Four methods and application fields of laser cleaning

As a world recognized manufacturing country, China has made great strides on the road of industrialization and made great achievements. At the same time, it has also caused serious environmental degradation and industrial pollution. In recent years, China's environmental protection laws and regulations have become more and more strict, resulting in some enterprises being shut down for rectification. The "one size fits all" environmental storm will have some impact on the economy. The key is to change the traditional production mode of pollution. With the progress of technology, people gradually explore various technologies that are conducive to environmental protection, and laser cleaning technology is one of them. Laser cleaning technology is a newly applied workpiece surface cleaning technology in recent ten years. It is gradually replacing the traditional cleaning technology in many fields with its own advantages and irreplaceable.

Traditional cleaning methods include mechanical cleaning method, chemical cleaning method and ultrasonic cleaning method. Mechanical cleaning method uses mechanical means such as scraping, wiping, brushing and sandblasting to remove surface dirt; Wet chemical cleaning method is to use organic cleaning agent to remove surface attachments by spraying, drenching, soaking or high-frequency vibration; The ultrasonic cleaning method is to put the parts to be treated into the cleaning agent and remove the dirt by using the vibration effect generated by the ultrasonic wave. At present, these three cleaning methods still occupy a dominant position in the cleaning market in China, but they will produce pollutants in varying degrees, and their application is greatly limited under the requirements of environmental protection and high accuracy.

Laser cleaning technology refers to the laser process that uses high-energy and high-frequency laser beam to irradiate the surface of the workpiece, so that the dirt, rust spots or coatings on the surface can be evaporated or peeled instantaneously, and the attachments or coatings on the surface of the cleaning object can be effectively removed at high speed, so as to achieve a clean laser process. Laser is characterized by high directivity, monochromatic, high coherence and high brightness. Through the focusing and Q-switching of the lens, the energy can be concentrated in a very small space and time range. In terms of methods, there are four laser cleaning methods:

1. Laser dry cleaning method, i.e. using pulse laser direct radiation to decontaminate;

2. Laser + liquid film method, i.e. first depositing a layer of liquid film on the surface of the substrate, and then decontaminating with laser radiation; When the laser is irradiated on the liquid film, the liquid film will be heated rapidly, resulting in explosive vaporization. The explosive shock wave will loosen the dirt on the surface of the substrate. And fly away from the surface of the processed object with the shock wave to achieve the purpose of decontamination.

3. The method of laser + inert gas, that is, the inert gas is blown to the surface of the substrate at the same time of laser radiation. When the dirt is peeled off from the surface, it will be blown off the surface by the gas immediately to avoid surface re pollution and oxidation;

4. After the dirt is loosened by laser, it is cleaned by non corrosive chemical method. At present, due to the development of China's high-end manufacturing industry and the continuous improvement of environmental protection requirements, the traditional cleaning technology (chemical method and mechanical polishing method) is far from meeting the needs of China's industrial production. The backward cleaning technology restricts the normal production and operation of some important industries in China. Therefore, as a representative of green and efficient manufacturing, laser cleaning technology has a broad market scale under the rapid development of China's high-end manufacturing industry.

Compared with the traditional cleaning method, laser cleaning is a "green" cleaning method, which has incomparable advantages: it does not need to use any chemical agent and cleaning liquid, and the waste material after cleaning is basically solid powder, small in volume, easy to store, can be adsorbed and recycled, no photochemical reaction, no noise and environmental pollution, and at the same time, it does not damage the health of operators, and is easy to realize automatic control, Realize remote control cleaning.

Laser cleaning is widely used in various fields:

1. Mold cleaning. The laser can realize the non-contact cleaning of the mold, which is very safe for the mold surface, can ensure its accuracy, and can clean the submicron dirt particles that cannot be removed by the traditional cleaning method, so as to realize the real pollution-free, efficient and high-quality cleaning. Precise de ester cleaning in precision instrument industry.

The precision machinery industry often needs to remove the esters and mineral oils used for lubrication and corrosion resistance on the parts, usually by chemical methods, and chemical cleaning often still has residues. Laser deasterification can completely remove esters and mineral oil without damaging the surface of parts. The explosive vaporization of the oxide thin layer on the surface of the parts caused by the laser generated shock waves, which led to the removal of dirt rather than mechanical interaction.

2. Rail cleaning. At present, grinding wheel and abrasive belt are used to clean the rail before welding. The base material is seriously damaged and the residual stress is serious. In addition, a large number of grinding wheel consumables are consumed every year, with high cost and serious dust pollution to the environment. Laser cleaning can provide high-quality and efficient green cleaning technology for the track laying production of high-speed railway in China, solve the above problems, eliminate the welding defects such as seamless rail holes and gray spots, and improve the stability and safety of the operation of high-speed railway in China.

3. Aviation. The surface of the aircraft shall be repainted after a certain period of time, but the original old paint shall be completely removed before painting. Chemical immersion / wiping is the main paint removal method in the aviation field. This method causes a large number of chemical auxiliary wastes and can not achieve local maintenance paint removal. This process is heavy and harmful to health. Laser cleaning can achieve high-quality removal of paint on aircraft skin surface, and it is easy to realize automatic production. At present, this technology has been applied to the maintenance of some high-end models abroad.

4. Ship field. At present, the sand blasting method is mainly used for the pre production cleaning of ships. The sand blasting method has caused serious dust pollution to the surrounding environment and has been gradually banned, which has led to the reduction of production or even the shutdown of the ship production enterprises. Laser cleaning technology will provide a green and pollution-free cleaning scheme for ship surface anti-corrosion coating.

5. Military industry. Laser cleaning technology is widely used in weapon maintenance. With the laser cleaning system, rust and pollutants can be removed efficiently and quickly, and the removal parts can be selected to realize the automation of cleaning. Laser cleaning is not only cleaner than chemical cleaning, but also has little damage to the surface of the object.

Source: Shengtong intelligent laser