This anodised aluminium laser marking/engraving sample kit, was produced by the manufacturer of aluminium extrusion section, to demonstrate the colour range within this particular group set.
Anodising is an electrolytic passivation, that is widely used across industry on aluminium for a variety of reasons. The process can also provide a huge 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. Laser marking performs exceptionally well on this combination of material and surface treatment
The laser is used, to vaporise the top surface to remove the area affected by the anodising process exposing the host material. Where a darker dye colouring is used, the contrast levels remain high between the two contrasting surface areas. Fibre lasers could be used to demonstrate this process as well.
To achieve consistent white marks on aluminium, the correct laser power, repetition rate, marking speed and image fill ratio must all be made. With most aluminium’s a slight deviation, either way, from your standard settings should be enough to pull back any variation you see. In some cases, it may also be worthwhile considering a second pass with much lower power settings to lightly skim the image, removing any burning caused by the initial process pass.
Aluminium corrosion: The general consensus is, as the laser removes the anodised layer an oxide layer, very quickly forms to the surface, providing protection to the material beyond the oxide layer thickness preventing corrosion.
CO2 lasers can also be used to process anodised aluminium. In this case, it is the dye that is directly affected rather than the material. The energy from the laser creates a heating action that removes the dye from the surface. The use of CO2 is generally not as well received as a fibre laser, due to the lower quality created by the mark process. This is directly related to the fact that the heating effect is difficult to control due to “heat creep”. The result is a fuzzy edge to the mark image, and not as crisp as with Nd:YAG. The main advantage is, that no material is removed, leaving the anodising closer to its original state, and that per unit cost will be slightly higher with CO2, due to the process time being slower.
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