DIY aluminium casting

fergal.b

Has anyone ever done this before, I got these windshield brackets for my boat and they are not cheep to buy so I would like to try and copy them just incase I build another boat I remember as a young lad making "Prince August" soldiers and a cannon in a rubber mould " I can actually smell it now":D and think this might be a good way to make a mould as it would give a better finish than sand and could be reused.
Any ideas welcome cheers.

CJhaughey

Use casting silicone to make the mould.
Make a wooden box and position the part in the position that you want.
The part has to be supported in a manner that will allow complete submersion in the silicone.
This is probably best done by wires that hang it and also allow the air to vent from the lower parts.
Your biggest problem will be finding good alloy to cast with.
Once you cast the part and the silicone has hardened then you need to cut the silicone around the part so you can remove it. You need a very sharp knife and cut carefully so the join is not too ragged.
Put the rubber back in the box and pour the alloy.
You'll probably find that you need a few goes to get it right.

slimjimmc

Well you'll certainly not be able to use rubber moulds, aluminium has a melting point of 660 degrees celsius. You'll need a suitable heat source and a crucible and tongs.
You'd have to make a mould out of casting sand (a special type of fine sand) and that's a skill in itself. You wont get it right the first time, or the 5th time for that matter.
Once you get an acceptable cast you'll then spend ages grinding and polishing to get any way near that sort of finish in your photo.

In essence unless you're planning on making a lot of these, the time, expense and frustration won't be worth it imo.

Gen.Zhukov

slimjimmc wrote: »

Well you'll certainly not be able to use rubber moulds, aluminium has a melting point of 660 degrees celsius. You'll need a suitable heat source and a crucible and tongs.
You'd have to make a mould out of casting sand (a special type of fine sand) and that's a skill in itself. You wont get it right the first time, or the 5th time for that matter.
Once you get an acceptable cast you'll then spend ages grinding and polishing to get any way near that sort of finish in your photo.

In essence unless you're planning on making a lot of these, the time, expense and frustration won't be worth it imo.

+1

fergal.b

Cheers guys, and here's me after buying 4000 cans of Bulmers to melt down what a waste

jack of all

I have fond memories of Prince August casting myself, but the lead/ tin casting metal is not comparable to aluminium alloy. I did some foundry experience way back in my college days and as the previous poster pointed out it's not really viable for DIY. Making the sand moulds for anything other than simple shapes is tricky enough and the sand casting does leave a rough enough finish (not to mention the flash where the two mould halves meet) so you could expect to spend a lot of time with files and buffing wheel to get anything like the finish you want. I'd imagine those parts are die cast.

fergal.b

Yep I think I will give it a miss, anyway the wife will only let me play with things below 500 degrees till I grow up

deandean

Do you know a metalwork teacher? Some of the schools have casting facilities.

If you can sort out the mould, there are a few companies that do aluminium casting, you could prob bring your moulds along and they'd fill them. There's Douglas foundary in Waterford, there's a place in Enniscorthy doing chairs, etc etc.

Note you'll have a bit of work after casting getting that nice finish.

Are you sure they're aluminium? Many small items like that are case in zinc or pewter or the likes IIRC.

fergal.b

I had a hard enough time trying to clean up these exhaust trumpets so I'd say to clean rough casting I would have to buy some proper polishing equipment.
I guess the brackets are the price they are because of the work involved

jack of all

That looks well Fergalb, can I ask you what you used to clean it up? I've used various methods to clean up cast metal and alloys in the past but I've had great success with Autosol for removing tarnish and polishing.

fergal.b

I got this polishing kit in Halfords. http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_764631_categoryId_165594_langId_-1?cm_sp=Intelligent_Offer-_-Product_Details_Zone_1-_-Blank&iozone=PDPz1

jack of all

That's a handy little kit alright. Cheers.

Mat the trasher

Not to mention that the casted parts would be smaller than the original parts due to thermal expansion/contraction.

bbam

Another problem would be getting a suitable aluminium alloy.. I'd bet that isn't pure aluminium and if you don't match it well it won't have any strength or durability..

aujopimur

There's an unproven link between aluminium smelting and alziemers.

fergal.b

aujopimur wrote: »

There's an unproven link between aluminium smelting and alziemers.

I'd forgotten about that