Ok so my shop whats me to weld some stuff up with my Miller 175. Its aluminum 7075-T6. I've got the whole machine set-up and ready to go, but I've never welded aluminum before any pointers. Yeah Yeah I know a Miller 175 isn't the ideal set-up for this type of work, but it's not alot of welding that I need to do.
Problems I'm having it's not flowing at all and I can't keep a bead going. It's sputtering and poping. Whats a good wire speed and amp ratio? Come on make me look like a hero here.

crank up the heat alot more than you would think. i have never had that good luck using the pusher gun that comes with a smaller mig machine. the spoolmatics seem to run fine off the 200 and up machines. that is about all i can offer. sorry, i know it's not much help.

what are you using for a sheilding gas? i like to use heliem for aluminum.

Try preheating the pieces before hand.

JP

7075 is not weldable.

Aluminum has very high thermal conductivity, you will have to be going faster at the end of the weld than you were at the beginning, it's really dramatic with aluminum. When I was learning I'd have a beautiful weld till the end when it just like melted apart it was aweful. So strike the arc hot and as you go you'll have to let off, it took me a while to get aluminum on tig but once I got it I could lay down some pretty sweet beads. I hope that helps a little. Sorry I may have just confused you more.
-Nate

first off 7075 isn't usually considered weldable. It is very likely to crack. Second if you can make a weld and not have it crack the HAZ will be about 1/5 the yield strength of the T6 material. If strength isn't really an issue then go for it. As far as settings to use I don't have enough info to help you there. At home I have a MIG Stick and gas welders and for aluminum I always use gas, because changing the wire in the mig is too much work stick is too hard for me and gas welding aluminum is not really that hard. Of course it isn't that strong either. Good luck. Good shielding gas question too, should use helium or Argon no CO2 or CO2 argon mix.

Like dean and gordon said 7075 is not a weldable alloy but it can be done but at great loss of strenght and probability of cracking . We weld 2024 T3 at work for aircraft insturment panels and that also is considered a non weldable alloy but it is in a non structural application and we never had a problem.

I don't have a lot of aluminum mig experiance as I always use tig but if your part is on the heavy side I would preheat a bit to get some temp into the part before you start and make sure to use straight argon or helium, also make sure you clean the weld area before you start, a stainless steel brush works best .

rich

I just started welding aluminum, takes pratice I'll say that!:)