Laser marking describes the process of marking the marking materials with laser technology. Here, a focused laser beam is guided over the component to be marked. The energy of the laser beam hitting the component triggers a reaction, leaving a resistant and permanent marking. Depending on the material, there are various options for creating the contrast required with the base material. The selection of the appropriate marking method for the respective application is crucial.
Lasers are categorized according to the thermodynamic aggregate states of their laser medium. A laser medium is the material that is suitable for generating laser beams through stimulated emission. In addition to the pump source and the resonator, the laser medium has a decisive influence on the wavelength, power, and pulse properties of the laser. A laser-active medium can be a solid, a liquid, or a gas. Depending on the properties of the marking material to be marked, the selection of the wavelength, and therefore the laser type, is crucial.
Lasers are also differentiated based on their operating mode. While continuous wave lasers emit a constant light wave with the same intensity, pulsed lasers generate pulsating radiation that achieves higher energy peaks with the same laser power. Metal materials are mainly marked by pulsed lasers because they require a higher energy density. Organic materials, on the other hand, are processed with continuous laser beams.
Marking materials have different compositions and therefore only absorb certain wavelengths. Creating an identification on a metallic material, for example, requires a different wavelength than a wooden material. A laser generates a single wavelength, so the laser type must be selected based on the material to be marked.
| Yb: YAG laser | CO₂ laser | UV laser | |
|---|---|---|---|
| Laser type | |||
| Laser medium | Solid state | Gas | Liquid |
| Wavelength of the laser | 1,064 nm | 10.6 µm | 355 nm |
| Material to be labeled | Specially for high-contrast lettering on plastics, steel, and aluminum | Non-metallic materials such as wood, leather, glass, and stone | Specially for sensitive materials |
The TOPMARK NEO laser marker from our portfolio is a fiber laser. This is a special form of solid-state laser. The active medium in solid-state lasers is doped glass or crystal. Foreign ions are included in a range of concentrations (doping) in the host crystal. Typical doping materials are neodymium, ytterbium, titanium, and erbium. The active medium of the TOPMARK NEO is a fiberglass doped with ytterbium ions. The pulsed ytterbium fiber laser feeds radiation from multiple pump laser diodes into a single-coupling optic. After exiting the central part of the fiberglass doped with ytterbium ions, the laser beam enters an optical fiber. A special optic then focuses the beam. The laser beam, which is guided through the laser-active fiber, undergoes a very high amplification due to the large length. Fiber lasers also offer high electrical-to-optical efficiency and an outstanding beam quality. Due to the short wavelength, these lasers can be focused on a smaller surface, thereby achieving a higher resolution than a CO₂ laser.
Laser engraving is based on powerful laser pulses. The power density of the laser pulses is so high that the material to be processed melts and vaporizes. When engraving solid material, the laser beam hits the surface of the solid material, removes some of the material to create an indentation – the engraving.
When engraving through abrasion of the top coating, the marking is created by the contrast between the top coating and the base material that becomes visible through the laser beam. This process is typically used for anodized aluminum, coating layers, or special laser marking films.
In annealing marking, the laser applies an oxide layer in the workpiece. The color of the layer depends on the temperature. No material is removed in this case, so the surface of the workpiece remains smooth and even.
This method creates a marking by melting the material. Carbonization is suitable for light-colored plastics because it causes a darkening of the material. By contrast, foaming forms small gas bubbles in plastic that reflect the light and thus create light-colored markings on dark plastic.
After laser marking, the laser beam can be used to cut out various contour shapes. Here, the laser continuously removes the material along the desired contour and completely separates the parts.
Particles and gases can be produced during laser marking. These must be removed from the processing room to ensure that a consistently high level of quality is maintained. Extraction that suits the respective application is also necessary for occupational health reasons. Using a combination of different filter classes is recommended to ensure the highest possible degree of extraction.
Filters are differentiated based on the particle size:
In an ideal scenario, the air from the processing room is pre-filtered first using different fine particle filters. In a second step, small particles are also filtered from the air using a HEPA filter. In this way, an overall separation efficiency of over 99.9% can be achieved.
