Everlast PowerMTS 251Si Operator's Manual page 38

Section 3
But pulsed-spray is also used with mild or car-
bon steels to allow out of position welding and
to maintain production welding speed levels.
In comparison, Short-circuit transfer is a cooler
and slower MIG process where the MIG wire
has to extend out from the contact tip into the
puddle before the arc shorts and the wire
melts and is forced violently into the puddle
several times a second. Pulse MIG combines
both processes. Most single-pulse MIG weld-
ers, are in spray mode for most of the pulse
cycle, but drops below the spray transfer
threshold into the short circuit or globular
transfer range long enough to provide a cool-
ing effect on the puddle, but not long enough
for any metal to transfer into the puddle. In
effect, the goal is to transfer one droplet of
metal per pulse cycle. Standard axial-spray
MIG, although the fastest method of welding,
is not intended for out-of-position-welding as
the puddle is quite hot and will not hold in
place when used overhead or vertically.
Pulsed spray helps to resolve this issue. In
steel and stainless use, whether in Pulsed
spray or Axial spray special gases which enable
a lower transition point into Spray should be
used to be controllable and practical. These
gases are much higher in Argon (90% or great-
er). As for aluminum, most MIG welding of
Aluminum is already done in spray mode to
prevent incomplete fusion. All MIG welding is
done, regardless of transfer method is com-
monly done with Argon, or more rarely, an Ar-
gon/Helium mix.
Most double Pulse MIGs are largely used for
Aluminum welding, though they can be used
for Stainless or Steel welding. The double
Pulse MIGs, are completing full cycles at a fre-
quency of 5 Hz or less (though there may be
many steps within one full cycle). This is the
PULSE MIG OPERATION
Basic Theory and Function
type of Pulse MIG commonly associated with a
"TIG" look, with well defined ripples. The
heating and cooling is done at a level and
speed that allows the weld to pool and solidify
between the high pulse stages of the pulse cy-
cle much more so than single pulse MIGs.
While heat management is the goal, they are
most sought after as they can mimic the style
and look of TIG while offering an improved
speed over TIG without the same required lev-
el of skill. The single pulse is not comparable
in look to the look of the double pulse MIG
weld, even though some refinement of the
weld is possible in a single pulse MIG.
Both pulse types have many variations from
brand to brand and model to model. But
most modern forms of pulse are complicated
to set manually, with most of the parameters
taken out of the control of the user, and only
allow minor fine tuning by the user, if any at
all. The controls that do exist in these pulse
models are often not clearly defined in their
function or adjustment values. Older Pulse
MIGs from generations ago, allowed more ad-
justments. However, these older transformer
based and early inverter based pulse MIGs
were often too difficult to set without consid-
erable training and experience. New models
are controlled by digital programs which are
programmed at the factory for a one-size-fits-
all approach based off of testing and user ex-
perience. These synergic versions keep fre-
quency, voltage, inductance, wire speed and a
few other parameters all within a tightly con-
trolled range that prevents the user from go-
ing too far astray. While this is a great devel-
opment that helps the untrained welder to
learn and setup the equipment quickly, the
lack of commonality in terms, clearly defined
references to values, and even differences in
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