Tweco Hefty II CC CV Voltage Sensing Wire feeder - Manual (Page 27)

Welding Procedure:
WARNING: In semiautomatic or
automatic wire welding, the
welding wire, wire reel (if used),
input guide, feed rolls, output
guide, feedhead, and welding
gun metal parts are all ELECTRI-
CALLY “HOT”.
Refer to Figure 5-1.
1. To start the weld, position the welding gun
above the work piece and depress the gun switch
trigger. The solid state control then enables the gas
valve, wire feed motor, and power source.
2. To end the weld, release the gun switch trigger
while pulling the welding gun away from the work
piece. The solid state control then disables the gas
valve, wire feed motor, and power source.
NOTE: After the weld is completed, it is
recommended to pull the welding gun away
from the work while releasing the gun
switch. This allows the welding arc to par-
tially extinguish at the work piece which
reduces the arcing at the contactor con-
tacts. Using this procedure will lengthen the
life of the contactor contacts especially
when welding at high amperage.
3. At the end of the work day or when welding has
been completed, it is recommended that the gas be
SHUTOFF at the cylinder, and the wire feeder and
power source be turned OFF.
Welding In CC Mode vs. CV
Mode:
Refer to the CC/CV Mode Switch located in the
Internal Controls And Connections section of this
manual for further details.
WELDING IN CC MODE
When welding with a constant current (CC) power
source, changes in wire feed speed will affect weld-
ing voltage.
To adjust the amount of welding current from the
CC power source, a control knob on the power
source or an “optional” control knob on the wire
feeder will have to be adjusted.
The solid state control of a “slow run-in” circuit
automatically reduces the initial wire feed speed
when operating with a CC power source. This initial
reduction in wire feed speed will compensate for the
high open circuit voltage associated with CC power
sources and improve arc starting performance.
WELDING IN CV MODE
When welding with a constant voltage (CV) power
source, changes in wire feed speed will affect weld-
ing current. Changes in wire feed speed can be
obtained by adjusting the wire feed speed control
knob.
To adjust the amount of welding voltage from the
CV power source, a control knob on the power
source or an “optional” control knob on the wire
feeder will have to be adjusted.
Theory Of Operation:
Refer to the Connection and Schematic Diagram
in the Diagrams chapter of this manual.
Input power is supplied through the on/off switch
(S1) and input circuit breaker (CB1) to the bridge
rectifier (CR1). CR1 ensures that the proper polarity
input voltage is fed into the p.c. boards independent
of the welding polarity.
When the gun switch on the welding gun is pulled,
a short is provided on the gun switch receptacle (J4)
causing the wire feed motor (B1) to turn feeding
wire, the gas valve (L1) to open allowing gas flow,
and the contactor (K1) to close making the welding
wire electrically “hot.”
When the gun switch on the welding gun is re-
leased, the short on the gun switch receptacle is
removed causing the wire feed motor to stop feed-
ing wire, the gas valve to close stopping gas flow,
and the contactor to open making the welding wire
electrically “cold.”
Adjusting Burnback Time:
Burnback time is set at the factory, but the motor
control printed circuit board contains a component
that permits adjustment of burnback time.
Burnback time relates to the amount of welding
wire remaining at the end of the welding gun after
the welding process ends. Increasing burnback
time results in less wire remaining at the end of the
welding gun at the end of the weld. Decreasing
burnback time results in more wire remaining at the
end of the welding gun after the welding process
ends.
430429-456
OPERATION
5-2 November 17, 1999