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7.0
MIG WELDING FAULTS
FAULT CLASSIFICATION AND DESCRIPTION
MIG welds may be affected by various defects, which are impor-
tant to identify. These faults do not differ in form or nature from
those encountered during manual arc welding with coated elec-
trodes. The difference between the two applications lies rather in
FAULT
UNEVEN LEVEL
EXCESS THICKNESS
INSUFFICIENT METAL
OXIDISED BEAD
INSUFFICIENT PENETRATION
OVER PENETRATION
LACK OF FUSION
CHANNELS
8.0
GENERAL MAINTENANCE
DISCONNECT THE POWER SOURCE FROM THE MAINS BE-
FORE PERFORMING ANY MAINTENANCE WORK.
Every 5-6 months, remove accumulated dust from the inside of
the welding unit with a jet of dry compressed air (after removing
side panels).
BE EXTREMELY CAREFUL TO AVOID BENDING MOVE-
MENTS, WHICH COULD DAMAGE AND CHOKE THE TORCH.
NEVER MOVE THE POWER SOURCE BY PULLING THE
TORCH.
PERIODICALLY CHECK THE CONDITION OF THE TORCH,
WHICH IS THE PART MOST SUBJECT TO WEAR.
TYPE OF BREAKDOWN
No functions operate.
Irregular wire feed.
MIG WELDING FAULTS
APPEARANCE
POSSIBLE CAUSES
Faulty power cord (one or more phases
disconnected).
Blown fuse.
Insufficient spring pressure.
Wire-guide sheath blocked.
Wrong race - unsuitable for wire, or exces-
sively worn.
Braking on coil excessive.
Oxidized, poorly wound,poor quality wire,
with tangled or overlapping coils, etc.
the frequency of defects: porosity, for example, is more common
in MIG welding, while inclusion of slag is only encountered in
welding with coated electrodes.
The causes and prevention of faults are also quite different. The
following table illustrates the various faults.
CAUSE AND REMEDY
- Poor preparation.
- Align edges and hold during spot welding.
- No-load voltage or welding speed too low.
- Incorrect torch inclination.
- Wire diameter too large.
- Welding speed too high.
- Welding voltage too low for welding application.
- Weld in the channel if using a long arc.
- Regulate voltage.
- Wire is bent or over-protruding from the wire guide tube.
- Incorrect wire feed speed.
- Incorrect torch inclination.
- Irregular or insufficient distance.
- Wire guide tube worn.
- Wire speed too slow for voltage used or for welding speed.
- Wire speed too high.
- Incorrect torch inclination.
- Excessive distance.
- Distance too short.
- Rough out or grind the weld, then repeat.
- Welding speed too high.
(This fault is easily detected on sight by the welder, and should be correct-
ed immediately.)
8.1
TORCH MAINTENANCE:
1.
GAS NOZZLE: periodically apply welding spray and clean
nozzle interior of residue.
2.
WIRE GUIDE TUBE: check the wire passage of the tube for
wear. Replace as necessary.
8.2
CONNECTING THE TORCH
Before connecting the torch to the machine, make sure that the di-
ameter of the wire liner, the groove of the motor-rolls and the con-
tact tip corresponds to the wire used.
Ensure that the wire guide hose doesn't touch the roll.
CHECKS AND REMEDIES
Check and remedy.
Renew.
Try tightening regulating knob.
Renew.
Turn roller over or change it.
Loosen brake using adjusting screw.
Remedy by removing defective coils. If problem persists, change the wire
reel.
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