Figure 8-29.Striking the arc (GMAW).
motion, as shown in figure 8-29. To prevent sticking,
you should pull the torch back quickly, about 1/2 of an
inchthe instant contact is made between the wire
electrode and the workpiece. The arc strikes as soon as
contact is made and the wire-feed motor feeds the wire
automatically as long as the trigger is held.
A properly established arc has a soft, sizzling sound.
Adjustment of the wire-feed control dial or the welding
machine itself is necessary when the arc does not sound
right. For example, a loud, crackling sound indicates
that the arc is too short and that the wire-feed speed is
too fast. You may correct this problem by moving the
wire-feed dial slightly counterclockwise. This decreases
the wire-feed speed and increases the arc length. A
clockwise movement of the dial has the opposite effect.
With experience, you can recognize the sound of the
proper length of arc to use.
To break the arc, you simply release the trigger. This
breaks the welding circuit and de-energizes the wire-
feed motor. Should the wire electrode stick to the work
when striking the arc or during welding, release the
trigger and clip the wire with a pair of side cutters.
In gas metal-arc welding, the proper position of the
welding torch and weldment are important. The position
of the torch in relation to the plate is called the work and
travel angle. Work and travel angles are shown in figure
8-30. If the parts are equal in thickness, the work angle
should normally be on the center line of the joint;
however, if the pieces are unequal in thickness, the torch
should angle toward the thicker piece.
The travel angle refers to the angle in which welding
takes place. This angle should be between 5 and 25
degrees. The travel angle may be either a push angle or
a drag angle, depending on the position of the torch.
Figure 8-30.Travel and work angle for GMA welding.