Aluminum Extrusion vs Aluminum Casting

What are the differences between aluminum extrusion vs aluminum casting?

1. Process
2. Suitable Alloys
3. Products
4. Advantages
5. Disadvantages
6. Applications

Aluminum is a great material for various applications and is easy to work within manufacturing. If you’ve decided to make your new product out of aluminum, and are exploring the manufacturing options available to you, you may have heard of two major contenders — extrusion and casting. But what are the differences between aluminum extrusion vs aluminum casting? How do these two work, and what do they mean for your aluminum product?

Process

Extrusion and casting are two fairly straightforward processes. Extrusion entails heated bars of aluminum or aluminum alloys to be forced through a die. This forces the metal into the desired shape. This can then be cut to the appropriate length and put through further processing to create a finished product. Extruded aluminum parts can be made through different extrusion processes: cold extrusion, hot extrusion, micro extrusion, friction extrusion, and more. 

On the other hand, casting uses molten aluminum ingots. This is poured into a die or mold using a piston. Once the mold is full, the aluminum is left to cool and solidify to the mold’s shape. The process involves more steps than extrusion (such as adding alloying elements). Aluminum casting can be done through different methods, such as hot and cold chamber casting, sand casting, die casting, permanent mold casting, and others.

Suitable Alloys

Different aluminum alloys serve different purposes because they have varying mechanical and chemical properties. For example, some are more ductile, while others are more durable. Likewise, different aluminum alloys are more suited to certain processing methods. 

A few aluminum alloys that are suitable for extrusion are:

• 6000 Series Alloys — Most suitable alloys for aluminum extrusion. In particular, 6005 is most popular as it offers higher durability and strength than others in this series. 6063 is also popular for its attractive surface finish.
• 1050 and 3003/3103 Alloys — Non-heat treatable but they have good thermal conductivity, corrosion resistance, and weldability. 
• 5083 Alloy — Better weldability compared to 6000 series alloys. Offers high rust and corrosion resistance against salt. 

Some of the aluminum alloys that are suitable for casting are:

• A380 and A383 Alloys — Lightweight, stable, and strong even at high temperatures. Offers good thermal conductivity and corrosion resistance. 
• A360 Alloy — Offers improved resistance and ductility than the previous. Also suited for complex aluminum parts, though harder to cast. 
• ZA8, ZA12, and ZA27 Alloys — Zinc-aluminum alloys. They vary in melting points but offer better density. ZA8 is better for hot chamber casting while ZA12 is for cold chamber casting.

Products

Aluminum extrusion and aluminum casting also differ in the product’s size, shape, and finish that they can produce. With aluminum extrusion, the sizes of products (or parts) are limited to the billet size used. The shape that it can create is also relatively simpler than cast products, due to the extrusion process. But, extrusion creates a very smooth surface finish and can create consistent products or parts.

With aluminum casting, the size of the products can be as big as you want — its size is dependent on the mold, not on the size of the ingots. Aluminum casting can also create more complex geometries than extruded aluminum. However, casted parts tend to have a rougher finish.

Advantages

There are key advantages to using either process. Extruded aluminum products offer a variety of benefits for manufacturers and clients, such as:

• Lightweight products with high strength-to-weight ratios.
• Affordable and cost-effective manufacturing needs less equipment investment and ongoing operation costs.
• Can conform to tight tolerances.
• Creates a smooth and attractive surface finish.
• Flexible manufacturing operation.
• Suitable for a wide range of products.
• Improved mechanical properties (durability, strength, corrosion resistance, etc).
• Ideal for short production runs.

On the other hand, aluminum casting has ways that it pulls ahead of extrusion. Some of the advantages of aluminum casting are:

• Capable of creating more complex and intricate shapes.
• Has excellent dimensional accuracy with close tolerances being consistently held.
• Allows for complex products with thinner walls to be made.
• Can produce near-net-shape parts.
• Products tend to withstand higher operating temperatures.
• Highly cost-efficient for high-volume runs.

Disadvantages

Though they offer many benefits, each manufacturing process also has its downsides. The disadvantages of aluminum extrusion are:

• Limited to the number or complexity of shapes it can create.
• There are more constraints on assembly methods.
• Tends to require more secondary steps to create a finished aluminum product.
• Additional parts may need to be produced separately
• Requires consistent cross-sections.
• Size is also limited by the size of the aluminum billet.

Likewise, aluminum casting has its share of disadvantages, such as:

• Higher upfront and ongoing costs as it requires more tools and molds.
• Porosity is a common problem with casting — a result of air being trapped in the mold during the injection process.
• Generally not as strong as extruded products.
• Creates a rough surface finish. Seams and other imperfections are more likely with casted products.
• Casting dies and molds are costly to make and do not last as long as extrusion dies.
• Process changes are time-consuming and expensive due to the need for new tooling. 

Applications

Given their advantages and disadvantages, extrusion and casting are suited for different applications. For instance, aluminum extrusion creates strong products and parts. These are suited for high-load applications, such as for automobiles, electronics, telecommunications, and commodity items. Extruded aluminum can also be used in indoor and outdoor applications, such as aluminum windows and furniture.

Aluminum casting can create more complex shapes that offer excellent heat conductivity and corrosion resistance. The most common uses of this process include making components in small appliances and mechanical equipment. Aluminum casting is also essential to making electronic components, such as connectors and housings. It can enhance toughness or flexibility for hand-held tools without adding weight, which is ideal for medical applications.

Key Takeaways

Both aluminum extrusion and aluminum casting are excellent manufacturing methods. Either one of them can create your aluminum products — but the best choice between aluminum extrusion vs aluminum casting depends on the specifics of your product. Each one will give different advantages, properties, and limitations, so choosing the right one is crucial to your product’s value. 

In need of expertly-made aluminum products? AMC Aluminum can help! With years of experience, we can supply you with high-quality products — or help you find the right manufacturing process to meet your project needs. We also offer a wide variety of ready-made aluminum accessories for your convenience. Contact us today to learn more!