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Thread: Proper and complete grounding

  1. #1
    Join Date
    Sep 2008
    Location
    Tam Arte Design Studio, Downingtown PA
    Posts
    125

    Default Proper and complete grounding

    Hi all,
    Not much on the forums for posting.. mostly perusing existing problem solving :-) An interesting phenomena happens from time to time on my Bot - an ancient PRT, running from an updated control box. My machine sits on a concrete floor (well, the leg posts) and I have a 12 gauge copper wire running from one corner bolt of the rail out through the wall and onto a metal stake driven into the ground as my "ground". 99% of the time the machine runs flawlessly.. until that 1% that happened today. Much of my machine work is with Duna or Signfoam HDU board which can build up some static, but not as much as pvc. I do not use a dust collection system - I'm still working on a system that I like and I prefer to see the cutting bit while it's working. Anyway, many items I do involved cutting .stl files, which are the 2.5D dimensional images which can take hours to carve. Today, I was finishing an 18 hour job (cut 12 - hit pause, let the spindle cool down and restart next morning) which involved two passes of the cutting bit. I was there when it hit the 50% mark which is when the spindle etc would normally go back to the starting mark on the job and do the second part of the carve (depth) when the machine paused at 50%, started to make it's move back to the zero mark and stopped dead in a odd buzzing sound. No errors on the computer screen showed. But the machine started the second part of the carve where it came to a halt - obviously not in the right spot. Since I was there I was able to E-stop it and keep it from destroying a very expensive piece of material.
    So, my though is that it is not nearly grounded enough, especially in times of high humidity like we've been seeing for weeks here. I've read on here that at least one member has ground straps from the spindle to carriage; Z carriage to Y carriage; Y gantry to X rails and each leg individually grounded to the table/rails. And then all that tied to a common ground plate somewhere. Seems excessive, but I get it. Does anyone have even a sketch on proper grounding - where everything should be grounded, if there is such a thing? I know metal to metal is paramount; I just don't quite know what would be considered the best way to get everything to earth.
    Thanks!
    Rick

  2. #2
    Join Date
    Dec 2008
    Location
    Diamond Lake, WA
    Posts
    1,709

    Default

    You need to run a ground wire from every part of the machine that does not have a DIRECT metal to metal connection. For example, a ground wire from bare metal on the spindle to bare metal on the Z car. Then a ground wire from bare metal on the Z car to bare metal on the gantry. then a ground wire from bare metal on the gantry to the rails. All the legs that don't have metal to metal contact should have a grounding wire tying them to each other. Then a ground wire to a common ground plate that your computer and table or connected to. Then a good ground wire to an outside ground rod. Also, a BARE ground wire from bare metal on the dust collector, thru the inside of the dust collector hose to your common grounding plate. This will shunt static.

    The goal is to have each piece of the machine that is not already metal to metal connected, connected by a good grounding wire. I use 12 gauge green for my grounding wire.
    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.

  3. #3
    Join Date
    Dec 2011
    Location
    Piedmont, SD
    Posts
    722

    Default

    2 points:
    1> I had recent problems similar to yours. SB support advised full remove/reinstall of SB3, then, if still experiencing issues, based on age, my control computer internal hardware was failing (at 9yrs old)
    Turns out, it was the latter. I paid $600 for a Shopbot prepared laptop, which they will do upon request now. A month later, I am cutting with confidence again - machine really smoothed out too.

    2> To more directly answer your question, based on above issues, I too sought proper grounding and found this awesome, thorough write-up that I wish I'd known about years ago:

    https://www.shopbottools.com/ShopBot...%2008%2007.pdf

    It is precisely what you're looking for, and I don't doubt that it contributed to better performance for my 2011 PRS Alpha.

    Good luck!

    Jeff

  4. #4
    Join Date
    Mar 2013
    Location
    Memphis TN
    Posts
    890

    Default

    High humidity means low static. It's the dry air that is more problematic for static. I suggest it's not a grounding problem.
    ShopBot Details:
    2013 PRS Alpha 96x60x12
    4hp Spindle
    12" indexer
    Aspire
    Rhino
    Fusion 360
    Ferrari 360
    Prusa MK3S+

  5. #5
    Join Date
    Sep 2008
    Location
    Tam Arte Design Studio, Downingtown PA
    Posts
    125

    Default

    Quote Originally Posted by jTr View Post
    2 points:
    1> I had recent problems similar to yours. SB support advised full remove/reinstall of SB3, then, if still experiencing issues, based on age, my control computer internal hardware was failing (at 9yrs old)
    Turns out, it was the latter. I paid $600 for a Shopbot prepared laptop, which they will do upon request now. A month later, I am cutting with confidence again - machine really smoothed out too.

    2> To more directly answer your question, based on above issues, I too sought proper grounding and found this awesome, thorough write-up that I wish I'd known about years ago:

    https://www.shopbottools.com/ShopBot...%2008%2007.pdf

    It is precisely what you're looking for, and I don't doubt that it contributed to better performance for my 2011 PRS Alpha.

    Good luck!

    Jeff

    Interesting. My upgraded control box is only a year old or so. But, my installation of SB3 is older than that. I'll look into a complete re-install just because. And thanks for the link/.pdf!

  6. #6
    Join Date
    Sep 2008
    Location
    Tam Arte Design Studio, Downingtown PA
    Posts
    125

    Default

    Quote Originally Posted by coryatjohn View Post
    High humidity means low static. It's the dry air that is more problematic for static. I suggest it's not a grounding problem.

    :-) Have you ever cut HDU? Believe me, it generates it's own electrical charge. The machine is covered...

  7. #7
    Join Date
    Jun 2021
    Posts
    3

    Default

    I believe he was referring to the fact that dry air is more static friendly versus humid air.
    You are correct though, some plastics generate lots of static electricity.
    I have considered trying some anti-static spray such as Cling to see if that helps, but haven't tried that.

  8. #8
    Join Date
    Sep 2008
    Location
    Tam Arte Design Studio, Downingtown PA
    Posts
    125

    Default

    Yes, I understand humid vs dry air. It could be pouring outside and I'd still have stuff flying up and sticking to the metal :-) And I've done the Cling/Static-guard thing.. only helps for a few minutes. Interestingly, I was talking with a supplier today who runs 2 large frame MultiCam machines, both sitting on a concrete floor. He has vacuum hold-downs and uses MDF for a spoilboard. We were talking about static issues and he said that he's never ever had a static problem, no matter what he was cutting.

  9. #9
    Join Date
    Jan 2007
    Location
    Henrico, NC
    Posts
    114

    Default

    This may not apply to this thread but my understanding of grounding, particularly when digital communications is involved, is that ALL devices (Shopbot, computer, dust collector, etc) must be grounded to the same common ground. If a common ground is not used then a 'ground loop' can occur causing all kinds of comm issues. See Wikipedia: https://en.wikipedia.org/wiki/Ground...electricity%29

  10. #10
    Join Date
    Sep 2008
    Location
    Tam Arte Design Studio, Downingtown PA
    Posts
    125

    Default

    Quote Originally Posted by fredtoo View Post
    This may not apply to this thread but my understanding of grounding, particularly when digital communications is involved, is that ALL devices (Shopbot, computer, dust collector, etc) must be grounded to the same common ground. If a common ground is not used then a 'ground loop' can occur causing all kinds of comm issues. See Wikipedia: https://en.wikipedia.org/wiki/Ground...electricity%29

    Absolutely applies to this thread! In fact, it's been discussed in another thread not far below. And that never occurred to me.. I thought ground was ground, so yesterday I took the minor step of taking my "ground" wire that was buried in soil, snipping it short to be close to the machine and attaching it to a modded three wire extension cord (primary prongs were cut off so all that was left was the ground prong) and plugged it into the circuit with the other equipment. We'll see. I still am going to take the extra step of using flexible copper ground cable on everything else to tie everything on the machine together, I just have to order everything.

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