Basic Theory And Function; Basic Mig Operation - Everlast PowerMTS 251Si Operator's Manual

Section 3
General Setup of Amps and Volts.
When welding with the Power i-MIG, the two main
functions that require adjustment are Voltage and
Wire feed speed. The function of voltage in MIG
welding is to control the overall width and to a great
extent, the height of the weld bead. In other words,
voltage controls the bead profile. The wire feed
speed directly controls the amps, and in turn amps
control penetration. When setting the welder up
you will notice that the wire speed is displayed in
Inches Per Minute. However, while actively welding,
the display will change function and display actual
amp output. The relationship between wire diame-
ter, wire speed and amps is easily figured with the
following approximate industry conversions:
.023": 3.5 x Amps = Inches per minute (IPM)
.025": 3.1 x Amps = Inches per minute (IPM)
.030": 2 x Amps = Inches per minute (IPM)
.035": 1.6 x Amps = Inches per minute (IPM)
.045": 1 x Amps = Inches per Minute (IPM)
To convert wire speed (IPM) into approximate Amps,
use the following conversion formula:
.023": IPM ÷ 3.5 = Amps
.025": IPM ÷ 3.1 = Amps
.030": IPM ÷ 2 = Amps
.035": IPM ÷ 1.6 = Amps
.045": IPM ÷ 1 = Amps
Keep in mind these are approximate conversions
and do fall off in accuracy as amps are increased into
the upper current limits for the given wire diameter.
Even though you will find general recommendations
about setting the Amps, Volts and even shielding gas
through a variety of free downloadable apps and
online calculators, every filler metal manufacturer
has its own specific parameters for Volt and Amp
settings for each wire diameter and class of wire.
The ranges of volt and amp parameters generally
varies somewhat from brand to brand, so be sure to
read the packaging and/or manufacturer literature
to determine what range of settings are recom-
mended. The wire diameter also limits the practical
maximum thickness of what can be reasonably weld-
ed. The issue with following charts, graphs and cal-
culator recommendations is that most people find

BASIC MIG OPERATION

Basic Theory and Function

them either too hot or too cold. For some people, it
may not even close. However, nothing can substi-
tute for watching the arc and listening to the sound
of the arc. A crisp, steady sound, frequently re-
ferred to as a "Bacon frying sound"" should be
heard. The actual frying sound can vary somewhat
and may have somewhat of a high pitch whine to it
somewhere between the sound of a flying bee and a
mosquito. If these sounds are present, look at the
arc to see if it is steady, and producing low amounts
of spatter. If large amounts of spatter are present,
the puddle seems fluid (appears wet) and the wire
speed is within the targeted range, decrease volts a
little at a time to reduce the spatter. If this does not
correct the problem, change the torch angle and
torch height. Hold the torch more vertical, with less
than a 15 degree deviation from vertical and reduce
stick-out of wire to 3/8" or less. If this still does not
help, reduce the wire speed. Some spatter is nor-
mal, though it should be minimal overall.
The wire can also pop and spatter if the voltage is
too low for the wire speed and/or wire diameter.
This is mostly observed as flying bits of red-hot but
un-melted wire, along with popping as the wire in-
consistently stubs into the puddle. This is followed
by the wire pushing back against your hand pressure
while the wire visibly turns white/red hot before
burning off. Too low of voltage will also produce a
high piled bead with the toes (edges) of the weld not
properly wetting in resulting in poor fusion.
Arc Force Control.
The third important variable in setting up the Power
i-MIG is the arc force control. This third adjustment
can greatly vary the feel of the arc at any given volt
and amp setting. It is used to balance the stiffness of
the arc against the wetness of the arc. Some profes-
sionals refer to the "buttery-ness" of the arc.
" Buttery-ness" is arguably somewhat a subjective
term. However, it generally refers to how smooth
and fluid the arc feels and looks. In fact, the induct-
ance alone can affect how much wire speed or volt-
age is needed in any given application. It does not
typically require altering of the Volts or the Wire
Speed settings. However the arc force control can
expose poorly selected Volt/Wire Speed parameters
by magnifying the effects.
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