In this example, we are laser marking blue anodised aluminium, removing the anodising, to expose the base material beneath.
The device used in the petrochemical industry, contains both branding details and identification information. The part number identifies the part for ordering. The batch number is used for traceability.
This is a combination of the contrast created by laser marking, blue anodised aluminium and large characters enables the product to be readable at a distance, which is a maintenance requirement for the product.
Anodising explained
This electrolytic passivation, in this case blue, is widely used across industry on aluminium for a variety of reasons. The process provides a range of colour variations through the use of colour dying. The process changes the microscopic texture of the aluminium, by modifying the crystal structure near the surface.
The laser marking is used to vaporise the surface of the part, removing the anodising from that area, to expose the aluminium below. We have used an Nd:YAG Q switched laser, in a low order mode to get the best results. The resulting image is very sharp and clean. Fibre laser could be used for this application as well.
Corrosion
The general consensus is that, as the laser removes the anodised layer, then an oxide layer very quickly forms on the surface, providing protection to the material beyond the oxide layer thickness preventing corrosion.
Processing with CO2 lasers
CO2 can also be used for this type of laser marking application on anodised materials. With CO2, processing the dye is removed without any surface disruption taking place. While this can provide certain advantages (corrosion), the quality of the mark is difficult to maintain. CO2 will heat the plate, while attempting to remove the dye through a chemical reaction and, in doing so heat creep can occur. This shows up as blurred edges to the mark, and requires a very concise set up of the laser parameters.
The combined precision of the beam placement, along with our tooling design means the part and mark are precisely aligned every time we set up a new batch.
If you would like further information on this laser marking application, or any other application, please request a call back, or talk to one of our laser marking specialists on 01737 826902
