An easy-to-understand guide to different expendable casting methods suitable for 12-year-olds.
Expendable casting is a process used to create metal objects by pouring liquid metal into a mold. The mold is usually made from materials that can't be reused after the metal has cooled and solidified, which is why it's called 'expendable.' Let’s break down the different types of expendable casting methods:
In sand mold casting, sand is mixed with a binding material to form a mold. This mold is created by pressing the sand around a model of the object you want to make. Once the metal is poured in and cools, the sand is broken away to reveal the finished piece.
Shell mold casting uses a shell made of a thin layer of sand and chemical binder. The shell is created around a pattern. After it’s hardened, it is filled with molten metal. This method gives a smoother surface than sand mold casting.
In lost foam casting, a foam model of the object is covered with a coating. When molten metal is poured in, it vaporizes the foam, leaving a cavity for the metal to fill, creating an exact replica of the foam model.
For this method, a model is made, and then plaster is poured around it. After the plaster hardens, the model is removed, creating a mold that is used to pour in the metal.
Similar to lost foam, lost wax casting uses a wax model covered in a ceramic shell. When the metal is poured in, the wax melts away, allowing the metal to take its shape.
This process involves placing the mold in a vacuum chamber to remove air. This helps in getting better detail and reduces the chances of bubbles in the final piece.
Unlike expendable methods, permanent casting uses molds that can be reused. But sometimes, this term is used interchangeably with expendable casting to describe molds that don’t decompose or break apart.
In permanent mold casting, the mold is made of metal, allowing it to be reused many times. This method is often fast and produces high-quality parts.
This technique involves pouring molten metal into a mold, letting it cool just long enough to harden on the surface, and then pouring out the remaining liquid metal, creating a hollow piece.
In pressure casting, the molten metal is forced into the mold under pressure, allowing for better filling of the mold and reducing porosity in the finished product.
Die casting uses high pressure to inject molten metal into hardened steel molds. It’s a fast process and very efficient for producing large quantities of the same item.
Centrifugal casting involves spinning the mold while the molten metal is poured in. The force of the spin helps distribute the metal evenly and reduces defects.
In squeeze casting, the metal is poured into a mold, and then hydraulic pressure is applied. This reduces porosity and improves the density of the final product.
These methods of expendable casting help us create all sorts of metal objects, and understanding them can give you a solid foundation if you're interested in future engineering or design projects!