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Thread: Help needed to cast human skeleton out of aluminum

  1. #1

    Help needed to cast human skeleton out of aluminum

    UPDATE 6/4 : Been a long journey but I think I'm finally heading in the right direction, a lot of my casts are linked on page 19. Here's my favorite so far;

    http://imgur.com/QqaoA7I
    IMG_3815.JPG

    I'll still be here a lot chatting and asking questions. You all are awesome! Thank you!

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    UPDATE 3/26 : Finished building the flask box and painting everything. Updated the build thread and am ready to cast tomorrow. Thank you all!

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    UPDATE 3/11 : Finished building propane burner, forge and crucible tongs. Build here :
    http://www.alloyavenue.com/vb/showth...nd-Tool-Builds

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    UPDATE 3/1 : Wow, sorry for the long delay in posts. I've been super busying finalizing the plan and purchasing materials. Update on page 12.

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    UPDATE 1/29 : Hi everyone. I have learned a ton since this initial post and a lot has changed. As of now, I am planning out the furnace set up and have some tangible calculations on page 7. Thank you all for your support! Let's make something cool!

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    Hello, everyone! I am high school student that is looking to get into metal casting after watching Grant Thompson's series on making a mini-metal forge and casting aluminum poke-balls. My school has mandatory "senior projects" in which students are encouraged to pursue special interests to either learn a new skill or produce something at the end of the year. I've always been interesting in trying metal-casting and after watching Grant's videos, researching other DIY possibilities and reading tons of articles on professional metal casting, I have an idea in mind but have a lot of questions about how I would go about producing my project. I was hoping you all could help!

    My idea right now is to forge a to scale replica of the upper half of a human skeleton in aluminum and then posse it as an art piece. I know it’s ambitious project and after doing research, I need advice to make this project possible to complete in a DIY manor, stay within a reasonable budget and do the project safely. I will list what my current plan is and the questions I need answered. Number one and two are mostly planned out. Question three is my main concern on how to cast these bones.

    Side note : I am using one of the school's plastic skeleton replicas from the bio department on the condition that I make an extra metal skull for the teacher . So I can't destroy the skeleton during the process .

    1. Creating the metal-foundry and tools : as stated before, I plan on following Grant's advice and create a mini-metal forge out of plaster of paris, sand and steel wool along with a top fashioned out of the same materials with steel for handles. Before using the foundry, I know I need to purchase proper safety wear and tools : crucible, tongs, steel spoon for dross, gloves, mask, apron and any others needed (Suggestions greatly welcomed). For a work space, I was going to place a plastic tarp over an area of the yard and cover it with a thick layer of sand. I could also work on asphalt or dirt if those are safer (I've heard that it is a bad idea to work with molten aluminum on concrete). As for a heat source, I was planning on following Grant's advice and using lump charcoal or fashioning a propane torch (Luckily my school has the same tools that Grant uses in his video and I have the support of the shop teacher to create one if I go that direction). I know I will sound naive, but I feel confident about creating the foundry and gathering the tools needed to use it but I greatly welcome advice on this part of the project if something looks wrong.

    The one question I have I have about the forge is the degassing process. After reading about degassing and degassing rods, is it worth purchasing one or creating one myself? Where could I buy a degassing rod?

    2. Finding a source of Aluminum : I know I could go out and purchase aluminum to forge with but I was curious if I could start collecting hundreds of cans over the next few months and then melting down the cans to forge. (My school does these kind of drives all the time so I would just have to state what I am using them for and the collection would be easy) However, I read that the cans are very impure and would take some refining before casting. Is it worth collecting the cans or should I just go out and buy/scavenge for pure aluminum?

    3. Making casts for the bones : this is the part of the project that I feel completely lost on. I know that sand casting would be the simplest form of casting and could be handled by a beginner. However, I feel that it will be impossible to accurately cast a lot of the bones because of their shape : most of the sand casting I've seen requires one side of the object to be flat and the bones will be impossible to remove from the imprint without messing it up (I'm worried especially for the vertebra, ribs, end of bones). Is there a way to use sand casting to cast these bones? I was wondering if there was a way to imprint half the bone in one side of the sand and one side on the other but couldn't find any tutorials or videos on how to go about it. Another method I thought about we be to place a wax duplicate in the sand, dig a trench to the let the wax flow out and pour the aluminum in : my hope is that the wax would melt and flow away leaving the cavity open to be filled with the metal. This was an idea I came up with as a solution but I have no idea if it would actually work. Sand casting would be the cheapest and easiest way to go about casting all of these bones. I'm hoping for solutions in which I could use sand casting to make the bones still.

    The other option I've read about is investment/lost wax casting but see major issues with DIYing this process. After watching Grant's videos, my over-simplified plan goes as followed :
    a. Create silicone molds of the bones and create a wax models of the bones using the molds
    b. Attach two wooden dowels to the wax bone and glue the dowels to the bottom of the mold container and pour mixture over.
    c. Remove the mold from the container, remove the dowels and proceed to melt out the wax and set the mold in an oven.
    d. Pour aluminum, set and remove piece.

    I have a lot of issues with this plan. Firstly, I understand that I would need a vacuum chamber or a vibrating table to drive the bubbles out of both the silicone and plaster solutions to avoid air pockets. Should I purchase one of these tools or build one myself? Some of the bones will be fairly large so I was thinking out using a vibrating table since it would be hard to find a large vacuum chamber. Advice?

    Secondly, I would need an oven to burn out the wax from the mold and set the mold. Is there a way to DIY this process without an oven? Would it be safe to use the ovens in my house? (I have my parents permission to use the ovens) My father also has an old, still functioning propane grill : could I possibly use this to burn out the wax and set my molds? I am really lost on a way to DIY the lost-wax method for these bones but it seems like the best way to cast these bones as the piece would come out extremely detailed. Advice on this issue is greatly needed!

    I know this is going to be costly and difficult process for a beginner. The due date is far out but I knew I needed to start early if I really want to get this project done. I am going to build the foundry in the coming weeks and begin gathering equipment to start practicing casting random things before I get to the real project. I would really appreciate advice on how to cast the bones as that is my main issue right now. I am new to both metal casting and the forum so all advice is welcome. Thank you everyone!
    Last edited by Menth; 06-04-2017 at 04:35 PM.

  2. #2
    Moderator DavidF's Avatar
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    Menth, welcome to the forum. I will respond in detail when i get home, if no one else beats me to it.
    Sand casting will be your best bet for most parts. I would forget about the degasing all together.
    Cans? They will work, but if there is an automotive shop near by you would be better off finding some used heads or intakes or pistons.....
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

  3. #3
    Hi and welcome!
    Pick a simple bone and give it a go!

  4. #4
    Thank you DavidF! I can't wait for full reply.

    I live near by a scrap yard that sorts their metals so I might be able to go over there and find pure enough material. My school is relatively small ~600 students but people occasionally collect empty cans for various projects and get A TON of donations so that's why I thought about using cans, refining the metal and then using it to cast. I was just worried about the quality of the metal.

  5. #5
    Moderator DavidF's Avatar
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    Aluminum cans are actually a pretty pure alloy with just a hint of magnesium and manganese. They are horrible for casting. You want an aluminum alloy like 356.
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

  6. #6
    O. Understood! I'll ask the shop teacher about that since he buys a lot of different metal for the robotics team and might know where to find that alloy. Thank you!

    How should I go about sand casting the bones? Why should I ignore degassing?

    Thank you!

  7. #7
    Moderator DavidF's Avatar
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    You will be coping down to sand cast the bones.
    Since your not casting a strength critical part, and if done incorrectly you degasing could cause more trouble than if you did nothing at all, just take it out of the equation all together.

    Have you put much though into how large a furnace you will need???
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

  8. #8
    Menth; You don't necessarily need A356. That's a high strength alloy used for things like engine blocks, heads, and modern suspension parts. It will work for what you're planning, but any CAST aluminum scrap will do what you need. Computer hard drives, pots/pans, lawnmower engines, etc.

    Roger

  9. #9
    DavidF, Could you explain "coping down"?

    I was going to first do some math to determine how much aluminum I will need for some of the bigger pieces. Then I will find a crucible that is able to hold that much or more aluminium.
    Based on the size of the crucible, I will then create a mini metal foundry large enough to hold it and heat properly.

    - - - Updated - - -

    GTS225, would a scrap yard have those types of parts separated into different piles? Where would be a good source of these materials or a source of aluminum for casting?

  10. #10
    Moderator DavidF's Avatar
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    Quote Originally Posted by GTS225 View Post
    Menth; You don't necessarily need A356. That's a high strength alloy used for things like engine blocks, heads, and modern suspension parts. It will work for what you're planning, but any CAST aluminum scrap will do what you need. Computer hard drives, pots/pans, lawnmower engines, etc.

    Roger
    Key word being "cast". 356 is a general purpose alloy for casting it is very common, inexpensive, easy to cast, low shrink, and not as susceptible to hydrogen as other alloys like 6061. This makes it a perfect alloy for the beginner.
    Sure you can melt most any aluminum and it will work, but I would avoid cans if you can. The produce alot of dross when melting and you may only get back 50% of the weight you put into the melt. To me this is a real waste of fuel and time.
    On the Grant "king of random" Im a subscriber on his channel and find him very entertaining, but alot of what he does should be viewed as exactly that "entertainment". His furnace material choice will not hold up as long you you will need it to. Not to mention the bound moisture in the POP could cause the furnace to have a steam explosion. Metal casting is very addictive. Once you get started in it you will be hooked for life. Construct your furnace to last. A good commercial refractory is highly recommended.
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

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