[MosquitoMoto]

Here's the thing.

In his original post the OP says he's been having good success on aluminium plate. So he knows what a puddle looks like, he's just wondering why he can't get a puddle on this tube setup. So he's not a rank newbie, he's seen a puddle and welded aluminium.

So I stand by what I said earlier - crank some amps into that piece and get your puddle going faster, then work with it in a similar way to what you have on plate.

As a beginner (still am...) I really started learning aluminium once I got that puddle going, and one of the things I learned was that when welding aluminium you have to be ready to move fast.

Kym

[zank]

I never mash the pedal. I light up easy, let the cleaning action do its thing for a bit, then give it more juice until I get a shiny puddle. Don't get me wrong; I'm not hanging around for too long. But when I blast at it, I find I am fighting crap floating in the puddle more oftan than not. It could be that the 7005 that I normally weld is a good bit dirtier than a nice piece of high quality 6061.

I guess my point is that there is a window of heat/speed/technique that you can work in. But you need to eventually give it enough juice to get a puddle going, which is what it seems to me that the OP is struggling with.

[shipj0]

It looks to me like you are lighting up right on the joint where the round tubing meets the base tubing and don't have enough amps so the heat is climbing up the round tubing and melting it out before the base metal puddle forms. The base metal tubing is also larger so it does not heat and form a puddle as fast as the round tubing. I agree starting with more amps so the puddle forms in 2 - 3 seconds, as a beginner that is the gauge I use for my amp setting for aluminum. I would also recommend starting at a point where the round tubing is further from the edge of the base tubing. Form the initial puddle on the base tubing, just slightly away from the joint then wash the puddle into the joint and add filler and start moving around the tubing. I would also set my cleaning to 15% - 20% EP. Less cleaning may not be the best for every application but it my learning experience it narrows the arc, puts more heat into the base metal and makes learning a lot easier. My $0.02 anyways.

[GFab70]

Here is a video of what I was trying yo put to words. At the 1:45 minute mark in the video it begins to describe and goes on to the 3:00 minute mark.

https://www.youtube.com/watch?v=HY30i_t1Da8