Pure Tungsten electrodes do tend to get "wobbly" when over-heated.
If your making a hat rack than pure tungsten electrodes are ok. But of all electrodes, pure has the lowest melting temp. and the worst arc emmitting qualities.
Here are a couple of hints that will help.
Try one size larger electrode.
If the balled end of your pure tungsten becomes more than 1.5 times the diameter in width than stop and fix it. A large ball just eats more amperage and reduces the transferred arc energy.
Zirconium electrodes work well for aluminum, cerium are also excellent. (these electrodes you prep the tip with a blunted point rather than a balled end)
When possible use a full length of tungsten. It will absorb more heat and won't melt as soon as a partial length of electrode.
Water cooled torch will make the biggest difference.
Balence control, If your machine has a dial that indicates balence control or (max cleaning/max penetration) try adjusting this control more toward the max penetration side. (If your etching disappears completely around the toe of the weld or you observe a grey scum on top of your puddle than you have gone too far towards max pen.)
Keep your torch as perpendicular as possible to the work, this will concentrate your arc energy in a small spot. If your electrode is at an angle (leading or trailing) it will make an oblong weld puddle that takes more amperage to melt. When your electrode starts to wobble, back off on your foot pedal and it will solidify again, soon you should have enough heat to proceed.
If you put some or all of these trade tricks together you will surely get a performance improvement.
Keep in mind this is not the best way to weld aluminum. It likes to be welded hot and fast. But if your not doing code work (hat racks) than these tips may fix a thing that might otherwise become scrap.
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