Tweco VA 2000 Ultra-Feed - Manual (Page 35)

ULTRAFEED VA 2000
February 27, 2006 4-9
4.08 Welding - 4 Step Operation
Refer to Figure 4-5.
NOTE
When welding in 4 step operation, the
Ultrafeed VA 2000 must recognize an arc
(based on Arc Established or current feedback
from the power source) within 1.5 seconds
after the wire begins feeding. If the Ultrafeed
VA 2000 receives a gun switch trigger and
release while in 4 step operation and no arc is
recognized, the Ultrafeed VA 2000 will feed
wire for 1.5 seconds and then stop. This is
done to prevent the possible injury that could
result with the unwanted feeding of wire while
not welding.
Position the welding gun above the workpiece and depress
the gun switch trigger. The gas will begin to flow. Release
the gun switch trigger while maintaining the welding gun
in the same position. At this point, the contactor to the
power source will enable its output, and the wire will begin
feeding, and an arc will get established. The time from
releasing the switch to establishing an arc is allowed to
be 1.5 seconds, after which the feeder will return to
Standby.
To end the weld, depress the gun switch trigger again.
The wire will stop feeding, and the power source output
will go off. The gas will continue to flow for as long as
the gun switch is depressed. Release the gun switch to
shut off the gas, ending the postflow period.
NOTE
In 4-Step welding, the user can independently
control the amount of preflow and postflow
time by adjusting the amount of time the gun
switch is depressed.
EXAMPLE:
For no preflow, depress and release the gun switch
trigger as quickly as possible. For 5 seconds
preflow, depress the gun switch trigger for 5
seconds before releasing the gun switch trigger. The
procedure is the same for postflow.
Gun Trigger
Arc Established
Gas
Contactor
WireFeed
Runin %
Postflow Preflow
Ramp Rate
Art # A-06986
Figure 4-5: Welding - 4 Step Operation