Tecnologia de limpeza a laser: princípios e aplicações

Laser cleaning technology: principles and applications

1. Introduction:

With the advancement and development of technology, laser processing technology has been widely used in production practice.

Laser processing (Laser Beam Machining, LBM) can be used for drilling, cutting, fine-tuning electronic devices, welding, heat treatment, etc.

2. Principle of laser cleaning technology:

1. Forms of contaminants:

Contaminants are mainly bound to surfaces through covalent bonds, dipole-dipole interactions, capillary action, hydrogen bonds, adsorption, and electrostatic forces.

Among them, capillary action, adsorption and electrostatic forces (as shown in Figure 1) are the most difficult to break.

Figure 1. Three Basic Pollutant Adsorption Forces on Solid Surfaces

Observation:

Capillary force comes from the cohesion of a very thin layer of liquid (such as atmospheric moisture) that forms in the small gaps between the particles and the surface of the substrate. Adhesion force is the main adhesion force for microscale pollutants.

2. Cleaning mechanism

The laser beam can produce at least three effects:

(1) Induce mechanical resonance on the solid surface, causing the disintegration and detachment of dirt or deposits from the surface;

(2) Heating the surface dirt to expand, thereby overcoming the adhesion force of the base material to the dirt particles and separating it from the surface of the object;

(3) Instantly vaporize, gasify, or decompose dirt molecules.

3. Cleaning Method 1 – Dry Cleaning.

Figure 2 Schematic diagram of the dynamic laser dry cleaning process

Adopting pulsed direct radiation for cleaning, the laser is absorbed by the substrate or particles, resulting in vibration that separates the substrate from contaminants.

4. Cleaning Method 2 – Liquid Film Cleaning.

Figure 3 Schematic diagram of the dynamic laser cleaning process in the presence of liquid film
  1. Incident laser.
  2. Liquid film.
  3. Contaminant particle.
  4. Explosive evaporation.
  5. Substrate.

First, deposit a layer of liquid film on the surface of the substrate, and then use laser radiation to clean it.

5. Cleaning Method 3 – Laser + Inert Gas.

When laser irradiating, blow inert gas toward the surface of the workpiece. When dirt is removed from the surface, it is gas expelled away from the surface to prevent re-pollution and oxidation of the clean surface.

3. Applications of laser cleaning technology.

1. Cleaning works of art.

  • 1a. Original appearance of the artwork.
  • 1b. Laser cleaning used on the top of the painting and chemical solvent used on the bottom.
  • 1c. Comparison of the original appearance with the effect after laser cleaning.
  • 1d. Combined laser and chemical solvent cleaning.

2. Mold Cleaning

3. Removing old paint from airplanes.

In Europe, laser cleaning systems have already been used in the aviation industry. After a certain period of time, the surface of an airplane needs to be repainted, but the old paint needs to be completely removed before repainting.

Traditional mechanical paint removal methods are prone to damaging the metal surface of the aircraft, posing safety risks to flight operation.

However, by using various laser cleaning systems, the paint layer on the surface of an Airbus A320 can be completely removed in two days without damaging the metal surface.

4. Duct Cleaning Inside Nuclear Reactors.

By using optical fibers to guide high-power laser beams into nuclear reactors, radioactive dust can be removed directly and the clean material can be easily disposed of.

Furthermore, as the operation is carried out remotely, it guarantees the safety of workers.

4. Conclusion

Laser cleaning technology can be used for liquid and solid cultural relics and space debris, as well as in situations where the waste is explosive or the substrate is easily damaged. The use of lasers has advantages such as safety, high efficiency and reliability.

Its applications in removing rust and removing paint from metal surfaces such as airplanes and ships, cleaning building surfaces, and cleaning crystal surfaces in the microelectronics industry show excellent superiority.

It can be inferred that with the development of laser technology and the decrease in laser costs, the application of laser cleaning technology will become even more widespread.

Recommended for you:

  • Metal surface engineering: the definitive guide
  • Laser Cleaning 101: Basics for Beginners
  • Sheet Metal Manufacturing Manual – Surface Treatment
  • 3 types of anodizing defects in aluminum alloys
  • Laser Welding 101: A Beginner's Guide
  • Laser cleaning machines: influence of mechanism and parameters

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