There is some important information you need to learn about aluminum casting. Here, we are going to discuss what aluminum casting is, the benefits of aluminum casting, the different types of aluminum casting processes, and much more.

What is Aluminum Casting?

Aluminum casting refers to the technique for creating high-quality and high-tolerance components. First, a highly precise mold or die is created, then molten aluminum is poured into it. It is considered a very efficient process, especially when creating intricate, complicated, and extremely detailed components that should accurately match the original design.

What is Reusable Aluminum Mold Casting?

Reusable Aluminum Mold Casting is a particular technique for casting aluminum wherein the molten aluminum is poured into a steel mold. It is important that the mold be precisely designed and created to guarantee that the outcome has a smooth surface and can satisfy the dimensional tolerances. Whether it is a permanent or a reusable mold, they are usually created from metal, typically made of steel since they have a higher melting point compared to aluminum.

Permanent or reusable molds are usually used when producing high-volume parts. They are economical since they can be reused multiple times. Parts with complicated shapes along with complex designs can be created with fewer labor costs.

The finished products have highly accurate dimensions. Additionally, there is only minimal waste when permanent molds are used for the casting process. As a result, manufacturers and their clients can enjoy significant cost savings. However, creating and tooling these permanent reusable metal molds is a highly labor-intensive process.

Permanent Mold Casting

When it comes to aluminum permanent mold casting, much of the expense can be attributed to the machining and shaping of the die or mold. Typically, this is created from steel or gray iron.

Depending on the design of the part, the mold is commonly formed into a geometric shape. Then the shape and specifications of the part will be divided into two particular halves. During the injection process, it is essential to ensure that the two halves of the mold are tightly sealed.

This can guarantee that there won’t be any air or contaminants within. Before the molten aluminum is poured into the mold, the mold should be heated first. Aside from pouring, the molten aluminum can also be injected or ladled into the mold.

Once the process has been completed, the mold will be left to cool down. This will give time for the aluminum part to harden. After it has cooled down, the part should be removed from the mold right away so that any formation of defects won’t occur. It might seem that this is a simple and easy process; however, take note that this is a technically and scientifically engineered technique for creating high-volume components.

Die Casting

Die casting is a specific method wherein pressure is applied to put the molten aluminum into the mold. At the end of the process, you can be assured that the components produced are highly accurate, hence minimal machining or finishing is required.

Keep in mind that the die casting process is quick, making it perfect for producing high-volume parts. There are two types of die casting processes – hot and cold. The only difference between these two is the way the molten metal is poured into the mold. In hot die casting, the hot chamber must have a connection with the melting pot.

A plunger is used to force the molten metal into the mold through the gooseneck. In cold die casting, there is no connection between the die casting system and the melting pot. Additionally, a ladle is used to pour the molten metal into the cold chamber, and a plunger is used to force it inside the mold.

Vacuum Die Casting

Vacuum die casting uses an airtight bell housing with a vacuum outlet at the upper portion and a sprue opening at the bottom. First, the sprue is submerged underneath the surface of the molten aluminum. A vacuum is created in the receiver, resulting in a pressure differential between the molten aluminum and the die cavity.

Due to this pressure differential, the molten aluminum flows into the sprue, then into the die cavity, where it solidifies. The die is then removed from the receiver, opened, and the component ejected.

Managing the pressure differential and vacuum between the molten aluminum and the die cavity is essential to control the required fill rate of the part and gating. Controlling the fill rate improves the capability of ensuring the integrity of the finished product.

Submerging the sprue underneath the surface of the molten aluminum ensures that the molten aluminum does not include oxides and dross, resulting in the purest alloy. As a result, clean and sound parts can be produced with fewer foreign materials.

Investment Casting

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Otherwise known as lost wax casting, the investment casting process starts by injecting wax into the die to create the pattern of the finished part. The waxed patterns are attached to a sprue, resulting in a tree-like configuration. As the tree is submerged into a slurry a couple of times, a tough ceramic shell will be formed around the wax shape.

When the ceramic has solidified, it will be placed in an autoclave where it will be heated to accomplish the dewax burnout. Additionally, the shell should be preheated before it is filled with molten aluminum so that the desirable temperature can be obtained.

The molten aluminum will pass through several runners and gates once it is poured into the sprue. Once the parts have solidified, the ceramic will be broken down, and the connected parts will be removed from the tree.

Lost Foam Casting

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Another type of investment casting is the lost foam casting process. In this method, rather than using wax, polystyrene foam is used. Polystyrene is used to mold the pattern in a cluster assembly, similar to the sprues and runners of investment casting.

The aluminum molds are heated at low pressure, then polystyrene beads are poured into it. The steam helps in expanding the polystyrene so that the cavities are filled up.

The pattern is then placed in tightly packed dry sand. Any air pockets or voids can be eliminated as it is vibration compacted. While the molten aluminum is injected into the sand mold, the foam starts to burn off, resulting in the formation of the casting.

What is an Expendable Aluminum Mold Casting?

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In this casting process, the mold will be destroyed once the cast part has been removed, hence it is not permanent. Expendable aluminum casting includes sand casting, lost wax casting, investment casting, and lost foam casting.

When expendable molds are used for casting aluminum parts, the mold will be broken down from the solidified metal. This method can be applicable to a wide variety of metals and is also cost-effective. This is because creating expendable molds only requires less expensive materials.

Compared to producing permanent reusable molds, tooling is not required. The drawback of this process is that it lacks precision and accuracy which can be achieved through permanent molds.

Sand Casting

In this method, the reusable pattern that contains the configuration, details, and shape of the part will be packed with sand. Risers will be included in the pattern, allowing the molten metal to be injected into the mold. Additionally, hot aluminum will feed the casting while the part is solidified, preventing any shrinkage porosity.

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