Tweco 211i Thermal Arc Fabricator - Manual (Page 65)

BASIC WELDING FABRICATOR 211i
Manual 0-5157 4-5 BASIC WELDING
4.02 MIG (GMAW/FCAW) Welding Troubleshooting
Solving Problems Beyond the Welding Terminals
The general approach to fix MIG (GMAW/FCAW) welding problems is to start at the wire spool then work through
to the MIG Gun. There are two main areas where problems occur with GMAW; Porosity and Inconsistent wire feed.
Solving Problems Beyond the Welding Terminals - 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 during solidification of the molten metal.
Contaminants range from no gas around the welding arc to dirt on the work piece surface. Porosity can be reduced
by checking the following points.
FAULT/CONDITION CAUSE
1 Shielding gas cylinder contents
and flow meter.
Ensure that the shielding gas cylinder is not empty and the
flow meter is correctly adjusted to 31.75 CFH.
2 Shielding gas cylinder contents
and flow gauge.
Ensure that the shielding gas cylinder is not empty and the
flow meter is correctly adjusted to workshop welding: 28-35
CFH or outdoors welding: 35-46 CFH.
3 Gas leaks. Check for gas leaks between the regulator/cylinder connec-
tion and in the gas hose to the Power Source.
4 Internal gas hose in the Power
Source.
Ensure the hose from the solenoid valve to the MIG Gun
adapter has not fractured and that it is connected to the MIG
Gun adapter.
5 Welding in a windy environment. Shield the weld area from the wind or increase the gas flow.
6 Welding dirty, oily, painted,
oxidized or greasy plate.
Clean contaminates off the work piece.
7 Distance between the MIG Gun
nozzle and the work piece.
Keep the distance between the MIG Gun nozzle and the work
piece to a minimum.
8 Maintain the MIG Gun in good
working order.
A Ensure that the gas holes are not blocked and gas is exiting
out of the MIG Gun nozzle.
B Do NOT restrict gas flow by allowing spatter to build up inside
the MIG Gun nozzle.
C Check that the MIG Gun O-rings are not damaged.
Table 4-2: Solving Problems beyond the Welding Terminals - Porosity