Re: Grounding HF plasma torch
If you find the hypertherm tech note on how to ground a plasma table, follow that. Add a ground rod through your floor, attach to the table star ground point. Add seperate ground wires back to the star point to every stepper motor and also to the torch holder etc. Also consider adding an RFI filter on the AC power input to your control box. You can find an IEC connector with built in filter so this could be a simple job if you've used an IEC connector to AC. I did not have a HF torch but the biggest help for me was the RFI filter on the AC inlet.
Rod Webster
www.vehiclemods.net.au