Extrusion is a metal-forming operation for fabricating strips of material with a consistent profile. Aluminum alloys are commonly used in this process.
Here we’ll cover the process of aluminum extrusion, design considerations, and more.
What is Aluminum Extrusion?
In aluminum extrusion, a very hot, but not molten, piece of aluminum alloy is pushed through a die. The die is cut with the desired profile shape, causing the hot metal to take that shape as it passes through it.
The emerging extrusion is cut to a manageable length and transferred to a cooling area. Once at room temperature, it can be cut down, heat treated, painted, or coated.
Initial Design Considerations
Design considerations in aluminum extrusion include:
- Complex vs. Simple Designs. Complex or large profiles with multiple angles or features require more time and expense for die preparation. They may also need more raw materials and design troubleshooting.
- Part Specifications. All parts include specifications the manufacturer must meet. In extrusion, common specifications include:
- Angles
- Flatness
- Cross section size
- Profile symmetry
- Features that add strength or relieve fatigue
- Wall thickness
- Solid or hollow profile shapes
- Alloy properties
- Surface finish
- Tolerances. This is how closely a manufactured part matches specifications, such as the acceptable variation in length. Tight tolerances leave less room for error and require careful planning and execution.
Step-by-Step Process Breakdown
Before extrusion, a detailed cross-sectional drawing of the profile shape is made. That profile is then cut into a disk of metal to make the die, which shapes the extruded aluminum.
Once the die is prepared and an aluminum alloy material is selected, the extrusion process follows these steps:
- Preparation of the aluminum billet. A long cylinder of aluminum alloy, called a billet, is placed in a special furnace and heated to approximately 900 °F. The metal remains solid but is easier to extrude.
- Heating and extrusion through the die. Hot aluminum feeds into a chamber and pushes up against the die with a ram and hydraulic press. Continuous pressure forces it through the die and into the profile shape.
- Cut and cool extruded parts. The extrusion exits the die in a continuous piece. It is cut to a manageable length and moved to a table or enclosure to cool. This process, called quenching, is done with air or water. Then a stretcher machine straightens any twists in the extrusion.
- Aging. Extrusions may be left to age in open air or in an oven. This process enhances the piece’s mechanical strength.
- Finishing. Extrusions are cut to the final length and any finishing processes are completed, including painting, coating, or anodizing.
Applications of Aluminum Extrusion
The strength and light weight of aluminum alloys make them ideal for many applications in the aerospace, architectural, automotive, construction, energy, and electronics industries, among others.
Overview of Extrusion Applications
Extruded aluminum parts are a good choice when long and strong supportive or structural components are needed. Examples include:
- Beams and railings
- Enclosure and cabinet panels
- Corrugated panels
- Framing and structural members
- Cylindrical or square tubes for carts and furniture
- Electrical raceway tracks
- Lighting components
Customization Options for Specific Needs
Aluminum extrusion is a versatile and reliable way to create custom parts. Opportunities for customization include:
- Solid, hollow, and semi-hollow profile and cross section size
- Length
- Alloy properties
- Wall thickness
- Weight per linear foot
- Structural support features (e.g., grooves, indexing marks)
- Surface treatments and finishes
Technology Behind Aluminum Extrusions
Aluminum extrusion technology is always changing to improve the process.
Tools and Machinery Used
Some of the tools used include:
- Furnaces. Specialized furnaces heat aluminum billets to high temperatures. A built-in metal grate moves the billet in and out.
- Dies. Made of H13 or other hardened tool steel, a die is a flat disk of metal with the desired profile cut into it. As the aluminum passes through, the die forces it into that shape.
- Extrusion Press. A hydraulic press with a ram pushes a hot aluminum billet up against and through the die with constant pressure.
- Shearing Machines. These machines use automated blades to cut the extrusion to a manageable length as it exits the die.
- Pullers. The extruded piece moves along a track of rollers to the cooling or quenching area.
- Cooling table. Extrusions sit on the cooling bed until they reach room temperature.
- Quenching system. An enclosed platform with nozzles to spray, flood, or mist the extrusion with water to quickly cool it to room temperature.
- Aging Furnace. A special oven in which the extrusion is heated in order to further strengthen or harden it.
Advancements in Aluminum Extrusion Technology
Extrusion tools and materials continue to develop in order to make the process more efficient.
For example, computer assisted design (CAD) is used to model profiles and dies in 3D for improved outcomes. It can predict how changes may impact part performance in the real world before manufacturing.
Additionally, internet-enabled equipment and manufacturing software track details like material use, pressure of the hydraulic press, or speed of extrusion. They may also control and adjust equipment remotely in real-time.
Advantages of Aluminum Extrusions
Aluminum extrusions offer advantages such as:
Lightweight and Durability
Aluminum materials are lighter than other metals without sacrificing workability or strength. Because they resist corrosion and can be tempered for added strength, they are durable and perform well in many applications.
Cost-Effective Production
Several things make aluminum extrusion cost-effective, including:
- Ease of availability
- Minimal secondary machining required
- Continuous production
- High volume production
- Limited waste
- High repeatability for consistent output
Challenges and Considerations
Consider whether a design or specifications can be adjusted for better manufacturability, or if the constraints of the application preclude extrusion as a manufacturing process.
Material Selection
Choose an alloy with the appropriate combination of properties needed for the application, such as strength, thermal conductivity, or corrosion resistance. Also consider whether and how the alloy can be tempered, and what it can be used for, such as the ability to weld or further machine it.
Design Complexity
Some design characteristics, like overall cross section size, wall thickness variations, bend angles, solid or hollow profiles, and other factors may prove challenging to achieve reliably and repeatedly. In some cases, the desired profile may be better suited to an alternate method such as press braking, rotary draw bending, or die-casting.
Aluminum Extrusions from PSI Industries, Inc.
For expert aluminum extrusions and finishing services from prototypes to high-volume production runs, turn to PSI Industries, Inc.. We’re a full-service custom aluminum extruder and aluminum fabricator with ISO 9001:2015-certified facilities and fast lead times.
To learn more about our capabilities contact PSI Industries, Inc. or request a quote today.