234 Modern Welding Copyright Goodheart-Willcox Co., Inc. GMAW Troubleshooting Guide Trouble Possible causes How to correct Difficult arc start Polarity wrong Insufficient shielding gas Poor ground Open circuit to start switch Check polarity, try reversing Check valves, increase flow Check ground—return circuit Repair Irregular wire feed, burn back Insufficient drive roll pressure Wire feed too slow Contact tube plugged Arcing in contact tube Power circuit fluctuations Polarity wrong Torch overheating Kinked electrode wire Conduit liner dirty or worn Drive rolls jammed Conduit too long Increase drive roll pressure Check, adjust wire feed speed Clean, replace contact tube Clean, replace contact tube Check line voltage Check polarity, try reversing Replace with higher amp gun Cut out, replace spool Clean, replace Clean drive case, clean electrode wire Shorten, install push-pull drive Welding cables overheating Cables too small Cable connections loose Cables too long Check current requirements, replace Check, tighten Check current-carrying capacity Unstable arc Cable connections loose Weld joint area dirty Check, tighten Clean chemically or mechanically Arc blow Magnetic field in DC causes arc to wander Rearrange or split ground connection Use brass or copper backing bars Counteract “blow” by direction of weld Replace magnetic workbench Undercut Current too high Welding speed too high Improper manipulation of gun Arc length too long Use lower current setting Slow down Change angle to fill undercut Shorten arc length Excessively wide bead Current too high Welding speed too slow Arc length too long Use lower current setting Speed up Shorten arc length Incomplete penetration Faulty joint design Welding speed too rapid Welding current too low Arc length too long Improper welding angle Check root opening, root face dimensions, including angle Slow down welding speed Increase welding current Shorten arc length Correct faults, change gun angle Incomplete fusion Faulty joint preparation Arc length too long Dirty joint Check root opening, root face dimensions, included angle Shorten arc length Clean chemically or mechanically Dirty welds Inadequate gas shielding Dirty electrode wire Dirty base metal Hold nozzle closer to work Increase gas flow Decrease gun angle Check gun and cables for air and water leaks Shield arc from drafts Center contact tube in nozzle Replace damaged nozzle Keep wire spool on welder covered Keep unused wire in shipping containers Clean wire as it enters wire drive Clean chemically or mechanically Welding and Fabricating Data Book Figure 8-74. A troubleshooting guide for problems that might occur during GMAW (Continued).