Aluminum is the most common alloy used in metal casting. There are several reasons for this, but the main one seems to be availability and quality. Many metal casters have access to a large amount of aluminum with soda and beer cans that they crush and melt down. Aluminum has several desirable properties for the metal caster no matter if they are a hobbyist, artist, or are casting needed parts for home repairs. Many who cast aluminum also love the alloy since it can be used in all of the varying casting processes giving it a wide range of possibilities. Aluminum is often used as a practice alloy for the first time metal caster or for casters who are trying out new methods and ideas.
Many of the small home furnaces that are found in most hobbyists’ foundries will be able to easily melt aluminum. It may even be possible to use charcoal though many just use propane since they have it on hand for other alloys. For your first run at casting, charcoal should be fine.
If you do choose to use soda cans for your source of aluminum you are going to need a fair amount depending on the size of the item to be cast. Make sure to crush the cans as much as possible before placing in the crucible or other area that will be used to melt the alloy.
Since any metal casting process can be used with aluminum the choice will rest with you. There are three casting methods out of the numerous methods available for aluminum that seems to be preferred by small time metal casters. These methods are sand casting, lost foam casting, and investment casting.
Remember, though, aluminum can be used with any metal casting process so do not be afraid to experiment.
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.
Many choose not to use sand casting since it does not allow for fine detail whereas other casting does, but it is inexpensive.
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.
Given the number of options that aluminum presents to the caster finding the right casting method will involve some time. To help decide which aluminium casting process is best consider factors like quality and cost.
Many metal casters use aluminum far more then they use other alloys like brass sand casting, bronze sand casting, or iron sand casting