Idle Roll Pressure Setting; 2-Roll Wire Feeders - Lincoln Electric SVM138-A Service Manual

B-18

IDLE ROLL PRESSURE SETTING

The idle roll pressure is set at the factory backed out
two turns from full pressure for 2-roll feeders, three
turns from full pressure for 4-roll feeders. This is an
approximate setting. For small wire sizes and alu-
minum wire, the optimum idle roll pressure varies with
type of wire, surface condition, lubrication and hard-
ness. The optimum idle roll setting can be determined
as follows:

2-ROLL WIRE FEEDERS

1. Press the end of the gun against a solid object that
is electrically isolated from the welder output and
press the gun trigger for several seconds.
2. If the wire "birdnests," jams or breaks at the drive
roll, the idle roll pressure is too great. Back the
pressure setting out 1/2 turn, run new wire through
the gun, and repeat step 1. See Figure B.9.
3. If the only result is drive roll slippage, loosen the
gun cable clamping screw in the gearbox conduc-
tor block and pull the gun cable forward about six
inches. There should be a slight waviness in the
exposed wire. If there is no waviness, the pressure
is too low. Increase the pressure setting 1/4 turn,
lock the gun cable in place and repeat steps 1 and 2.
4-ROLL WIRE FEEDERS
1. Release the incoming idle roll and perform the
pressure setting procedure for two-roll wire feeders
to set outgoing idle roll pressure.
2. After the outgoing pressure is set, determine how
many turns away from full pressure the setting is.
3. Set both idle roll tensions to this setting. Engage
both idle rolls before welding. For most applica-
tions, best wire feeding will occur when both idle
roll pressures are set the same.
OPERATION
FIGURE B.9 – IDLE ROLL PRESSURE SETTING
PRESSURE
ADJUSTMENT
KNOB
LN-9 GMA Wire Feeder
FOR TWO-ROLL FEEDERS
B-18