Unless you can afford a High Definition plasma cutter (starting in the 25k range) then the best option would probably be oxyfuel. I can't see the heat from the torch affecting the gantry too much, but it depends on the manufacturer, height of gantry above plate, etc.
You can cut 1" with conventional plasma, but you will get a heck of a bevel to go with it.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
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