need more power. welding 1/4 cold I would want 250 amps minimum, more would be nice for start up. Can you turn the freq up higher. my ta/am stops at 150 I almost never move it from there except for dirty alum from time to time. Balance I usually run 70-75% If its thicker and towards the end of what my machine is capable of I will make your its really clean and run it as high as 90 % just to get all the juice out of it. Needs to be super clean though. Did you grind a bevel on those pieces or just butt weld them. If you put a bevel you won't need anywhere as much heat on first pass, then turn it up and weld and second quickly after the piece will already be preheated. Helium mix gas will help also.
Some my have different option but this is what I find.
-The higher the freq the more concentrated the arc = more heat where you want to weld instead of dancing around.
-Balance the lower you run it the more cleaning you get but the heat input spends more time jumping back and forth. That's why you see the tungsten ball faster the lower the bal. Higher bal and your putting more heat into the metal with less cleaning. "prep as always is key"
-Tungsten at these amps your close to wanting a 1/8 tungsten, I like 2% lanthanated can't find them around here I have to order them from on the line, With that inverter make the tungsten sharp,sharp,sharp it will help to focus the arc. 1.5% still works just fine tough.
-Preheat when you welding something near the limit of the machine a little preheat goes along way. I have full pen welded 1/4 and repaired thick casting with only my ta 185 but it wasn't a sit down and weld situation. With casts I preheat with a oven, torch, gas grill what ever I have handy. "The microwave didn't work out so good though"Kidding of coarse. The 1/4 6061 I did was just goofing around to see if I could do it but lots of cleaning,preheat, and multiple passes were needed and I melted the argon line off my torch in the process. For the time being 1/4 up for me is done with a spool gun till cash flow allows for bigger tig. I would suggest getting really comfortable with thiner aluminum first. Really pay attention to the puddle learn to read it. With alum they're are plenty of times you can put a bead down on something like a fillet weld with little penetration if you don't know what to look for. Pretty much you get a bead barely wetted into the edges with very limited strength and prone to cracking. depending on the joint you either want to see the puddle wet all the way to the corner or keyhole a little. Even on a fillet I like to see it key hole a little.
One last thing. Use a smaller filler. A smaller filler will let you keep the puddle hotter. When you learn to feed a smaller rod faster you will get a hotter puddle and better puddle control which make for nicer looking welds.
