Laser marking is clearly superior to other marking processes thanks to a number of advantages. First, laser marking is a process that can generally be implemented without mechanical intervention. Since the tool is a laser beam with no mass, there is no need to clamp the semi-finished product to be marked, substantially reducing set-up time.
Another advantage of the process is that it generally does not require auxiliary materials or other consumables, which keeps maintenance requirements and investment costs low in the short and long term. The laser marking process merely changes the material properties, meaning that all types of marking are activated working from the properties of the material to be marked.
Laser systems are also a largely wear-free production system. The amount of mechanical work performed is low, which reduces the likelihood of faults and therefore extends maintenance intervals.
Last but not least, this marking process offers extremely high flexibility. Information can be changed quickly in CAD systems and immediately applied to the material that is to be marked. Whereas it was previously also necessary to manufacture expensive dies with the right contours, it is now possible to scan in any required contour using the laser beam.
Marking in black
A common request for laser marking is to achieve a high visual contrast without causing any mechanical damage to the surface. In the food industry and medical technology in particular, these criteria are extremely important. However, this is often also required for rotationally symmetric bodies, since bumps or engraving would change the moment of inertia and make it impossible to ensure concentricity in the long term. To produce a marking in black, the laser heats up the surface of the material and the volume underneath. This causes the metal lattice to vibrate, causing carbon trapped in the microstructure to be diffused to the surface. This precipitation is perceived as black marking.
Black marking and anneal marking are often used interchangeably. However, black is not listed in the table of annealing colours. The process of anneal marking contrasts clearly with black marking. Rather than creating the marking by precipitating a layer of carbon, it involves introducing oxygen into the metal lattice structure. The laser causes the lattice molecules to vibrate, and oxygen is deposited in the structure. This forms an oxide layer which takes on the properties of a visible layer system. Different layers cause interference in the visible light reflected back by the material, causing certain colour components to be nullified or amplified. As a result, anneal marking is characterised by creating a coloured appearance on the relevant metals. However, in practice, the mechanisms of black marking and anneal marking overlap, so using the terms interchangeably is sufficiently accurate for most purposes.