practice, with so far no problems, there was a post here a while ago where a poster was experiencing all kinds of intermittent stoppages of his system where he had followed the isolation method, I suggested that he use the ground all method, where possible, the problem went away, there have been others where it has fixed the problem.
    A star ground termination point is also very important.
    There used to be a paper on the Siemens site on Equi-potential bonding in enclosure installations, but after they changed their web site, it dissapeared, I may have a copy somewhere.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  4. #28
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    Re: Any pics of cnc control cabinets?

    STAR grounding: everything to a single solid ground point.
    Essential to prevent 'ground loops', which can be really disruptive.

    Cheers
    Roger

  5. #29
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    Quote Originally Posted by RCaffin View Post
    STAR grounding: everything to a single solid ground point.
    Essential to prevent 'ground loops', which can be really disruptive.

    Cheers
    Roger
    I understand the importance of star grounding to avoid loops, but are you grounding both ac ground and dc common to this single point, or isolating the 2?

  6. #30
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    Re: Any pics of cnc control cabinets?

    I use star grounding for all DC electronics, then I tie that star ground point to the the incoming mains ground. I do not gain or lose axis Step pulses.

    I suspect that workplace safety laws will require full connection to the mains ground in all cases unless the entire machine is double isolated - which would be pretty much impossible for a CNC machine.

    Cheers
    Roger

  7. #31
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    Quote Originally Posted by RCaffin View Post
    I use star grounding for all DC electronics, then I tie that star ground point to the the incoming mains ground. I do not gain or lose axis Step pulses.

    I suspect that workplace safety laws will require full connection to the mains ground in all cases unless the entire machine is double isolated - which would be pretty much impossible for a CNC machine.

    Cheers
    Roger
    Currently I have my machine wired the same way. Dc grounded to earth. I have hundreds of hours of run time without a single lost step or any hiccup at all. I think I'll just stick to how it's been. Right now it's just kind of messy and needs to be better organised with a few things added. Servo driven mill turn spindle, multiple solenoids for brake, coller closer, and coolant lines.

  8. #32
    Community Moderator ger21's Avatar
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    Re: Any pics of cnc control cabinets?

    Some components require the DC supply to be isolated. Connecting the DC- to ground loses the isolation.
    Gerry

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

  9. #33
    Super Moderator Al_The_Man's Avatar
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    Re: Any pics of cnc control cabinets?

    Quote Originally Posted by ger21 View Post
    Some components require the DC supply to be isolated. Connecting the DC- to ground loses the isolation.
    And often component suppliers will stress not to earth ground the common of their equipment, from what I have personally gleaned it is often not because of a technical reason, but to avoid any blame if you do ground it and if something inadvertently goes wrong with the installation you can blame their equipment.
    If there is no technical reason otherwise, I have always ignored it and grounded anyway, with no ill results.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  10. #34

    Re: Any pics of cnc control cabinets?

    A little late to the discussion, but I have been running the DC return to earth ground for years, works for me. One instance of where you would not want to do this is in the case of direct rectified line power without an isolation transformer, Anilam built a lot of systems like this. Grounding that would cause a dead short. As Gerry noted there are some other exceptions, but normally it is a good practice IMHO
    Jim Dawson
    Sandy, Oregon, USA

  11. #35
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    Quote Originally Posted by Jim Dawson View Post
    A little late to the discussion, but I have been running the DC return to earth ground for years, works for me. One instance of where you would not want to do this is in the case of direct rectified line power without an isolation transformer, Anilam built a lot of systems like this. Grounding that would cause a dead short. As Gerry noted there are some other exceptions, but normally it is a good practice IMHO
    Ok, I know you've set up a lot of control cabinets so I'll just continue to do it this way. It's how I'm set up currently and my machine has been 100% reliable.

  12. #36
    Super Moderator Al_The_Man's Avatar
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    Re: Any pics of cnc control cabinets?

    Also one publication aimed at machine/enclosure wiring is NFPA79, you most likely can find a copy out there in PDF.
    I would add that just about anything used in a PC desktop/tower environment is going to be earth grounded simply because it is automatically done in the PC, e.g. P.ports, USB ports. Kmotion etc as well as any card that plugs into a PC slot, Galil, Acroloop, etc. are all connected to the PC ground plane that is earth grounded via the service supply.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

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