5.2.4 MMA welding
Under MMA welding for coated electrode, three parameters including hot start current, welding current and
arc-force current are adjustable on digital panel. Hot start current is at “initial segment” of “welding process selection
zone”; welding current is at “process” of “welding process selection zone”; arc-force current is at “MIG arc force, MMA
Arc-force current indication” of “Voltage/arc force/parameters set, etc displaying and setting zone”.
I I
h
I
a
t
h
2s
U U
0
U
VRD
Fig 5.4 MMA processing
1、 I
h
(hot start current) = I
Δh
（arc start current）+ I
a
(welding current); Fixed hot start time: t
h
= 500ms
2、 I
f
(arc-force current)= I
Δf
(arc-force current)+ I
a
(welding current);Arc-force current should be set based on
electrode diameter, set current and process requirement. With strong arc force, droplet transfer is so fast that it
can be anti-stick, but too strong arc force can increase the spatter; with low arc force, spatter is reduced and
weld bead has nice shape, but arc is weak or electrode is easily stuck. Therefore, arc force should be increased
when welding with thick electrode under low current. Generally, arc force is 2070 during welding.
3、 After short-circuit time is over 2s, anti-stick current of 25A comes out until electrode is separated from the
workpiece;
4、 U
VRD
, VRD of about 15V, conforming to Australian standard 1674.2 2007, is switched off by default. After
being switched off, welder outputs no-load voltage U
0
when MMA welding is not started.
5、
Note: Max current limit limits I
h
and I
f
.
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