MIG Aluminum or buy a TIG?

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Greetings, I have been MIG welding using both fluxcore and gas shielded MIG for about three years off and on. However, I am interested in doing some work with aluminum to fabricate a frame for a camper I am working on designing and building. The camper will be made out of tubing that will be constructed using triangulated space frame/truss based design in order to maximize its strength while minimizing weight so that it can be taken into rough country without coming apart. I have been debating using aluminum for the tubes in the frame and that brings me to the decision to buy either just a spool gun and an Argon Cylinder or go the whole 9 yards with TIG. The caveat here is that I would rather not spend a ton of money if I don't have to because its not like I weld daily for a profession; its just a hobby. I will never be a professional welder as I have computer skills that bring home far more bacon for the family than I could bring home with welding. I suppose I could sell my Lincoln 180HD and buy a thermal arc rig (do they make any that do AC TIG I wonder) but then I will have to learn to TIG weld in all positions and that could be a learning curve. On the other hand if I MIG the aluminum, will that produce good quality joints that I can trust to the multi-thousand dollar camper? I am decent with MIG on steel but never have done it on aluminum and I dont know if I would have to post weld heat treat or something else so I have a learning curve there, just not as steep as the TIG one. I am interested in opinions about what my best option will be.
Reply:Spool gun is bulkier than a TIG torch.  This could be an issue with tubing, depending on  the design.
Reply:There is really no advantage to using aluminum to save weight, unless you plan to have the aluminum heat treated after welding. Aluminum is probably the worst material choice in terms of fatigue strength. DOM or 4130 would probably be more appropriate. I've found that a spool gun requires proper positioning to make good welds and lots of fine tuning to get the desired weld profile. I like my spoolgun for production type repetitive work, because it's so fast, but for one off parts and awkward positions (like going around a 1" round tube) I go for the TIG.Ian TannerKawasaki KX450 and many other fine tools
Reply:Does your model 180HD have the direct connect spool gun ability?If so just buy the spoolgun and a tank of argon and start practicing.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Originally Posted by Broccoli1Does your model 180HD have the direct connect spool gun ability?If so just buy the spoolgun and a tank of argon and start practicing.
Reply:Originally Posted by yorzaxtThe 180HD does indeed have that capability. As for steel Vs aluminum, I still havent decided. If I can use fewer cross members or thinner wall  with steel to get equivalent weight, I will do steel. However, I am targeting the whole frame to be under 500# if possible and 1000# at the very very outside limit.
Reply:Originally Posted by SnuffyWhat kinda camper you tryin to build? Got pics?
Reply:With no prior tig experience you may find out of position tig more of a challenge than a spool gun.REAL TRUCKS DON'T HAVE SPARK PLUGS
Reply:What type of floor and roof construction do you have planned? What will the exterior surfaces be? Aluminum, wood, plastic?Ian TannerKawasaki KX450 and many other fine tools
Reply:Keep in mind that campers are designed to have the roof and walls act as part of the intergral support of the frame structure.   I don't see you took that into consideration.   Same reason stripped dow mobile home and camper trailers make lousy flatbed trailers.   I am wondering why u think u can engineer a better camper than the companies thar build them for a living and have professionally engnieered them for weight to structure ratio?  Aluminum is not a good choice unless it is being professionally engineered.  You are just stabbing in the dark hoping to hit the right combination..    Certainly don't think its gonna save u any weight.Tiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:Mig aluminium is good for somethings but Tig is better for somethings as well, so i guess you need to decide whats best for the job your doing.I did some Aluminium Ramps a few years back with Mig, its quicker than tig and welding 3"x2" box Ramp frame was a damm site quicker with Mig than Tig.Tig is far cleaner and neater than Mig, but if you see my Mig Pictures below you'll see that Mig can also look clean and neatIts upto you to decide whats best for the Job, Mig i would say would be fine for large jobs and Tig for smaller more precise jobs
Reply:Gerry, what wall thickness is that Aluminum in your pics..if you look at most commercially built Aluminum trailers you will see that are done with MIG,  probably a push pull gun setupTiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:Originally Posted by soutthpawGerry, what wall thickness is that Aluminum in your pics..if you look at most commercially built Aluminum trailers you will see that are done with MIG,  probably a push pull gun setup
Reply:Originally Posted by soutthpawKeep in mind that campers are designed to have the roof and walls act as part of the intergral support of the frame structure.   I don't see you took that into consideration.   Same reason stripped dow mobile home and camper trailers make lousy flatbed trailers.   I am wondering why u think u can engineer a better camper than the companies thar build them for a living and have professionally engnieered them for weight to structure ratio?  Aluminum is not a good choice unless it is being professionally engineered.  You are just stabbing in the dark hoping to hit the right combination..    Certainly don't think its gonna save u any weight.
Reply:Originally Posted by yorzaxtCase in point, although it isnt the frame, there is not a single trailer on the market that I know of that has a shelf that will take the weight of 10 soup cans. They all fall through, all are using very thin, almost cardboard, laminate board called luan. Go tour a Fleetwood, then a Heartland then and Arctic Fox, then ... name it. Until you get in the post 200k area, they are all almost exactly the same. Forget about the floorplan and look in the walls if you can (they wont let you probably). Ask for a diagram of stud locations (they wont give it to you) look at all the HEAVY OSB and MDF used in even their "lightweight" trailers.
Reply:Originally Posted by yorzaxtI did take that into consideration. I know through personal experience their lack of durability. This isnt a theory exercise for me. As for why I would be able to do better, I am not convinced the companies do much engineering. They essentially build the same trailer and throw on different paint and decals. I have toured several factories and its always the same. There is essentially no innovation going on. There is not a hell of a lot of difference between construction of a Fleetwood and Northtrail trailer, no matter what the marketing material states. Furthermore, neither one will hold up much under anything by smooth pavement conditions. Since most of their customers only do smooth pavement, they get away with it. Case in point, although it isnt the frame, there is not a single trailer on the market that I know of that has a shelf that will take the weight of 10 soup cans. They all fall through, all are using very thin, almost cardboard, laminate board called luan. Go tour a Fleetwood, then a Heartland then and Arctic Fox, then ... name it. Until you get in the post 200k area, they are all almost exactly the same. Forget about the floorplan and look in the walls if you can (they wont let you probably). Ask for a diagram of stud locations (they wont give it to you) look at all the HEAVY OSB and MDF used in even their "lightweight" trailers. They even use the same furniture, fabrics, wallpaper and so on. There is almost no difference. And each trailer is roughly a facsimile of the one before it. They dont want you to mod it, they dont even want you to repair your own window. First mod you make voids all waranties. In short, construction of most campers and trailers is utter crap. That is why airstream attracts customers with the money to spend 60k on a short 12 foot, 2 man camper. Because that airstream will still be running in 60 years because it isnt built like the other Indiana based line companies. Ok, I warned it would be a rant.
Reply:Gerry, nice beads. I'd wondered if you were using pulse on that..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Originally Posted by Gerry1964Not sure of the Gauge, but metric i would guess its about 3mm about 1/4" or just underHelps as well if you have a Pulse set
Reply:Originally Posted by soutthpawPulse explains the appearance of those beads too heh!
Reply:Originally Posted by DSWGerry, nice beads. I'd wondered if you were using pulse on that.
Reply:Your little 180 HD will not do pulse. If you try to do a series of spot or tacks like I believe you are describing, you will not get sound welds. The starts on mig are almost always cold. This is especially true with alum mig. A continuous series of "tacks" with alum mig will not have the strength you are looking for for your project.Shovelon has recently done some good descriptions about the issues with run in on mig alum at the start and how better machines can be adjusted to change the wire speed at the start to help with some of these issues. Originally Posted by shovelonAW, I just looked at Miller's website and may indeed be available now that Fabtech has released it's new products. It looks like my 350P but optimized for alum. And yes it will still be up there in price. Usually my LWS discounts to get close to online pricing.The thing you want know about the 350P is that it has "hot start" and "slow run-in" control for starting your arc, Then the current and wire speed fall to correct weld settings for a decent bead. Standard migs tend to crash the wire into the metal before a nice hot start can be intiatited. So if you tune for start, the weld is crap. If you tune for weld, the start is crap.  I have been dicking with alum mig since 1983, and never liked it until I got my CobraMig with "PosaStart" run-in control. That made it all worth while. That 350P-Aluminum might have to be mine soon.
Reply:Hmm that was what I was afraid of. I am afraid that the rigs that will do pulse are far out of my price range. I might be able to swing a 1k (neighborhood) machine if I can sell my 180HD. But a 2k rig just aint gonna happen. The only thing is that I still dont have resolution to my problem, LOL. I dont know whether to use Aluminum or Steel, I dont know what size and I dont know what welding method if I go with aluminum. In short I just dont know.  Oh I did find a post with an avion (an old 1960s era camper) gutted. Interestingly enough it uses bent 1.5" C channel for ribs and then skin over the whole thing, very much airplane style. Except apparently its all riveted.The quest goes on.
Reply:Why don't you just buy some 1 inch square thin wall tube and use your mig welder,  Its light enough, and stronger than aluminium plus you won't have the expense of buy a tig set or Pulse welder
Reply:Originally Posted by Gerry1964Why don't you just buy some 1 inch square thin wall tube and use your mig welder,  Its light enough, and stronger than aluminium plus you won't have the expense of buy a tig set or Pulse welder
Reply:Originally Posted by yorzaxtI thought about square tube but my research indicates round is actually stronger for its weight.There is definitely a lot of information to go on in this thread. Thanks.
Reply:Originally Posted by Gerry1964Not sure of the Gauge, but metric i would guess its about 3mm about 1/4" or just underHelps as well if you have a Pulse set
Reply:Originally Posted by Gerry1964Mig aluminium is good for somethings but Tig is better for somethings as well, so i guess you need to decide whats best for the job your doing.I did some Aluminium Ramps a few years back with Mig, its quicker than tig and welding 3"x2" box Ramp frame was a damm site quicker with Mig than Tig.Tig is far cleaner and neater than Mig, but if you see my Mig Pictures below you'll see that Mig can also look clean and neatIts upto you to decide whats best for the Job, Mig i would say would be fine for large jobs and Tig for smaller more precise jobs
Reply:Im guessing u will be using thin wall tube. With a spool gun you have to move fast and with something like 1 inch tube you might either have cold spots or burn through. Sounds like a reason to buy a tig. I would keep.the mig. Last year i bought a nice tig inverter but still use my mig a lot.Hobart Handler 210 with SpoolgunHypertherm PM30 PlasmaHTP 221 Tig WelderHF BandsawHF Auto Dark Helmet