Ground plasma table.

Greetings everyone, can someone help me with this confusing grounding problem, I finished making my plasma and it works fine with the isolated plasma table (not grounded) the only thing that is connected is the control box and the plasma. Well, today I installed a screen to the metal structure of the plasma and now it is connected to ground through the hdmi cable to the computer in the cabinet, as the plasma clamp is positive and at that point there is also the ground there is some damage that can happen?

Was thinkng about this and the typical patterns I have seen on the forum.  Isn’t the control box presenting the same ground link back to the computer as the screen would be? 

Actually I have all the earths together the same with the positive of the torch I saw it in a hyperterm tutorial but in other forums they say that the structure of the table is not connected to earth so I am confused.

I think you would take this field service article from Hypertherm as gospel.   From my reading of it all grounds from table, control cases, psu's, THC's cnc console (which is going to contain a computer and screen I would expect), motors and other components like solinoids are all ultimately linked via bus bars and wires together back to a ground.

When looking at the diagram on the 2nd to last page I read (interprate) that as showing the plasma work lead attached to the table bus bar. Which makes sense in a commercial style machine. Why use a work clamp?   The blue line back to the power supply is a ground to the case NOT the torch. That case grounding will go back out to the AC ground.

As always, do your own due dilligence. 

Cheers.

I ended up buying an oscilloscope when I was chasing noise related issues.
Most noise entered the control box via the mains ground. 
Fitting an EMI filter totally resolved the issue. I replaced my IEC connecter with a EMI filtered version which only cost $10 and a few minutes to install.

But this is where using a Mesa ethernet card is an advantage becasue the the ethernet cable adds a layer of galvanic isolation between the dirty plasma side and the PC.