This is part 1 of our series on rail aluminium components, where we explore critical structural elements used in modern train manufacturing. As rail manufacturers continue to push for lighter, stronger, and more energy-efficient vehicles, aluminium carbody structures have become a key design solution across high-speed trains, regional rail, and metro systems.
One critical structural element in these lightweight designs is the curved vertical aluminium pillar — a load-bearing component that connects the roof, sidewall, and floor structures of the train carbody.
At Sjolund, we specialise in precision profile bending of aluminium extrusions for demanding applications in the rail industry. Curved aluminium pillars represent a good example of where advanced bending, heat treatment, and machining must work together to achieve reliable structural performance.
In this article, we explore the role of curved vertical pillars in aluminium train car bodies — and why manufacturing them requires a tightly controlled production process.
In modern rail vehicle design, the carbody functions as a load-carrying structure that must withstand complex forces during operation, including vibration, bending loads, and crash scenarios.
The structural frame typically consists of extruded aluminium profiles that are welded together to form a lightweight yet stiff shell.
Within this structure, vertical pillars play several important roles:
These pillars are often curved to match the geometry of the vehicle shell, particularly in high-speed trains where aerodynamic design and interior layout influence structural form.
Today, aluminium alloys are widely used in passenger rail vehicles because they enable lightweight construction without compromising structural performance.
Common aluminium alloys used in railway extrusion profiles include 6xxx-series alloys, often delivered in tempers such as T4 and T6, depending on the required forming and strength characteristics.
For railway OEMs, aluminium offers several advantages:
However, once extruded, these profiles often require precise bending and post-processing to match the structural geometry of a train carbody.
Producing curved aluminium profiles for railway structures is far more complex than standard metal forming. The challenge lies in maintaining tight tolerances and stable material properties throughout multiple manufacturing steps, including:
Controlled profile bending
Railway structures frequently require large-radius bends or complex geometries.
Achieving these curves without deformation, wrinkling, or wall thinning requires specialised profile bending processes and precise tooling.
Heat treatment from T4 to T6
Many aluminium extrusions are bent in the T4 temper, where the material remains formable. After bending, heat treatment is required to reach the T6 condition, which provides the mechanical strength needed for structural applications.
Maintaining dimensional stability during this transition is a major engineering challenge.
Distortion control
Heat treatment can introduce material distortion or residual stress, particularly in curved components.
To ensure final dimensional accuracy, manufacturers must apply distortion compensation strategies before final machining.
Structural welding
In many carbody designs, aluminium pillars are integrated into larger assemblies through welding processes compliant with railway standards such as EN 15085.
For rail OEMs and system integrators, managing these processes across multiple suppliers can introduce risk.
That is why many projects benefit from a single supplier managing the full process chain, including:
When these steps are integrated into a single, controlled process, manufacturers benefit from a simpler supply chain and more consistent production outcomes. Managing bending, heat treatment, machining, and welding within one workflow helps ensure stable geometry after heat treatment and reduces the number of interfaces involved in critical structural components.
For high-volume rail production, this level of consistency and reliability is essential for maintaining efficiency and quality across every production batch.