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  • #16
    http://weldingweb.com/showthread.php...ma+table+build

    The whole thread is interesting but a discussion on using small caps to filter noise starts around post #35.You might also consider it in conjunction with grounded shielding of vulnerable parts.---Meltedmetal
    ---Meltedmetal

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    • #17
      Thanks for the direction Melted! That is a very useful thread! Right down my alley!

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      • #18
        Ok, when you say single ground point should it be at the computer console or the plasma unit? Are about 15' apart.

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        • #19
          Originally posted by B&M Welding Inc. View Post
          Ok, when you say single ground point should it be at the computer console or the plasma unit? Are about 15' apart.
          If it were me I would bond a single ground rod at the panel where the power enters the building..
          aside from using split ferrites on the data cables I would also look at how you have roured cables... you would be amazed at how cable placement can affect RFI and EMI...

          Would guess that Jim Colt at Hypertherm has run into and resolved most RFI problems that you might be encountering...
          Last edited by H80N; 11-05-2014, 07:21 PM.
          .

          *******************************************
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          • #20
            In the early days of CNC plasma we had noise issues on virtually every installation. These machines had microprocessor based cnc controls....and high frequency start plasma cutters. We resorted to every tactic in the book....such as:

            - 1 good quality earth ground rod driven as close as possible to the machine.
            - Earth ground wiring from every electrical cabinet directly to the rod (no daisy chaining of wires). Use heavy gauge multi stranded wiring for this....flat braided wire is best......this is because RF travels on the outside of conductors....so multistranded and flat braid were most efficient at returning RF to earth ground.
            - Torch leads were shielded (with braided tubular cable), and grounded at the high frequency generator end only. Torch leads were routed away from all other cables.
            - All cables, wires, torch leads for computer, drives and plasma....were as short as possible so no coiling was required. All cables were placed neatly in power tracks....parallel to each other (no looping, twisting). Torch leads stayed in their own power track...preferably plastic.

            -All sensitive control wiring was overall shielded, and the shield drain wires connected at the end that was closest to the ground rod....the other end of all cable shields was not grounded (minimize ground loops).

            -High frequency generator was placed as close to the torch as possible, with short torch leads.

            I do have a general cnc / plasma grounding document that I can email as a .pdf file.

            The rule of thumb today: If your cnc plasma machine uses a standard office PC or Laptop as the cnc control......use only blowback start plasma cutters (not high frequency start). In most cases a blowback start (such as a Hypertherm Powermax) can be used with little or limited earth grounding strategies, a high frequency start plasma (such as all Hypertherm heavy industrial plasma's) should only be used on purpose built machines with industrially hardened cnc controls.....these controls are designed with optically isolated I/O as well as with electrical line isolation and shielded I/O cabling designs.

            Jim Colt [email protected]

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            • #21
              Thanks for coming here with that advice Jim! I am collecting information so I have heard most of what you have offered, however that PDF would be great to have on hand. My email is [email protected] Thanks, Brian

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              • #22
                Wow Brian, that is a great looking cnc table. Quite the job for the first one!

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                • #23
                  Originally posted by pgk View Post
                  Wow Brian, that is a great looking cnc table. Quite the job for the first one!
                  Thank you! I have my HyDef plasma almost hooked up. Hopefully I'll have a few more pictures soon if I get that going.

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