Lincoln Electric POWER FEED 25M Operator's Manual page 60

B-44
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.
RUN-IN:
After preflow time expires, the power source regulates
to the start output and wire is advanced towards the
work piece at the Run-In 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.
Idle
On
Shieldin g
Gas
Off
Weld
Power
Source
Start
Output
Off
Weld
WFS
Run-in
Off
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OPERATION
FIGURE B.20
2 Step Trigger
Start = ON
Crater = OFF
Burnback = ON
Preflow Strike Upslope
Start tim e
1.5 sec max.
POWER FEED™ 25M
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 set-
tings 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 contin-
ues for the burnback time.
POSTFLOW:
Next, the machine output is turned OFF and shielding
gas continues until the post flow timer expires.
Weld Burnback
Burnback Time
B-44
Postflow Idle