Newbie Grounding shielded cables - help needed


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  1. #1
    Member Nametag's Avatar
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    Default Grounding shielded cables - help needed

    I’m building my first hobby CNC and could use some help with grounding my stepper motor and limit switch cables.

    I’m using shielded cable for stepper motors and limit switches, but I am clueless on where to attach the drain wires.

    The build videos for my CNC (CNC4Newbie New Carve) use a Demon Controller, which has a ground screw. However I have an Openbuilds Blackbox controller, which doesn’t appear to have a ground point to attach the drain wires.

    The only ground point that I know of is on my Huanyang VFD, which is where I will be attaching the drain wire for the spindle cable. Should I attach the stepper and limit switch drain cable to the VFD ground as well, or is there a better place?

    Thanks in advance for the help!

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    Community Moderator Al_The_Man's Avatar
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    Default Re: Grounding shielded cables - help needed

    You normally would set up a Star ground point, and take all ground conductors to this point. including any shields conductors, grounded from the source end.
    The service ground conductor also is connected to the star point.
    Al.

    Last edited by Al_The_Man; 12-02-2020 at 04:20 PM.
    CNC, Mechatronics Integration and Custom Machine Design

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    Default Re: Grounding shielded cables - help needed

    Quote Originally Posted by Nametag View Post
    I’m building my first hobby CNC and could use some help with grounding my stepper motor and limit switch cables.

    I’m using shielded cable for stepper motors and limit switches, but I am clueless on where to attach the drain wires.

    The build videos for my CNC (CNC4Newbie New Carve) use a Demon Controller, which has a ground screw. However I have an Openbuilds Blackbox controller, which doesn’t appear to have a ground point to attach the drain wires.

    The only ground point that I know of is on my Huanyang VFD, which is where I will be attaching the drain wire for the spindle cable. Should I attach the stepper and limit switch drain cable to the VFD ground as well, or is there a better place?

    Thanks in advance for the help!
    You Don't attach the drain wire to anything, you can wrap it around the shield, all shields must be clamped or they will not work correctly, and you will have noise problems, here are some snips of how to Ground a Shield

    A Ground plane is required for everything to be mounted on, ( A metal Plate that is Grounded to you main Power supply Ground )

    A Power Filter is required mounted close to the VFD Drive for the input Power to the VFD Drive , all Grounds wires go to the ( 1 ) mounting Point on the Ground Plane ( Star Ground this can be a stud or a Bus mounting block )

    Attached Thumbnails Attached Thumbnails Grounding shielded cables - help needed-gounding-post-case-star-point-png   Grounding shielded cables - help needed-grounding-shields-6-jpg   Grounding shielded cables - help needed-grounding-shields-7-png   Grounding shielded cables - help needed-shield-clamp-png  

    Grounding shielded cables - help needed-grounding-bus-cabinet-png   Grounding shielded cables - help needed-shield-grounding-png   Grounding shielded cables - help needed-shield-grounding-1-png   Grounding shielded cables - help needed-vfd-shield-ground-motor-cable-png  

    Mactec54


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    Community Moderator Al_The_Man's Avatar
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    Default Re: Grounding shielded cables - help needed

    If you adopt a tried and true method of something called equi-potential bonding, where all sections of the machine are grounded, you can actually connect both ends of the shield to ground, if left unconnected, the shield is floating and essentially useless with no EMI protection and you may as well not use shielded cable...
    This is why it is referred to a drain wire.
    See the Siemens paper on it. Section 6
    They have been a leader in industrial electronics in Europe since after the second world war!
    Al.

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    CNC, Mechatronics Integration and Custom Machine Design

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Grounding shielded cables - help needed

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Grounding shielded cables - help needed