Fault Finding - NewArc WFU12A-ILS Operational Manual

4. Fault finding

MIG Welding Problems
Porosity (holes) in weld - Has two common causes:-
1. Lack of shielding gas caused by the flow-meter not being set correctly, damage to any of the gas
hoses or MIG torch, a build up of spatter inside the MIG torch nozzle or dispersal of the gas shield by the
wind or fume extraction system.
2. Poor surface condition of the weld metal caused by inadequate surface preparation or contamination
by oil, grease or paint.
Wire burns back to contact tip
Caused by voltage being too high for wire feed speed, wire feed restricted by blocked tip or liner,
insufficient tension on pressure roller or excessive brake tension on spool holder.
Cold arc with excessive spatter and weld bead too high (convex)
Caused by the voltage being too low for the wire feed speed or metal thickness, inductance control
on power source set too high, the power cables between the power source and wire-feed are either too
long or of inadequate cross section and are causing a volt drop or the MIG torch or earth lead are
damaged.
Hot arc with large irregular spatter and weld bead too flat, or even concave
Wire feed too slow or voltage set too high.
Wire glows red hot and reluctant to arc
Power source set to MMA (constant current), either change power source to MIG (constant voltage) or set
wire-feeder to constant current setting. When using the Wire-feeder in constant current mode, especially
with flux-cored wires, it improves the welding characteristic if reverse polarity is used (torch -ve).
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WFU12A-ILS