Sand Casting aluminum is very common and is a popular way to break in a new furnace. Casters use sand mixed with a bonding agent to create a mold around the item to be cast. The item, or pattern, is removed very carefully revealing the mold. If there will be any empty spaces in the finished product then a core is added to the mold. The core can be made of sand and is placed so that the molten metal fills the area of the mold around it. So, say you're making a picture frame you will place a cone where the glass will go so the molten aluminum will not fill that area.
Lost Foam Casting
Lost foam casting which is sometimes called evaporative casting. The lost foam casting is a form of sand casting. The entire process is relatively cheap and when used with old soda cans casting aluminum this way is great on the budget. A foam copy of what you want to cast is created and surrounded by a ceramic shell. You will place the copy in loose sand which will help to hold the shape during the pouring process. The molten aluminum is poured into a cup that in inserted into the copy. The foam vaporizes and the aluminum replaces it filling the area in the ceramic shell. Removing the shell will reveal the aluminum casting. This method is great for fine details but the copy is lost to the ages. Luckily, foam is not all that expensive.
Investment Casting is commonly used by jewelers as it allows precise castings with full detail. This form of casting has been around since ancient times under the name of lost wax casting. Investment casting involves creating a wax copy which is then covered in slurry creating a shell, much like the kind of shell in lost foam casting. The molten aluminum replaces the wax which melts out of the shell and can be collected for reuse. Artists and casters that need high precision parts favor this technique.
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