[stefuel]

Stick welding it's amps. Tig welding it's amps. Plasma cutting it's amps. Why is MIG welding volts?

[MinnesotaDave]

The wire feed speed is the amperage - more speed requires more amps to burn.

Since the wire diameter can be changed, setting amps to control wire speed would require more electronics.

Voltage only controls width and height of the bead - more volts equals a wider flatter puddle

Does that answer your question?

[Farmwelding]

Mig welding is amps as well. Dave said it pretty well though. Some machines that have a digtal readout show the amperage while you are welding.

[stefuel]

What got me thinking or perhaps over thinking this is how my friend interfaces his spool gun with his diesel powered stick welding machine. He bought this rig probably 25 years ago. I assume he must have some interface between the power source and the spool gun. I would guess this interface would have to provide variable power for the spool gun drive motor, a shielding gas solenoid valve and the ability to turn welding current on/off

[Farmwelding]

There are many different wire feeders available for engine drive welders. Different machines control different aspects of the wire feeding process at the engine drive but most is done at the wire feeder.