Instructions / Assembly

59
GMAW
www.lincolnelectric.com
T
he push-pull systems handle aluminum diameters from 0.030"
t
o 1/16” (0.8 - 1.6 mm), and they reliably feed aluminum wire
electrode up to 50 ft. (15.2 m) from the control cabinet.
3. Special Push–Pull GMAW Torches for Aluminum
There are a few "after market" push-pull GMAW aluminum
torches, which will retrofit onto most standard wire drives. This
permits the use of a more integrated approach for feeding
aluminum. The motor in the torch handle is variable torque,
constant speed, which permits the use of the wire feed speed
control at the standard drive. Figure 38 details one of these.
These add–on torches usually function such that the pull torch in
the gun is the slave and the push motor in the feeder is the
master. There is evidence that the gun (master) and feeder
(slave) arrangement gives more consistent results, but these
add–on pull torches have also been shown to be effective.
4. Spool Guns
Another solution for lighter duty welding is the spool gun shown
in Figure 39. In this system, a 1 lb. (0.5 kg) spool of filler wire is
mounted directly on the rear of the GMAW gun, so that it is only
pushed a few inches past the drive rolls. These torches are
usually air-cooled, so they are not recommended for higher
current or higher duty cycle welding.
Aluminum Feeding Enhancements
• Drive Rolls should always be highly polished "U" groove type
for aluminum. The ‘U" groove is designed to cradle the softer
electrode without altering its shape and the high polish prevents
the accumulation of aluminum oxide in the drive roll groove.
Steel electrodes use either knurled rolls or a "V" groove
configuration. Drive rolls designed for carbon steel electrodes
should not be used for feeding aluminum
• Inlet and outlet guides for steel wire are usually made from
steel. These should not be used to feed aluminum. Inlet and
outlet guides to feed aluminum should be made from teflon,
nylon, or other suitable plastic which will not scrape the wire.
• Both push and push–pull torches are available in air- and
water-cooled versions. It is recommended that water-cooled
torches be used for applications calling for welding current
greater than 150 amps or when higher volume production is a
factor.
• Torches are available in straight barrel pistol grip, curved
barrel pistol grip, or gooseneck styles. All are acceptable for
welding aluminum. However, if angled barrels are used,
anything greater than 45° should be avoided. They will
contribute to wire feeding difficulties.
• Liners for torches made to feed steel are usually made from
spirally wound small diameter steel wire. These types of liners
should not be used for feeding aluminum wire. They will
shave the aluminum wire and then quickly clog the path.
Instead, consider the use of either teflon or nylon liners for
aluminum electrode. Some of these types of aluminum liners
will have a short coiled brass liner section located at the front
of the plastic liner.
• Contact tips for welding steel are not suitable for welding
aluminum. Aluminum readily expands as it absorbs the heat
of the arc. Aluminum contact tips for a given size aluminum
wire are designed to accommodate the thermal expansion of
the electrode – the inside diameter of the contact tip is slightly
larger than those for the same size steel wire. Most manufac
-
turers make contact tips specifically for aluminum wire.
• The contact tip should be positioned either flush with the end
of the gas nozzle or slightly recessed [approximately 1/8”
(3 mm)]. The contact tip should never extend beyond the gas
nozzle.
FIGURE 37: Complete Push Drive System
FIGURE 38: Push-Pull GMAW Aluminum Torch
FIGURE 39: Spool Gun