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bonding aluminum - permabond?

Posted by bbcbggr54 
bonding aluminum - permabond?
May 19, 2018 10:42PM
i am bulding large core xy and want to make some pieces out of aluminum but would need to weld pieces to make a part {plates to tubes etc.}. i dont want to weld them as i dont use gas with my welder, dont have a spool gun, and dont want warpidge. therefore i must braze but that is allowing for warp. so glue together with permabond, or an epoxy. maybe what bodyshops use. any advice on if any type of bonding agent would be strong enough would be greatly appreciated.
Re: bonding aluminum - permabond?
May 20, 2018 01:35AM
Glues are nowadays used in aircraft manufacture to permanently bond aluminium parts together. Sorry, I don't know exactly what is actually used. But in general terms the big issue with glueing aluminium is the thin surface layer of oxide that forms very quickly... you don't want the glue to adhere to the oxide which then lets go of the metal. If I was going to glue aluminium, I'd roughen the surface with Scotchbrite or similar (not steel wool, which leaves small iron particles that can start corrosion) to give a mechanical grip, then clean the surfaces with acetone or similar, then immediately glue together with some kind of high-strength epoxy. Maybe apply an alodine coating or acid etch before glueing.

Another possibility is to use mechanical fasteners (e.g. rivets, screws) to attach parts; again, this is standard practice in aircraft manufacture. The trick here is to ensure that the fasteners are stressed in shear rather than tension.

As for "strong enough"... it's not possible to give advice unless you quantify that. smiling smiley
Re: bonding aluminum - permabond?
May 20, 2018 02:46AM
The oxide layer of aluminum has better mechanical strength than pure alu. I wouldn't be too concerned to glue it directly.
AFAIk the aircraft industry uses CA-based glue ( superglue )
VDX
Re: bonding aluminum - permabond?
May 20, 2018 04:48AM
... you can mix some fine aluminium powder into the epoxy or CA-glue, so it would be slightly better in terms of thermal expansion and prevent thermostress-cracks winking smiley


Viktor
--------
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Call for the project "garbage-free seas" - [reprap.org]
Re: bonding aluminum - permabond?
May 20, 2018 08:58PM
I use JB Weld (kwik weld-5 min.) for aluminum all the time.
Just scuff sand both surfaces with ~80 grit, wash the debris off with dishsoap and rinse in hot water.
When dry, epoxy and clamp.

As for how much heat it can take: I have angle brackets glued to my hot plate in place of clips to keep the print surface in place.
I've printed to 160C bed temp, and they've been stuck tight for over a year now.

If you have clearance, let the epoxy set then drill and tap a bolt through once the parts are bonded together...no way that will shear.
Re: bonding aluminum - permabond?
May 20, 2018 10:09PM
sounds like noone seems it to be an issue. i understand how to clean prep material, i will definetly use something like an epoxy over superglue as i need some body to the glue. i will be using it to glue together XY carriages and bracing for tubes etc. so it does need to hold and be rigid.
VDX
Re: bonding aluminum - permabond?
May 21, 2018 02:44AM
... I've had to refix the sensor on/into an experimental hotend (where it's only clamped on the ouside, not inserted into a bore), which is regularly heated to around 300degC and the normal cement thermoglue failed several times for brittleness and thermal stress eye rolling smiley

Then mixed a 2K epoxy with gray iron dust and it's running pretty fine 'til now winking smiley


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
Re: bonding aluminum - permabond?
May 22, 2018 08:21AM
When I built my CF bike and mounted aluminum drop-outs for the wheels, I pretreated the aluminum with chromic acid- that's the recommended procedure when epoxying to aluminum (at least by West System epoxy). The dropouts have been on the bike for 10 years.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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