Join Date: Dec 2001
Location: Belleville, Illinois
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Re: Miller millermatic 135 mig welder questions
Welding aluminum with your machine is tricky, but if you know the tricks it works fine.
1. Use only 4" spools of wire.
2. Adjust the liner as close as possible to the drive wheel. The liner should actually touch the drive wheel lightly.
3. Use as little drag on the wire spool as you can get away with. Set it so that when you release the trigger you get about a third to a half turn of the reel before it stops.
4. Switch the drive roller to the smooth groove. Never use the toothed groove with aluminum.
5. Use as little pressure on the drive roller as you can. To set it, back the pressure knob off until the wire won't feed. Then turn it down until it just starts to feed. Then tighten it down a tiny bit more.
6. Use a tip one size larger than the wire. If you're using .023 wire, use an .030 tip, an .035 tip with .030 wire, etc.
7. Keep the liner as straight as you can. Move the welder if necessary so that the wire doesn't have to make any U-turns.
8. Cut the ball end off the wire every time you stop. The wedge point left by the cutter will start the arc easier than the ball that's left when you stop welding.
When everything is right in your settings the machine will feed wire consistently, but if you run the tip into a block of wood and pull the trigger, the wire won't birdnest inside the machine.
All of these are necessary with any push-feed MIG system using aluminum wire. The Miller is no better or worse than any other machine in that regard. It's just the nature of the beast.
There are two common aluminum alloys used for MIG; 4043 and 5356. 5356 is a much harder, stiffer wire, and more forgiving of the settings, but 4043 usually gives better welds, so be meticulous in your setup and practice until you can use it.
As for heat, aluminum does have a lower melting point than steel, but is MUCH more conductive of heat. For that reason you need more heat than for similar thickness of steel. That is really a limiting factor for the 110 Volt welders in aluminum.
You can't get around the problem by making multiple passes as you can with steel. If you're underpowered in aluminum the bead will just sit on top of the base metal. You can make as many passes as you want, but you won't do much other than weld one bead to another.
But there is a workaround - preheat. I've welded 3/8" aluminum pipe with my Miller 135 by preheating it with a torch to 400*. Then the aluminum puddles nicely and bonds perfectly. Without preheat the limit is probably 3/16". Go to your welding supplier and get a 400* temp stick. It's like a very hard Crayon. It won't leave much of a mark until the metal gets to 400*.
MIG welding aluminum is tricky. It takes a different technique from steel, and you have to move faster or else it will melt through. Again, it's just the nature of the beast. Practice.
Also, consider looking for a different welding supplier. Yours either doesn't know their business, or they are putting sales ahead of integrity and the customer's best interests. Either way, it's not a good sign.
When I first tried aluminum with my Miller, nothing worked. I went back to the dealer and he took me to their demo room and went through the whole procedure. In half an hour I was welding like a pro.
My welding supplier suggested using a different liner for aluminum because aluminum is very sensitive to contamination, and the wire can pick up traces of the previous wires run through the liner.
On the other hand, an old timer told me that that was one of those mainly theoretical deals; significant in really critical work, but not everyday welding.
You don't need anything else to weld stainless, except for wire and a bottle of tri-mix. The setup is the same, and the technique almost the same, as for mild steel.
I don't know why anyone would use a spool gun for stainless. A spool gun is a natural for aluminum, where pushing the soft wire through a liner is a problem. I've never had a problem pushing stainless. Again, I think that your supplier is putting sales ahead of your interests.