30
Basic Theory and Function
Section 3
BASIC MIG OPERATION
General Setup of Amps and Volts.
When welding with the PowerMTS units, 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 no-
tice that the wire speed is displayed in Inches Per Mi-
nute. However, while actively welding, the display will
change function and display actual amp output. The
relationship between wire diameter, wire speed and
amps is easily figured with the following approximate
industry accepted 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 recommended. The wire diame-
ter also limits the practical maximum thickness of
what can be reasonably welded. The issue with fol-
lowing charts, graphs and calculator recommenda-
tions is that most people find them either too hot or
too cold. For some people, it may not even close.
However, nothing can substitute for watching the arc
and listening to the sound of the arc. A crisp, steady
sound, frequently referred 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 normal, 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 inconsistently
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 professionals
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 inductance alone can affect how
much wire speed or voltage is needed in any given ap-
plication. 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.
While Everlast uses the term
“
arc force
”,
it is known
by many different terms. Often it is referred to as in-
ductance, choke or slope. Simply put, the arc force
(Inductance) adjustment controls how long it takes the