Incompletely filled groove

An incompletely filled weld groove occurs when you don't get enough weld metal into the joint. This usually happens when the travel speed is too high or the wire isn't aimed correctly. The weld then lacks full fusion with the base material, which greatly reduces strength and can promote cracks or corrosion. Make sure the joint is clean and free of dirt, and run the weld calmly and evenly. If you see the weld isn't filling completely, go over it again or adjust your technique. Better to work a bit slower than to risk a weak joint.