Weldclass FORCE 160MST MK2 Operating Instructions Manual page 14

Whether the operator is left handed or right
handed has to be considered to realize the effects
of each angle in relation to the direction of travel.
Nozzle Angle, Right Handed Operator
(Fig 1-10)
Leading or "Pushing"
Angle (Forward Pointing)
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 or 18 gauge (1.5mm or 2.0mm) mild steel plate
(150 x 150mm). Use (0.8mm) flux cored gasless
wire or a solid wire with shielding gas.
Setting of the Power Source
Power source and Current (Wire Speed) setting
requires some practice by the operator, as the
welding plant has two control settings that have
to balance. These are the Current (Wire Speed)
control and the welding Voltage Control.
The welding current is determined by the Current
(Wire Speed) control, the current will increase with
increased Current (Wire Speed), resulting in a
shorter arc. Less Current (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 Current
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Direction of Travel
o Trailing or "Pulling"
90
Angle (Backward Pointing)
(Wire Speed) to achieve the same current level.
A satisfactory weld cannot be obtained if the
Current (Wire Speed) and Voltage settings are not
adjusted to suit the electrode wire diameter and
the dimensions of the work piece.
If the Current (Wire Speed) 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 Current (Wire Speed) can be
seen in the shape of the weld deposit and heard by
a smooth regular arc sound.
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