Everlast PowerMTS 251Si Operator's Manual page 42

Section 3
settings on the pulse, you will find that de-
sirable frequencies have a fairly broad
range. To simplify pulse frequency adjust-
ment, start with the maximum pulse fre-
quency of 250 Hz, adjusting downward in
50 Hz increments at first. Once you feel
you are close to a frequency you like, halve
the adjustment range to 25 Hz increments.
Then, further fine tune up or down in 5 Hz
increments. Following this adjustment
model will help you expedite the setup
process. The pulse frequency will change
the tone of the arc. You should hear a
slight buzzing sound coming from the arc,
similar to a sound of a bumble bee. The
pitch of the sound will go higher as the fre-
quency is increased. And, of course, the
pitch drops as the frequency is decreased.
In practical terms, the pulse frequency
effects the pulse arc stability and concen-
tration. By adjusting the pulse frequency
higher or lower, the arc cone shape and
stability will be affected. Typically, when
the frequency is increased, you will a nar-
rower arc cone and you may notice chang-
es in the puddle agitation. You'll also see
the bead is more tightly formed and pene-
tration is pinpointed. The lower the pulse
frequency, the arc cone will widen. A low-
er pulse frequency will result in a wider
more fluid puddle as well. Lowering the
pulse frequency when the pulse balance is
set to approximately 50% (setting used as
an example only) will increase the wet-in
of the filler. Wire diameter affects the de-
sirable frequency of the pulse. Smaller di-
ameter wires will work better on lower
pulse frequencies for the same given thick-
ness of metal being welded. Thicker wire
diameters may seem to work better at
higher frequencies. However, this com-
PULSE MIG OPERATION
Basic Theory and Function
ment is also based off of pulse voltage and
pulse time-on remaining unchanged during
pulse frequency adjustment. A change in
one of the other two main settings may
affect actual desired pulse frequency. The
goal of setting the pulse frequency is to
develop a controllable arc, bead and pud-
dle. If welding on thin metal, the goal is to
maintain wet in and travel speed without
burning through. When using a thicker
wire, you'll want to use a higher pulse fre-
quency to prevent burn through. If stub-
bing of the wire is felt between pulses, or
the puddle is overly agitated by the action
of the wire digging into the puddle, the
pulse frequency has dropped too low to
allow the wire to properly burn off. Either
that, or the welding voltage or pulse volt-
age is set too low. If a low pulse frequency
is desired, then a higher pulse voltage per-
cent should be used, providing the welding
voltage is high enough. If raising the weld-
ing voltage/pulse voltage doesn't solve the
stabbing/over agitation issue, decrease
wire speed slightly or raise pulse frequency
until this issue disappears. Puddle agita-
tion can be useful when used moderately,
but too violent of agitation can create de-
fects in the weld and poor or irregular fu-
sion. Even though low pulse frequencies
are allowed to be selected, general pur-
pose welding settings below 25-30 Hz will
rarely be useful. However, it is good to
test and experiment below this range so
that you will see the effects and be able to
gain valuable reference points when ad-
justing the pulse in the future.
3. Pulse Time-On (%). Pulse Time-On is ex-
pressed as a percent of time of one pulse
cycle that the pulse spends in the Peak
voltage stage of the cycle. This is some-
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