Aluminum Extrusions: Shapes, Alloys, and Applications

Aluminum extrusion is one of those manufacturing processes that seems simple until you try to explain it. You heat aluminum to around 900 degrees Fahrenheit, push it through a shaped opening, and out comes a continuous length of material with that cross-section. The simplicity is deceptive—extrusion enables designs that would be impossible or prohibitively expensive with other methods.

Understanding what extrusion can and can’t do helps you design better parts, choose appropriate shapes, and communicate effectively with suppliers.

How Extrusion Works

The process starts with a billet—a cylindrical chunk of aluminum alloy, typically 6 to 12 inches in diameter and a few feet long. The billet is heated until soft but not molten, then loaded into the extrusion press. A hydraulic ram forces the softened aluminum through a steel die, and the material emerges in the die’s profile shape.

The emerging extrusion is hot and soft. It’s guided along a runout table where it cools and straightens, then cut to handling lengths (often 20-40 feet), stretched to correct any twist or bow, and cut to final length. Heat treatment brings the material to specified mechanical properties.

This continuous process creates lengths of constant cross-section. Unlike machining, which removes material, or casting, which requires draft angles and wall transitions, extrusion produces the exact profile defined by the die, with the same geometry from one end to the other.

Standard vs. Custom Shapes

Before investing in custom tooling, check what’s already available. Standard shapes cover many applications at lower cost and faster delivery.

Structural shapes like angles, channels, I-beams, and tees follow established dimensional standards. These load-bearing profiles are stocked in multiple sizes and alloys, and if your design can use a standard structural shape, you avoid die charges entirely.

Architectural shapes include tube and pipe in round, square, and rectangular cross-sections. Common sizes are commodity items available from multiple distributors, and these hollow sections provide excellent strength-to-weight ratios for frames and supports.

Specialty standards exist for specific industries as well. T-slot framing profiles are standardized across manufacturers, enabling mix-and-match assembly systems. Heatsink profiles with fins and mounting features are available in standard configurations.

Custom shapes make sense when standard profiles don’t meet your requirements. The die cost amortizes across your production volume, so for a profile you’ll use repeatedly across multiple projects, custom tooling pays for itself through optimized designs that reduce secondary operations.

Alloy Selection

Not all aluminum extrudes equally well. The alloy affects what shapes are achievable, the surface finish, mechanical properties, and cost.

6063 Aluminum

This is the workhorse extrusion alloy, sometimes called “architectural aluminum” for its extensive use in windows, doors, and trim. Its chemistry is optimized for extrusion—it flows smoothly through complex die shapes and produces excellent surface finish.

The mechanical properties are moderate, with tensile strength around 30,000 psi in T6 temper. For many applications, this provides adequate strength with the benefit of easy processing. 6063 anodizes beautifully, accepts paint well, and resists atmospheric corrosion without additional treatment.

Choose 6063 when surface appearance matters, when the profile is complex with thin walls or intricate features, or when strength requirements are modest.

6061 Aluminum

When 6063’s strength isn’t enough, 6061 provides a significant upgrade—around 45,000 psi tensile in T6 temper. The higher strength comes from additional magnesium and silicon in the alloy.

The tradeoff is reduced extrudability. 6061 doesn’t flow as smoothly, which limits achievable complexity. Very thin walls, sharp corners, and intricate hollow sections that work in 6063 may not be practical in 6061. Surface finish typically isn’t as good, though this can be addressed with subsequent finishing.

Choose 6061 when structural performance is the priority, when the profile geometry is relatively simple, or when the extrusion will be machined extensively (6061 machines slightly better than 6063).

For a detailed comparison of 6061 with other aluminum alloys, see our aluminum alloys guide.

Other Extrusion Alloys

Some applications require alloys beyond the 6061/6063 duo. 6005 offers properties between the two, sometimes allowing complex 6063-style profiles with better strength. 6082 is a European standard with properties similar to 6061. The high-strength alloys like 2024 and 7075 are rarely extruded due to processing difficulty—these alloys typically come as bar, plate, or forgings instead.

Design Considerations

Designing for extrusion means understanding the process constraints and leveraging its strengths.

Wall Thickness

Extrusion excels at producing constant wall thickness across the profile. Varying thickness is possible but adds die complexity and may create distortion as thicker and thinner sections cool at different rates.

Minimum wall thickness depends on the alloy and the size of the profile. For 6063, walls down to 0.040 inches are achievable in smaller profiles, while larger profiles need thicker walls to maintain shape during handling. Your extruder can advise on minimum practical thickness for your specific geometry.

Corner Radii

Sharp interior corners are difficult to extrude and create stress concentrations. Design with generous radii—0.030 to 0.060 inches minimum for small profiles, larger for bigger sections. Sharp exterior corners are more achievable but still benefit from small radii to reduce die wear.

Hollow Sections

Extrusion can create hollow profiles—tubes, rectangular sections, complex multi-hollow shapes. These require “porthole” dies where the aluminum flows around support legs and re-welds inside the die. The weld lines are typically invisible and mechanically sound, but they exist.

Hollow sections provide excellent torsional stiffness with minimal weight. A square tube is far more rigid than the equivalent weight of solid bar.

Asymmetry

Unlike machining, extrusion doesn’t care about symmetry. A profile can be asymmetric in any direction without adding cost. This freedom enables designs that combine multiple functions—a single extrusion can include mounting channels, wire ways, structural flanges, and cosmetic surfaces.

Length

Extrusions are produced in long lengths, typically 20-40 feet depending on the press and the profile. You can order cut-to-length pieces, but pricing is generally per pound regardless of cut length. Very short pieces may have minimum charges.

Secondary Operations

Extruded profiles rarely go directly to assembly. Most applications require additional processing to transform the profile into finished parts.

Cutting to length is universal. Saws, shears, or laser cutting produce finished lengths from extruded stock, with tolerances depending on the cutting method. Sawing typically holds plus or minus 0.030 inches while laser cutting can achieve plus or minus 0.005 inches.

Machining adds features the extrusion process can’t create. Holes, pockets, threads, and tight-tolerance surfaces all require secondary machining. Because the profile is already close to final shape, machining operations are often minimal—drilling and tapping mounting holes, milling end profiles, facing reference surfaces.

Bending and forming work best in softer tempers. If significant bending is required, order T4 temper, form the part, then age to T6 for final strength. Bending T6 material risks cracking, especially at tight radii.

Finishing options include anodizing (clear or colored), painting, powder coating, and polishing. Anodizing provides durable corrosion protection and can match specific colors. Mill finish (as-extruded) is acceptable for many industrial applications where appearance isn’t critical.

Ordering Extrusions

When specifying extruded aluminum, clear communication with your supplier prevents problems.

Provide a dimensioned cross-section drawing for custom profiles. Include tolerances on critical dimensions—standard extrusion tolerance is roughly plus or minus 0.012 inches for small dimensions, proportionally more for larger features. Tighter tolerances require either grinding the die or machining after extrusion.

Specify the alloy and temper explicitly. If you just say “aluminum,” you’ll likely get 6063-T5. If you need 6061-T6 for higher strength, say so clearly.

Indicate quantity as total weight or total length. Extrusion is sold by the pound, and pricing improves at higher volumes. Be clear about piece length requirements and whether you need certified material documentation.

For custom profiles, discuss minimum order quantities early in the process. The die cost is fixed, but there’s also setup time on the press. Small orders may face minimums that make extrusion uneconomical—in those cases, machining from standard shapes may be more practical.

Working With NextGen Components

We supply aluminum extrusions in standard and custom profiles, with machining to complete your parts. Our capabilities include cut-to-length, precision cutting, drilling and tapping, CNC machining, and finishing coordination.

Need help designing an extrusion profile or determining if extrusion makes sense for your application? Contact our engineering team to discuss your project.