Laser ablation is the phenomenon of precise removal of coatings using a laser beam. As a result of its contact with the surface of the material, energy is exchanged. Selective evaporation of various types of layers then occurs. Laser ablation works on the surface of the object and removes material from this surface with an absolute minimum of interference. Its level can be easily changed and adjusted, depending on the material, the intensity of the laser beam, the pulse length and the wavelength of the laser. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates, whereas at high laser flux, the material is usually converted into plasma. When the so-called power density is selected properly, contaminants can be safely and precisely removed from virtually any surface. This includes metal alloys, composites, ceramics and even paper.
The simplest advantage of using laser ablation is the removal of material from a solid surface in a controlled manner. Very short laser pulses ensure that the coating is removed in such a short time that the surrounding material absorbs very little heat. An example of the application of this phenomenon is the removal of a wide range of materials such as heavy metals, paints, corrosion, lubricants and industrial compounds.
Environmentally friendly approach
Laser ablation is a far more cost-effective and environmentally friendly technique for removing coatings than any other abrasive or chemical method. When applying it, the use of abrasives, solvents or chemicals is not necessary. Fibre laser also offers other environmental benefits compared to other types of laser cleaning processes.
- Much lower energy consumption, as the fibre laser is approximately twenty times more efficient than its crystal or gas laser counterparts.
- Extended diode lifetime. Crystal or gas lasers typically have an average diode lifetime of 10,000 to 20,000 hours. Most fibre optic systems have a much longer lifetime ranging from 50,000 to 100,000 hours.
- Fibre lasers do not use gas during operation, as in the case of their counterparts.
Principle of operation of mobile laser systems
The FLASER lasers enable ablation based on a pulsed laser. This is an environmentally friendly process, much gentler than the abrasive technology, and material heating is minimal.
As a result of contact between the laser beam and the cleaned material surface, energy is exchanged. Laser ablation is a result of irradiation of the material surface with a pulse of laser radiation of the appropriate energy density in time (power density) and subsequent selective evaporation of various types of layers.
A single pulse of laser radiation from the presented device (200 W laser) has a circular shape. Uniform power distribution is achieved due to the shape and the relatively large area of the radiation incidence in a single pulse. The appropriate selection of parameters, i.e. the frequency, laser beam scanning speed and head feed rate, enable uniform distribution of "spots" of pulses striking one next to another. This results in even cleaning of the entire surface.
With a different combination of parameters, it is possible to obtain a different result. The parameters of the laser beam can be programmed in such a way that the individual pulses partly overlap and "hit" one next to another (cf. Fig. variant B) or so that there are gaps between them (cf. Fig. opposite; variant A). The result of such cleaning (variant A) is non-uniform development of the microstructure of the active surface. This cleaning method results in a much better preparation of the cleaned surface for painting, welding or glueing.
Laser cleaning brings benefits that give this method an advantage over other traditional methods of cleaning and preparing various surfaces. This is because this method is:
No mechanical and chemical impact on the cleaned surface. Due to the advantages presented above, the laser cleaning method is successfully used in heavy industry, electronics industry, aviation (e.g. for aircraft repairs), as well as in the restoration of historical paintings, sculptures, architecture and technology.
Cleaning of metal, composites and other plastics, ceramics, wood, stone and more. There are situations when an object is composed of various types of materials and the application of standard techniques becomes problematic since the different characteristics of each material necessitate the application of a different conservation technique.
Selective removal of individual layers from a given surface. If the surface of an object is covered with several layers of coatings, we can (by predetermining the so-called laser ablation threshold) uncover successive paint layers.
No generation of harmful substances. The use of lasers eliminates the formation of harmful substances, thus limiting the destructive impact on the cleaned object. Moreover, the laser method (as opposed to the commonly used sandblasting) is clean and dust-free, which makes it applicable in practically any conditions.