Hello Dave, As you probably already know, welding aluminum studs is difficult to begin with. Welding close to the edge of a piece is even more difficult. I would suggest trying the following when welding aluminum on the edge of a part, as arc blow generally is a problem. Aluminum welds are always wetter than SS or MS.
To help control the arc blow you can:
1. Grind and or clean the area to be welded
2. Use 2 ground cables – generally attached opposite each other on the pc so the current will not be drawn more strongly from one ground.
3. Be sure to ground directly to the part
4. Don’t locate part on edge of welding table
5. Use heavier spring pressure to speed up the weld
6. Sometimes placing another piece or material right up to the edge of your part will help eliminate arc blow
7. Sometimes coiling the weld cable around the spot where the stud is to be welded will eliminate arc blow.
If you can eliminate the arc blow with one of these techniques, then you can slowly reduce the voltage until you get less splatter but still a strong enough weld.
Hope this helps. Call 440-327-3200 if you have any additional questions.