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  1. #1

    Default Grounding... That Dark Art

    Grounding... That Dark Art-mycnc-jpg
    Hi Looking for some help. In the attached PDF is a diagram of my setup. Everything was working fine I had even cut a few jobs on it with no errors. Then yesterday all hell broke loose when I hit run on the VFD the stepper motors went mental and also my keyboard on the PC locked up. So after reading stuff online and watching lots on Youtube as you will have already guessed it must be EMI especially when you consider that not a single cable is a shielded type, Stepper motors or the VFD to Spindle. I have ordered some and will have to wait for it to arrive. Although this will be a major factor it will also be the lack of proper grounding, replacing the the cables with shielded is a task I'm capable of, but my real fear is the grounding. Even in this forum there are lots of conflicting opinions. I would be terrified of making a mistake like a ground loop or mixing AC with DC grounds. So my fellow cnc'rs if someone can look at the PDF I've attached and direct me where to put ground wires on the VFD and Spindle, The CNC chassis or anywhere else they think fit. I would be extremely grateful.

    Coco

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    Default Re: Grounding... That Dark Art

    Quote Originally Posted by hootsmangreen View Post
    Grounding... That Dark Art-mycnc-jpg
    Hi Looking for some help. In the attached PDF is a diagram of my setup. Everything was working fine I had even cut a few jobs on it with no errors. Then yesterday all hell broke loose when I hit run on the VFD the stepper motors went mental and also my keyboard on the PC locked up. So after reading stuff online and watching lots on Youtube as you will have already guessed it must be EMI especially when you consider that not a single cable is a shielded type, Stepper motors or the VFD to Spindle. I have ordered some and will have to wait for it to arrive. Although this will be a major factor it will also be the lack of proper grounding, replacing the the cables with shielded is a task I'm capable of, but my real fear is the grounding. Even in this forum there are lots of conflicting opinions. I would be terrified of making a mistake like a ground loop or mixing AC with DC grounds. So my fellow cnc'rs if someone can look at the PDF I've attached and direct me where to put ground wires on the VFD and Spindle, The CNC chassis or anywhere else they think fit. I would be extremely grateful.

    Coco
    May not be just EMI do you have the correct Shielded Cable from the VFD Drive to the Spindle with the Shield correctly Grounded at each end, is the spindle 4th Pin Grounded to the Spindle body, if not this will have to be corrected by removing the top cap of the Spindle

    Dc Com is the return Path for the Dc supply, it is not a Ground

    You need to add a Ground Bus or Stud the Ground Plane needs to be Grounded so the input Mains Ground would connect to the Ground Bus and all other Ground need to connect to that ( 1 ) Point ( Star Point Ground ) then any shielded cables then connect direct to the Ground Plane, your Ground Plane is the metal plate that you mount everything on

    Attached Thumbnails Attached Thumbnails Grounding... That Dark Art-grounding-bus-cabinet-png   Grounding... That Dark Art-ground-plane-png  
    Mactec54


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    Community Moderator Al_The_Man's Avatar
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    Default Re: Grounding... That Dark Art

    See the Siemens paper on equi-potential bonding.
    There are generally two schools of though on grounding of power supply commons, I am one who has always Earth grounded the commons of all power supplies where possible. This has served me well as I do not remember any instances of spurious noise problems.
    In the past here, it has cured problems of those that had reactions when L.S. tripped etc.
    BTW, the E-stop is intended to remove power, not be just an advisory condition.It should be via electro mechanical means. A common mistake with DIY builders.

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    Last edited by Al_The_Man; 02-12-2021 at 11:41 AM.
    CNC, Mechatronics Integration and Custom Machine Design

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  4. #4

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    Quote Originally Posted by mactec54 View Post
    May not be just EMI do you have the correct Shielded Cable from the VFD Drive to the Spindle with the Shield correctly Grounded at each end, is the spindle 4th Pin Grounded to the Spindle body, if not this will have to be corrected by removing the top cap of the Spindle

    Dc Com is the return Path for the Dc supply, it is not a Ground

    You need to add a Ground Bus or Stud the Ground Plane needs to be Grounded so the input Mains Ground would connect to the Ground Bus and all other Ground need to connect to that ( 1 ) Point ( Star Point Ground ) then any shielded cables then connect direct to the Ground Plane, your Ground Plane is the metal plate that you mount everything on
    Thanks mactec, see right away there is a conflict i understand the gnd from vfd to spindle but after watching corvetteguy50 on YouTube he says only Ground the shielded at one end preferably at the vfd end. But any how your reply has helped so thanks for that. I am getting a bit better understanding of it. But what I was really looking for and I know this is being lazy and/or thick was for someone to draw little circles saying connect wire here and here. Lol



  5. #5

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    Quote Originally Posted by Al_The_Man View Post
    See the Siemens paper on equi-potential bonding.
    There are generally two schools of though on grounding of power supply commons, I am one who has always Earth grounded the commons of all power supplies where possible. This has served me well as I do not remember any instances of spurious noise problems.
    In the past here, it has cured problems of those that had reactions when L.S. tripped etc.
    BTW, the E-stop is intended to remove power, not be just an advisory condition.It should be via electro mechanical means. A common mistake with DIY builders.
    Thank Al, the doc had some bits I understood but tbh most of it went right over my head. I know there are people who think well if you don't understand it then you shouldn't be doing it but thats why we have Google, forums, and YouTube.
    The estop as I have it is good enough for my needs its only a 6040 Chinese table not a hass.



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    Default Re: Grounding... That Dark Art

    Quote Originally Posted by hootsmangreen View Post
    Thanks mactec, see right away there is a conflict i understand the gnd from vfd to spindle but after watching corvetteguy50 on YouTube he says only Ground the shielded at one end preferably at the vfd end. But any how your reply has helped so thanks for that. I am getting a bit better understanding of it. But what I was really looking for and I know this is being lazy and/or thick was for someone to draw little circles saying connect wire here and here. Lol
    Yes be careful with watching videos the one you mention is not always correct with what he does and how he does it, so you have to make your own assessment when you watch videos and who the person is doing them most are not qualified electrical engineer's or industrial electricians

    For VFD wiring just look in any good quality VFD Drive manual they will show you how wires need to be connected and shields are to be Grounded to comply, to find VFD manuals there are many available on line in PDF format

    These snips may help with your shield Grounding understanding, I try to keep it simple so most can understand without having to be an engineer what is required to have an almost EMI noise free environment

    Attached Thumbnails Attached Thumbnails Grounding... That Dark Art-shield-termanation-3-png   Grounding... That Dark Art-shield-grounding-vfd-drive-png   Grounding... That Dark Art-shield-grounding-plate-clamps-1-png  
    Mactec54


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    Default Re: Grounding... That Dark Art

    Quote Originally Posted by Al_The_Man View Post
    There are generally two schools of though on grounding of power supply commons, I am one who has always Earth grounded the commons of all power supplies where possible. This has served me well as I do not remember any instances of spurious noise problems..
    If done incorrectly noise is created

    No only one school doing it the correct way yes commons can be connected to Ground but not normally how most hobby users connect it which is incorrect

    The Dc common must first return to the source before going to Ground this is a 2 wire example this is the most common way to do it, but 3 wire can also be used

    Attached Thumbnails Attached Thumbnails Grounding... That Dark Art-dc-grounding-2-wire-png  
    Mactec54


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    Member MML102783's Avatar
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    Default Re: Grounding... That Dark Art

    You have a floating dc 24v output. You need to short the pe terminal and v- terminal. Also where is your field ground coming from? An outlet? You really need a ground rod sank and connect it to the ground buss. Are you using reactors on the input/output side of the VFD?



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    Quote Originally Posted by hootsmangreen View Post
    Thanks mactec, see right away there is a conflict i understand the gnd from vfd to spindle but after watching corvetteguy50 on YouTube he says only Ground the shielded at one end preferably at the vfd end. But any how your reply has helped so thanks for that. I am getting a bit better understanding of it. But what I was really looking for and I know this is being lazy and/or thick was for someone to draw little circles saying connect wire here and here. Lol
    I have watched all of corvetteguys videos and he is not keeping up with information regarding emi. You absolutely don’t want to use a drain wire soldered to a connector then pigtailed to a ground bus.



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    Default Re: Grounding... That Dark Art

    Quote Originally Posted by MML102783 View Post
    You have a floating dc 24v output. You need to short the pe terminal and v- terminal. Also where is your field ground coming from? An outlet? You really need a ground rod sank and connect it to the ground buss. Are you using reactors on the input/output side of the VFD?
    Every system already has a Ground Rod there is no need to add one, if one was added then it has to be bonded to the Main Power Supply Building Ground Rod

    Mactec54


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    Default Re: Grounding... That Dark Art

    Quote Originally Posted by MML102783 View Post
    I have watched all of corvetteguys videos and he is not keeping up with information regarding emi. You absolutely don’t want to use a drain wire soldered to a connector then pigtailed to a ground bus.
    Correct there are a lot of uneducated people doing incorrect videos to earn money from those that don't no any better

    Mactec54


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    Default Re: Grounding... That Dark Art

    Quote Originally Posted by hootsmangreen View Post
    Thanks mactec, see right away there is a conflict i understand the gnd from vfd to spindle but after watching corvetteguy50 on YouTube he says only Ground the shielded at one end preferably at the vfd end. But any how your reply has helped so thanks for that. I am getting a bit better understanding of it. But what I was really looking for and I know this is being lazy and/or thick was for someone to draw little circles saying connect wire here and here. Lol
    I just saw something else in your design that may be one of you main problems

    Do you have or are you using ( 2 ) different Power outlets to supply your control panel, it looks like you are but can't tell buy your drawing layout

    If you are using ( 2 ) different outlets 230v Power sources then you have a Ground loop and this will create all kind of noise problems

    Mactec54


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