A Complete Guide to Aluminum Extrusion

The History of Aluminum Extrusion

In 1797, Joseph Bramah got a patent for the first extrusion process to make a pipe out of soft metals. The process required preheating the metal and then driving it through a die using a hand-driven plunger.  In 1820, Thomas Burr used a hydraulic press to implement that process for the lead pipe. Back then, the process was known as “squirting”. In 1894, Alexander Dick added copper and brass alloys to the extrusion process.

By 1904, the first aluminum extrusion press was in operation. Aluminum was immediately used in the automobile and construction industries. Extruded aluminum was in high demand, particularly during the two world wars. The process extended into the expanding residential housing market after World War II.

Extruded aluminum has grown in use since then and is now a part of nearly every area of life. The material has altered how we live, from subway cars to our cars, from building to medical devices.

How does Aluminum Extrusion Work?

You may still be curious about the way aluminum extrusion works. Here is a step-by-step breakdown of the aluminum extrusion process:

Step 1: Prepare the Extrusion Die and Load It into Extrusion Press

The first step is to machine a round-shaped die. Or you can use one that is already available. Preheat the die to 450-500 ℃ before beginning the extrusion operation. This maintains even metal flow and extends the life of the die. Following the preheating procedure, the die may be loaded into the extrusion press.

Step 2: Preheat Aluminum Billet before Extrusion

Next, you can cut the billet, a solid cylindrical block of aluminum alloy, from a long log of alloy material. Then the billet is preheated in an oven to 400-500 ℃. This process makes the billet malleable enough for the extrusion operation and prevents it from becoming molten.

Step 3: Move the Billet to the Extrusion Press

After preheating the billet, move it mechanically into the press. However, you must apply lubrication before loading the billet into the extrusion press. Additionally, remember to apply the releasing agent to the extrusion ram. This process will prevent the ram and billet from sticking together.

Step 4: Push Billet Material into the Extrusion Press Container

The malleable billet is already in the extrusion press at this point. Here, the hydraulic ram can apply around 15,000 tons of pressure. The pressure of the ram pushes the billet material into the extrusion press container. The aluminum material then expands to fill the walls of the container.

Step 5: Press Up the Material Against the Extrusion Die

The aluminum material fills the container’s wall and is pressed against the extrusion die. Because continual pressure is applied on the material, its sole path is through the openings in the die. Therefore, the material emerges from the die’s opening in a completely formed shape.

Step 6: Quench the Extrusion

After the extrusion emerges, it is gripped by a puller. Here the puller moves the extrusion along the runout table at the same pace as its exit from the press. A fan or water bath cools the profile evenly as it moves along the table. This is known as “quenching.”

Step 7: Shear the Extrusions to the Table Length

Shear the extrusion using a hot saw as soon as it reaches the entire table length. Temperature is critical at every step of the extrusion process. Despite being quenched after exiting the press, the extrusion is not yet completely cooled.

Step 8: Cool Extrusions to Room Temperature

When the shearing operation is completed, the table-length extrusions are transferred from the runout table to a cooling table. The profiles remain there until they reach room temperature. Stretching should be operated as profiles reach room temperature.

Step 9: Move Extrusions to the Stretcher and Stretch Them into Alignment

You will observe some natural twisting in the profiles, which must be corrected. It would help if you moved extrusions to the stretcher to perform this correction. Grip each profile mechanically on both ends and pull them until they are straight and meet the specification.

Step 10: Move Extrusions to the Finish Saw and Cut Them to Length

When the table-length extrusions are straight and fully work-hardened, they may be transferred to a saw table. You can cut them into lengths ranging from 8 to 21 feet. After the sawing process is completed, you may place the extrusions in an oven for aging to the proper temperature (T5 or T6).

Step 11: Carry Out Secondary Operations (Heat treatment, Fabrication, and Surface Finishing)

After the extrusion is completed, profiles can be heat-treated to improve their properties like tensile strength and yield stress. Then, following heat treatment, adding different surface finishes to the profiles can improve their look and corrosion resistance. In addition, they may go through fabrication processes to get their ultimate dimensions.

The Common Types of Aluminum Extrusion

Aluminum extrusion lies in its ability to enable manufacturers to create strong, durable, and customizable products that meet their specific needs and requirements. The common types of aluminum extrusion are direct extrusion, indirect extrusion, hot extrusion, warm extrusion, and cold extrusion.

Direct Extrusion

The most prevalent method of metal extrusion is direct extrusion, often known as forward extrusion. A high-pressure ram pushes a billet of material through a container in this extrusion. And then, the material flows in the direction of the ram action and exits through the stationary die’s opening. 

Direct extrusion allows for bigger profile designs and a higher-quality surface finish than indirect extrusion. However, it would help if you considered some disadvantages when using this extrusion method. A large amount of friction develops between the material and the container’s walls, which reduces die-face pressure and temperature variations. These factors make controlling dimensional consistency and material properties more difficult.

Indirect Extrusion

During indirect extrusion, the material is put within a container and secured. The extrusion die travels over the material using a hollow ram, pushing the material through the die opening. Because the material flows in the opposite direction of the ram action, indirect extrusion is also known as backward extrusion. This process generates less friction, lower energy use, and less heat since there is no relative movement between the material and the container.

Compared to direct extrusion, indirect extrusion provides better control over dimension consistency, material properties, and grain size since it uses less heat. However, this extrusion method has a greater restriction on the total die profile size since it must fit within the hollow ram. Surface impurities from the billet might migrate into the extruded product, diminishing its overall surface quality and attractiveness.

Hot, Warm, and Cold Extrusion

Hot, warm, or cold extrusion is defined by the billet temperature relative to the temperature of the room and material recrystallization. Hot extrusion occurs when the billet is heated much above the material’s recrystallization temperature and is frequently connected with direct extrusion. Heating the material softens it and avoids work hardening. This makes it easier for the material to flow through the die, which wears down the tools less. Warm extrusion is when a material is heated above room temperature while remaining far below the recrystallization point. The material is not heated in cold extrusion, so it stays at room temperature.

Due to the lack of excessive raw material heating, warm and cold extrusion can enhance the hardness and strength of the extruded product. These methods operate well with materials with great ductilities, such as aluminum. Warm and cold extrusion are typical methods of indirect metal extrusion. While avoiding overheating the material might be advantageous, it makes the tooling harder and reduces the die’s lifespan. With this in mind, the majority of manufacturers choose hot extrusion methods.

What Shapes can be Extruded?

One of the features of the extrusion process is that it can produce an almost limitless variety of profiles. The main categories of extruded shapes are:

1. Solid Shapes: Such shapes include solid bars and rods with varying cross-sections (such as circles, rectangles, squares, etc.).
2. Semi-solid Shapes: Shapes like angles, channels, and other partially open forms.
3. Hollow Shapes: The shapes include tubes or profiles with varied cross-sections (such as circles, rectangles, squares, etc.).
4. Custom Aluminum Extrusion Shapes: These shapes frequently include many extrusions. They might be interlocking shapes with different color profiles. These shapes are often created to the needs of designers.

What Aluminum Alloy can be Extruded? 

The most common aluminum alloys that can be extruded are:

1100 — It’s soft and contains almost no added ingredients. Despite not being heat-treatable, it may be extruded into intricate shapes with an excellent brilliant finish. This alloy is used in decorative objects and heats exchanger tubes.

3003 —The alloys in the 3000 series are typically exclusively extruded for heat-exchanger tubes.

6063 — Suitable for ornamental applications with a good surface finish or difficult-to-extrusion features like thin walls or fine detailing. It can be extruded with relative ease and is offered in various tempers. It is resistant to corrosion but has low weld strength while easily welded.

6061— this alloy is stronger than 6063 and can be used as a structural staple in the transportation and machined parts industries. The alloy is easy to extrude and weld. With its high fracture toughness and good fatigue strength, the 6061 series alloy is a good choice for welded structural members like vehicles, trucks, trailer frames, railroad cars, and pipelines.

7004 — One of the “low-end” 7000 series (Al-Zn) alloys that is press heat treatable, easy for extrusion, and somewhat more expensive than 6061. The 7000 series has been utilized extensively in the sports goods, bicycle, and motorcycle industries.

What Factors Would Affect Aluminum Extrusion?

Several factors can affect the quality and success of an aluminum extrusion process. Some of the most important factors to consider are the following:

Alloy Selection: Different aluminum alloys have different properties and are suitable for different applications. Choosing the right alloy is important for the finish extrusion’s strength, durability, and other characteristics.

Extrusion Temperature: The temperature of the aluminum during the extrusion process can significantly impact the quality of the finished product. The temperature must be carefully controlled to ensure that the aluminum is soft enough to be extruded but not so hot that it becomes brittle or begins to degrade.

Die Design: The die used in the extrusion process plays a critical role in shaping the finished product. A well-designed die can minimize defects and improve the overall quality of the extrusion.

Lubrication: Proper lubrication of the aluminum and the die is important to help reduce friction and prevent the aluminum from sticking to the die.

Speed of Extrusion: The speed at which the aluminum is extruded can affect the quality of the finished product. Extruding too quickly can lead to defects and poor dimensional accuracy while extruding too slowly can increase production times and costs.

Cooling Rate: The rate at which the extruded aluminum is cooled can affect its strength and other properties. Proper cooling is important to ensure that the aluminum maintains its desired properties.

Tongue Ratio: The tongue ratio is also important in influencing a part’s extrusion performance. The tongue ratio of an extrusion may be determined by squaring the smallest opening to the void. Then, calculate the full area of the shape and divide the opening squared by this area. The higher the tongue ratio, the more difficult the part would be to extrude.

The Advantages and Disadvantages of Aluminum Extrusion

Due to its exceptional toughness and lightweight, aluminum extrusion is favored by most manufacturers over alternative manufacturing methods. Here are some of the main advantages and disadvantages of aluminum extrusion:

Advantages:

Design Flexibility: Aluminum extrusions can be shaped into a wide variety of complex and detailed shapes, making it a good choice for products with intricate designs.

Lightweight: Aluminum is a lightweight metal, which can be advantageous in applications where weight is a concern, such as in the automotive or aerospace industries.

Strong and Durable: Extruded aluminum is a strong and durable material that is resistant to corrosion and can withstand harsh environments.

Cost-effective: Aluminum extrusion can be a cost-effective manufacturing process, especially for high-volume production runs.

Recyclable: Aluminum is highly recyclable, making it an environmentally friendly choice for certain applications.

Disadvantages:

Limited Strength: While aluminum extrusions are strong and durable, they may have a different level of strength than other materials, such as steel.

Surface Finish Limitations: It can be difficult to achieve certain surface finishes with aluminum extrusion, such as a high-gloss finish.

Tooling Costs: The initial tooling costs for aluminum extrusion can be expensive, especially for complex shapes.

Scrap and Waste: Some scraps are often generated during the aluminum extrusion process, which can increase production costs.

The Applications Of Aluminum Extrusion

Aluminum extrusion is an effective and efficient manufacturing process for numerous sectors due to its material properties. Following are some common applications for aluminum extrusions:

Automotive Parts: Aluminum extrusions are commonly used in the automotive industry for various parts, including frames, chassis, and structural components.

Building and Construction: Aluminum extrusions are used in the construction industry for various applications, including window and door frames, curtain walls, and structural support.

Electrical and Electronics: Aluminum extrusions are used in the electrical and electronics industries for products such as heat sinks, enclosures, and connectors.

Consumer Products: Aluminum extrusions are used in various consumer products, including appliances, furniture, and sporting goods.

Aerospace: Aluminum extrusions are used in the aerospace industry for structural components and other applications where a strong, lightweight material is required.

Transportation: Aluminum extrusions are used in the transportation industry, including in manufacturing buses, trains, and other vehicles.

Industrial Equipment: Aluminum extrusions are used in the manufacture of a variety of industrial equipment, such as conveyors, cranes, and robotics.

Medical Equipment: Aluminum extrusions are used in the medical industry for various applications, including in manufacturing hospital beds and other medical equipment.

It is vital to notice that aluminum extrusions possess excellent reflectivity. Consequently, they are ideal for protecting products from infrared radiation, visible light, and radio waves.

Conclusion

Aluminum extrusion is an important and cost-effective manufacturing process with design flexibility in various industries. This process can create a wide variety of complex and detailed shapes, making it a good choice for products with intricate designs. In addition, extruded aluminum is a lightweight, strong, and durable material that is resistant to corrosion and can withstand harsh environments. 

Aluminum extrusions can be used in various industries and applications, including automotive, aerospace, building and construction, electrical and electronics, and many others. At LEADRP, we offer top-notch aluminum extrusion services to help you achieve the desired result. Contact us today to discuss your project and see how we can bring it to life. 

References:

Extrusion – From Wikipedia

What is Aluminum Extrusion? The Process in 10 Steps – From Gabrian