Aluminium extrusion involves different phases, from billet preparation to heat treatment and finishing. One of the fundamental operations to ensure the dimensional quality of the profile is stretching.
What is stretching?
Drawing is a mechanical operation carried out after extrusion and cooling of the aluminium profile. It consists of applying a longitudinal traction on the profile in order to:
- Correct geometric deformations generated during extrusion (bending, twisting).
- Improve the straightness of the profile.
- Remove residual internal stresses.
- Adjust final dimensions within industrial tolerances.
This is a standard process in the industrial manufacture of high dimensional accuracy aluminium profiles, especially when structural stability and compatibility with subsequent processes such as heat treatment, machining or surface finishing (anodising or lacquering) is required.
How is this done?
Once the extruded profile has reached room temperature, both ends of the profile are clamped together and controlled tension is applied. This elongation, which varies according to geometry and alloy, is usually around 100 mm per piece.
Thus, during stretching:
- Se corrigen imperfecciones geométricas generadas durante la extrusión.
- The internal stresses of the material are redistributed.
- The uniformity of the mechanical behaviour of the profile is homogenised.
Why is this a key phase?
The main function of drafting is to ensure the dimensional quality of the profile and to optimise its subsequent performance. Its benefits include:
Deformation correction and geometric improvement
Eliminates curvatures, twists or deviations that make cutting, packaging or assembly difficult. Improves profile straightness, simplifying integration into automated processes or modular structures.
Improved dimensional stability
Controlled tension compensates for residual stresses and corrects small deviations in the section, reducing accumulated tolerances. This results in more stable and precise profiles, especially in long formats or complex designs.
Improved mechanical properties
Stretch increases parameters such as yield strength, stiffness and tensile strength. It is especially relevant in structural, architectural or transport applications, where mechanical reliability with the lowest possible weight is required.
Optimisation of downstream processes
A correctly stretched profile:
- Facilitates uniform heat treatment of the aluminium profile.
- Guarantees better results in anodising or lacquering.
- Reduces rejects and rework on automated production lines.
Thus, the stretching of aluminium profiles is not only a geometrical correction step: it is a strategic process that ensures the functional quality of the profile, improves its performance and guarantees its smooth integration into downstream industrial processes.
