Bonding aluminum to aluminum - Doable? How?

[Arquibaldo]

Dear expert machinists:

Here is the problem: I have a lot of aluminum extrusions, but they are all a little thin: 1/8".
Now, when I need a thicker piece, I was wondering if I could bond together a few thinner
pieces, with some type of adhesive, and end up with a material "almost as rigid" as
the real thing: say, three 2"x1/8" bars to make a 2"x3/8" bar.

Is this doable? What kind of adhesive would strongly bond aluminun to aluminum?
Epoxi? How to prepare the surfaces and conduct the cure?

Thanks a lot for your suggestions

Nelson

[Kool Parts]

This is a cut and paste of a answer I gave to a similar question a while back.
Gary

I have done some extensive testing with different adhesives and 6061. The best by far is Locktite E-30-CL. Used to be known as Locktite glass bonder.

Its clear and has a 30 min working life. Found this as a tip from a Locktite engineer years ago. He said that it outperformed all of there other products for alum.

I have put this stuff through shear tests you wouldn't believe..That said it might just eat plastic for lunch! But for $8.00 you get a 50ml twin syringe set...so a pretty cheap test. Part #29329
Gary

[RotarySMP]

To bond aluminium you need to get the epoxy to bond to Al, and not to the oxide. You need a method of stripping off the oxide, then keeping it from reacting with oxygen wheil applying the glue.

Is this job structural or just decorative.

[wildwestpat]

Hi Nelson

Forgive me asking but why? The cost of the glue could exceed the cost of some new bar stock. The problem with any laminated material is that the glue lines represent possible fault lines if the part is stressed. The exceptions being where the laminated material is porus as in wood or cloth where the composite laminate can be stronger than the materials used on their own.

If the parts are stressed take into account that the glue used may soften with exposure to water or other solvent - shatter under impact - have a restricted usage temperature range. In other word know the glues limits.

Hope this helps

Pat

[Arquibaldo]

Thanks a lot, fellows - All very good replies.

RotarySMP : unfortunately, it is a structural job.

wildwestpat: yes, I know - adhesives have a lot of restrictions - not to mention temperature;
they are organic compounds, so they give up at 200 to 300 Centigrade max, while most
metals are still holding...

My problem is actually the supplier: The people I buy extrusions from only sell them in whole
pieces, ie: 6 meters minimum. @ around US$12 per kilo, it gets expensive pretty fast for
the thicker stuff... I have to find someone that sells cut pieces...

Thanks again

Nelson

[ger21]

Use this before epoxying.
http://www.westsystem.com/ss/surface-prep

[ckirchen]

Unless my math is out, a 6 meter piece of 2" x 3/8" is going to run you about US$95. If it is a paying job, I don't see how it's worth the hassle to bother with epoxy. Actually, even if it is a non-paying job, I would still use a solid extrusion.

If you can't transport pieces 6 meters long, you could always bring along a hack saw and make 1 or 2 cuts before loading the material into your vehicle.

[wildwestpat]

Hi Nelson

Try ebay or Google for a mail order supplier. Think this is your best bet.

Regards

Pat

[lancut]

Try rivets, in the aircraft industry this is done on structural assemblies that have to stand up to bending and extreme temperature effects. Google for more info...

[307startup]

Yes...it's called welding. Seriously...laminated aluminum extrusions in lieu of using whole material? Sounds dodgy to me. Just make sure you don't try to sell any of that crap to me.

[Arquibaldo]

ger21: Thanks, I'll see if this product is available here.

ckirchen: Unfortunately, it isn't a money-making job - it is a money-wasting job: my poor
attempts at building a tabletop CNC router... Any single expense larger than
20 or 30 dollars is a red flag in front of "the one who must be obeyed".
Besides, there is a problem of availability: Thin extrusions are easy to find,
while anything beyond 1/8" is almost always out-of stock.
As for transporting the extrusions, I've been doing that for years: they cut the
pieces in half for me, and they then fit precisely in my car...

wildwestpat: Yes, ebay... If only I lived in a first-world country...

bronek: Yes, I know - Rivets aren't practical for me, but I would make sure that no piece
would depend only on the adhesive - there would always be a few screws
contributing to keep the laminations together. The adhesive would only be
responsible for additional rigidity.

307startup: Very cute and elegant contribution - don't worry - I won't try to sell this crap
to you or to anyone else - it is crap for strictly private use.

Nelson

[307startup]

Well if that is the case, what would be wrong with offset holes in each layer of extrusion, and plug welding these holes as you stack the layers? This would in effect make your available extrusions all one piece.

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Originally Posted by Arquibaldo ger21: Thanks, I'll see if this product is available here. ckirchen: Unfortunately, it isn't a money-making job - it is a money-wasting job: my poor attempts at building a tabletop CNC router... Any single expense larger than 20 or 30 dollars is a red flag in front of "the one who must be obeyed" As for transporting the extrusions, I've been doing that for years: they cut the pieces in half for me, and they then fit precisely in my car... wildwestpat: Yes, ebay... If only I lived in a first-world country... bronek: Yes, I know - Rivets aren't practical for me, but I would make sure that no piece would depend only on the adhesive - there would always be a few screws contributing to keep the laminations together. The adhesive would only be responsible for additional rigidity. 307startup: Very cute and elegant contribution - don't worry - I won't try to sell this crap to you or to anyone else - it is crap for strictly private use. Nelson