Firepower MST 180i Operating Manual page 57

Longitudinal
Angle
Transverse and Longitudinal
Nozzle Axes
Figure 4-9
Establishing the Arc and Making Weld Beads
Before attempting to weld on a finished piece of work, it is recommended that practice welds be made on a sample metal
of the same material as that of the finished piece.
The easiest welding procedure for the beginner to experiment with MIG welding is the flat position. The equipment is
capable of flat, vertical and overhead positions.
For practicing MIG welding, secure some pieces of 16 ga. (1.6mm) or 1/8" (3.2mm) mild steel plate 6" (150mm) x 6"
(150mm). Use 0.035" (0.9mm) gas shielded steel or gasless flux cored wire.
Setting of the Power Source
Power source and Wirefeeder setting requires some practice by the operator, as the welding plant has two control settings
that have to balance. These are the Wirespeed control (refer to section 3.06.3) and the welding Voltage Control (refer
to section 3.06.9). The welding current is determined by the Wirespeed control, the current will increase with increased
Wirespeed, resulting in a shorter arc. Less wire speed will reduce the current and lengthen the arc. Increasing the welding
voltage hardly alters the current level, but lengthens the arc. By decreasing the voltage, a shorter arc is obtained with a
little change in current level.
When changing to a different electrode wire diameter, different control settings are required. A thinner electrode wire
needs more Wirespeed to achieve the same current level.
A satisfactory weld cannot be obtained if the Wirespeed and Voltage settings are not adjusted to suit the electrode wire
diameter and the dimensions of the work piece.
If the Wirespeed is too high for the welding voltage, "stubbing" will occur as the wire dips into the molten pool and does
not melt. Welding in these conditions normally produces a poor weld due to lack of fusion. If, however, the welding voltage
is too high, large drops will form on the end of the wire, causing spatter. The correct setting of voltage and Wirespeed
can be seen in the shape of the weld deposit and heard by a smooth regular arc sound. Refer to the Weld Guide located
on the inside of the wirefeed compartment door for setup information.
Electrode Wire Size Selection
The choice of Electrode wire size and shielding gas used depends on the following
• Thickness of the metal to be welded
• Type of joint
• Capacity of the wire feed unit and Power Source
• The amount of penetration required
• The deposition rate required
• The bead profile desired
• The position of welding
• Cost of the wire
Manual 0-5339
Transverse
Angle
Axis of Weld
Art # A-08998_AB
Leading or "Pushing"
Angle
(Forward Pointing)
Nozzle Angle, Right Handed Operator
4-3
Firepower MST 180i
Direction of Gun Travel
90°
Trailing or "Pulling"
Angle
(Backward Pointing)
Art # A-08999_AC
Figure 4-10
BASIC WELDING GUIDE