Operation – Lincoln Electric POWER FEED SVM185-A User Manual
Page 56
OPERATION
B-38
B-38
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.
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.
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 supply
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