Any ideas on what might cause expulsion on aluminum laser welds?  So far I have turned up oxides as a major suspect.  We have little burrs that are trying to jump out of the weld puddle.  Sometimes the disruptions cause a hole and sometimes just a frozen burr that is trying to jump out of the weld puddle.  We have two different lasers that are running what in theory at least should be the same process with the same materials and the same product.  I suspect our gas purity.