I’m unable to get a puddle to form on the upper and lower piece of aluminum (3/8″). I’ve tried different amp from 150 to 200 at 20 CFM. I’ve extended the electrode, 3/32 pure tungsten-green tip, to reach the inside corner. I hammer down on the pedal and I can see the cleaning process begin. I can see the puddle begin to puddle a little on the bottom piece, but not the top. I thought if I can put filler into the puddle and walk the puddle to the top piece (didn’t work either). When I tried to stick filler in the puddle, it would melt away and blow off before it reach the puddle. I think my angle is too low too. If I hammer down too long, it would distort the electrode causing me to re-sharpen the electrode. No problem with the butt-join and outside corners. Any help is greatly appreciated.