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Thread: Grounding HF plasma torch

  1. #13
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    Default Re: Grounding HF plasma torch

    Quote Originally Posted by Bradnicent View Post
    What I did was install all my electronics “ power supply, bob, drivers” inside a completely enclosed steel box with only the power cable and 1 stepper motor cable coming out of it using shielded cable for both as in attached picture, the inside of the box is grounded via a earth of the power cable sheared with the power supply... I closed off the air gaps between the cables and the box with foil tape ... the shielded cable of the stepper motor coming from the box is attached to the unshielded wires of the stepper motor, so I wrapped foil tape around it for shielding and ensuring the tape is wrapped all the way to attach to the body of the motor, also made sure the tape is firmly attached to the breaded shielding of the cable which is also grounded to the box .... I proofed to myself that the steel box do actually shield my electronics from emi by triggering the plasma switch and holding it in for 1 second without cutting anything with only the ground cable and trigger switch plug connected to the plasma machine ,but as soon as I connect the plasma torch then (ALL HELL BREAKS LOOSE!!!) .... can someone please explain to me why????


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    Would have to have a photo of the whole setup, just using the foil tape is not enough of a bond to Terminate the shield it has to be clamped to a solid Grounded surface, tape over exposed wires is good, air gaps are not normally a problem for your setup

    Have you Grounded the Shielded cables in the box either through the metal gland ( cable restraint ) or with a clamp inside your Grounded metal box

    if you have a Ground wire from the torch that is not shielded then that wire will put out the nasty EMI

    This metal Gland ( cable Restraint ) has an internal ring for shielded cables keeps cables with braid shielding grounded to the body of the grip to maintain the shielding's ability to block electromagnetic interference (EMI).

    Attached Thumbnails Attached Thumbnails Grounding HF plasma torch-metal-gland-wire-restraint-png  
    Mactec54


  2. #14
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    Default Re: Grounding HF plasma torch

    In my setup, I used 5 wire microphone connectors (4 for stepper, 1 for shield) and used one pin to pass the shield through and added a spade connector to the shield right at the stepper controller. Each shield is then terminated to a copper grounding post on the enclosure that is designed for this purpose (part of the enclosure). The stepper controllers are located quite a way from the cable entry point. This has worked a treat and it would have been difficult to adapt the clamping method to this enclosure with ending up with extended unshielded wiring. Plus you can disconnect the stepper cables.

    Rod Webster
    www.vehiclemods.net.au


  3. #15
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    Default Re: Grounding HF plasma torch

    My plasma torch needs to make contact with the plate in order to work.... there is a half a second time period between triggering the torch and making a pierce and in that period the torch gives off emi .... how do I drain the emi from the torch?


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    Default Re: Grounding HF plasma torch

    Quote Originally Posted by rodw View Post
    In my setup, I used 5 wire microphone connectors (4 for stepper, 1 for shield) and used one pin to pass the shield through and added a spade connector to the shield right at the stepper controller. Each shield is then terminated to a copper grounding post on the enclosure that is designed for this purpose (part of the enclosure). The stepper controllers are located quite a way from the cable entry point. This has worked a treat and it would have been difficult to adapt the clamping method to this enclosure with ending up with extended unshielded wiring. Plus you can disconnect the stepper cables.
    The shield can be clamped anywhere near the end, there is no need to have unshielded wires out the end of a cable

    I would say you got your Grounding of your machine done correctly, when this happens the rest does not matter so much

    Attached Thumbnails Attached Thumbnails Grounding HF plasma torch-shield-grounding-png  
    Mactec54


  5. #17
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    Default Re: Grounding HF plasma torch

    Quote Originally Posted by Bradnicent View Post
    My plasma torch needs to make contact with the plate in order to work.... there is a half a second time period between triggering the torch and making a pierce and in that period the torch gives off emi .... how do I drain the emi from the torch?


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    Your main problem is I think you are using to different power supply sources, ( 1 ) being 240v supply and the other being 120v supply

    So what you need to do now is make a Grounding point on your machine Main Frame, attach all your Ground wires to this one point, run a Heavy Ground wire from your Ground Rod to your machine make sure it is bonded to the Rod

    To isolate the computer and electronics you may need a UPS and a Power line Filter the line filter may be enough to start with, what are you using to connect the computer to the Breakout Board for the CNC Control part

    Here is a PDF on How to do the Grounding for the Plasma side, this is a little conflicting but the basics for Grounding is ok

    Attached Thumbnails Attached Thumbnails Grounding HF plasma torch-grounding-plasma-torch-pdf  
    Mactec54


  6. #18
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    Default Re: Grounding HF plasma torch

    I am using a db 25 parallel port plug from pc to bob (not shielded) ..... I think my main problem is the torch.... if I can find a way to drain emi from it my pc will probably stop freezing


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    Default Re: Grounding HF plasma torch

    how do I drain the emi from the torch?
    Hypertherm in the attached document above would have you run a separate ground wire on the torch holder back to the star ground point on your table. There s a lot more wires her now...


    So I think the idea is that the groundwires skip over any connections on linear rails etc so there is a clear ground wire back from every point in the machine that could generate noise. Stepper housings, the lot.

    Rod Webster
    www.vehiclemods.net.au


  8. #20
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    Default Re: Grounding HF plasma torch

    Are you trying to say that there is a difference in grounding for emi and grounding for electricity? ..... and the must be grounded separately?


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    Default Re: Grounding HF plasma torch

    I'm not saying anything. I just followed the Hypertherm recommendations in the document and a friend donated a very old "star" grounding point and set up my stepper motor cabling very carefully with noise in the back of my mind. Having 24 volt electronic controllers also helps as the higher voltage is less susceptible to noise.

    Rod Webster
    www.vehiclemods.net.au


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    Default Re: Grounding HF plasma torch

    Quote Originally Posted by Bradnicent View Post
    I am using a db 25 parallel port plug from pc to bob (not shielded) ..... I think my main problem is the torch.... if I can find a way to drain emi from it my pc will probably stop freezing


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    This would have to be a shielded cable, this would be a good starting point, go for Double Shielded Premium D-sub 25 Position DB25 Male/Female Cables - Fully Populated, Double Shielded

    Your Torch Grounding and connection should be as per the PDF

    Mactec54


  11. #23
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    Default Re: Grounding HF plasma torch

    Quote Originally Posted by Bradnicent View Post
    Are you trying to say that there is a difference in grounding for emi and grounding for electricity? ..... and the must be grounded separately?


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    Here is a video for you and anyone else, this is long it starts with the basics and you may get confused or you will end up with a great understanding of Grounding and what it means



    Mactec54


  12. #24
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    Default Re: Grounding HF plasma torch

    Will a plasma cutter with pilot arc be a better choice regarding emi? .... a recent google search reveals that it reduces emi ...

    https://www.bakersgas.com/weldmyworl...plasma-cutter/



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