Mig nozzles

For Aluminum MIG, it will depend on whether you are running Globular, Short Circuit or Spray.

For Globular and Short Circuit, you want the tip flush with the nozzle, or just slightly proud of it by maybe 1/16".

For Spray you want the tip recessed about 1/8" to 1/4" inside the nozzle.

If you try running spray with the tip out too far, the wire will burn back and fuse to the tip.

If you try to run short circuit with the tip recessed you won't get enough heat into the weld, and will get cold welds.

On Sat, 24 Apr 2004 12:47:24 GMT, Ernie Leimkuhler vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email

Interesting Ernie.

Today I was welding and started to weld a bit "hot". IT was behaving ike spary, with a "flame" rather than the usual crackle. I was running

220A. The welder is not really designed for this at all. I have "faked" the spray at lower current settings before, with good results.

The wire kept welding to the _base_ of the tip, where it joined to the liner steel atop the gun. It would stick, and in the end I had to change tips. I tried adjusting tip-to-work gap quite a bit, but it still gave trouble.

When you say "the tip too far out", do you mean too far from the nozzle/gas shield, or simply with too long a tip distance?

I am always trying things. This "spray" mode gave beautiful welds after I changed the tip. Really smooth and deep. I was working in fiarly heavy stuff, and was able to "go for it"

**************************************************** I went on a guided tour not long ago.The guide got us lost. He was a non-compass mentor.........sorry ........no I'm not.

With aluminum MIG welding the machine settings are critical for each combination of joint design, materiels thickness and direction of travel. When you find a combination of voltage / wire speed that works, you write it down for future use. The welding itself is pretty easy, once the machine it dialed in.

Spray is very good for materiels 1/4" or thicker, but it runs much hotter and will eat tips quickly if you don't have the balance of settings just right.

How do I tell if it is spray, globular or short circuit?

By sight and sound. Globular transfer produces lots of spatter, spray doesn't. Short circuit makes a "frying bacon" sound, spray makes a hissing noise. The differences are distinctive enough that once you've seen and heard them, you'll have no trouble recognizing them.

Your voltage, wire speed, wire thickness, and shield gas will determine which mode you get. Spray requires the highest voltage, short circuit the lowest, with globular in the middle. High CO2 can't get to spray, so you'll only be able to do short circuit or globular with CO2. Argon is needed to spray, a fairly big welder is required too, since you need close to 300 amps to get into spray with the usual wires. (Small wire lets you get into spray at somewhat lower current, but there will be problems with the wire welding to the tip.)

Gary

Globular is slow and makes lumpy welds. It is possible to actually see each drop of metal as it falls to the weld. It sounds like : pop, pop, pop, ...

Short Circuit is faster and louder. It sounds very much like Steel MIG welding. The Frying bacon analogy is often used, but I think it sounds more like a coarse heavy fabric being torn.

Spray is just a high pitched hum, and hiss. Very fast, and very hot.

Globular is good for buildup and jumping gaps.

Short Circuit is best for thin metal, under 1/4".

Spray is best for heavier metal above 1/4".

Well after some aluminum welding I have hundreds of little aluminum balls all over the place and I am at 170 amps, this must be short circuit.

Specifically

Keep your gun at a higher angle and you will get less of the bead spray effect.

80 degrees from the table works well, so you are technically still pushing the bead.