As the angle between the electrode and the plate determines the point of impingement and direction of the arc force, it has a critical effect on the weld bead profile and depth of penetration.
Welding can be carried out with the electrode wire leading, trailing and normal to the plate surface and the effects on weld shape, penetration and undercut are shown in Fig.1a for flat plate. For most applications it is usual to weld with the electrode wire pointing forwards, i.e. leading by 10°, in order to obtain the best combination of bead shape, penetration and resistance to undercut.
The effect of the electrode angle on horizontal-vertical fillet welds is shown in Fig.1b. Penetration into the root of the joint can be increased by reducing the electrode angle whilst also aiming the arc more onto the vertical rather than the horizontal plate.