mig nozzle/contact tip for aluminum

[Alex]

Anyone got any suggestions for a contact tip/nozzle combination that works well on aluminum with a MM251 and M-25 gun?

Thanks a heap,
Alex

[hankj]

Use it like it is, but size your contact tip one size bigger than your wire to allow for the aluminum to expand when it gets hot. .030 wire = .035 tip.

Hank

[Paul Seaman]

Right on hank.
Keep the torch hoses as straight as possible.
Run straigh argon, and push your puddle instead of dragging.

This should get you started.

[dyn88]

Im confused, I thought the companies that manufacture the tips had extensive and expensive reserch and development departments. This said why wouldnt they manufacture the .030 tip to measure .0365 as most .035 tips do. This may sound rude but I dont understand why you would use a tip manufactured for a different wire size.
Also, wouldnt the tip expand when it gets hot not the wire, since the wire is constantly being replaced with fresh cold wire?
Finally if one or the other does expand and you use an over sized tip, The theory is that when you start an arc you have less current available, due to the wire not coming in contact with the correct amount of tip, and as heat and subsequently "expansion" set in you have more available curant and, do you stop and reduce wire speed to reduce current or is it so inconsequential that you dont even notice?

[HAWK]

dyn88,

I run an oversized tip for the following reason. Regardless of actual size I can feel the Al wire throbbing within the tip or so I thought I could. I could also see some absence of beauty in the welds. When I tried an oversized tip the throbbing went away. I replaced the tip size for size and it came back. That's why I use an over sized tip. Many probably do it just on hear say and have never tried it size for size and just the opposite.

[paulrbrown]

Alex, I use .035 and .046 Al wire with a .053 tip, as the wire has a helix to it, it stays in contact with the tip ' wire curves'. The main thing to do is make sure you clip off the ball of the wire, or you will be pretty much be guarented of a 'stub' because the ball takes alot more amps to start melting, which then results in a 'birdnest'....hope this helps, Paul

[Alex]

Any opinions on flush tip vs recessed tip?

Thanks again for all the input,
Alex

[dyn88]

As I dont mig weld aluminum I dont know the ins and outs but this is one more thing that may help me on my way to being able to weld aluminum.

[hankj]

dyn88,

Quick note: thermal expansion rates: Al = 13.1, Cu = 9.8. Al gets fatter faster.

Hank

[Alex]

Tips and Techniques

Thanks for all the help guys. I'll be sure to post some pics as soon as I make an acceptable aluminum pass.

Be cool,
Alex

[GunLocators]

Do you have to use a Teflon Liner running Aluminum wire. If not why use a teflon liner at all?

[HAWK]

Alex,

I prefer a flush tip for spray and short arc. Some Al welders like a slightly recessed tip. The recess may minimize burn back some. I use a flush tip/nozzle configuration for everything.

[Alex]

Great input

Again, thanks for the great input. For the record, I've got the Teflon liner, etc. Just can't get used to spool guns so I'm settin' up my MM251 with a second gun dedicated to aluminum, a second cylinder with pure Ar, and I'm in the process of designing amendments to my cart to add the second bottle without changing the footprint.

Y'all be cool,
Alex

[ASKANDY]

There are many types of tips and tip sizes (not just hole size but total tip size) The aluminum wire is not what's swelling even though it does heat up faster than the copper. The Al wire is feeding out and not being stationary to get a chance to swell. The tip being the constant does see total heat all the time and does swell a % based on amps and time welding. If you are welding for long runs you will need an oversize tip. Short runs no. There is no set tip for every need and everyone will do this differently. A good rule would be to upsize one size and go from there. If you are still getting swell where the tip pinches the wire and it burns back, go up more. I prefer the tightest without affecting the wire. It assures of proper electrical contact with the wire.

Hope this helps
Andy

[dyn88]

thanks andy