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  1. #1
    Join Date
    Feb 2008
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    Australia
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    146

    Default Melting aluminium

    Hi, I was looking to get a bed made out of aluminium, I would expect ~ 50kg of aluminium there.

    Where would I go to find a foundry who will melt my scrap aluminium I have about 15KG now (offcuts from some little projects I have been doing) but I will go hunting for more soon (buying billets would be a huge waste of money)

    Also how does aluminium machine if I wanted to face the bed?

    Its a new thought on how to make a small cnc router as the chinese seem to do this alot but with steel.


    Or does anyone in NSW have a big furnace


    I have found a few companies I will call tommorow but just wondering if someone can recomend a smaller business who will not charge through the roof to melt the alu.

    What price should I expect from the larger companies? $500, $1000?

  2. #2
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    near Rockhampton
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    Default

    Foundries do not melt metal you supply (AFAIK)...You give them the pattern and you tell them what you want and they supply you with the finished article..

    With foundry work you need special fluxes and other stuff to get good clean metal...

  3. #3
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    Feb 2003
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    formerly from Sydney (north of The Harbour), NSW, Oz
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    Default

    my take is that supplying and melting the Al is a small cost compared to the cost of preparing the pattern and then the mold

    You might be able to get a partial credit for your scrap Al if you toss it into foundary's scrap bin

    Lastly, others will know more, but compared to steel does Al have the properties — stiffness, heat capacity, etc — needed in a lathe bed?
    regards from Canmore

    ian

  4. #4
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    Feb 2007
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    Katherine ,Northern Territory
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    736

    Default

    Lathe bed ? I though he was talking about a bed to sleep on .
    Glad I didn't jump in and make a fool of myself

    Kev.
    "Outside of a dog a book is man's best friend ,inside a dog it's too dark to read"
    Groucho Marx

  5. #5
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    Feb 2008
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    Australia
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    Default

    Quote Originally Posted by ian View Post
    my take is that supplying and melting the Al is a small cost compared to the cost of preparing the pattern and then the mold

    You might be able to get a partial credit for your scrap Al if you toss it into foundary's scrap bin

    Lastly, others will know more, but compared to steel does Al have the properties — stiffness, heat capacity, etc — needed in a lathe bed?

    na router bed, I will design a example and post some pictures.

    added pics of a quick mockup.


    Now that I think about it I think it would be closer to 100KG

    Mockup is max 1050x850x120 so its massive.

  6. #6
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    Aug 2008
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    Charlestown NSW
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    Default

    Mate
    For that size I reckon you would be better off watching the auctions and /or scrap yards for a 2nd hand cast iron marking out table or even an old worn out radial arm drill. strip the drill down and salvage the base. I know you are probably looking for lightness but I reckon a one off in that size would cost a bit to get cast and then you would have the cost to machine it as well. Something that size is not what your average home shop machinist has the machine capacity to handle.
    Something else might be worth thinking about, though it would be pricey as well, is trying to buy part of a billet of alloy. There is a smelter near where I live and I quite often see billets on trucks. they look about 200mm thick X about 1000mm wide X 2 or 3 metres long. If you could find out who buys them maybe you could buy part of one and machine it. Either way its going to be an expensive exersize.

    bollie7

  7. #7
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    Apr 2009
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    Hunter Valley
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    Ch4iS,

    Based on my experience in the Aluminium industry......
    It is most unlikely that anyone will cast the bed you designed up.
    For the likes of Alcoa and Alcan, when these smelters do their casting of ingots, they normally cast 10 tonne ingots at a time.
    However, Alcoa (Victoria) do cast small (approx. 250kg) sough ingots.
    Alcoa has a plant at Yennora (they recycle aluminium there), that would be your best bet in NSW.
    You may be able to find some smaller companies that do their own in-house castings, but majority still source their aluminium from either Alcoa or Alcan.
    You would be better maching one of those, not casting.

    For a casting, you will need to consider the following options.......
    The casting would be a typical "sand box" casting.
    (Don't go for "lost foam" casting, costs more than sand box)
    You will need a professional designer to desin the cast model....$1k (min. thats what I do)
    Pattern made for the casting....$1k (min)
    No engineering business will be able to use your 3d model either, CAD software is far more complex than Google SketchUp.
    You are looking at quite a expensive and complex process, thats why eveyone gets thsi done in China.
    Hope this helps
    Glenn

  8. #8
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    Apr 2008
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    Canberra
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    Default

    Try google, there are a number of small companies that cast small run specialist parts out of aluminium in Australia. I have no idea what they charge or whether they will do your job, but when I was researching my DIY home foundry I stumbled accross a number of these sites. One of them had pics up of some castings they did and they were magnificent.

  9. #9
    Join Date
    Oct 2006
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    Tallahassee FL USA
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    Default

    Quote Originally Posted by Ch4iS View Post
    na router bed, I will design a example and post some pictures.

    added pics of a quick mockup.


    Now that I think about it I think it would be closer to 100KG

    Mockup is max 1050x850x120 so its massive.
    Rule of thumb: For equivalent stiffness of flat bars, aluminium should be about 1.5 times the thickness of steel, width held constant. Slightly more complicated for other shapes.

    The shape depicted can have stiffer torsional resistance, with the ribs oriented diagonally each way, instead of rectangular. Refer to Blodgett's book on welded structures.

    Cheers,
    Joe
    Of course truth is stranger than fiction.
    Fiction has to make sense. - Mark Twain

  10. #10
    Join Date
    Apr 2002
    Location
    Brisbane
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    Default

    A mate of mine used to cast ram tubes and manafolds in his back yard, and thera re plenty like him... BUT.... a 50Kg lump... thats a bit of an ask for most back yard set ups......you need a lot of heat to deal with that amount of ally..........


    cheers
    Any thing with sharp teeth eats meat.
    Most powertools have sharp teeth.
    People are made of meat.
    Abrasives can be just as dangerous as a blade.....and 10 times more painfull.

  11. #11
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    Ideal pouring temp for aluminum is 750-800 degrees.
    Also, aluminium does not change colour at any temp either.
    You must also remember, get any water trapped by pouring and you create a hydrogen bomb....
    ie; sand must be dry.

  12. #12
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    Canberra
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    Hydrogen Bomb? Not really. All green sand mixtures used for casting contain a certain amount of water in them, the sand will have no strength if it doesnt. If you have too much water, you get excess steam which can bubble through the molten aluminium, potentially spitting it around the place, but you will never get a hydrogen explosion.

    Of course if you use oil bonded sands like petro bond you dont have to worry about this.

  13. #13
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    19brendan81,

    I have seen this first hand, the water is trapped in the casting and cannot escape.
    In the dropcast method, water does not "bubble" and does not escape.
    The water content becomes steam before the molten metal even touches the water.
    The water becomes superheated steam, and it then expands immensly.
    A small explosion occurs, which is exactly the same principle of a hydrogen bomb.
    This is why casting aluminium is very dangerous process.

  14. #14
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    Canberra
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    800 degrees in nowhere near hot enough to make water seperate into hydrogen and cause an explosion. What you are describing is the result of poor venting in a mold that has been too tightly packed causing steam to blow through the molten aluminium, as I described earlier.

    All metalworking processes have their own risks, most of which can be mitigated. In this instance, if people are worried about foundry explosions, use $90 a bucket petrobond sand instead of green sand...no water, hence no steam or explosions of any kind.

    P.S for the record, a hydrogen bomb uses a regular nuclear bomb to compress and initiate fusion in a secondary nuclear bomb, releasing prodigal amounts of energy in the process. This has not, and never will occur in any foundry work of any kind.

  15. #15
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    Jun 2008
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    Victoria, Australia
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    Default

    Interesting project, it might be overreaching a bit for a backyard furnace, but lets crunch the numbers and see what would be needed...

    1. 1050 x 850 x 50 would be 44.6 liters volume of Aluminium.
    2. The density of Aluminium is 2700 Kg per m3. (2.7 kg per liter)
    3. So a guess at the weight would be 44.6 * 2.7 = 120 Kg
    4. Allowing for slag and degassing etc, you would want at least 50-60 liter capacity crucible, a little bigger is always better.

    5. The weight of the crucible plus the 120Kg of aluminium is going to be of the order of 200Kg (just a guess)

    6. 200 Kg will need some mechanical lifting and pouring mechanism, remembering that this is stuff at 700 degrees plus.
    This is going to require OH&S considerations to be taken seriously

    7. The amount of heating required, is doable with an air forced propane burner and good insulation.

    Ok, suppose, we now have 50 liters of molten aluminium and the means to safely handle and pour it.

    8. We need to prepare and pack a sand mold that is bigger than 1m x 1m, and make sure we can pour it without too many defects.
    This is going to depend on the design of the pattern and making sure we have correct venting, gating and so on..

    9. The chances of success in getting a good casting is dependant on how much experience you have in the design and implementation of the casting process.

    Conclusions.
    This is not a job for the backyard. The amount of material is beyond what is reasonable for a backyard caster could handle safely.
    The design of the pattern and casting strategy requires someone with experience to provide input to the design.


    I would try to find a smallish firm that will do it on the basis that you make the pattern, to their design parameters.

    Scrap Aluminium, sell it as scrap and buy ingots of a known alloy composition if it's a critical component.
    I have been buying 6kg ingots of DA601 for $3.50/Kg.
    I'm not adverse to melting down whatever is to hand, but when you want a known alloy it's cheaper and quicker to buy ingots.

    Regards
    Ray

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