A 360 degree scale has been produced by laser marking black anodised aluminium. The disk is 350 mm in diameter, and forms part of a jigging plate used for an aerospace application.
This electrolytic passivation, in this case black, 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.
In this case, an M series laser marking system with galvo beam delivery optics has been used. Because the galvo delivery is limited to a process area of 200 mm, the part has to be marked in 4 sections. Specialist jigging was created along with added holes being machined into the plate, to ensure perfect alignment for each quadrant to each other.
Laser marking black anodised aluminium. with CO2 lasers
CO2 can also be used for laser marking anodised aluminium. 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.
If you would like further information on this application, or any other application, please request a call back or, talk to one of our laser marking specialists by going to our contact page – link below.