GUN Cable Cleaning

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MAINTENANCE

D-2

SAFETY PRECAUTIONS

1. Be sure the nozzle insulator is fully screwed onto the

gun tube and does not block the gas holes in the dif-

WARNING

fuser.

• Have a qualified electrician do the

2. Slip the appropriate gas nozzle onto the nozzle insu-

lator. Either a standard .50" (12.7 mm) or optional

maintenance

and

troubleshooting

.62" (15.9 mm) I.D. slip-on gas nozzle may be used

work.

and should be selected based on the welding appli-

• Disconnect

the input power off

cation.

Adjust the gas nozzle as appropriate

for the

using the disconnect switch at the

GMAW process to be used. Typically, the con-

main input supply before working

tact tip end should be flush to .12" (3.2 mm)

inside machine.

extended for the short-circuiting transfer process

• Unplug the power cable if it is connected to a

and .12" (3.2 mm) recessed for spray transfer.

receptacle.

GUN TUBES AND NOZZLES

------------------------------------------------------------------------

GENERAL MAINTENANCE

a. Replace worn contact tips as required.

In extremely dusty locations, dirt may clog the air

b. Remove spatter from inside of gas noz-zle and from

passages causing the welder to run hot. Blow dirt out

tip after each 10 minutes of arc time or as required.

of the welder with low-pressure air at regular intervals

to eliminate excessive dirt and dust build-up on internal

parts.

To help prevent feeding problems, clean cable liner

The fan motors have sealed ball

bearings

which

after using approximately 300 pounds (136 kg) of elec-

require no service.

trode. Remove the cable from the wire feeder and lay

it out straight on the floor. Remove the contact tip from

DRIVE ROLLS AND GUIDE PLATES

the gun. Using an air hose and only partial pressure,

gently blow out the cable liner from the gas diffuser

After every coil of wire, inspect

the wire

drive

end.

mechanism. Clean it as necessary by blowing with low

pressure compressed air. Do not

use solvents for

CAUTION

cleaning the idle roll because it may wash the lubricant

out of the bearing.

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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.

CONTACT TIP AND GAS NOZZLE INSTALLATION

a.Choose the correct size contact tip for the electrode being used (wire size is stenciled on the side of the contact tip) and screw it snugly into the gas diffuser.

b.Screw the appropriate fixed gas nozzle fully onto the diffuser. Either the standard .50" (12.7 mm) flush nozzle or other optional flush or recessed (spray arc) nozzle sizes may be used. (See Table D.2 in this section.)

c.If using optional adjustable slip-on noz-zles, see Table D.2 in this section.

Excessive pressure at the start may cause the dirt to form a plug.

Flex the cable over its entire length and again blow out the cable. Repeat this procedure until no further dirt comes out. If this has been done and feed problems are experienced, try liner replacement, and refer to trouble shooting section on rough wire feeding.

LINER REMOVAL AND REPLACEMENT

NOTE: Changing the liner for a different wire size requires replacement of the gas diffuser per Table D.1 to properly secure the different liner.

POWER MIG 255C