Riddle me this: electrical anomaly

[LenMcC]

I have an odd condition. We recently built a Torchmate 2. On the back 2ft of the table where there is no usable cutting area we made into a welding table. Whenever we TIG weld and initiate the arc, the optical mouse on the CNC computer flickers, and our torch-mounted camera gets an error. Occasionally, we'll lose the mouse and keyboard altogether.

Ok, so probably a bad ground... I grounded the table chassis to two ground rods outside (one 6ft, one 8ft, 2-3ft apart) with 6ga solid copper wire. No change. So then I bonded the outlets to the ground rod and checked everything for continuity, and continuity is excellent. Any outlet to any outlet, the plasma table, the welding ground, and even the compressed air lines. They're all one circuit. Still no change.

Now here's where it gets interesting... I was using the CNC computer and someone else needed to weld, so I told them to do it somewhere else so my mouse doesn't screw up. He was doing a small piece, so he set up shop on our stomp shear, which is a good 30ft from the CNC computer and not touching anything but concrete. STILL, the mouse acts up. This is with the welder outlet bonded to the new grounding rods, too.

What's going on here?

[Al_The_Man]

Probably the PC supply is grounded just by the MB screws to chassis, which is not really a positive bond to system ground, who know what it is floating at?
With PC based systems, I make sure the PC PS common is bonded as close to system ground as possible.
Al.

[lamicron]

I builded a plasma table for steel seller, he used it to weld , as a work table , when the pc and machine were not working. then they weld with the machine on, .... the pc board, the c10 Breakoutboard and one driver got burn! So, take a good care of it!!

[Weldtutor]

Originally Posted by LenMcC Whenever we TIG weld and initiate the arc, the optical mouse on the CNC computer flickers, What's going on here?

Most TIG (GTAW) units use high frequency to initiate the arc without actually touching the work.

It sounds as if the HF is also radiating into the components you mention.

[LenMcC]

Originally Posted by Weldtutor Most TIG (GTAW) units use high frequency to initiate the arc without actually touching the work. It sounds as if the HF is also radiating into the components you mention.

this is it. is there anything we can do to get around this beyond spacing the pc and the welder? we even tried - mostly jokingly - to cover the welder with aluminum foil.

we tediously grounded or bonded everything we could think of, including the cart with all the cnc hardware, plugged and unplugged things, etc and nothing worked. eventually we figured out that there was a line about 15ft from the welder where the transition happens. at 14ft it acts up. at 16ft it's fine. funny stuff. at least now our table chassis is grounded properly.

[Weldtutor]

Originally Posted by LenMcC is there anything we can do to get around this beyond spacing the pc and the welder?

A somewhat similar problem causing TV interference from a welding machine HF unit was resolved by a 6' copper ground rod connected to the machines frame.
In addition copper (fly type) screening was placed over all openings in the welding machines case.

These 2 items were based on recommendations from a federal communications investigation of a complaint.