Everlast POWER i-MIG 253DP Operator's Manual page 41

Section 2
heat being put into the weld and over the di-
rectabilty of the arc. The basic reason for us-
ing a single-pulse MIG is to prevent over-
heating of the weld metal while maintaining a
rapid deposition rate that does not compro-
mise fusion of the base metals. Single-pulse
MIG welding is intended to be performed in
pulsed-spray mode. Pulsed-spray is a modifi-
cation of the Axial-spray mode, where the
metal actually pinches off before the wire
touches the weld puddle. During the Axial-
spray mode, the arc should never short circuit.
Axial-spray is accomplished by using higher
volts and amps than would be used in a short
circuit transfer process. By doing so, this forc-
es the wire to pinch and form a steady stream
of molten droplets somewhere between the
weld puddle and contact tip. These droplets
travel rapidly across the arc and direct into the
puddle. The result is fast travel speed and a
smooth, quiet arc that is not much more than
a steady, quiet "hiss". The down side is that
the puddle is hot and uncontrollable if used
out of the flat position. The puddle will simply
run off, or melt through when trying to keep
enough metal held in place.
When single pulse mode is engaged, the wire
continues to spray, but the Voltage drops low
enough to fall out of the range required for
Spray but not long enough for any metal to be
deposited. The goal is one pulse per droplet of
metal. The drop in voltage during the pulse
allows the puddle to cool between the high
stage portion of the pulses returns. The result
is no longer a quiet hiss, but a rather unique
sound that has often been compared to an
"angry bee" or a "swarm of hornets". More
importantly, the puddle becomes stable, heat
is controlled, and out of position welding be-
comes possible.
Setup Guide and component Identification
PULSE MIG OPERATION
Historically, the most common applications for
single Pulse-MIG welding are found in Alumi-
num or Stainless Steel fabrication or repair.
Currently, though, single Pulse-MIG welders
are being used to MIG braze with silicon
bronze in auto body repair shops. MIG brazing
is being used where auto manufacturers are
requiring this as process to repair and join
modern high carbon steels that are heat sensi-
tive and prone to cracking. The brazing pro-
cess creates a strong joint without having to
bring the Carbon steel up to a melting point.
Pulsed-spray is also used with mild or carbon
steels to allow out of position welding while
maintaining useful production welding speeds
without sacrificing penetration. In compari-
son, Short-circuit transfer is a cooler and slow-
er MIG process where the MIG wire has to ex-
tend out from the contact tip and travels down
and into the puddle before the arc shorts and
the wire melts in a relatively forceful "blast".
Pulse MIG combines both processes and re-
tains the best attributes of both short-circuit
and Axial-Spray welding.
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. The recom-
mended gas is 90/10 Ar/CO2 for steel. Howev-
er, Gases may be used as high as 98/2 Ar/O2
or as low as 80/20 Ar/CO2. For Stainless, nu-
merous combinations can be used, but the fac-
tory recommended setting that yields the best
results is 98/2 Ar/CO2, although 98/2 Ar/O2
may be used, or a Special Tri-MIX designed for
Spray. As for Aluminum, most MIG welding of
Aluminum is already done in spray mode to
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