Designing for Aluminium Extrusion: Key Considerations for Engineers and Architects

PT Damai Abadi .
Nov 3, 2025
4 min read

Aluminium extrusion is a cornerstone of modern manufacturing, offering designers unparalleled freedom to create complex, lightweight, and strong profiles.

For engineers and architects, mastering the principles of designing for aluminium extrusion is crucial for maximizing efficiency, minimizing cost, and ensuring manufacturability.

Designing for Aluminium Extrusion

The extrusion process forces a heated aluminium billet through a shaped die opening, producing a continuous profile. The success and cost-effectiveness of a design hinge on how well the profile shape interacts with the physics of this process.

Simple design choices early on can drastically affect extrusion speed, tooling costs, and final product quality. Therefore, a dialogue between the designer and the extruder is essential before finalizing the design.

Material Choice : The Importance of the Alloy

The first design decision is the aluminium alloy itself. The 6000 series (particularly 6061 and 6063) is most common due to its excellent extrudability, good strength, and finishing capabilities.

Stronger alloys are typically harder to extrude, requiring more pressure and slower speeds, thus increasing costs. Selecting the appropriate alloy based on required strength, corrosion resistance, and intended finish is paramount.

Symmetry and Balance

Profiles that are symmetrical tend to extrude more evenly, as the metal flow is balanced across the die. Asymmetrical or unbalanced shapes can cause unequal friction and heat distribution, leading to warping and requiring specialized, costly tooling.

If asymmetry is unavoidable, the design should incorporate subtle features that help balance the flow, such as thicker sections near the center of the profile.

Wall Thickness Consistency

A cardinal rule of designing for aluminium extrusion is maintaining the most uniform wall thickness possible throughout the cross-section.

Variations in thickness cause the aluminium to cool and solidify at different rates, leading to internal stress, twisting, and difficulties maintaining straightness. If varying thicknesses are necessary, the transitions should be gradual, employing generous radii rather than sharp steps.

Managing Extrusion Tolerances and Dimensions

Tolerances are the permissible variations in a dimension or shape, and they directly affect cost and manufacturability. Tight tolerances are expensive because they demand slower extrusion speeds, more rigorous quality control, and frequent die adjustments.

Standard vs. Custom Tolerances

Designers should always aim for standard tolerances as defined by industry specifications (e.g., the Aluminum Association, or EN standards).

Specifying unnecessarily tight tolerances (custom tolerances) should be avoided unless absolutely critical for the profile’s function. Tight tolerances on features like wall thickness, flatness, and straightness will significantly inflate the unit cost.

Flatness and Straightness

Achieving perfect flatness on wide surfaces can be challenging during the cooling and stretching phases. Deep, narrow grooves or fins can help break up wide surfaces and improve flatness.

Similarly, excessive length-to-width ratios make profiles prone to bowing. Incorporating features like small corner radii instead of sharp 90^O corners can improve straightness.

Corner Radii and Sharp Edges

Extrusion technology makes true sharp corners (0^O radius) impossible to achieve in reality. Designers should specify the largest possible inside radius to facilitate metal flow and extend die life. A minimum inside radius of 0.5 mm 1 mm is usually recommended.

Larger external radii on corners also help prevent potential cracking and sharp burrs, simplifying post-extrusion handling.

Optimizing Profile Geometry for Production Efficiency

Engineers and architects can significantly impact production efficiency, and thus unit cost, by designing shapes that minimize material use and maximize extrusion speed. Effective designing for aluminium extrusion is an exercise in material economy and process simplicity.

Hollow and Semi-Hollow Profiles

Profiles with voids, known as hollow profiles, require more complex "porthole" or "bridge" dies. While these dies are more expensive, they offer greater structural rigidity for the material used.

Designers should minimize the number of voids and keep the void shapes as simple as possible to ease die construction and flow control. The thickness surrounding the voids must be sufficient to support the mandrels in the die.

Tongue and Feather Ratio

The concept of tongue ratio refers to the ratio of the depth of an open channel (the "tongue") to its width.

Profiles with deep, narrow channels (high tongue ratio) are difficult to extrude because the thin metal section ("feather") in the die is weak and prone to deflection.

Engineers should aim for a tongue ratio of less than 3:1 to improve die strength and metal flow.

Designing for Fasteners and Assembly

Incorporating features into the profile to facilitate subsequent assembly saves substantial costs compared to machining features later. Examples include integrated screw ports (circular holes with internal threads), snap-fit grooves, and channels for sliding fasteners.

Designing for these features upfront simplifies manufacturing and speeds up final product assembly.

Post-Extrusion Considerations :

Finishing and Secondary Operations

The design phase must also account for how the profile will be treated after extrusion, as this impacts the geometry.

Designing for Anodizing

Anodizing is a common surface treatment for corrosion resistance and aesthetic finish. For optimal anodizing, the profile should allow for efficient drainage and rinsing.

Pockets or blind holes that can trap chemicals should be avoided or designed with drain holes. Furthermore, the aluminium alloy must be suitable for the desired color and finish.

Allowance for Fabrication

If the profile requires subsequent fabrication, such as bending, drilling, or punching, the design must accommodate these operations.

For instance, profiles intended for bending should have a uniform cross-section and generous internal radii to prevent material collapse. Positioning holes on thicker sections of the profile reduces the risk of blow-out during punching or drilling.

The successful deployment of aluminium extrusion requires a deep understanding of its technical constraints and capabilities. For architects and engineers, designing for aluminium extrusion is a powerful skill set that transforms abstract concepts into tangible, cost-effective, and high-performance components.

By prioritizing symmetry, uniform wall thickness, and realistic tolerance specifications, designers can ensure their profiles are not just aesthetically pleasing, but also structurally sound and efficiently manufacturable. Engaging early with experienced extruders will always be the fastest path to optimized design and production success.

Don't navigate these technical considerations alone. Contact the design and engineering experts at PT Damai Abadi today to utilize our in-house design and molding center, ensuring your profiles are optimized for manufacturing precision and final application performance.