I thought that was the other way around, first measure the metal thickness, tem set up the voltage (amps) and then fiddle around with the wire speed. Can anyone give me some technical details about mig welding? The more i dove into it the more i´m confused. With mma or tig amperage is one of the key factores on welding but on mig its voltage and wire feed. I know that mig transfer modes differ with different gas and voltage . So for example i can´t get globular or spray transfer with co2 . I want to have more theoretical details on mig welding than just push some buttons on the welder.