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Old 08-17-07, 06:59 AM   #1
ivegotabike
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Using MIG

Im planning a project for my welding class this year, a tandem recumbent trike, and i was wondering if there were any real problems with using MIG welding as opposed to the TIG they use on comertialy welded bikes. Asthetic problems like big beads on the welds dont really concern me, Im wondering if using MIG to weld aluminum tubing is going to be detrimental to the strength of the bike. Does anyone have experiance using MIG on aluminum tubing? Thanks in advance.
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Old 08-17-07, 03:07 PM   #2
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MIG welding aluminum bike tubes is not the best idea. The aluminum gets its strength from a heat treatment that is done after the is finished. When you weld it, you take this all away. So if its going to be aluminum and welded using any method, its going to need to be heat treated. This would require a jig, which you won't have. What am I getting at? Use steel.

If you use steel, you can mig it. Its not the greatest idea, but it can be done. You biggest problem will be the lack of accurate heat control while welding. This can cause you to burn away a thin tube when welding to a thicker and can cause distortion. Its possible, but you should practice on some test pieces you can check penetration on.

Also over build it. if its nice and beefy, you will be stressing all of your welds less and you will have more of a chance of success.

Good luck.
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Old 08-17-07, 04:15 PM   #3
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i was wondering if there were any real problems with using MIG welding as opposed to the TIG they use on comertialy welded bikes.
Mig is what most aluminum frames are done with (mass produced)
you'll be fine.
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Old 08-17-07, 04:44 PM   #4
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^^^ While I'm not positive, I'm highly skeptical of the above comment.

MIG welders need to be specially fitted with a gun mount wire feeder to properly weld aluminum. I don't think any mig welders are ready to weld aluminum out of the box. And even when setup properly, the results are mediocre. Since your voltage is fixed, you will start welding at a temperature that is too cold to make a proper bead, and by the time you are half way around the tube, the temperature will be too hot. It's really frustrating.

Almost anything commercially produced in aluminum is welded with a TIG process. Since aluminum is so efficient in heat transfer, the ability to control the arcs voltage and contact is critical to keeping the aluminum from sucking up the heat, deforming and blowing through. TIGs do this by using a Tugsten elctrode for its arc, hand fed filler material, and a pedal to control the arc temperature. TIG setups are expensive and hard to use in an uncontrolled enviroment when you need to attack from all angles, in all positions.

I'd recommend using MIG and using steel. Steel is easy to work with, and a MIG is pretty easy to learn. A competent MIG welder will have no problem welding together .065" (1/16") wall and fatter tubing. You won't learn it over night though. Practice, practice, practice. Get the motion in the ocean... you want to stich the metal together with a repeating zig zag or spiral pattern.

Just remember to tack your entire project together before finishing the joints with strong welds. That way you can change your design mid project without ruining your tubes with a grinder, and more importantly, your project will not deform.
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Old 08-17-07, 04:55 PM   #5
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float the puddle and get good penetration
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Old 08-17-07, 08:44 PM   #6
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mig and steel is the way to go if you arent experienced welding aluminum, it is more tricky to weld (both mig and tig) than steel. I thought it was easier to learn to mig aluminum than tig it, but I could be wierd.

I manage an aluminum flatbed shop, so I'm around Aluminum welding all day, all we do is mig. That is what the factories do as well. If you learned aluminum welding (mig or tig) you could do it out of that, i'm assuming your school has the proper equipment.
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Old 08-17-07, 09:36 PM   #7
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Is that so? I stand corrected.

Why do you guys MIG aluminum instead of TIG? Cost of equipment, portability?

Cassidy
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Old 08-18-07, 02:52 AM   #8
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mig and steel is the way to go if you arent experienced welding aluminum, it is more tricky to weld (both mig and tig) than steel. I thought it was easier to learn to mig aluminum than tig it, but I could be wierd.

I manage an aluminum flatbed shop, so I'm around Aluminum welding all day, all we do is mig. That is what the factories do as well. If you learned aluminum welding (mig or tig) you could do it out of that, i'm assuming your school has the proper equipment.

MIG on big stuff (flatbed) is not so bad because the aluminum doesn't overheat itself before you finish your bead. On tubes and such, TIG is really the only way to go. It's tougher to get the hang of using both hands AND a foot but being able to control the voltage in realtime makes all the difference. MIG on steel, on the otherhand is awesome all the time. (It's just so fast and easy )
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Old 08-18-07, 03:13 AM   #9
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Is that so? I stand corrected.

Why do you guys MIG aluminum instead of TIG? Cost of equipment, portability?

Cassidy
Higher speed of production, lower skill required, more consistent results with equivalent skill level thanks to semi-automation with synergic pulse mig equipment.
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Old 08-18-07, 10:29 PM   #10
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Ive tried both (TIG only briefly) on steel. And from my experiance MIG is like stealing candy from a baby compared to stick, and tig is a *****.
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Old 08-19-07, 11:46 PM   #11
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Damn

Well, I just got done welding up a cool long utility bike frame. Tons and tons of welds on 1/2" and 3/4" tubing.

Even with the MIG, it was a major PIA. I forgot how frustrating it is to weld tiny tubes together. I consider myself a competent welder, but some of these beads are definitely "functional" looking.
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Old 09-07-07, 10:10 PM   #12
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What is the problem with lugged steel, gas welded with brass or silver????
Bud
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Old 09-07-07, 11:10 PM   #13
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float the puddle and get good penetration
you sound like my instructor :B
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Old 09-10-07, 10:01 AM   #14
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What is the problem with lugged steel, gas welded with brass or silver????
Bud
Ummmm,,,,, you gotta have lugs first? For an oddball frame, where would you get the lugs?

-----

I prefer gas-torch welding buyt trying to make stuff out of thin-wall aluminum is generally not worth the effort, I find. Brazing it is slightly easier, but still has problems.

Steel is FAR easier to work with all around, and retains more strength besides.
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Old 09-24-07, 06:15 AM   #15
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Just finished 2 semesters of welding at the local community college. The easiest way was to use MIG and a gas Argon/CO2 set up on thin wall stuff, oh, and alot of practice not to burn thru.
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Old 09-26-07, 11:01 PM   #16
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I have never, ever, seen an aluminum bike MIG welded. Problem with MIG is controlling the heat. Even with the above comments very skeptical about the comment that many cheaper bikes are produced with the MIG process. You can clearly see from the welds (on every aluminum bike I own) that is is a TIG process. It is possible to make MIG welds look like TIG welds but it is hard and still not completely consistent or nearly as clean. Even with cleanup it would show.

I have also welded aluminum and do large amounts of steel welding both thin and thin, mostly MIG. I suppose my common technique is "MIG that looks like TIG" or as close to it. I have built a frame with my MIG and it worked and would work fine for steel. But I just don't see it with aluminum. Perhaps you could correct me if I am wrong...
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Old 10-01-07, 08:32 AM   #17
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Guess I should have made my comments a little more clearer, we used mig with gas on steel, tig was used on all aluminum welds.
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Old 10-01-07, 01:05 PM   #18
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yes agreed. Particularly with low heat mig welders it is very easy and can be very strong and capable to MIG weld a steel frame. That said I think TIG is still a much better all around option particularly with strength, control of the weld, and final appearance...

Again, with aluminum, I am high skeptical of claims that you can MIG weld an aluminum frame with any degree of quality (or even possibility) remotely close to a TIG-welded aluminum bike frame... I have personally never seen a mass produced MIG welded bike frame, period, steel or aluminum ...
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Old 10-01-07, 03:45 PM   #19
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On all aluminum II have welded I have opted to use TIG since its readily available in my tech class. I have heard of people doing repairs to aluminum using MIG only to have the weld stress or completely fail on them later.

When i make my fist recumbent I'll be using steel for the frame since it is a trial and error process to make the product perfect for me.
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