Hi Plas - Well the 5mm pitch ballscrew will move a small truck so don't worry about weight now. Use a large Nema 23 or 24 and it will be fine. Since a plasma does not cut ie there are no tool loads only inertial loads usually you would use a 10mm or 20mm pitch so it moves faster... What is the target cutting speed? I'm not up with plasma parameters. Just remember that steppers will run out of grunt at 700rpm so your machine speed will be limited to say 700*5=3500mm/min if you have to go faster then that then you will need a bigger pitch screw. Peter
I looked up the max45 cuttings speeds and I think your going to have to change the 5mm pitch. The chart shows for thin stuff you'll need 10m/min. So a 10mm pitch will give you 1000rpm and this could be a stepper flat chat so no torque. I think a 20mm pitch direct drive or you will need to gear it. Plus at these speeds its best to have a high voltage driver 48V or more.... Need to work thru your target speeds and sort that out before going fwd. Peter