A variety of metals — such as aluminum, stainless steel, copper, and brass — can be marked or engraved with a Trotec laser system. A fibre laser offers the greatest versatility with regards to processing metal workpieces. However, with the assistance of a specially formulated marking compound, a CO2 laser can also create metal markings.
You can find more information about CO2 and fibre laser systems here.
The annealing process involves applying heat to the surface of an uncoated metal workpiece. An oxide layer is created on the processing area, which feels smooth to the touch. Steel and titanium are well suited to annealing, as a high-contrast black oxide layer is formed on these metals.
In order to mark — rather than engrave — the material, the laser beam must be defocused so that a lower amount of energy is applied to its surface. What's more, slower processing speeds are needed to produce the oxide layer.
Due to its adjustable pulse frequency, a MOPA fibre laser can mark steel in a variety of colours such as blue, red, green, and purple. The markings disappear, however, when the metal is heated to approximately 200°C.
A fibre laser applies a high amount of energy to a metal workpiece to produce engravings. The intensity of the emitted radiation is sufficient to vaporize the material, which is why depressions are formed on its surface.
Since matter is, in effect, removed, the engravings are are highly resistant to abrasion and corrosion.
Removing the Coating
If a metal workpiece is coated, its top layer (i.e., the coating) can be removed to expose the metal substrate. This process can be carried out at high speeds, which is advantageous when marking large workpiece quantities.
To achieve high-contrast markings, we recommend using metals with dark coatings. For example blue, black, and red anodised aluminum yields easily legible results.
Uncoated metal workpieces can only be marked with a CO2 laser if they are treated with a specially formulated compound — which is available as a spray, paste or tape — prior to processing. The laser beam's heat activates the compound, enabling it to thermally bond to the metal's surface. In other words, the compound is burned onto the workpiece.
When laser processing is complete, remove any remaining residue from the workpiece by using water and a soft cloth.
A laser marking compund can also be used when processing workpieces with a fibre laser.