I wonder if an optically isolated USB connection would help.
Marc
I wonder if an optically isolated USB connection would help.
Marc
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.
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.
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Last edited by Gary Campbell; 10-18-2018 at 09:19 AM.
Gary Campbell
GCnC Control
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"We can not solve our problems with the same level of thinking that created them"
— Albert Einstein
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
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:
2013 PRS 96x60x12 (Centroid upgrade)
4hp Spindle
12" indexer
Aspire
Rhino
Fusion 360
Ferrari 360
Prusa MK3S+
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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....
thanks for the report back even though I am sure you are very busy now.
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.
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.
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