Welding Aluminum Frames?

[HughDog]

Hi Gang-

Just short of calling FWC and /or ATC, I'm curious to know what the weekend warriors and full scale builders are using to weld their aluminum camper frames.

I'm pricing out the options for a new welder and I'd love to hear what setups folks are running for frame repair or fabrication.

Anything from cheap and effective to overkill would be helpful.

HughDog

 

[DanoT]

Don't most DIY RVers buy a shell, leaving ATC or FWC to do the aluminum welding?

 

[HughDog]

DanoT

Last one I bought and stripped went down exactly like that, except that the frame had some cracks that needed welds...

Beyond resto repairs, I took my last fwc to the frame, then started to think about all of the vehicle specific and personal mods I would do if I had better weld skills and the right setup.

Fast forward to the next... I’ll either mod a frame or build it from scratch....

 

[jrwdlw]

HughDog,

I'm using an HTP Pro Pulse 200 Mig (USAWeld.com) to weld an aluminum flatbed. It's an inverter type unit, and is a maximum of 200 amp output, at a low duty cycle. It has a pulse and double pulse processes, that works pretty nicely. I've welded as thin as 1/16" 5052.

 

[PokyBro]

Hey HughDog,

I have a mig set up, but no experience welding aluminum. I hired a guy I found on craigslist that was pretty reasonable I thought at $50/ Hr including materials. That being said it took him 11 hours to complete what I wanted welded. I added a lot of reinforcement, and two inches to both the top and bottom of the frame. He used a Lincoln tig welder to do the work. After the fact, I considered that I might have bought a tig welder set up, learn how to weld aluminum, and would have sold it afterwards (Of course it seems you rarely sell tools). I know I couldn't have done as good a job though, as he was really good. So thats one option for you, but finding an affordable welder is not very easy, I got lucky on that one.

Poky

 

[jrwdlw]

Welding aluminum is definitely tricky. Without a pulse mig unit, you have to move really fast to avoid burning through the material. Another issue is that the metal has to be really clean. I wipe it down with acetone, and then wire brush with a stainless brush. It's also best to preheat the weld area prior to welding. On the joints for 2 x 4 x 1/8 rectangular tubing, I would preheat for 40 to 60 seconds with a propane plumbing torch. Without that, the start of the weld is very cold, with poor penetration. I will admit that some of my welds are pretty ugly, but I don't think the flatbed is going to come apart.

 

[ntsqd]

In teaching people to GTAW weld I've only had one guy who only wanted to do aluminum and took to it right away. Everyone else struggled. AL takes a different mental approach than does ferrous metals.With a GTAW I've found that thin AL works best on DC-Reverse Polarity. Thick stuff, like cylinder heads, needs what I call "back-ground" heat. AL dissipates heat fast enough that it takes a lot of power to weld. By adding some back-ground heat to the part it slows the dissipation rate. On a camper frame I'd expect to only need back-ground heat on the heavier sections if the machine has enough power. the shorter on power that the machine is, the more pre-heating will need to be done. With GTAW using helium on AL reduces the power requirement by about 1/3. I've not tried it using GMAW on AL because I've done very, very little GMAW welding of AL.

In the town that I went to college in there was a boat builder who built Rogue River type AL hulls and they used spool guns exclusively. There is merit to this, the liner in a traditional GMAW system should be changed to an AL exclusive liner when running AL wire. For whatever reason the liners don't seem to last as long with AL running thru them. A spool gun removes all of that from consideration.

 

[jrwdlw]

ntsqd,

The welder doesn't have quite enough power when trying to do 3/16" or 1/4" tabs welded to the frame. There is a setting that allows boosting the start current to 135% of the current setting, but machine doesn't have enough reserve, when you are running 165 amps, and the top end is 200 amps. So, I discovered preheat is the way to go. It also helps when doing "T" welds with the 1/8" wall 2x4 tubing. I'm running straight argon at the moment. The welder is not perfect, but it's light years ahead of a Millermatic 200 MIG with spool gun I tried 30 years ago! The pulse program is the key. The next choice for pulse welding aluminum is a Miller 350P with XR gun, but that is a $7000 solution. For a hack, hobby welder, it was out of the question.

 

[HughDog]

Thanks Gang, this is great information.

 

[ntsqd]

If you have a metronome in your head doing the pulse method manually can be done. The automatic probably has some hidden advantages, like being able to change the high and low dwells for cleansing the weld metal and such, but can simply pulse the trigger for the basic effect. I've been known to do this with the GMAW on ferrous metals and to "saw" the foot pedal on my GTAW when the situation needs it.

 

[HughDog]

Liking the ideas and suggestions.... Probably have about about a month before I pull the trigger, but seems like it's time well spent.

PokyBro's approach on top of the notes between equipment and technique (ntsqd / jrwdlw) might be the ticket.... Hire a Pro-Tig guy to help out on some initial projects, practice a little, then get the equipment.