Gentlemen,
I have an old (1978) 30 foot aluminum dump trailer ("gravel bucket) that is in need of some welding TLC.
It is shot through with fatigue cracking. While I do not remember the exact alloy, it is one of the "imminently weldable" flavors.
Most of the fatigue cracks are in the sides. Therefore, all welding to these cracks will be vertical.
Additionally, some of the reinforcing gussets welded between the bottom of the floor and the aluminum cross members are either cracked or missing. Therefore, there will be a considerable amount of overhead welding.
An added complication is that I have no experience welding aluminum.
The only bright side to this picture is that I have a couple of excellent machines. The first, a Miller Syncrowave 500 (625 amps of maximum output!) has virtually all the bells and whistles. In fact I believe it has everything EXCEPT a sequencer.
The other weapon is a Millermatic 250X with Miller spool gun.
I have been told on good authority that over the decades, especially in dump trailers, the aluminum sucks up all kinds of contaminants, which you cannot adequately remove by merely cleaning the metal.
Although thorough cleaning is obviously mandated, "the word on the street" is that, to get a good weld, you have to weld a bead, grind it out, weld it up, grind it out - repeatedly - until FINALLY the goop will boil out and you'll finally get a good weld.
The above was communicated to me by the honcho who works for the factory. Therefore, I trust this to be good information.
Because of this, it would seem to me that the better option would be to TIG weld as much of the repairs as possible. My understanding is that, especially with the pulse and other controls on the Syncrowave welders, and provided you dial it in correctly, I should be able to sit there and stir the puddle without burning through and glopping a big wad of aluminum onto my boot.
Has anybody been there and done that? Obviously, I'm not gonna just strike up either machine and produce perfect welds. As a matter of fact I have virtually no experience (as yet) with either machine even with steel. So the plan is to start practicing rather intensively.
What I'm hoping to get from this post is an orientation by somebody who's actually experienced at doing out of position aluminum patch welding with both processes - and ideally - with these very machines.
I take this opportunity to thank everybody in advance for your sagacious input.
Regards, Vernon