When engraving aluminium, it is most common to use anodised aluminium. It can be engraved with a laser or rotary machine and allows for fine detail engraving on a product strong enough to withstand most external factors.
There are many different variations of anodised aluminium available, differing in the aluminium grade itself, as well as in the anodisation process and colour pigments applied. The different variations strongly influence factors such as strength and durability, UV-stability and the engraving result. Trotec anodised aluminium features an anodised coating of up to 22 microns, which is best in its class in terms of product durability and withstanding external factors.
Basically, anodised aluminium consists of an aluminium core and an anodised exterior coating. The anodisation is created using a chemical / physical process, the anodisation. So, when looking at anodised aluminium sheets, we have a two layer material:
- The aluminium core, which provides substance and stability while still being somewhat flexible.
- The anodised layer on top, which is very thin (approx. 6-22 microns) but also very hard and strong, protecting the aluminium from chemical and physical influence.
The anodised coating itself is white in colour. Once applied, the anodised layer is coloured by embedding colour pigment in to the surface of the material, providing the final finish.
When engraving anodised aluminium with a CO2 or fiber laser, the colour pigments are removed. This creates a white engraving image by exposing the plain white anodised coating. Very little of the anodised coating itself is removed, which keeps the full protective characteristics intact.
When engraving with a mechanical engraving machine, the accuracy of the engraving machine determines how deep the rotary cutter will engrave into the aluminium material. Usually, mechanical engraving will be deeper than laser engraving, resulting in engraving through the anodised coating and removing the protective layer, exposing the blank metal to the elements.
A decisive factor for a successful outcome is a high quality . Working with aluminum requires a resolution between 600 and 1000 ppi.
Why? The anodized layer on the top does not melt because it is very hard and strong. The material vaporized precisely at the point where the laser pointer hit the material. There are no more effects, such as wood for example (dot bleeding). This means that a high resolution is necessary to ensure a homogeneous engraving.
A detailed focus is very important for a good result. Blurred edges are a sign of an imprecise focus.
Therefore, accurate work with the focus tool is very important.
See our video tutorial which shows how to laser engrave anodised aluminium labels: