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  • B&M Welding Inc.
    replied
    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.

    Leave a comment:


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

    Leave a comment:


  • B&M Welding Inc.
    replied
    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

    Leave a comment:


  • jimcolt
    replied
    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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  • H80N
    replied
    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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  • B&M Welding Inc.
    replied
    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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  • B&M Welding Inc.
    replied
    Thanks for the direction Melted! That is a very useful thread! Right down my alley!

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  • Meltedmetal
    replied
    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

    Leave a comment:


  • H80N
    replied
    a single point ground is a better idea,,,

    multiple grounds encourage a difference in potential.... eddy currents and oscillation...

    every piece of wire can look like an inductor when subject to an AC field...
    Last edited by H80N; 11-05-2014, 10:42 AM.

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  • B&M Welding Inc.
    replied
    Thanks for the reply! I have some ferrite choke that I am putting on. I also am working right now at putting in a couple 10' ground rods in the shop floor to ground the control console and plasma power unit separately.

    Leave a comment:


  • H80N
    replied
    Originally posted by B&M Welding Inc. View Post
    Yes that is a huge motor. I guess it weighs near 20 lbs. I am working on some grounding/filtering procedures to help combat interference. I'm open to ideas on how to deal with HF interference.
    You might look at some split Ferrite beads and or torroidal cores on some of the lines to help attenuate some of that RFI
    Last edited by H80N; 11-05-2014, 10:25 AM.

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  • B&M Welding Inc.
    replied
    Double post. This iPhone app ain't too up-to-date!

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  • B&M Welding Inc.
    replied
    Yes that is a huge motor. I guess it weighs near 20 lbs. I am working on some grounding/filtering procedures to help combat interference. I'm open to ideas on how to deal with HF interference.

    Leave a comment:


  • PlasmaGuy
    replied
    Nice work

    When you said 4200 oz/in I had to take a double-take. That is a HUGE stepper.
    Are you expecting any HF issues with the 3070 and your electronics?

    Thanks for posting the pics.

    Tom

    Leave a comment:


  • B&M Welding Inc.
    replied
    More on the electronics!

    Here is some pictures of my control box. When I built this I was on a budget so I just used the cheapest of everything I could find on eBay! That worked for some components, not to well for others. The steppers and drivers are Long Motors, seem to work very well and are cheap. The motion controller is an Ethernet Smooth Stepper mounted on a CNC4YOU breakout board. I originally used a cheap USB motion board but that didn't support the torch height control function very well so I switched to the ESS, love it too!! My computer is a Dell 2020 all-in-one w/touchscreen. Running Win. 8.1 with Mach3 CNC control software. The electronics all work great right now other than my THC needs to be upgraded to a higher quality system before I use the HD3070 unit that I'm installing. The steel scrap is 3/4" cut with the 80A 1250 Hypertherm.
    Attached Files
    Last edited by B&M Welding Inc.; 11-04-2014, 08:10 PM.

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