Product Description - Lincoln Electric LF-72/74 Service Manual

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PRODUCT DESCRIPTION

General Physical Description
The LF-74 is optimized for GMAW and FCAW welding.
The powerful 4 roll MaxTrac™ drive, heavy duty enclo-
sure and wire reel stand combine to make an easy to
install, easy to use wire feeder for everyday welding.
Powering the wire drive is a high performance motor
gearbox. A heavy duty hinged door opens easily, which
provides an ample amount of room for assembling pre-
cision drive components and the welding gun.
MaxTrac™ technology delivers great feeding because:
• Patent pending drive rolls improve traction.
• The precision machined, rigid aluminum alloy frame
results in maximum drive roll clamping pressure.
• Drive hubs with steel inner cores have 3 ball bear-
ings inside each hub.
• The drive hubs are supported by large, heat treated
and ground shafts for maximum rigidity and accurate
drive roll alignment.
• Patent pending dual spring pressure arms have sen-
sitivity for feeding soft wires without crushing them,
and have plenty of compression force for feeding
solid or stiff wires.
Easy to configure, easy to service parts give
MaxTrac™ drives the edge in productivity.
• Patented split wire guides fully support the wire and
virtually eliminate birdnesting.
• No tools required to change the drive rolls and wire
guides.
• Changeable gun bushings easily accept guns from
many manufacturers.
• Brass-to-brass connections between the electrode
connection and the gun minimize voltage drop varia-
tions, resulting in consistent arc performance all day,
every day.
Three models of the LF-74 are available to satisfy
many customer set-ups:
• The base model is enhanced for GMAW welding with
consumables from bulk packages or when a boom
mounting is required.
• The bench model with heavy duty wire reel stand tar-
gets operators performing GMAW or FCAW welding
using consumables on spools.
• The high torque model features high ratio gearing for
feeding larger diameter FCAW or GMAW wires.
All models use a high performance motor-gear box
with an integrated tachometer.
OPERATION
General Functional Description
The LF-74 fulfills the need for an economical wire feed-
er with a high performance wire drive. Functional fea-
tures included are those that offer the most value – a
WFS knob with a calibrated printed scale, cold-feed/
gas purge switch, trigger interlock switch and tachome-
ter motor control.
RECOMMENDED PROCESSES
•
GMAW
•
FCAW
PROCESS LIMITATIONS
• The LF-74 is not recommended for GMAW-Pulse
Synergic, GTAW, GTAW-Pulse, CAG, SMAW
• The LF-74 is not compatible with push-pull equip-
ment.
• For the heavy duty bench models K2426-2 and
K2426-3, the maximum spool size = 60 lb. (27.2 kg).
REQUIRED EQUIPMENT
Lincoln's LF-74 is designed for use with the CV and DC
family of power sources. These include:
• CV-250
• CV-300
• CV-305
• CV-400
• CV-655
OTHER COMPATIBLE POWER SOURCES
• Ranger 250
• Ranger 305
• Commander 300
• Vantage 300
• Vantage 500
• Air Vantage 500
EQUIPMENT LIMITATIONS
• Maximum GMAW gun length = 25' (7.6m)
• Maximum FCAW gun length = 15' (4.6m)
• Maximum conduit length = 30' (9.1m)
• Maximum total control cable length = 100ft (31m)
• The LF-74 operates on 24-42VAC and not 115 VAC
• The K1733-1 and K1733-3 wire straighteners are not
compatible with the LF-74
• Gun bushings are required for welding guns that do
not have a Magnum (Tweco #2-#4 compatible) back
end.
• The LF-74 does not attach to K303 or K377 wire reel
stands.
LF-72/74
• DC-400
• DC-600
• DC-655
• Invertec V350
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