Embarrassed to even ask this electrical question

Ok So I have been doing electrical work for years now No certifications just some corporate classes. and know the last 4 years wiring in control panels for CNC that have been my own. 

Soooooo. I've been having what appears to be mystery voltages appearing and today I was going to run through some testing on the plasma. all set up and the Hypertherm throws 0-99 look it up and oh lovely major power issue. ok maybe i just need to place the ground directly on the material and that's when it kissed me. a nice little trickle of voltage coming out of the water and through my little knubs. 

Go to check to see what I'm dealing with, and the voltmeter shows I've got about 24vdc running through the entire table. This issue just appeared as I had no issue two weeks ago when I ran the first test cuts on the new setup. 

Here's the embarrassing question. does the common ground go to earth ground at any time. while I understand how to wire panels in, I guess I haven't spent much time understanding how grounding actually works. the table itself has a welding cable as its earth ground (4Gauge) runs outside to a rod driven deep into the ground. I have 120vac coming into a filter that is grounded to the console chassis. it than runs to a 48vdc power supply that is used to for the Drivers. from the 48vdc power supply I have a 12vdc supply and a 5 vdc supply. So nowhere in the system is there 24vdc. Each one of the power supplies has a grounding block that the commons come back to. But none of that returns to the console chassis. 
I'm running shielded cable and the only cable where the shield is grounded is the one going to the THCad2 located on the side of the hypertherm. 
So, when grounding is any of that supposed to go to the chassis / earth ground?
One thing to note is that when the E-stop is pushed in it kills all power to the drivers. When doing so the Table frame drops down to about 1 - 2 vdc.

The one item that changed since the last test cuts was I added in better supports for the water pan and put the water pan back in place and added water. So its possible that this mystery voltage was there all along and i just never noticed it.

I'll go through and verify those items. As far as Daisy Chain, I have the ground coming off the 48vdc power supply and to a terminal block where all the grounds terminate is that sufficient or do I need to return all grounds to the power supply?

I just ran through and disconnected the motors one at a time and tested each time for power to frame and my X axis motor was going to ground on one of the legs. of course, it was my mess up as I've added motor caps to allow for mounting of aviation plugs and to give it a cleaner look. My design requires the back plate to be drilled through for passing wires. and I did that because the other style was pinching the wires. the irony lol.

But I still have 1-2vdc in the frame. so Ill go through your list and verify those items
On shield wire does that get soldered to the ground lug or the casing on one side?
And my power supplies are just 48vdc supply off amazon. I guess I'll look at the mountable style as Im running out of room in this case.

Everything is working nicely now. no voltage to frame or water pan. Ran a few tests cuts this morning and all is well. I'll have some more questions but I'll ask them in the right forum later today