Miller Bobcat 250 Diesel, Owner'S Manual

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OM-258413 Page 63
Lack of Penetration
Good Penetration
Lack Of Penetration − shallow fusion between weld metal and base metal.
Possible Causes Corrective Actions
Improper joint preparation. Material too thick. Joint preparation and design must provide access to bottom of groove.
Improper weld technique. Keep arc on leading edge of weld puddle.
Insufficient heat input. Increase amperage. Select larger electrode and increase amperage.
Reduce travel speed.
Good Penetration
Excessive Penetration
Excessive Penetration − weld metal melting through base metal and hanging underneath weld.
Possible Causes Corrective Actions
Excessive heat input. Select lower amperage. Use smaller electrode.
Increase and/or maintain steady travel speed.
Burn-Through − weld metal melting completely through base metal resulting in holes where no
metal remains.
Possible Causes Corrective Actions
Excessive heat input. Select lower amperage. Use smaller electrode.
Increase and/or maintain steady travel speed.
Waviness Of Bead − weld metal that is not parallel and does not cover joint formed by base metal.
Possible Causes Corrective Actions
Unsteady hand. Use two hands. Practice technique.
Base metal moves
in the direction of
the weld bead.
Distortion − contraction of weld metal during welding that forces base metal to move.
Possible Causes Corrective Actions
Excessive heat input. Use restraint (clamp) to hold base metal in position.
Make tack welds along joint before starting welding operation.
Select lower amperage for electrode.
Increase travel speed.
Weld in small segments and allow cooling between welds.