Aluminium Profile Explained

Aluminum profile is common name for a type of aluminium extrusion which has been designed to work as a modular system. It comes in many shapes and sizes and generally sold as a compatible series of extrusions and parts for building mechanical frameworks and various other applications. This article provides an overview how it works and why it has become such a successful product.

The aluminium extrusion is designed with longitudinal embedded t-shaped slots used with specialist connectors to enable inter-connection with other profiles or for attaching various components. It is a highly effective and versatile engineering product designed for modular building of frameworks and other structures.

A particular series of profile would ensure compatibility by having a standard sized "t-slot", with a standard modular base size. For example, a profile 5 system, would have a 5mm slot opening, to take M5 bolts. The base size may be 20mm and so have the slots spaced 20mm apart, and depending on the section size would have the first slot starting 10mm from an edge. The section sizes on offer would typically be: 20x20, 20x40, 40x40, 20x60, 40x60, 20x80, etc. The t-slot groove is more a mushroom shape, ideal for slotting button head bolts along the slot, or using specialist t-slot nuts inserted into the slots. With other specialist connection methods, combined with the ability to cut and drill the profile with mobile power tools, makes it a very easy system to work with and assemble.

The attraction to using aluminium for this type of system is its cost, weight, relative strength, suitability for extrusion, and its anodised finish. No other metal has the same combined advantages.

To put a perspective on the availability and value of aluminium as a resource, it is the most abundant metallic element in the Earth's crust, and the third most abundant element behind that of oxygen and silicon. As with most metals used for engineering, aluminium is alloyed with other elements to improve its strength and workability properties. Another abundant element silicon which is also a common alloying constituent.

Abundance does not mean it is the easiest to discover and process. It has only been known to be an element as early as the 18th century, but not established as a metal until the 19th century. Pure aluminium is highly reactive with oxygen therefore very susceptible to oxidising. It owes its excellent corrosion resistance to this oxide film bonded strongly to the surface, which is only a fraction of a micron thick and self mending if broken.

The metal originally obtained its name from the Latin word for alum, alumen. In 1807, Sir Humphrey Davy proposed that this metal be referred to as aluminum. As many elements had a "ium" ending, it was later altered to aluminium. This is the most accepted spelling used throughout the world. However, the American Chemical Society in 1925 officially changed the spelling back to aluminum (pronounced "aloo-min-um"), and that is how it is now spelled in the United States. In the United Kingdom the spelling is aluminium and pronounced "al-u-min-ium".

It would take years of research to find an efficient method to extract the metal from its ore. Extracting aluminium from its oxide alumina, is generally performed by the Hall-H¨¦roult process. Alumina is extracted from the ore Bauxite by means of the Bayer process at an alumina refinery. This is an electrolytic process, so an aluminium smelter uses large amounts of electricity and tend to be located very close to large power stations.

Aluminium extrusion is a process of forcing a aluminium billet through a steel or ceramic die. The aluminium goes through a plastic deformation aided by being heated to an optimal temperature. The billet is typically a lot larger than the aperture of the die and a lot shorter than the resultant extrusion which can reach lengths of 25 to 45 metres. The extrusion is cooled immediately using air or water. the profiles are stretched after cooling to ensure that they are straight and to release internal stresses. The profiles are then cut to the appropriate length, typically 3 to 6m depending on the section size of the profile. It is then subjected to natural aging or artificial aging to bring it to its final level of tensile strength.

An extrusion in its raw state has a fairly satisfactory appearance and surface quality, and with its natural resistance to corrosion, it can be left unfinished. However, the finish can be improved with an anodising process, which not only gives it a clean look, but also provides a hard, tough, wear resistant, electrically insulated, surface which absorb dyes during the process to give a full spectrum of colours, including metallic finishes.

Anodising is an electro-chemical process, which physically alters the surface of the aluminium to produce a tough oxide layer. This oxide layer is a lot thicker than that produced naturally. The thickness applied varies from 5 to 25+ microns and depends on the required application, with 5 microns providing decorative appearances, 25 microns for external architectural applications. During the anodising process the oxide layer is initially porous, and it is at this point that it is possible to add a coloured dye before finally sealing.

The final aluminium profile is a strong, light, versatile, hard wearing product with an attractive finish. It is used for all sorts of applications including building mechanical frameworks such as CNC machines, workshop units, factory production lines, machinery jigs, etc.