To late but still, get RID of all that grounding, stars etc. Computer ground = power supply minus rail, BOB = no ground never ever, drives = no ground = grounded through power supply or not at all, Plasma gound clamp = POSITIVE power rail on plasma. Also using the same PS for Z axis drive and BOB = no good unless you know exectly the inner workings of both and the said PS = short between PS in some cases.
As a rule for plasma: short wires, no wires going paralell with torch ang clamp wires, and a good clamp to workpiece contact.
Regards,
Tom