There are many processes that are used to shape aluminum. Four of these are rolling, extrusion, forging, and casting. Forging and extrusion are explained here. Look here for information on rolling. All of these are important, but casting is, by far, the most versatile method of all. In fact, casting is used widely in a variety of applications. Here, we’ll take a look at the different methods of casting aluminum, including the pros and cons of each.
Molds Used in Aluminum Casting
There are two types of molds used in casting aluminum. The first is a permanent mold. This is made from metal, and may be reused. The other uses sand to form a temporary mold.
What Are The Casting Techniques Used For Aluminum?
There are other casting techniques that can be used for aluminum. However, these are the most popular:
· Die Casting
· Permanent Mold Casting
· Greensand Casting
Die Casting Aluminum
The die casting process involves the use of a permanent mold. Here, molten aluminum is injected into the mold, frequently at high pressure. The result is that the end product has better detail, and a cleaner surface finish. Unfortunately, die castings may not be as durable because this process can leave pockets of air. Die casting is frequently used when a job requires mass production of smaller parts. However, it is difficult to manufacture complex parts using this method.
Advantages of Die Casting
· The dies used for casting are frequently made from high-grade steel, and quite durable.
· This method can be used to create parts with a better finish, and more detail.
Disadvantages
· Limited capacity for complexity, especially when parts are hollow.
· High costs up front.
· Air pockets and pores can impact product integrity.
Permanent Mold Casting
In permanent mold casting, a reusable mold is created using metal that has a high melting point. When the cast material is aluminum, the mold is often steel or gray iron. With this method, the two halves of the mold are attached. The mold is then pre-heated. The caster pours the molten aluminum into the mold with a ladle. The product is left to rest until it sets enough to remove the casting. After that, the casting is allowed to cool. If it isn’t taken out at that point, defects could be introduced as the cast aluminum contracts during cooling.
Advantages of Permanent Mold Casting
· The molds are reusable which reduces the overall cost of tooling.
· Casting can be repeated immediately after the prior object is removed, and allowed to cool.
· If the mold is machined properly, the dimensions of the product can be nearly perfect.
Disadvantages
· Molds lack flexibility, so parts can be damaged if the castings are not removed quickly.
· Tooling a permanent mold is more expensive than creating one from sand.
· Permanent molds will break eventually, potentially creating a delay during long runs.
Greensand Casting
Here, a temporary mold is made by packing moist sand around a pattern. This forms the mold cavity. Each mold cavity is 1/2 of the completed mold. When the two pieces are put together, molten metal is poured into the cavity. The liquid metal is kept in place until it solidifies. Then, the mold is broken away. A grinder or sander is then used to smooth away any unnecessary characteristics. The sand can be reused in many cases. This leads to lowered costs for the aluminum foundry.
Advantages of Greensand Casting
· An extremely versatile method that can be used to create an array of parts.
· Cost of materials and tooling is low.
Disadvantages
· Lower dimensional accuracy compared to other casting methods.
· Rougher surface finish
Final Thoughts
It’s clear that each method has its benefits and drawbacks. Because of this, it’s important to know what your expectations are for the final product, how many parts you have to produce, the removal of those parts, even how long the mold needs to last. Once you answer these questions, you can make an educated choice as to whether sand casting or die casting is best.
