Tweco 400 MST Arc Master - Manual (Page 28)

6
BASIC TROUBLE SHOOTING
6 – 1
BASIC TROUBLE SHOOTING
WARNING
There are extremely dangerous voltages and
power levels present inside this product. Do not
attempt to open or repair unless you are an
Accredited Thermal Arc Service Agent and you
have had training in power measurements and
troubleshooting techniques.
If major complex subassemblies are faulty, then
the Welding Power Source must be returned to an
Accredited Thermal Arc Service Agent for repair.
The basic level of troubleshooting is that which can
be performed without special equipment or knowl-
edge.
1
Solving MIG Problems
Beyond the Welding Termi-
nals
The general approach to fix Gas Metal Arc Welding
(GMAW) problems is to start at the wire spool then
work through to the MIG torch. There are two main
areas where problems occur with GMAW:
1.1 Porosity
When there is a gas problem the result is usually
porosity within the weld metal. Porosity always
stems from some contaminant within the molten
weld pool which is in the process of escaping dur-
ing solidification of the molten metal.
Contaminants range from no gas around the weld-
ing arc to dirt on the work piece surface. Porosity
can be reduced by checking the following points:
1. Gas cylinder contents and flow meter.
Ensure that the gas cylinder is not empty
and the flow meter is correctly adjusted to
25 cubic feet per hour.
2. Gas leaks.
Check for gas leaks between the regulator/
cylinder connection and in the gas hose to
the Wire Feeder. Internal gas hose in the
Wire Feeder.
3. Internal gas hose in the Wire Feeder.
Ensure the hose from the solenoid valve to
the MIG torch adapter has not fractured and
that it is connected to the MIG torch adapter.
4. Welding in a windy environment.
Shield the weld area from the wind or
increase the gas flow.
5. Welding dirty, oily, painted, oxidized or greasy plate.
Clean contaminates off the plate.
6. Distance between the MIG torch nozzle and the
work piece.
Keep the distance between the MIG torch
nozzle and the work piece to a minimum.
7. Maintain the MIG torch in good working order.
Ensure that the gas holes are not blocked
and gas is exiting out of the torch nozzle.
Do not restrict gas flow by allowing spatter
to build up inside the MIG torch nozzle.
Check that the MIG torch O-rings are not
damaged.
WARNING
Disengage the drive roll when testing for gas flow
by ear.
1.2 Inconsistent Wire Feed
Checking the following points can reduce wire-
feeding problems:
1. Wire spool brake is too tight.
Feed roller driven by motor in the cabinet
will slip.
2. Wire spool brake is too loose.
Wire spool can unwind and tangle.
3. Worn or incorrect feed roller size.
Use 'U' groove drive feed roller matched to
the aluminium wire size you are welding.
Use 'V' groove drive feed roller matched to
the steel wire size you are welding.
Use 'knurled V' groove drive feed roller
matched to the flux cored wire size you are
welding.
4. Misalignment of inlet/outlet guides.
Wire will rub against the misaligned guides
and reduce wire feedability.
5. Liner blocked with wire debris.
Wire debris is produced by the wire passing
through the feed roller, if excessive pressure
is applied to the pressure roller adjuster.
Wire debris can also be produced by the
wire passing through an incorrect feed roller
groove shape or size.