Weldmatic 200i AC/DC
Model No MC105, Iss A 02/16
13
13.6.5 Down Slope
The DOWN SLOPE time is the
time taken for the weld current
to transition from the WELDING
CURRENT value to CRATER
CURRENT value. The time can be
adjusted from 0 to 25 seconds.
13.6.6 Crater Current
The current at the end of WELD
can be adjusted to a value which
will allow controlled finish of the
weld. The end of weld pool (Crater)
can be filled.
13.6.7 Post Gas
The Post Gas time can be adjusted
to allow gas to flow after weld has
stopped. This feature can be used to
provide a gas shield to the cooling
weld pool. Adjustable from 0 to 30
seconds.
13.7 AC Frequency
When AC mode is selected by button
(10) then actual AC frequency can be
adjusted from 20 to 200Hz.
Increasing the frequency makes the
welding current change direction at a
faster rate. The arc becomes constricted,
more stable and directional, providing
deep penetrating narrow welds.
When the frequency is lower the arc is
wide with shallow penetration, suitable
for butt or edge welds on thin material.
13.8 AC Balance Or Arc Force
13.8.1 AC Balance
When AC TIG mode is selected
then the proportion of positive
and negative in the cycle can be
adjusted. This is referred to as the
BALANCE and is expressed as a
% of the time that the polarity
is negative. Adjustment is from
15% - 65%.
Arc Welding of aluminium is difficult
because the metal readily forms an
oxide layer, which is an electrical
insulator, and inhibits arc formation.
The Oxide needs to be “cleaned
off”. Electrode positive will remove
the oxide off the surface as the
electrons flow off the aluminium to
the tungsten electrode. Continuous
electrode positive will burn the
tip away, so the current has to be
reversed to electrode negative, for
some of the time.
For new clean aluminium an
AC BALANCE of 65% is a good
starting point.
+
+
% −
% −
Fig 5
AC Balance
