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Thread: static causing communication problems...again

  1. #21
    Join Date
    Mar 2016
    Posts
    31

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    I wonder if an optically isolated USB connection would help.

    Marc

  2. #22
    Join Date
    Jun 2017
    Location
    Glendale, WI
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    103

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    Quote Originally Posted by Brady Watson View Post
    Brian,
    Do a continuity test using a multimeter on your bare copper ground wire inside the DC hose. You'll need a long insulated wire hooked to the spindle end of the ground wire to allow you to get your test leads on the other end. Test between the insulated 'helper' wire at the DC end and the DC chassis ground where your bare wire is terminated. It's really the only reliable way to test if your ground wire is doing its job & isn't broken. Then test your DC chassis ground (where the bare wire is terminated) and touch the ground lug in the electric panel or your driven ground rod. You should have continuity on both. Even a cheap HF meter will beep on continuity/a closed circuit path. This is the number 1 test method when troubleshooting anything electrical. Just because you don't know much about electricity now doesn't mean you're stuck that way - right?

    To reiterate - you want a bare copper wire (.023/030 Cu coated MIG wire is fine) that is tied to the DC chassis (which is tied to electrical sys gnd) on one end & running through the hose and only folded over the end of the hose @ the DC foot end. It needs to function as an antenna with nothing metal touching the tip or the rest of the bare wire until it gets to the DC termination point.

    -B
    Thanks Brady. I can definitely learn

    Regarding the bare copper wire in the DC flex hose, right now it exits the hose and attaches to metal ductwork with a sheet metal screw. You are saying that, instead, I should run that bare copper wire from the dust foot, where it exits the flex hose and is clamped to the dust shoe, through the inside of the flex hose, out the top of the flex hose, and then directly to the electrical system ground?

    Also, I am not sure what/where my electrical system ground is. That driven rod is new -- added by an electrician I hired. And it doesn't connect to the electrical panel in any way.

  3. #23
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,870

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    Brian,
    One long wire is best - you can use the duct as an electrical conductor between flex hoses - but to keep it simple, just wrap a MIG wire around a rag and let the DC pull it through the hole deal. Throttle it by hand obviously & don't let it get sucked into the DC.

    Then....

    Attach the wire to the chassis of the DC - which *should* be connected to the electrical system ground. Unless you get zapped or your hair stands on end every time you go near/touch the DC while it is running in dry conditions - then it's probably grounded to the electrical system just fine. Just make sure your bare wire is screwed to the chassis properly.
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  4. #24
    Join Date
    Apr 2007
    Location
    Marquette, MI
    Posts
    3,372

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    Last edited by Gary Campbell; 10-18-2018 at 09:19 AM.
    Gary Campbell
    GCnC Control
    GCnC411(at)gmail(dot)com
    ShopBot Controller Upgrades
    http://www.youtube.com/user/Islaww1


    "We can not solve our problems with the same level of thinking that created them"
    Albert Einstein


  5. #25
    Join Date
    Jun 2017
    Location
    Glendale, WI
    Posts
    103

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    Well, I think I fixed it, although I've learned not to celebrate too early. I will give it a week or so before I claim victory.

    Today I systematically made a series of small changes to how the DC is grounded, each of which did not stop the stuttering/loss of position, until I removed the ground wire that runs from the DC to the driven rod and wrapped it around nearby electrical conduit instead. Now I am cutting without problems.

    If that's the solution, it certainly tracks with anyone who said, "Don't have two competing grounds in your system!!!" It does not, however, explain why everything worked fine last winter once I added the driven rod and connected the DC directly to it. Oh well.

    To summarize for the sake of anyone in the future who searches this thread:

    In my particular case, I was able to consistently isolate the stuttering/loss of position to only when the dust collector was running, and even then only when I was actually making chips versus air cutting. So the hypothesis was that something was wrong with my DC grounding. I already had a bare copper wire clamped to the outside of dust shoe, running inside the flex hose until it exited at the gimbal joint where the flex hose connects to the metal ductwork. The inner wire of my flex hose connects to the bare copper wire where it exits the flex hose, and that bare copper wire is then attached to the ductwork with a sheet metal screw. My flex hose is also attached to a standoff of plywood and rigid foam that keeps the hose from contacting any part of the machine.

    The change I made that works (at least for now): at the dust collector, there's a thick, bare stranded copper wire bolted to the frame that is attached to nearby electrical conduit that runs directly to the electrical panel (instead of being attached to a driven ground rod, which was likely creating a situation where I had two competing grounds).

    Notably, the frame of my ShopBot has no ground wires at all.

    I will report back if anything changes. Thank you all for the help!!!!

    Back to work....

    Brian

  6. #26
    Join Date
    Mar 2013
    Location
    Memphis TN
    Posts
    673

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    You should read Gary's PDF on grounding and follow those instructions. Not having the frame of your machine grounded is just asking for problems.
    ShopBot Details:
    PRS Alpha 96x60x12
    4hp Spindle
    12" indexer
    Aspire
    Rhino

  7. #27
    Join Date
    Jun 2017
    Location
    Glendale, WI
    Posts
    103

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    Quote Originally Posted by coryatjohn View Post
    You should read Gary's PDF on grounding and follow those instructions. Not having the frame of your machine grounded is just asking for problems.
    I agree. For the sake of clarity, I wanted to state that the problem seems to be fixed and explain how it was fixed -- with a note that my frame isn't grounded, so that's likely NOT the cause of this particular problem. That doesn't mean it shouldn't be grounded. That is next....

  8. #28
    Join Date
    Jan 2011
    Location
    gleason, wi 54435
    Posts
    427

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    thanks for the report back even though I am sure you are very busy now.

  9. #29
    Join Date
    Jun 2017
    Location
    Glendale, WI
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    103

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    Well, good thing I didn't celebrate yet. I have had some jobs cut without incident, but at this point I am back to a 100% failure rate if the DC is running, and a 100% success rate if it is not. If necessary I will run certain jobs with no DC. But I make a lot of trays, and a 1.25" diameter bowl bit taking 1/4" passes at 16000 rpm requires dust collection given the massive amount of chips.

    I've done everything in Gary's PDF about static reduction in dust collection systems. So even though the problem only happens with the DC running, I guess either my DC grounding is incorrect or it's something else, like the CNC itself not being grounded directly to the panel. So I will hire an electrician to ground the ShopBot; and while he is at it, he can take a fresh look at my DC ground.

    I am not at a full panic yet, but close....the work is mounting, and I can't get any of it done right now.

  10. #30
    Join Date
    Aug 2012
    Location
    Davenport Iowa
    Posts
    169

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    Just a final thought. How old is your DC? Could you have a motor failing causing electrical noise in the ground leg? Seems odd the only time you have trouble is when its turned on.
    Life is like a project you continue to work on until it's finished.
    Never start a project you don't intend to finish!

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