Pulse Welding - Lincoln Electric POWER WAVE SVM156-A Service Manual

B-8

PULSE WELDING

Pulse welding procedures are set by controlling an
overall "arc length" variable. When pulse welding, the
arc voltage is highly dependent upon the waveform.
The peak current, background current, rise time, fall
time and pulse frequency all affect the voltage. The
exact voltage for a given wire feed speed can only be
predicted when all the pulsing waveform parameters
are known. Using a preset voltage becomes impracti-
cal, and instead the arc length is set by adjusting "trim."
Trim adjusts the arc length and ranges from 0.50 to
1.50, with a nominal value of 1.00. Trim values greater
than 1.00 increase the arc length, while values less
than 1.00 decrease the arc length.
Most pulse welding programs are synergic. As the wire
feed speed is adjusted, the Power Wave will automati-
cally recalculate the waveform parameters to maintain
similar arc properties.
FIGURE B.3 – PULSE WAVE CONTROL CHARACTERISTICS
Wave Control -10.0
Current
Wave Control 0.00
Wave Control +10.0
Time
OPERATION
The Power Wave utilizes "adaptive control" to compen-
sate for changes in electrical stick-out while welding.
(Electrical stick-out is the distance from the contact tip
to the work piece.) The Power Wave waveforms are
optimized for a 0.75" (19mm) stick-out. The adaptive
behavior supports a range of stickouts from 0.50"
(13mm) to 1.25" (32mm). At very low or high wire feed
speeds, the adaptive range may be less due to reach-
ing the physical limitations of the welding process.
Wave control in pulse programs usually adjusts the
focus or shape of the arc. Wave control values greater
than 0 increase the pulse frequency while decreasing
the background current, resulting in a tight, stiff arc
best for high speed sheet metal welding. Wave control
values less than 0 decrease the pulse frequency while
increasing the background current for a soft arc good
for out-of-position welding. (See Figure B.3.)
POWER WAVE 455/R
B-8