Originally Posted by 2door
All MIG machines are not the same. I have settings for volts, amps and wire feed speed.
For deeper penetration on thick material you'll want to slow the feed and increase output voltage. That way the arc stays concentrated longer in a given area, hence deeper penetration. On thin stuff you'll want to move fast to decrease the chance of burn through.
The copper backing idea is a good one for thin materials. The copper absorbs some of the heat and makes longer beads without stopping possible. I've used copper to back up behind a hole I needed to fill in sheetmetal. The steel filler won't stick to the copper and when the hole is filled just pull it off.
For deeper penetration using mig you would want more amps, more wire speed.
I went to school for welding and welded for years making a living.
I am sure more wire speed = more amps.
I also am an electronic tech.
Thick metal, turn up the wire speed, more amps and adjust the voltage so that the wire does not hit the puddle.
Thin metal, turn down the wire speed, less amps and adjust the voltage so the wire does not hit the puddle.
If you slow the wire speed and increase the voltage too much the arc will be too large and little pieces of metal will fly all over.
This is called spatter. Those little balls of metal around welds. This does not increase penetration.