Vertical down position (PG)
Welding from top to bottom on a vertical joint. It enables high travel speeds on thin sheet metal but carries a risk of lack of fusion on thicker components.
PG is the welding position from top to bottom. Gravity pulls the molten metal down, that's the main difference from other positions. You have to keep the arc short and choose the welding speed so that the pool doesn't run ahead. Otherwise, slag can get trapped ahead of the arc and cause defects. Penetration is shallower than in other positions, and you'll quickly get lack of fusion if you don't work clean. Use this only for thin sheets where you need a flat weld. For thicker materials or load-bearing welds, better use the vertical-up position, as you have more control over the pool and penetration.