[mactec54]

Interesting. Also, I was thinking about ground loops (and reading forums from years ago that you, Mactec, were a main contributor for!) and I was wondering, couldn't I just ground everything to my CNC frame? It is all made of steel, and so it would be like a car where things are grounded to the chassis. I could then run the ground back to the outlet. Would that work, or is the principal different with AC systems?

Your Auto 12v Dc wiring you can not compare to AC electrical systems

Your machine is already Grounded to your electrical cabinet or should be adding more Grounding points only complicates it even more, unless it all goes to ( 1 ) point ( Star Ground )

Supplying ( 2 ) outlets to the cabinet you will have ( 2 ) Safety Grounds connected ( 1 ) for each outlet you are using, this is where your problem is, this can only be ( 1 ) Ground for it to work correctly

Draw a diagram of using the ( 2 ) outlets to your cabinet and you will see how the Ground loop is formed this goes all the way back to the mains supply so start your drawing from the Main supply Breaker box

[Al_The_Man]

Interesting. Also, I was thinking about ground loops

There is a current practice now called equi-potential bonding, this is in order to reduce or eliminate earth GND loops etc, this is to GND all metalic parts of the machine and enclosure.
Siemens Electric published a paper on this subject that explains it in detail, including the ability to ground both ends of shielded cables now when using the equi-potential bonding method.
Also there are two schools of thought regarding earth bonding all electrical power systems, one is to keep all systems separate and isolated from each other, the other, which I have always subscribed to, is to earth GND one side of all power supplies etc.
Both AC and DC, this is often done in industrial package systems where one purchases a pre-made system, rather than most DIY systems that are made up from different modules and units etc.
This grounding has tended to eliminate many such things such as spurious tripping of limit inputs etc by those posting here with the issue..
Your desk top PC has this built into its DC supply already, i.e. service grounded through the P.S. common via the MOBO ground plane.
I have used this methodology throughout my career without experiencing any ground nuisance faults.
BTW a ground loop is defined as a condition where a potential exists between various points on a ground plane in a earth bonded system.
Al.