You need the force of the compressed air to remove the molten metal and to direct heat away from the tip through the surrounding cup. It should be at the pressure the manufacturer suggests. If I remember right, the plasma is only the medium (sometimes refered as the envelope) in which heat is generated. I use to do a lot of steel and metal fabrication years ago, and really appreciated this process over oxy-acetylene for how clean and precise it was.
edowney3
Shootah
