Lincoln Electric Power Feed 25M Operator's Manual page 54

POWER FEED™ 25M
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 accom-
plished 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 established within 1.5 seconds, the
power source output and wire feed speed skips to the weld set-
tings.
UPSLOPE:
Once the wire touches the work and an arc is established, 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 contin-
ues until the post flow timer expires.
FIGURE B.20
B-38
OPERATION