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What is Laser Cleaning? How Does it Work?

By Published On: August 8, 2022Categories: Application1500 wordsViews: 77

What is Laser Cleaning?

Laser cleaning is an eco-friendly process used to remove rust, paint, oxide and other contaminants from metal surfaces. Because of its efficiency, it is being used in an increasing number of applications. Laser cleaning requires a pulsed fiber laser (typically 50 watts or more).

Traditional industrial cleaning methods are often seen as tedious (and for good reasons). Rust removal can be time and labor consuming. Oxide removal may involve hazardous chemicals specific to each material that needs to be removed. In some cases, paint removal by sandblasting can damage the metal underneath.

Dealing with these problems usually comes at a significant cost, but laser cleaning is changing this: it is a cost-effective solution that reduces cleaning times and maintenance.

If you are skeptical about these claims regarding laser technology, keep reading for the key facts about what a laser does when removing contaminants and coatings.

laser-rust-remover-tool

Basic Principle of Laser Cleaning

Essentially, laser cleaning is laser ablation applied to some kind of unwanted substances on some workpiece. Usually, the hit material exhibits substantial absorption of the incident intense laser light. The highly localized conversion of optical energy to heat leads to a very rapid temperature rise and consequently to evaporation of the material – possibly also involving partial or complete chemical destruction of the material. The strong temperature gradient resulting from the localized heating creates substantial mechanical stress which often supports the removal process.

The laser radiation often needs to be tightly focused to the surface of the target area, because the required ablation process works only above a certain intensity threshold. Cleaning may be possible with relatively low average power, but then requires tight focusing, which in turn leads to longer processing times. If a higher laser power is available, one may use a beam shape which is much elongated in one direction in order to clean a correspondingly wider stripe in one go. Often, the laser beam is systematically moved over the surface to be cleaned, covering the relevant area with a suitable pattern.

The laser radiation often needs to be tightly focused to the surface of the target area, because the required ablation process works only above a certain intensity threshold. Cleaning may be possible with relatively low average power, but then requires tight focusing, which in turn leads to longer processing times. If a higher laser power is available, one may use a beam shape which is much elongated in one direction in order to clean a correspondingly wider stripe in one go. Often, the laser beam is systematically moved over the surface to be cleaned, covering the relevant area with a suitable pattern.

In many cases, one exploits substantially stronger absorption in the material to be removed, compared with the less absorbing substrate material which is supposed to remain. One may then exceed the intensity threshold for ablation of the dirt while not reaching it for the substrate material. It can further be helpful that the substrate material is often more robust in other ways, e.g. concerning hardness or thermal conductivity.

Sometimes, additional selectivity may be introduced by so tightly focusing a laser beam that the intensity rapidly decreases for longitudinal positions behind the beam focus. Shallow beam incidence can then also help.

Beam parameters like wavelength, average power, focus beam diameter etc. may need to be adjusted when applying the cleaning process to other circumstances.

portable-laser-rust-removal-machine-for-sale

What kind of lasers are suitable for cleaning processes?

It is common to apply pulsed lasers with nanosecond or even shorter pulse durations for cleaning purposes, because compared with continuous-wave operation this leads to a lower heat load on the cleaned material (“cold ablation”). A high pulse repetition rate is usually wanted for a high enough processing speed. Pulsed fiber lasers and more conventional Q-switched solid-state lasers are often used. In some cases, one uses an excimer laser, because the ultraviolet light is particularly well absorbed in some materials.

Some continuous-wave high-power lasers are also used. For example, direct diode lasers are attractive because of their high wall-plug efficiency and relatively low installation cost, despite their very limited potential for pulse generation. CO2 lasers, partly in continuous-wave operation, are also still in use. One of their advantages is the lower risk for the eyes .

laser-rust-remover-for-sale

Advantages of Laser Cleaning

Traditional laser machines have some limitations, such as cleaning with chemical solvents, using media blasting, which is very abrasive, dry ice blasting, and causing severe environmental pollution. But to solve this, there was a need for a modernized equipment technology. With that said, let look at its advantages;

  • Eco-Friendly

The process does not use harmful products that might harm the environment, such as solvents, acids, or toxic chemicals. This reduces the risk of contamination or exposure of employees to dangerous materials. There are also no exhaust emissions, and all residues are recycled, and low noise is produced.

  • Contact Free / Non-Abrasive

Laser cleaning removes impurities from the surface of an object without touching the underlying material as no chemicals are used, and no mechanical or thermal strain is placed on it. Thus, unnecessary wear is not caused; hence the quality of content is not degraded.

  • Online Automation

It puts the worker far away from the operation as it requires very little input from an operator; hence the element of safety is maintained. Due to its automatic nature, operations can be run fast with a high degree of accuracy, making the technology reliable and has excellent power output, pulse parameters, and wavelengths. This results to lower costs compared to other cleaning systems.

  • Spatially Selective

The cleaning process is straightforward as the machines can clean various types of contaminants to achieve cleanliness. Its small spot size focuses on the preferred area and ignores all locations that do not require cleaning, therefore saving on time.

  • Cleaning of Micro-Application

The laser cleaning machine can clean organic contaminants and inorganic materials like metal corrosion, dust, and metal particles. It can be achieved through a long-distance operation. It can easily clean sites that traditional cleaning systems can’t reach. This is important as it is used in dangerous places to ensure the safety of the personnel.

  • Cost Saving

Although the purchase price is quite an investment, you can use the machine for an extended period without having to buy another one. The maintenance and operation

The cost is low and favorable to companies or individuals.

rust-cleaning-laser.

Applications of Laser Cleaning

Laser cleaning is used under quite different circumstances; the most important laser cleaning applications are explained in the following.

Cleaning of Industrial Workpieces in Factories

In numerous industrial fabrication processes, workpieces consisting of some metal (steel, cast iron, brass etc.), glass or ceramic material, for example, need to be freed of unwanted layers of substances like a paint or other coating, an oil film, an oxidized layer (e.g. rust) or a possibly not well defined kind of dirt. Such tasks occur in a wide range of industries, including automotive manufacturing, electronics, medical technology, aerospace and defense, plastics manufacturing and power plants. Depending on the circumstances, hand-held or highly automated cleaning machines are used.

Gas and Oil Pipelines

The inner sides of gas and oil pipelines can be affected by various kinds of depositions, which occasionally need to be removed. This is done with automated cleaning robots, which may apply different techniques, including laser cleaning. Here, a specific advantage of laser cleaning can be that no consumables are required, which would possibly need to be supplied at remote locations and transported over a long length of pipeline; only the required electrical energy needs to be provided.

Aerospace and Ships

The bodies and various special parts of ships, for example propellers, need to be regularly cleaned, because they are strongly affected by the deposition of various substances from the water. Here, powerful laser cleaning machines can help to get such work done effectively and quickly.

Similar tasks exist for airplanes, where large surface areas and various special parts need to be kept reasonably clean. Cleaning operations may be combined with the search for material defects.

Apart from maintenance, many production steps for airplane or ship parts require cleaning processes.

Preparation of Sensitive Processes

Various industrial processes, such as bonding processes, the application of coatings or semiconductor lithography, work reliably only with carefully cleaned surfaces. Here, laser cleaning can often provide a good solution.

Restoration of Artworks

Valuable ancient artworks (e.g. outdoor statues, monuments, stoneworks) are often substantially affected by air pollution, for example by deposition of dust or soot particles. It can be challenging to remove such dirt without damaging the work. Here, both the highly targeted application – e.g. only to specific points under careful visual control – and the selective absorption (e.g. of dark dirt particles on a lighter background) can be very helpful.

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