Maintenance; Drive Rolls And Guide Plates; Contact Tip And Gas Nozzle Installation - Lincoln Electric 350MP Operator's Manual

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SAFETY PRECAUTIONS
WARNING
ELECTRIC SHOCK can kill.
• Have an electrician install and
service this equipment.
• Turn the input power off at the
fuse box before working on
equipment
• Do not touch electrically hot
parts.
GENERAL MAINTENANCE
In extremely dusty locations, dirt may clog the air pas-
sages causing the welder to run hot. Blow dirt out of
the welder with low-pressure air at regular intervals to
eliminate excessive dirt and dust build-up on internal
parts.
The fan motors have sealed ball bearings which
require no service.

DRIVE ROLLS AND GUIDE PLATES

After every coil of wire, inspect the wire drive mecha-
nism. Clean it as necessary by blowing with low pres-
sure compressed air. Do not use solvents for cleaning
the idle roll because it may wash the lubricant out of
the bearing. All drive rolls are stamped with the wire
sizes they will feed. If a wire size other than that
stamped on the roll is used, the drive roll must be
changed.
For instructions on replacing or changing drive roll,
see "Wire Drive Rolls" in Operation section.

MAINTENANCE

CONTACT TIP AND GAS NOZZLE
INSTALLATION
a. Choose the correct size contact tip for the elec-
trode being used (wire size is stenciled on the side
of the contact tip) and screw it snugly into the gas
diffuser.
b. Be sure the nozzle insulator is fully screwed onto
the gun tube and does not block the gas holes in
the diffuser. (NOTE: Insulator is not required when
using the optional fixed gas nozzles.)
c. Slip the appropriate gas nozzle onto the nozzle
insulator. Adjustable gas nozzles are available with
a .62" (15.9 mm) or .50" (12.7 mm) I.D., and in both
standard (flush) and recessed design. The proper
nozzle should be selected based on the welding
application. Different length fixed nozzles are also
available to fit 350MP and 400 amp gun tubes to
allow either spray or short-circuiting transfer weld-
ing.
Choose the gas nozzle as appropriate for the
GMAW process to be used. Typically, the contact
tip end should be flush to .12" (3.1 mm) extended
for the short-circuiting transfer process and .12"
(3.1 mm) recessed for spray transfer. For the
Outershield (FCAW) process, 1/8" (3 mm) recess is
recommended.
GUN TUBES AND NOZZLES
a. Replace worn contact tips as required.
b. Remove spatter from inside of gas nozzle and from
tip after each 10 minutes of arc time or as required.
GUN CABLE CLEANING
To help prevent feeding problems, clean cable liner
after using approximately 350MP pounds (136 kg) of
electrode. Remove the cable from the wire feeder and
lay it out straight on the floor. Remove the contact tip
from the gun. Using an air hose and only partial pres-
sure, gently blow out the cable liner from the gas dif-
fuser end.
POWER MIG 350MP
®
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