Tweco VS 212 PortaFeed - Manual (Page 34)

PORTAFEED VS 212
OPERATION 4-2 Manual No. 0-4994
4.02 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
ELECTRICALLY HOT.
Refer to Functional Timing Diagram on the previous
page.
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
partially extinguish at the work piece which
reduces the arcing at the contactor contacts.
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
SHUT OFF at the cylinder, and the wire feeder and
power source be turned OFF.
4.03 Welding In CC Mode vs. CV
Mode
1. Welding in CC Mode: When welding with a
constant current (CC) power source, changes in
wire feed speed will affect welding 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.
B. Welding in CV Mode: When welding with a
constant voltage (CV) power source, changes in
wire feed speed will affect welding 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.
4.04 Theory Of Operation
Refer to the Connection and Schematic Diagram in
theAppendix 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 PC 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 released,
the short on the gun switch receptacle is removed
causing the wire feed motor to stop feeding wire, the
gas valve to close stopping gas flow, and the contactor
to open making the welding wire electrically cold.