Instructions / Assembly

19
GMAW
www.lincolnelectric.com
GMAW-P Waveform Components
Front Flank Ramp-up Rate (1)
The ramp-up rate determines how rapidly the current will
i
ncrease from the background current to the peak current. The
ramp-up rate assists in the formation of the molten droplet at
the end of the electrode. The rate is measured in terms of
amps/millisecond. The rate of rise can reach 1000
a
mps/millisecond. As the slope of the ramp-up rate increases,
the stiffness of the arc also increases. A fast ramp-up rate is
associated with arc stiffness and louder arc noise. Decreasing
the rate of rise contributes to a softer sounding arc.
O
vershoot (2)
Overshoot describes the condition where the front flank increases
to a predetermined level beyond the level of the peak current. It
is expressed in units of percent. Increasing overshoot is
associated with a more rigid arc that is less prone to deflection.
Overshoot adds to the pinch current and it increases the elec-
tromagnetic pinch force applied to the molten droplet.
Peak Current (3)
Peak current is the nominal current for the high energy pulse. It
is adjusted to a level that is set consistently above the globular
to spray transition current. Peak current is expressed in units of
ampere. During the time when the peak current is delivered, the
molten droplet detaches from the electrode. An increase in
peak current increases the average welding current and the
weld penetration.
FIGURE 13: Waveform Development Editor
P
eak Current Time (4)
P
eak current time describes the length of time that the current is
at its peak. It is associated with droplet size. Peak time is
expressed in terms of milliseconds. As the peak time increases,
the droplets decrease in size. As the peak time decreases, the
d
roplet size increases. The traditional expectation is that a single
molten droplet is transferred with each pulse peak. The effective
time at peak can range from less than 1 millisecond to 3 or more
milliseconds. An increase in peak time increases average current,
a
nd it also increases weld penetration.
Tail-out (5)
Tail-out is associated with current decay from the peak to the
background current. It generally follows an exponential path to
the background current. The increase in tail-out time increases
the average current and marginally increases penetration.
Tail-out time is increased to provide an increase in droplet fluidity.
This results in improved toe wetting, a softer arc sound, and
increased puddle fluidity.
Tail-out Speed (6)
Tail-out speed defines the rate at which the waveform moves
from the peak current to either the step-off current or the
background current. Manipulation of this portion of the waveform
increases or decreases the exponential fall to the background
current.
Step-off Current (7)
Step-off current defines the current level at the portion of the
waveform where tail-out ends. It can add to, or take away from,
the area under the waveform. It is associated with stabilizing the
arc with stainless or nickel alloy filler metals.
Background Current (8)
Background current refers to the lower nominal current of the
output. The unit of measure for the background current is
ampere. Increases in background current will increase penetra-
tion.
Pulse Frequency (9)
Pulse frequency is responsible for how often the pulse cycle
occurs in one second. As the frequency increases, the arc nar-
rows, the average current increases, and the molten droplets
become smaller. As the frequency decreases, the weld bead
and the arc become wider. Frequency is generally proportional
to the wire feed speed.
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TIME (mS)
(1) Front Flank Ramp-up Rate
(2) Overshoot
(3) Peak Current
(4) Peak Time
(5) Tail-Out
(6) Tail-Out Speed
(7) Step-off Current
(8) Background Current
(9) Period and Frequency
Time (mS)
Current
(4)
(2)
(3)
(5)
(6)
(7)
(8)
(9)
(1)