Question about Hypertherm Grounding Document

[laserblazerturbo]

Hi Everyone,

I designed/built a cnc plasma table without knowing anything about emi emissions.

Yes, I'm still laughing at myself also.

I just had a question about this diagram if anyone could help?

https://forum.langmuirsystems.com/uploa ... f6767f.png

As I understand it,

the grounding rod is connected to everything via a star ground / busbar.

My questions are,

1) The plasma cutter ground that plugs into the 220v wall outlet, is that still connected or should it diverted to the grounding rod?
2) Same question for the control box, is the power supply ground connected to the 120v wall outlet still connected, or is that diverted to the grounding rod?
3) The working ground on the table (which i believe is positive) this really connects to the star ground / bus bar?
4) The shielded cable that supply the stepper motors, they are grounded to the control box chassis which is grounded to the star ground / bus bar?

I would appreciate any help.

The plasma cutter is a so called "cnc compatible" CUT60P off of amazon.

The control box contains the Novusun NVUM ethernet Mach3 controller
TB6600 stepper drivers
relay to trigger plasma cutter
24v power supply

thanks guys!

Rob

[WyoGreen]

Hi Rob,
Welcome to the madness!
Leave the electrical grounds where they are, that is part of the AC system, and you don't want to connect it to the Table ground.
The plasma cutter work clamp, some people connect it to the table ground, then to the material being cut. Others just connect it straight to the material, which is what I do.
Only 1 end of the shielded cables is connected to ground. If the control box chassis is bolted to the table, you should be ok. If the control box is separate from the table then you may need to connect it to the star ground. I'd just try the table out, and if you get any weird troubles, then take a look at grounding, there are a lot of posts on here on that subject. I have a cable and clamp that I put on a ground bus bar when I use the table, and about half the time I forget it, and things still work just fine.
Steve

[weldguy]

You may find that a ground rod is not required. I would just be sure all your electrical outlets have a proper functioning grounds and you will likely be just fine.

[laserblazerturbo]

Steve,

Thanks so much for your reply. I really appreciate the help.

When i first built it (at a friend's auto repair shop) there was a lot of feedback through the building's electrical system when both the CNC and plasma cutter were on. I blew the wall wart transformers on the cctv system, then an electric car charger on another occasion.

Im a bit apprehensive now. I added a AC line filter to the control box, and am working on the grounding this week. Good idea to mount the box to the table.

Ill let you know how it goes.

Thanks again,

Rob

[laserblazerturbo]

You may find that a ground rod is not required. I would just be sure all your electrical outlets have a proper functioning grounds and you will likely be just fine.

Thanks weldguy!

[weldguy]

So when I first replied I had looked up Cut60 plasma and came across a PrimeWeld unit which stated a blowback start system so I figured high frequency interference from the arc start was not the issue. Now i see you mentioned your Cut 60 came from Amazon and if its the blue unit I saw it does not appear to have blowback start so high frequency interference is likely your issue when arc starts. This can be a tough problem to cure and a ground rod will be needed. If it were me I would buy a better plasma cutter and make the money back cutting parts and spare yourself any additional trouble.

[laserblazerturbo]

Hi Weldguy,

Thanks for looking into this further. Its disappointing that it clearly says 'cnc compatible' right on the darn thing, but has ended up causing a ton of havoc.

Its passed the return window at amazon but ill let them know.

Ill take your advice on this. I cant take anymore chances with my friend's shop.

Really appreciate your help!

Rob

[weldguy]

Hey Rob, no problem, I enjoy to try and figure these things out.

That plasma likely is genuinely cnc compatible, all that takes is an external port where you can wire in a remote trigger and possibly bring arc voltage out but the high freq start is not something that is fun to deal with.

Many higher end plasma tables are well protected from high freq interference for higher amperage plasma sources so its not uncommon in the cnc plasma world, it just sucks in comparison to blowback start.

Def get yourself a better plasma unit, it will pay off fast. Let us know what you end up with.