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Science might say no but after a period of non use, rolling the tank sure seems to help the arc smooth out.
When you Mig weld after a long period of non use. It seems to help to roll the tank
The 3G plate test is sometimes used for MIG welding certification tests.
This video will be particularly helpful for a 3G certification test with uphill and downhill root passes.
Weld sequence can help prevent distortion.
Jody Collier from WeldingTipsAndTricks explains "the bird's nest".
Working with your machine to start getting better (less frustrating) results right out of the gate.