MIG welding and advice

[DampRobot]

Originally Posted by DonRotolo

Friction stir welding. That's what I want to try. I have my cordless drill....

Handheld friction stir welder... Yeahbuddy!

SpaceX does friction stir welding to make their rocket bodies, it's really a extremely cool process. Worth a google for all those looking at this thread.

On a side note, I've heard the reason that we beat the Russians to the moon was because we had better welders. Ours could figure out how to weld tanks which were good enough to hold liquid hydrogen, whereas the Russians could only make kerosene tanks. We ended up with the slightly smaller and more reliable Saturn V for our moonshot, and they ended up with that massive kerosene powered rocket that looked like a Christmas tree--which turned out to be impossible to control in the sky.

[DonRotolo]

Originally Posted by DampRobot

We ended up with the slightly smaller and more reliable Saturn V for our moonshot...

I have never before seen the words "smaller" and "Saturn V" used in the same sentence. Wow.

[Ian Curtis]

Originally Posted by DampRobot

Handheld friction stir welder... Yeahbuddy!

SpaceX does friction stir welding to make their rocket bodies, it's really a extremely cool process. Worth a google for all those looking at this thread.

On a side note, I've heard the reason that we beat the Russians to the moon was because we had better welders. Ours could figure out how to weld tanks which were good enough to hold liquid hydrogen, whereas the Russians could only make kerosene tanks. We ended up with the slightly smaller and more reliable Saturn V for our moonshot, and they ended up with that massive kerosene powered rocket that looked like a Christmas tree--which turned out to be impossible to control in the sky.

For what it's worth, this is one of those great sounding stories that is almost certainly false. The Soviets never invested in hydrogen rocket engines, despite repeated funding requests from Korolev, who was basically their Von Braun. As such the Soviets were way behind, particularly because the military had been building the engines for the Saturn V long before NASA even planned to go to the moon. The military recognized that the engines are typically the schedule driver on aerospace projects, and figured they could develop vehicles to go with them later. Or another way, they just wanted bigger more expensive toys than the other branch, since the Air Force and the Army both wanted in on the missile game.

The N1 was actually lighter (still weighing several million pounds) and shorter (still nearly 350 feet tall), than the Saturn V, but it had a ridiculous number of rocket engines (43!!) compared to the Saturn V's 11. It also had an additional stage to make up for the performance loss of Kerosene vs. H2.

Taming Liquid Hydrogen is a wonderful book (if you're a huge nerd like me ) that NASA put together that describes the technical and political challenges of designing the Centaur upper stage that is still in use today.

I love Kerosene Christmas Tree... great name!

EDIT: Moral of the story I forgot: Rocket development (and aerospace product development in general) is so complex it rarely gets held up for just one thing.

[EricH]

Originally Posted by DonRotolo

Friction stir welding. That's what I want to try. I have my cordless drill....

Originally Posted by DampRobot

Handheld friction stir welder... Yeahbuddy!

SpaceX does friction stir welding to make their rocket bodies, it's really a extremely cool process.

Handheld stir welder? Try a mill instead, it'll work slightly better. (Trust me on this. I spent a good portion of my work day today on one of the SpaceX stir welders--and that's actually pretty typical for me.)

BTW, friction stir welding is one of the FEW new technologies with almost no practical application to FRC robots. Maybe the sheet metal bots could use it, but even they'd have a hard time. Not saying it isn't cool to watch, though.

[bake]

Wow, A lot of confusion about welding here. MIG (GMAW) and TIG (GTAW) are not related at all except that they use an electric Arc. For your application with your welder a spool gun would probably be the best bet for Aluminum MIG. It is difficult(but not impossible) to push the soft aluminum wire through the liner. Argon is the correct shielding gas. The filler wire will have to match the material being welded. Cleaning is the key to Aluminum. The oxidation that forms on Aluminum has a higher melting point than the Material itself. Wipe parts clean with Acetone. SS wire brush to remove oxidation. MIG Aluminum is difficult but can be done. If you have any specific welding questions I can probably steer you in the right direction.

[MrForbes]

Just to throw a monkey wrench into the whole discussion....in 2011, we built a steel robot chassis. A freshmen borrowed a MIG welder, and did all the welding. If you use thinwall steel tubing, the weight isn't really very much more than using thicker wall aluminum. And MIG welding steel is easy. Even I can do it.

[MrBasse]

Originally Posted by bake

Wow, A lot of confusion about welding here. MIG (GMAW) and TIG (GTAW) are not related at all except that they use an electric Arc.

Not a lot of confusion, just different discussion from different sources. Both use an arc, both use a stable shielding gas (many times the same type of gas too), neither make use of flux due to said shielding gas, and both commonly (MIG always) use a filler material added to the arc to create strength in the weld. The book I used for my welding classes lists TIG as a GMAW process that is also known as GTAW. The more acronyms you throw in the mix the more confusing things get. Tungsten is a metal and that is where the M comes from in GMAW, so I don't feel bad about saying what I said. If the world has changed since then and dropped my views, I'm happy to change my ways.

While this thread has remained educational, it has completely derailed off topic, which is so strange for CD...

That being said, if I was the OP I would make use of that welder and build a steel chassis. Every time we build an aluminum chassis, we swiss cheese the thing for days to make weight. Every time we build with steel we come in comfortably under weight.

[JamesCH95]

Get the PN, call Lincoln, make sure you can use it to weld aluminum before you go through any more hassle. They will also be able to give you PNs for the appropriate equipment you'll need (spool gun, gas controller, wire, etc) Also consider keeping your welding table surface steel, it will be easier to maintain in general.

I think that if you keep your expectations realistic, you'll do fine welding aluminum. However, those realistic expectations may be no welding anything thicker than 0.093in in aluminum.

Having said that... MIG welding aluminum can be tricky. It isn't rocket surgery, but requires careful setup and very clean equipment and material. The setup chart inside the cover is a good start.

http://www.weldingtipsandtricks.com/
^IMO this is the best online resource for welding. Not exactly text book, but Jody REALLY knows his stuff and how to get it done. Pay careful attention to his MIG welding Tip series.

Originally Posted by Justin Shelley

In order to weld Aluminum with a MIG you have to have a TIG gun. As far as getting gas I would contact a welding gas supplier near you and lease the tanks, OzarkGas is who I would contact first. They are extremely reasonable and highly qualified.

I think you mean to say "spool gun" as there is no such thing as a TIG "gun" only TIG torches, at least in general. It may be semantic, but these things matter.

Originally Posted by techhelpbb

If that MIG unit is less than 200A (it says 125 on the front) you'll likely run into some issues with aluminum.
As mentioned you want 100% argon as well.

My Hobart 210MVP has a spool gun but there's limits of what you pull off with low power delivery.

100% Ar is suggested by many, but is not always the best shielding gas. A helium/argon mix is best for welding aluminum (TIG or MIG imo) because helium has much better heat transfer properties. This lets gas-cooled torches run cooler, and transfers more heat to the work. Both of these increase the capabilities of the welder. I like 50/50 mixtures, but even 25% helium makes a big difference. Helium also helps create a more stable MIG arc.

Originally Posted by MrForbes

Just to throw a monkey wrench into the whole discussion....in 2011, we built a steel robot chassis. A freshmen borrowed a MIG welder, and did all the welding. If you use thinwall steel tubing, the weight isn't really very much more than using thicker wall aluminum. And MIG welding steel is easy. Even I can do it.

^ Agree 100%. Thin-walled steel (think 0.035in) can have a comparable weight to aluminum tubing of similar strength. Welding it is a helluva lot easier. Just keep some sharp drill bits (step drills are great for this) around, learn how to use riv-nuts, and don't cheap out on the hacksaw blades (Lennox bi-metal blades are the best IMO).

My qualifications on this topic:

-Formerly ASME & AWS certified TIG welder for alloy steel and aluminum
-2 years of experience developing MIG welding wave-forms (specifically for titanium), researching welding theory as well as experimentation. A lot of this effort's success was a result of understanding and implementing argon-helium mixtures.
-Taught welding for a year in college, also started and ran my colleges welding lab (BTW: I started every student off welding aluminum with 50ar/50he gas, no big deal)

[techhelpbb]

Originally Posted by JamesCH95

100% Ar is suggested by many, but is not always the best shielding gas. A helium/argon mix is best for welding aluminum (TIG or MIG imo) because helium has much better heat transfer properties. This lets gas-cooled torches run cooler, and transfers more heat to the work. Both of these increase the capabilities of the welder. I like 50/50 mixtures, but even 25% helium makes a big difference. Helium also helps create a more stable MIG arc.

Absolutely correct.

However I rarely do that because I have a handy propane torch to preheat if need be and my welder is getting up there in power capability.

So I was curious (it's been a while) I called AWISCO where I buy my gas and they are getting back to me about the cost difference between the custom mix of 25% Helium / 75% Argon (I bought my previous tank elsewhere and apparently this was something unusual for them) and 100% Argon.

Last I looked the cost of the mixed gasses can reach a point where the cost of savings of the machine (though a donate machine can skew this) can make more sense to buy a more powerful welder (because it's cheaper over usage). Course if your usage is really low maybe it doesn't matter.

You can get a welding gas mixer but they are not typically cheap.

[JamesCH95]

Originally Posted by techhelpbb

Absolutely correct.

However I rarely do that because I have a handy propane torch to preheat if need be and my welder is getting up there in power capability.

So I was curious (it's been a while) I called AWISCO where I buy my gas and they are getting back to me about the cost difference between the custom mix of 25% Helium / 75% Argon (I bought my previous tank elsewhere and apparently this was something unusual for them) and 100% Argon.

Last I looked the cost of the mixed gasses can reach a point where the cost of savings of the machine (though a donate machine can skew this) can make more sense to buy a more powerful welder (because it's cheaper over usage). Course if your usage is really low maybe it doesn't matter.

You can get a welding gas mixer but they are not typically cheap.

It's true that helium is pricey, and helium prices have spiked recently. My last price out was (in round numbers) $100 for Ar and around $250 for 50/50 (special order). This was for a 300ft^3 bottle refill. FWIW I have used 50/50 and 100ar with a Lincoln Precision TIG 375, their top-end TIG machine at the time, and much preferred 50/50 for aluminum as compared to 100ar.

At work we use a gas mixer, that was a little over a grand. I'm sure one could make their own crude gas mixer for not huge amount of money though, i.e. just 50/50, not 10/90-90/10 like a high-end mixer.

Looking around on the internet, some people think 50/50 is too much helium and suggest between 25/75 down to 5/95. Last time I checked 50/50, 25/75, and 10/90 are available OTS.