In laser ablation, a layer of material or coating is removed by a laser beam. This is the basic process in all laser cleaning applications.
Take the example of laser derusting of steel. When the beam hits the surface, the molecular bonds of the dust or rust layer are broken and detached from the substrate. All materials have an ablation threshold. You can fire a laser beam thousands of times, but as long as the energy is below the ablation threshold of the material being processed, nothing will be removed. In less technical terms, you can imagine that the layer to be removed is simply vaporised by the laser beam.
For example, the removal threshold of rust is much lower than that of common metals such as steel and aluminium. The same applies to paint and oil. Because the difference between these two values is so great, contaminants and coatings can be completely removed without damaging the underlying base material. There is simply not enough energy to do any damage.
The principle is that each material has different properties and therefore different molecular bonds. In other words, each material has a certain removal threshold. To successfully ablate a certain layer of material, the energy transmitted by the laser beam must be greater than the ablation threshold of the material in question.
Since each material has its own ablation threshold, laser cleaning can separate two or more materials when trying to remove an unwanted layer from an object. If the removal thresholds of the materials are sufficiently different, it is possible to select the material to be removed and leave the other material intact.
Since this cleaning method only uses a laser beam to vaporise the layer to be removed, there is literally no need for consumables. Since laser cleaning converts materials into vapours, a vapour extraction system must be installed near the laser to ensure that no paint, oil or dust particles are released into the air.
Furthermore, no chemicals or solvents are used in the lasers. This makes laser surface cleaning one of the safest methods of removing rust and coatings. Not only is there no chemical waste, but workers are completely safe working around laser cleaning machines that meet international laser safety standards. Workers do not need personal protective equipment and do not have to handle hazardous chemicals.
Fibre laser cleaning systems can remove a given layer in two different ways. The laser beam is either a continuous wave of light or a pulsed wave with a specific repetition rate. Although the result is almost the same, the removal rate varies greatly depending on the method.
For a given area, the power increases when the same energy is invested in a short pulse. A pulsed laser beam is a more efficient and faster removal method than a continuous beam. Short laser pulses clean surfaces faster, but also ensure that the underlying material does not get too hot.
1. Painting parts that would otherwise be discarded due to paint defects.
2. Laser coating of the surface to optimise paint adhesion.
3. Laser removal of oxides from special alloy ingots.
4. Pre-weld treatments to remove rust and other contaminants from weld areas.
5. Post-weld treatments to remove aluminium and stainless steel oxides
6. Laser ablation is not only used for cleaning, but also for a variety of other industrial applications.
7. Removing the coating immediately after the plating process replaces the coating of parts on production lines.