Lincoln Electric POWER FEED IM892-C - Manual (Page 63)

B-47 OPERATION B-47
POWER FEED™ 25M
EXAMPLE 5 - 4 STEP TRIGGER: Manual control of
Start and Crater times with Burnback ON. The 4 step
trigger sequence gives the most flexibility when the
Start, Crater and Burnback functions are active. This
is a popular choice when welding aluminum because
extra heat may be needed during Start and less heat
desired during crater. With 4 step trigger, the welder
chooses the amount of time to weld at the Start, Weld
and Crater settings by using the gun trigger. Burnback
reduces the occurrence of wire to sticking into the
weld pool at the end of a weld and conditions the end
of the wire for the next arc start. ( See Figure B.23)
In 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-inWFS. If an arc is not estab-
lished within 1.5 seconds, the power source output
and wire feed speed skips to the weld settings.
START:
The power source welds at the start WFS and voltage
until the trigger is released.
UPSLOPE:
During upslope, the power source 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.
DOWNSLOPE:
As soon as the trigger is released, the wire feed
speed and power source output ramp to the crater
settings throughout the crater time. The time period of
ramping from the weld settings to the crater settings is
called DOWNSLOPE.
CRATER:
During CRATER, the power source continues to sup-
ply output at the crater WFS and voltage.
BURNBACK:
When 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
Strike
Off
Weld
Off
Weld
Ar
c
Es
ta
bl
ish
ed
Tr
ig
ge
r P
ul
le
d
Tr
ig
ge
r R
el
ea
se
d
4 Step Trigger
Start = ON
Crater = ON
Burnback = ON
1.5 sec max.
Start
Burnback Time
Downslope
Crater
Power
Source
Output Crater
Start
Tr
ig
ge
r P
ul
le
d
Crater
Tr
ig
ge
r
Re
le
as
ed
Start
FIGURE B.23