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View Full Version : Tig VS Mig for aluminum 6061-T6 square tubes



PJet
02-27-2008, 01:22 AM
Hi,

We will start to produce a machine that will fit in restaurant kitchens. The frame of the machine is made of square tubes of 1" aluminum 6061-T6. We will have to cut the tubes and sold them afterward.

I was wondering which welding technique (Tig or Mig) coudl best fit our needs?

The inotial production will be quite small (batches of 50 units at a time). We will anodize the structure either before of after the welding process, depending on what will get us the best results.

Any suggestions would be greatly appreciated.

Many thanks!

DareBee
02-27-2008, 07:27 AM
You can make a prettier weld with the TIG but it takes a lot of skill/practice on aluminum.
MIG will be at least 10 times faster, still requires a decent level of skill. You should use a spool gun for the MIG.
Aluminum must be prepped properly and if doing starts and stops while welding it needs cleaned between. Make sure your scratch brush is stainless.
Key words are production, unless you are making a fortune on these or they are highly cosmetic MIG is the right way. If they are highly cosmetic better find yourself a welder with a lot of years practice on aluminum.

PJet
02-27-2008, 09:23 AM
Thanks for the tips!

According to you, you think a newbie like me would be able to do a pretty good job using MIG? I can afford wasting a few pieces for practice but do not have much time to learn to be an expert...

DareBee
02-27-2008, 11:10 AM
You had better allow a lot of practice material to get it decent.
Also
If you are buying the MIG and/or spool gun, the salesman will do setups and demos with you at your shop.
My Lincoln rep is superb that way and used to be a welder by trade.

Unless you are seeing the need to weld heavy items in the future a Lincoln SP180 and a spool gun kit would be ideal for you.
If you have a little better budget I would definitely get a 255.

DSL PWR
02-27-2008, 11:12 AM
If you can get a Lincoln 350 MP. This is the best welder for aluminum that I have seen. With a little practice you will have the speed of a mig with nearly the appearance of a tig. The MP is a push/pull system. The mig head has a second set of drive wheels in it, and helps pull the wire thru the cable.

PJet
02-27-2008, 11:23 AM
I was planning to get a second hand MIG. Is it recommended?

It means that I would not have the assistance of a sales rep but they are lot cheaper...

DSL PWR
02-27-2008, 11:42 AM
Well, if you can afford it buy a new machine. You aren't using this machine as a hobby, but to make a product. I know the push pull model is pretty spendy, but when you break it up, say over 3-5 years it is pretty reasonable. If you don't have the capital to do an outright purchase, just go to a leasing company and do it that way. Say you go hole hog and spend 7000 on a new welding rig. You put 1000 down on a lease, and have payments of about $190 bucks a month for 3 years. Say you only make 50 units a month, you need to take 3.80 of the profit per piece and you have a new welder. The best thing about a lease is you pay for it before the tax man gets his cut.

BTW you can structure most leases so you have a 1 dollar buy out at the end.

PJet
02-27-2008, 12:11 PM
Thanks for all those precious advices!

Since I will need to anodize the structure once welded together, I have been advised to use 5356 rods so the welding color will not change after anodization.

Is there any other considerations I should be aware of you think?

Many thanks (again)!

Med-Pac
02-27-2008, 12:49 PM
We have been welding alum. (tig and mig) for the past 20 some years. Don't get too down on yourself if you're having problems.......it took me 2-3 years to get production quality welds with tig. Took me about 6 months to a year to get good at mig. A lot of practice and patience are required. You can also get the 5356 alloy in Mig rolls.

Mike

DareBee
02-27-2008, 12:59 PM
I agree with what everyone is saying.

Especially DSL. If you (PJet) are going to be making a product you should easily have budget to buy a proper machine! The push/pull unit is the Cadillac.

If you feel that you should have a used machine, we won't stop you.

I am going to repeat this again though. You are buying this machine for welding ALUMINUM, to do it RIGHT you will at least need to invest in a SPOOL GUN (this is an aluminum specific attachment).

protman16
02-28-2008, 09:42 AM
PJet,

Not sure what skill level you have with regard to welding, but if I was doing small batches I would use TIG. Unless the small batches have long weld lengths and you have a short production/delivery time go with MIG. Some things you did not mention and is very important are things like material thickness and joint type. Without knowing the parameters it is difficult to give advice on a welding procedure.

Essentially both methods work well for aluminum as long as understand what your requirements are.

Med-Pac
02-28-2008, 10:06 AM
Inside corners are also a bigger trick to do with tig.

Mike

Geof
02-28-2008, 10:15 AM
Thanks for all those precious advices!

Since I will need to anodize the structure once welded together, I have been advised to use 5356 rods so the welding color will not change after anodization.

Is there any other considerations I should be aware of you think?

Many thanks (again)!

Before you go ahead and do a whole lot take some samples to your anodizer to make sure colors are going to come out okay. It is not just the filler rod that can change things it is also the annealing that occurs around the weld zone.

Toysrme
02-28-2008, 03:27 PM
You're not doing expencive x-ray welding. Use mig, it'll save you lots of money on general production costs. (time, materials)

I use a half dozen 300 & 350MP's every day and:
1) It sucks they can't do AC tig. SUCKS HORRIBLY.
2) Air-cooled tig torches in that amp range suck. (general statement)
3) The internal push wire feeds are not as stable as the seperate push Miller units. They don't deal with the wire uncurling from the spools as well.
4) They DO NOT come push-pull from the factory. They come with a regular push torch. You must buy your push-pull torches seperately (cobramatic = tits).
5) Probably the best general purpose units for the cost by 10 miles. So buy two. ;)



If you buy a brand new one without a pull gun, you won't have a problem for the first week of light duty welding. Then reality will set in and you'll hate yourself!!!!!





Welding 6061 to 6061 use 4043. It's more tolerant of begenning welders in regards to undercutting and cracking. The welds also flow more and are better looking for most welders. Unfortunately for you 4043 can turn black during anodization so if you use it instead of 5356. You must anodize the parts before hand, then clean that off the base metal around where you're welding.

Toysrme
02-28-2008, 03:29 PM
Oh and I really like using the MP's pulse VS the millers. wow its nice!

mxtras
02-28-2008, 10:05 PM
I am assuming your tubing is more than likely 1/8"wall?

And I am guessing your tube is actually 6063-T52 - rectangular and square tubing is typically only available extruded and wrought from 6063 here in the States - might be different in Canada. Just curiosity on the alloy - not a major factor in response to your question. The wall thickness does make a difference, though. I will assume it's less than 3/16" for this reply.

Unless it is a high amperage process (3/16"+ thick substrate), in the long run you will likely be more satisfied with TIG. Lower amperage MIG welding just plain sucks in my opinion - soot, spatter and cold start are issues that have to be dealt with with lower amperage MIG welds and if aesthetics are important, the spatter could really make your life miserable. Also in my opinion, the setting for the lower amperage configurations are extremely picky meaning that if you switch from a corner fillet to a lap or butt joint, the amperage and wire speed settings will need to be altered to achieve acceptable results to match other welds on the assembly. This can be a real pain if there are a lot of seams with different welding configurations.

The cold start is a problem inherent to the MIG process in general - even on steel. Preheating the material will NOT help this despite what some folks might tell you. The cold start could be a big problem with a 1" long, lower amperage Aluminum MIG weld as you are describing and you would be wise to research the cold start issue in depth before making your decision. On a 1" long weld at low amperages, the first 1/2"-3/4" will be cold with poor parent metal penetration.

A competent TIG'er can lay down more complete, more acceptable lower amperage weld in just a few seconds longer than the MIG. If you factor in clean up, the TIG is faster at the end of the job. And you will have a more complete weld that is better looking. It also allows you to pre-finish your material which could be a huge bonus for you. Lots of variables and a lot of it could be preferential.

The learning curve is steep and relatively expensive to achieve quality, consistent welds in Aluminum - no matter the process. No matter which process you choose, I advise locating an experienced Aluminum welder and have him watch over your shoulder for a few hours to get you headed in the right direction. Internet education will not get you where you should be.

I weld aluminum tubing daily. The stuff I weld is stressed, structural consumer products where the weld must not fail and must look good and consistent. I have been in business doing just that for 9 years and I have spent my share of cash trying to reduce costs and improve manufacturing.

Your mileage may vary.

Scott

PJet
02-29-2008, 04:43 PM
The tubes we will be using are square aluminum 6061-T6 with 1'' O.D. Thickness of the pipes is 0.120''

Regarding the joint types, I have no idea what it is exactly. All I know is that I want the weldings to show as little as possible.

Many thanks again!

Drassk
03-05-2008, 07:10 PM
I'm making a bunch of frames out of the same stuff (1" tube, 1/8" wall) and I'm wondering why this stuff http://www.aluminumrepair.com/ is a bad idea? If the amount of heat that needs to be put into the joint (joint needs to be heated to something just under 750F) won't distort the parts horribly, it could be a decent process...

That said, I know if things seem too good to be true...so that's why I'm asking here! If it matters, the joints will be 45 degree cuts (square frames) and they'll be a perfect fit (CNCed parts pre-welding)

mam
03-19-2008, 10:13 PM
don't forget that tig welding is more properly to weld thin wall aluminium (or other materials) than a mig weld,specially in the begining point ,the tig method guaranteed a "pure join",mig weld is cold started

tool_man
03-20-2008, 01:52 AM
Greetings Drassk.
In my personnal opinion,you are much better off using proven techniques.If that stuff is as good as they claim,welder manufacturers would be looking for a new product to produce.
If you weld with a tig,be sure to get an inverter.The A.C. is a square wave as opposed to a sine wave.Meaning...instant positve,instant negative.No need to superimpose high frequency on the arc.Use 2% cerriated tungstens and grind a sharp point to the tip.Personally,I like chem-sharp.A.C.balance is fully adjustable.Start off with 30% positive/70% negative if your metal is clean.
I don't understand why you are planning to CNC 45 degree cuts in square tubing.Sounds like overkill to me.I get great results using a good compound miter saw with a 80 tooth carbide tipped blade.Very fast clean cuts.Maybe I just misunderstood your explanation.

Just my 2 cents worth