Huh, I thought electron welding and plasma cutting where essentially the same, I mig weld almost everyday and to get better penetration on thick material, I usually prep the material by preheating it with a torch, or cutting into it so I can dump more weld in. In electron welding, I thought the advantage was not having to do the prep to get penetration or no foreplay as my machinist friend says, since it acts like a plasma cutter in the way of "blasting" apart atoms and shooting electrons into the material resulting in excitation heat/fusing of the material. As far as shielding the weld goes wouldn't it be cheaper to shield with an inert gas like mig or tig welding? Do you know what the benifit is by sheilding with plasma? The only benifit I see is that it could maybe heat prep the material first, but again that can be done with a torch.