Anodised Aluminium Profile

If you’ve ever played with construction kits as a child, this material might give you an immediate urge to build, as it is essentially the adult’s version of Meccano. Also known as T-slot structural framing, this incredibly versatile material is found in research laboratories, trade show booths or museum exhibitions, essentially whenever a structure needs to be erected quickly and semi-permanently. For instance, at the Institute of Making, the 3D printers in our workshop areas are housed in custom-built enclosures built entirely from these profiles. 

It is a lightweight yet strong material whose parts are designed to attach easily, without the need for welding. On each face of the profile, you can feel a nifty design feature: long continuous grooves. Slide a nut in one of these channels, and it can lock itself at any point along the profile with a corresponding bolt, enabling you to connect with another piece anywhere. This specific piece is a double-width profile, with two parallel grooves on its wider faces.

This piece was made through extrusion, the familiar everyday process of pushing material through a hole. We are doing extrusion every time we squeeze toothpaste from a tube. In the industrial version, plastics, foodstuffs or metals like aluminium can be made into very long objects with a fixed profile including square rods, round bars and the I-beams that hold up many of our buildings. This is done by pushing material through a die, the hard metal tool which gives the extruded material the desired profile (just like bronze dies turn pasta dough into fusilli, linguine or penne shapes).

This piece also stands out among other aluminium materials, as it does not have the usual metallic silver colour. Its black colour is the result of an electrochemical process known as anodising. Aluminium naturally forms a transparent, protective oxide layer just a few hundred atoms thick. Anodising boosts that natural oxidation process, increasing the thickness of that barrier a thousand times or more. The resulting aluminium oxide film is full of microscopic holes that can hold on to pigment molecules extremely well, making anodization suited to jewellery, architecture or any application requiring striking colours. To complete the process, the piece is submerged in boiling water, sealing the outer pores of the oxide film shut. This permanently traps the dyes for long-lasting colour, and makes aluminium even more resistant to corrosion and abrasion. This thick oxide layer is also electrically insulating, a useful property for structural components like our profile beam, which are often used alongside robotics or electronic equipment. Anodising is a chemical finish, and is applied after any desired mechanical finish (polishing, burnishing, brushing, etc.), so anodized pieces can be made with a variety of surface textures.