Arc Force control knob
An MMA welding power source is designed to produce constant output current (CC). This means
with different types of electrode and arc length; the welding voltage varies to keep the current
constant. This can cause instability in some welding conditions as MMA welding electrodes will have
a minimum voltage
they can operate with and still have a stable arc.
Arc Force control boosts the welding power if its senses the welding voltage is getting too low. The
higher the arc force adjustment, the higher the minimum voltage that the power source will allow.
This effect will also cause the welding current to increase. 0 is Arc Force off, 10 is maximum Arc
Force. This is practically useful for electrode types that have a higher operating voltage requirement
or joint types that require a short arc length such as out of position welds.
Hot Start control knob
Hot start provides extra power when the weld starts to counteract the high resistance of the electrode
and workpiece as the arc is started.
Lift TIG Mode
Lift TIG is an arc ignition system for basic TIG welding that removes the need to “scratch”
start or strike the tungsten on the work piece to start the arc, which can have a negative effect on
the weld quality due to tungsten contamination. Lift arc starting works by gently touching the
tungsten on the work piece and then lifting it off. The control circuit will sense when the tungsten
is removed from the work piece and send a pulse of electricity through the torch that will cause
the TIG arc to initiate.
VRD Function
VRD stands for Voltage Reduction Device. This is a safety system that reduces the output voltage
from the welding terminals in MMA mode while the welding output is not in use, to reduce the risk
of electric shock from the live output voltage. The disadvantage of this system is that it makes the
striking of the arc more difficult, especially on restarts and with some types of electrode such as low
hydrogen electrodes.
3.2 Installation & Operation for MMA Welding
3.2.1 Set up installation for MMA Welding
Connection of Output Cables Two sockets are available on this welding machine. For MMA welding
the electrode holder is shown be connected to the positive socket, while the earth lead (work piece)
is connected to the negative socket, this is known as DCEP. However various electrodes require a
different polarity for optimum results and careful attention should be paid to the polarity, refer to the
electrode manufacturers information for the correct polarity.
DCEP: Electrode connected to
“
+
”
output socket.
DCEN: Electrode connected to
“
-
”
output socket.