Lincoln Electric POWER FEED SVM185-A - Manual (Page 53)

OPERATION B-35 B-35
POWER FEED® 25M
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EXAMPLE 2 - 2 STEP TRIGGER: Improved Arc Start
and Arc End. Tailoring the arc start and arc end is a
common method for reducing spatter and improving
weld quality. This can be accomplished with the Start
and Burnback functions set to a desired values and
Crater set to OFF. (See Figure B.20)
For this sequence,
PREFLOW:
Shielding gas begins to flow immediately when the gun
trigger is pulled.
STRIKE:
After preflow time expires, the power source regulates
to the start output and wire is advanced towards the
work piece at the Strike WFS. If an arc is not estab-
lished within 1.5 seconds, the power source output and
wire feed speed skips to the weld settings.
UPSLOPE:
Once the wire touches the work and an arc is estab-
lished, both the machine output and the wire feed
speed ramp to the weld settings throughout the start
time. The time period of ramping from the start settings
to the weld settings is called UPSLOPE.
WELD:
After upslope, the power source output and the wire
feed speed continue at the weld settings.
BURNBACK :
As soon as the trigger is released, the wire feed speed
is turned OFF and the machine output continues for
the burnback time.
POSTFLOW:
Next, the machine output is turned OFF and shielding
gas continues until the post flow timer expires.
Shielding
Gas
Idle Preflow Strike Upslope Weld Burnback Postflow Idle
WFS
On
Off
Run-in
Off
Weld
Off
Weld
Ar
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ed
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2 Step Trigger
Start = ON
Crater = OFF
Burnback = ON
1.5 sec max.
Start
Start time
Burnback Time
Power
Source
Output
FIGURE B.20