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Thread: static causing communication problems...again

  1. #1
    Join Date
    Jun 2017
    Location
    Glendale, WI
    Posts
    98

    Default static causing communication problems...again

    Hi everyone,

    Last winter, my first with the ShopBot, I went ten rounds with static electricity from my dust collector and eventually won. I followed all of Brady and Gary's advice about running bare copper wire through the hose and attaching it to metal ductwork with a sheet metal screw. The DC itself is ground to a ground rod driven 6ft into the concrete, and I soak the ground rod hole/opening with water to improve conductivity (per electrician's advice) before running the ShopBot. My DC hose is attached to the Z car by a standoff made of plywood, rigid foam and zip ties so that the hose doesn't contact the spindle or the YZ car or gantry at all. All of this worked well last winter even on crazy cold days with extremely low humidity. The only time the problem resurfaced was the day I didn't realize my bare copper wire had come loose and wandered way up the hose, such that the static had nowhere to travel. Fixed that, and back to no problems.

    Until this week. Ahhhhhhh! Nothing has changed in my setup. Today I even dumped 2+ gallons of water down the ground rod hole. I ran tests air cutting with and without the DC on, and cutting wood with and without the DC on. I can confirm with 99% confidence that the stuttering/loss of position happens only when the DC is running. Sometimes the loss of position is so obvious that I hit the emergency stop before ruining something. Sometimes the machine stutters, but the loss of position was actually imperceptible until you, for example, get to the cutout toolpath and find out that you lost EXACTLY -.125" in X at some point during the cut, which you can see clearly here:

    IMG_4798.jpg

    Here's video of the subtle stuttering (versus obvious catastrophic position loss):

    https://youtu.be/b0GH2_MJR-s

    I am at a loss. In case it matters, here are some additional thoughts/data points:

    - This is happening MUCH earlier than last year, when the problem surfaced in January.

    - The only new things in my shop are some LED lights and a newer version of an Apple Watch.

    - I wondered if a neighboring shop was emitting something that was causing the problem, but that doesn't make sense if it happens only when running the DC

    Of course this is happening right when I am ramping up again with many projects and deadlines (I am not a hobbyist).

    Any help would be much appreciated!! Thanks.
    Brian

  2. #2
    Join Date
    Dec 2000
    Location
    Thorp, WI
    Posts
    2,595

    Default

    It's gotta be the Apple watch, as that one has never been blamed before! Check your neighbors wrist, I bet he has one too.

    Obviously I'm being facetious, but the sad sad year after year saga continues.....

    Sounds like the conductor in the hose is grounded well, but how about the carriages?
    Scott

    If guns kill people, I guess pencils misspell words, cars drive drunk and spoons make people fat.

    "Those who hammer their guns into plows, will plow for those who do not" - Thomas Jefferson


  3. #3
    Join Date
    Jun 2017
    Location
    Glendale, WI
    Posts
    98

    Default

    Quote Originally Posted by srwtlc View Post
    It's gotta be the Apple watch, as that one has never been blamed before! Check your neighbors wrist, I bet he has one too.

    Obviously I'm being facetious, but the sad sad year after year saga continues.....

    Sounds like the conductor in the hose is grounded well, but how about the carriages?
    It's always good to blame Apple

    What do you mean by carriages?

  4. #4
    Join Date
    Dec 2000
    Location
    Thorp, WI
    Posts
    2,595

    Default

    Well, it sounded like your hose and it's ground connection are insulated from the machine with the plywood standoff and while I don't, some people need to have each carriage (Z car, gantry, and then frame) grounded to the same common ground as well.
    Scott

    If guns kill people, I guess pencils misspell words, cars drive drunk and spoons make people fat.

    "Those who hammer their guns into plows, will plow for those who do not" - Thomas Jefferson


  5. #5
    Join Date
    Mar 2013
    Location
    Memphis TN
    Posts
    605

    Default

    I agree. Ground EVERYTHING that moves to the same grounding rod. That includes the X axis, Y and Z cars individually. Ground the DC to the machine. Ground the electrical outlets to the rod. Everything should be grounded to a common point. Be sure to use at least 10 gauge wire and bolts (I soldered lugs to the grounding wires and bolted them to the machine) to secure the grounding wires. You cannot be too anal about grounding.
    ShopBot Details:
    PRS Alpha 96x60x12
    4hp Spindle
    12" indexer
    Aspire
    Rhino

  6. #6
    Join Date
    May 2014
    Location
    Tucson, AZ
    Posts
    78

    Default

    You've checked all the obvious, not it's time to check the unobvious. I've worked for 35+ years in the aerospace industry, much of it designing/manufacturing missiles and bombs. We take static electricity and grounding very seriously, it's not just comm problems or missed steps, it's someones life when it static happens where it shouldn't. That being said, I recommend three things.

    First is, I think you and your electrician are very mis-informed about grounding rods. It sounds like you have more than one rod in your overall system. Is your machine electrical grounded via your building electrical system? Do you have a completely separate grounding rod just for your dust collection? If yes, that's a big problem. You have created electrical potential between the two grounds which can can all kinds of issues. Just use your the ground that your machine is electrically connected to. That way the operating computer, the control box, the machine structure, the router or spindle and the dust collector are all connected to same ground with the same potential.

    Second, pouring water on the ground rod is ill-informed. The soil has minerals in it, the water that you're adding either has minerals and chlorine or salt and chlorine in it. You are causing the soil to leach minerals towards and onto the grounding rod. Think how electrical plating or chroming works. Once enough minerals have attached themselves to the rod conductivity to the soil is significantly reduced. Depending on your soil this can happen quickly or slowly over time. Copper does not rust but I'm sure you have seen it "patina", that is simply chemicals and minerals changing the surface structure of the copper and making it less conductive.

    Third, you may think that everything is connected and grounded, but you need to actually test it for conductivity. Use a DVM (digital volt meter) and check for continuity between all the components of your system (building electrical ground, computer, control box, machine frame, machine gantry, dust collection hose or piping, and dust collector).

    Hope some of this helps.

    Jim
    Jim

    96 x 60 PRSalpha, 5HP Colombo spindle, Custom indexer, Custom vacuum table, Custom Fire Extinguishing System

  7. #7
    Join Date
    Jun 2006
    Location
    , washington
    Posts
    180

    Default

    Brian
    I do not run shopbot control,but,
    with what I do use when I had comm errors I found grounding the frame of the machine to the building ground fixed it.
    Theory is noise [" dirtypower"] introduced by the incoming ac.
    In one case it was single 18ga wire to the conduit,
    in another we used same 18 ga wire to the ground pin of a 120v plug and plugged that into a wall outlet. both solved the problem
    one machine was in an industrial area with a foundry across the street.
    every time they fired up those big induction furnaces ,we would have issues .
    Carl

  8. #8
    Join Date
    Jun 2013
    Location
    Pasadena, CA
    Posts
    947

    Default

    If you have a control PC with a grounded power supply (i.e. all desktops and some laptops), disconnect the power ground from the plug and connect it to the machine controller board ground as close/parallel to the USB cable as possible. Otherwise you will have a ground loop that goes through the USB cable which is obviously not good. Many newer laptops have only 2-prong plugs without ground and do not have this problem.
    Box Joint, Dovetail, Guilloche and MazeMaker Software Here

  9. #9
    Join Date
    Dec 2008
    Location
    Diamond Lake, WA
    Posts
    1,561

    Default

    Quote Originally Posted by coryatjohn View Post
    I agree. Ground EVERYTHING that moves to the same grounding rod. That includes the X axis, Y and Z cars individually. Ground the DC to the machine. Ground the electrical outlets to the rod. Everything should be grounded to a common point. Be sure to use at least 10 gauge wire and bolts (I soldered lugs to the grounding wires and bolted them to the machine) to secure the grounding wires. You cannot be too anal about grounding.
    Make sure when you bolt ground wires to the machine, you scrape any paint under the wire lug to make sure you get a GOOD metal to metal contact.
    Don
    Diamond Lake Custom Woodworks, LLC
    www.dlwoodworks.com
    ***********************************
    Life is not a journey to the grave with the intention of arriving safely in one pretty and well preserved piece; But to skid in broadside, thoroughly used up, worn out, bank accounts empty, credit cards maxed out, defiantly shouting "Geronimo"!

    If you make something idiot proof, all they do is create a better idiot.

  10. #10
    Join Date
    Aug 2012
    Location
    Davenport Iowa
    Posts
    164

    Default

    I agree with Jim.
    I you have two different grounds you will end up with dissimelar grounds and current can flow between them. Make suer your system is tied to the same ground. Not one from the house and one from your ground rod.
    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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