Your about beyond the range of that power supply... However here are a couple of things to try before giving up or changing gasses.

Set balence control to 90-95% EN and sharpen a 1/8 inch Cerium (orange) tungsten electrode and put a small blunt at the point. Do not make your point a long slim taper, make it thick and abrupt, this will allow more amperage into the electrode before the tip deforms. Use thorium as a secondary if you can't get cerium. Do not use pure tungsten for this operation.

Water cooled torch is mandatory on this one.

Set your AC frequency to its minimum (20-or 40 hz. depending on model). Don't think about high frequency settings to get into the center of the fillet.. The low frequency will allow more power to transfer, it sounds wierd but this is why Miller made the AC frequency adjustable in this direction.

The high percentage of EN will remove almost all of your cathodic etch function, this means that your surface prep must be pristine and absolutly fresh... Remove oxide with abrasive immedatly before arc strike.

Preheat as before.

Strike arc (on an edge if if you can) and slowly increase on foot pedal keeping electrode gap as close to the work as possible without it touching the work. Be patient and watch for one edge or the other of your fillet to shine, when it does than very gently weave your torch angle to the edge that isn't shined, slowly back and forth (agitating the pool and the remaining oxides) till they both are shined.

When both fillet edges shine you may dip your wire and begin to move forward. Keep your wire angle as close to the horizontal plane of your fillet as possible, This technique will keep the arc heat going into the work and help to avoid balling your filler wire. Keep your torch angle straight (not a push or a drag) focus the heat right on the center of the puddle.

Once your moving along nicely (I'm assuming this will take multiple passes) and the puddle is wetting without flooring your foot pedal, you might want to back your balence control down to 80 or 85% to get better wetting at the toes.

If you dip your electrode you must stop and clean it 100% or you will loose a great deal of power and directional control. With your preheat situation I would suggest having several electrodes ready so you can make a quick switch rather than stopping to re-prep after contamination occurs.

As a last resort set your work ends up on small blocks so that the bottom of your fillet is not touching the table except at the ends. If there is no heat sink you stand a better chance of getting your material to melt. This also increases the likelyhood of distortion.

What ever heat treatment your parent material (substrate) had originally will be compromised.

Last tips, Get a large steel block to rest your torch-hand on as your workpiece will become exceedingly hot and make sure your neck and other bare skin is covered well, aluminum is more than 5x more reflective than steel and at this amperage you can have 2nd degree blisters after a very short arc time.

If none of the above prove effective let us know and somebody will give you tips on welding aluminum DC- with 100% helium...

Adding 50% or more helium to your argon will make a tremendous difference.

A 75% helium/25% argon mix should be readily available from your gas supplier.

Stay away from Ceriated tungsten in this app. The high heat will cook the ceria out of the electrode.

I have a Dynasty 300 and use 1.5 Lanthanated on most everything.

If this does not do the trick for you, go to DC neg straight polarity, with
100% helium for a shield.

This process doesn't do much cleaning, but it does penetrate.

Contact me directly for details.


Good Luck

brande