Grounding...

Having been informed about the risks of interference from a plasma cutter affecting the Pc controlling it, I am doing some work prior to the cutter arriving next week. There is an excellent thread here as well..General CNC Plasma And Oxy Fuel Cutting Machines > Grounding CNC Plasma Question

So far, I have fitted screening braid to the stepper motor leads up to the point where they connect to the (now) shielded 4-core cables, this shield is connected at one end only to machine ground. The motor cable shields are connected at one end only, inside the steel control cabinet directly to my cabinet star earth stud.

I have connected the Z-axis to the gantry carriage at the steel terminal box, this point is the run back to the cabinet star point with its own ground cable. Next I have connected the gantry back to the star point with it's own ground cable. The steel cabinet is bolted directly to the chassis so I can't see much point in connecting another ground lead there??

The travel limit, e-stop and probing switch circuits are all relay isolated from the BOB and run on a separate 24v PSU, cables are just standard 2-core flex.

The e-stop relay also kills the torch control signal in case the board locks up with the torch on.

I have fitted several ferrite clamp-ons to supply cables etc.

The case of the PC is connected back to the control star point with a ground lead.

The keyboard and mouse have ferrite clamp-ons fitted at the PC end.


Now for the unknown bits....

The case of the plasma PSU has a bolt lug for grounding, I intend to connect this to a ground spike, the chassis of the machine also, as well as the slat bed with its own ground lead. Is this a good idea or should I just connect the slat bed ??

The torch lead will be suspended from above and not run in the cable-track.

How long can the ground leads be to the earth spike??
Where the machine will likely be going is about 15' from the ground outside, I could drill through the concrete floor but I have no idea how far down actual 'soil' is underneath the shop.

I could possibly drill through the wall and sink the spike there, that would be about 4' away.

Is it best to remove the ground clamp from the plasma and bolt the lead directly to the slat bed or just clamp it on??