4130metalworks wrote: ↑Wed Sep 04, 2024 6:13 am
Hi David, its only a theory at the moment and is going off someone else’s similar experience. My first sheet is always fine, it’s usually the 2nd that plays up. The idea is the emi builds up over time and releases, kind of like getting a shock when sliding your feet on the carpet
What sort of grounding scheme do you have with your plasma table, computer, controller, etc?
David
plasma cutter work lead to earth stake
earth stake to buss bar on the table, that is looped to multiple points on the frame and has a short lead with clamp for the metal getting cut
plasma is 3 phase and off a separate plug to masso controller
masso dthc and myohmic pro in a separate steel box diagonally opposite side to the masso (approx 2.5m distance), double shielded wires except for 24 volt supply
masso, relays, power supplies all in control box
all motor power and encoder wires double shielded
limit switches double shielded
power supply cables double shielded
all wiring other than alarm from motor drivers double shielded
all drains on controller end to central buss bar, that is connected to the ac mains earth
some 24 volt power supply wires and relay module wires are only twisted pair
240 volt input power for power supplies have an emi filter
x axis is grounded to table frame
The shed has its own power switchboard, this takes power from the main house and they all share the same earth stake
After watching plenty of YouTube there are plenty of extra grounds i can add. The other possible noise could be the wires from the masso dthc to the plasma, I could move the dthc to directly on the plasma cutter and shorten those wires
I did some testing with the plasma today. Doing an intricate cut on thicker material was causing some odd issues like usual. My z axis stopped working, a few crashes and loss of arc
Probing with the multimeter while the table was working gave some insight into my grounds. Most of the time my gantry had between 190-250 ohms resistance to the earth stake/ buss bar but in a few select spots went open circuit. The same went for the plasma sources case
From all referenced material 5 ohms or better is what you should have on a cnc to minimise electrical interference. I suspect that my random issues are happening when the gantry hits those open circuit spots
To prove my idea I temporarily clamped a 4ga cable to the gantry and earth stake. This allowed me to cut for the rest of the day fault free using the exact tap file that caused me nothing but headaches earlier that day
Hopefully this helps someone else out, and now for me to run a fresh set of ground cables to every inch of my table
To me your grounding system seems more complex than it needs to be unless your fighting a plasma cutter with a high frequency start. Do you know if yours is high freq start?
If it is not high freq start and despite your issue going away after grounding the gantry to your earth stake I think you may only be solving a problem that should not exist in the first place.
Please reply and let us know if this is high freq start, I looked at the manufacturer brochure for your cutter and it did not say.
Thats good news. So have you ever tried running it without all the grounding? Most cleanly wired simple setups like this run fine without elaborate grounding and not that you have but many others have actually created ground loop issues with their grounding techniques.
No i haven’t tried disconnecting al my grounds weldguy. It would be easy enough to try, just go straight from the plasma to my steel. That can be the next experiment before i add in the new ground system
4130metalworks wrote: ↑Fri Sep 13, 2024 5:47 pm
No i haven’t tried disconnecting al my grounds weldguy. It would be easy enough to try, just go straight from the plasma to my steel. That can be the next experiment before i add in the new ground system
If it's still giving you grief I certainly would try it with no added grounding and compare how it performs. If still having trouble I would ground the table to your ground rod only to start and test again. Also be sure that your AC wall plug is properly wired with a functioning ground and if your using any extension cords that they also have a functioning ground pin on them.
