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–
7
–
7.2 MMA/ARC WELDING FILLER ROD
(ELECTRODE) SELECTION – FIG.2
The correct selection of electrode size and type will vary
for each application dependent upon material thickness,
material type, amperage and equipment, however as a
guide the figures below provide an indication.
MMA Electrode Material
Thickness
Amp Range
≤1.6mm 1-1.5mm ≤50A
2.0mm 1.2-3mm 45 - 75A
2.5mm 2-5mm 75 - 110A
3.25mm 4-8mm 100 - 150A
2
FIG.
8. OPERATION
8.1 BASIC MMA/ARC WELDING
PROCESS OVERVIEW – FIG.3
During the MMA welding process, the arc created
between the work piece and the consumable electrode
rod melts the parent metal and the filler metal in a weld
pool.
The electrode’s flux coating reacts during this process
and develops into a shield gas protecting the weld bead.
Part of this reaction leaves a trail of slag which solidifies
behind the weld pool protecting the weld as it cools.
The most common varieties of electrodes are cellulosic,
rutile and basic, the latter two being the most general
purpose.
Selection of the appropriate specification electrode is
important to achieve a good quality weld. Seek guidance
if unsure of selection.
3
FIG.
8.2 MMA/ARC MACHINE OPERATION
– FIG.4
− Prepare the joint(s) to be welded.
− Insert the electrode suitable for the application into
the electrode holder (6) while pressing lever (6.1).
− With the earth clamp and electrode holder
connected, connect the machine to the power supply.
The power display will illuminate as confirmation. Set
the amperage appropriate to the selected electrode
size.
− Secure the earth clamp to a clean sound section of
the parent metal in the vicinity to the intended weld.
− With all safety equipment in place and personal
protective clothing on begin welding.
− Lower the electrode down toward the parent metal
and strike the arc.
− The position of the electrode is critical to the arc and
the end result.
− Achieving a good weld will take practice. For more
detailed information refer to a industry standard
welding publication and/or seek training on the
subject.
− Use of an anti-spatter spray – Draper stock
No.05709 – will help to achieve a cleaner finished
weld.
4
FIG.
(6)
(6.1)
8.3 DIRECTION OF WELD – FIG.5
− Strike the initial arc perpendicular to the parent metal
before moving the electrode holder in the direction of
travel 20-30° (Z,Y axis) and tilt it 20-30° (Z,X axis).
− Maintain a constant gap between the electrode tip
and the weld pool of approximately 1 – 1.5 × the
diameter of the electrode for a stable arc.
Z
-Z
-X-Y
XY
Direction
of weld
5
FIG.
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