Structuring/Texturing

Structuring and texturing

Precise creation of structures and textures using laser radiation

Variety of surface designs thanks to laser radiation

The ultrashort pulse laser is an extremely versatile tool for processing surfaces. Structuring and texturing are produced by laser ablation. In this way, regular structures can be produced in order to specifically adapt the technical properties of a surface. Furthermore, the optical and aesthetic characteristics as well as the haptic properties of a surface can be changed. Due to its precision of a few 10µm across the beam direction and a few µm in the beam direction, structures and textures can be created with extreme detail.

The advantages of structuring and texturing with the ultrashort pulse laser are:

Detailed structuring thanks to the flexibility and good focusability of the tool laser. The achievable accuracies are in the µm range in all three dimensions.
High-quality machining. Thanks to minimal heat input during machining with the ultrashort pulse laser, quality-reducing effects are prevented. For example, the formation of a burr can be avoided.
Low roughness (Ra < 1µm possible) of the laser-structured surfaces.

Laser structuring or laser texturing

In laser structuring or texturing, regularly arranged geometries are created on a surface by removing material. The individual elements of the structure can be only a few micrometres to several millimetres in size. The template for the structuring is typically a dxf file in which the geometries to be created are stored. A scanner system is used for structuring/texturing, which moves the laser beam quickly over the workpiece and removes the desired geometry layer by layer in several processing steps.

The technology of material removal with the ultrashort pulse laser

The creation of structures is one of the most diverse applications with the ultrashort pulse laser. The laser beam is typically moved over the workpiece with a scanner system and the material is ablated layer by layer. In this way, the desired geometry is created in several processing steps. This procedure is outlined in the following figure.
2.5D-structuring with the ultrashort pulse laser
Less than 1 µm of material is removed per laser pulse. Accordingly, several processing steps are needed to create the desired geometry. In order to obtain a high-quality machining result with low surface roughness, the process parameters must be set correctly. Important influencing parameters are, among others, the energy density of the laser beam in the focus, the pulse overlap as well as the hatching, which is processed in each machining step. In the following, a brief overview of the influence of the individual parameters will be given:
  • Energy density: With regard to process efficiency, there is an optimal energy density which, depending on the material, corresponds to approximately 5x to 15x the ablation threshold. However, this range of energy density is not only optimal with regard to process efficiency, but also with regard to the quality of the ablation result. Too high energy densities lead to a very roughened surface.
  • Pulse overlap: Since the laser beam has a Gaussian beam profile, the depth of ablation produced by a laser pulse is parabolic. In order to achieve a uniform ablation result, a certain overlap between the pulses is required. The limiting factor here, however, is the effect of heat accumulation. If the pulse overlap is too high, the heat introduced by each individual laser pulse accumulates so that the temperature of the workpiece exceeds a damage temperature and quality-reducing effects occur.
  • Hatching: In order to achieve uniform removal with low surface roughness, the hatching should be adjusted for each machining step. This prevents irregularities in the material removal from accumulating with each machining step due to the parabolic removal per pulse.
With the increase in industrial applications of structuring with the ultrashort pulse laser, further processing strategies are being developed. For example, burst pulses are used to increase the ablation rate compared to single pulses. The resulting rough surfaces can be subsequently smoothed using a nanosecond laser. Such further developments are constantly opening up new fields of application for the technology of structuring with the ultrashort pulse laser.
Only the correct combination of the different process parameters produces a high-quality structure.
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