Lincoln Electric PRO 155 Operator's Manual page 25

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MACHINE SET UP FOR THE GMAW (MIG)
PROCESS
1. See PROCESS GUIDELINES in the OPERATION
section for selection of welding wire and shielding
gas, and for range of metal thicknesses that can
be welded.
2. See the Application Guide on the inside of wire
feed section door for information on setting the
controls.
3. Set the "Voltage" and "Wire Speed" controls to the
settings suggested on the Application Guide for the
welding wire and base metal thickness being used.
The voltage control is marked "V" and the wire
feed speed is marked ''olo.''
4. Check that the polarity is correct for the welding
wire being used. Set the polarity for DC(+) when
welding with the GMAW (MIG) process. See Work
Cable Installation in the INSTALLATION section
for instructions for changing polarity.
5. Check that the gas nozzle and proper size liner
and contact tip are being used and that the gas
supply is turned on. If adjustable, set for 15 to 20
cubic feet per hour (7 to 10 l/min.) under normal
conditions, increase to as high as 35 CFH (17
I/min.) under drafty (slightly windy) conditions.
6. Connect work clamp to metal to be welded. Work
clamp must make good electrical contact to the
work piece. The work piece must also be grounded
as stated in the "Arc Welding Safety Precautions"
at the beginning of this manual.
WELDING TECHNIQUES FOR THE GMAW
(MIG) PROCESS
Four simple manipulations are of prime importance
when welding. With complete mastery of the four,
welding will be easy. They are as follows:
1. The Correct Welding Position
Figure B.16 illustrates the correct welding position
for right handed people. (For left handed people, it
is the opposite.)
When GMAW (MIG) welding on sheet metal, it is
important to use the "forehand" push technique.
Hold the gun (of the gun and cable assembly) in
your right hand and hold the shield with your left
hand. (Left handers simply do the opposite.)
LEARNING TO WELD
When using the GMAW process on light gauge mater-
ial, weld from right to left (if you are right handed).
This results in a colder weld and has less tendency for
burn through.
2. The Correct Way To Strike An Arc
PRO 155
FIGURE B.16
WARNING
ARC RAYS can burn eyes and skin.
When using an open arc process, it
Is necessary to use correct eye,
head and body protection.
Protect yourself and others, read
"ARC RAYS can burn" at the front
of this manual.
1. Be sure the work clamp makes good electrical
contact to the work.
2. Position gun over joint. End of wire may be
lightly touching the work.
3. Position face shield to protect face and eyes,
close gun trigger, and begin welding. Hold the
gun so that the contact tip to work distance is
about 3/8 to 1/2 inch (10 – 12 mm).
4. To stop welding, release the gun trigger and
pull the gun away from the work after the arc
goes out.
5. A ball may form at the tip end of the wire after
welding. For easier restrikes, the ball may be
removed by feeding out a few inches of wire
and cutting off the end of the wire with wire cut-
ters.
6. When no more welding is to be done, close the
valve on the gas cylinder, momentarily operate
the gun trigger to release gas pressure, then
turn off the machine.
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