1. #1
    Hi all,

    I have a small Chinese cnc router that I am currently working on. I need to change some of the wiring as it is not up to standard. They have used non shielded 3 core cable to wire the spindle, there is no earth which I think is unsafe, also the circular connected on the control panel is a 3 pin male connector, which is also unsafe as there is live power available if the spindle cable is removed.

    I have purchased 4 core shielded VFD cable but now I am in need of a circular connector to suit. Would like a female connector for the control panel.

    Just wondering what connector is recommended to use. Also do I want 4 pin or 5 pin. U - V - W + Earth wires but do I need to connect the braid to a pin as well?

    Also another question regarding shielding, should the actual machine frame be isolated from the stand which the control box is mounted to? I could isolate with maybe some sort of rubber. What I am trying to ask is do I wan't continuity between the machine and the control box.

    Thanks

  2. #2
    Send Jonathan a message, as I think he may have forsale just the right connectors (GX16) your looking for :).

    .Me
    Last edited by Lee Roberts; 17-06-2016 at 06:26 PM.
    .Me

  3. #3
    Those connectors are currently what I have on my machine right now, I need the gender swapped around the other way.

    http://www.ebay.com.au/itm/2-Sets-GX...QAAOSwkZhWSsFl


    Quote Originally Posted by Lee Roberts View Post
    Send Jonathan a message, as I think he may have forsale just the right connectors (GX16) your looking for :).

    .Me

  4. #4
    [QUOTE=ROBCNCAU;81130 Would like a female connector for the control panel.[/QUOTE]
    If you find them (and the matching male connector) please let me know where.

    Best of Luck

    Rob
    It takes all sorts to make a world, I am just glad I am not one of them.

  5. #5
    I've yet to see the GX-16 style connector with a female chassis / male floating plug combo. Save yourself the effort and search for a different, appropriate connector (RS Components have an Australian operation - I guess they supply the public as in the UK?). Run 4 core shielded cable, introduce the earth to one of the cores and (probably) adapt the spindle to carry the earth to the spindle enclosure. Conventional wisdom is to bond the shield at the VFD side to a common/star earth point, particularly if running the cable form close to other more EM-susceptible wiring.

    The machine and control box should be equipotential - achieved by exporting the earth from the bit that plugs into the wall (I guess the control box) to each conductive, exposed component. If you isolate them then you introduce the risk of electric shock. So, ideally you'd run an earth strap from the machine to the earth stud on the control box. More practically, you might take the earth from the cabling to the spindle and bond that to the machine body - and where the machine is constructed from multiple mechanical elements - to bond each of these with an earth strap. Most people find some compromise in this utopian solution for their own machines if they are not looking to certify their product safe for use.
    Last edited by Doddy; 19-06-2016 at 08:29 AM. Reason: missed a bit

  6. #6
    I wasn't looking for a GX-16 style connector, it could be anything as long as it is not too bulky or too expensive. So I guess I would need a 5 pin connector to implement the shield as well, is that correct?

  7. #7
    Quote Originally Posted by ROBCNCAU View Post
    I wasn't looking for a GX-16 style connector, it could be anything as long as it is not too bulky or too expensive. So I guess I would need a 5 pin connector to implement the shield as well, is that correct?
    If the connector shell is conductive (metal) then that should be bonded as well. Often the shield is connected to the connector shell, but if you can spare/spec a pin then this provides a predictable low-impedance path to earth, and would be a good thing.

    There's two goals here:

    1) Equipotential bonding of all exposed conductive elements - for that reason the metal connector shells should be bonded to earth.
    2) Electrical shielding of EM-emissive cabling - for that reason the shield should contain as much of the cable run as physically possible - achieved by bonding the braided sheaf to the connector shell.

  8. #8
    Ok,

    I think 4 pin should do the job then, at the spindle end I will have the braided shield isolated from the connector shell and then at the control box end I will connect the braided shield to the connector shell.

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