Laser cutting involves using a high-power density laser beam to concentrate light into a small spot, rapidly heating the material until it reaches its boiling point and vaporizes to form a cavity. The laser beam then moves along the surface of the material, creating a cut and completing the processing of the object.
Laser cutting is a kind of thermal cutting method, which can be divided into four categories: laser gasification cutting, laser fusion cutting, laser oxygen-assisted fusion cutting and controlled fracture cutting.
Laser cutting working principle
Compared to other cutting methods, laser cutting stands out for its fast cutting speed and high-quality results.
The benefits of laser cutting include:
- Excellent cutting quality: The small laser spot, high energy density and fast cutting speed result in better cutting quality.
- Thin and narrow incisions: The incisions made through laser gas cutting are thin and narrow, with parallel sides and good perpendicularity to the surface.
- Smooth, attractive surfaces: Cutting surfaces are smooth and visually attractive and, in some cases, can be used as a final processing step without the need for additional machining.
- Minimal impact on material properties: The width of the heat-affected zone is small after laser cutting, which means that the material properties near the cut are hardly affected. Furthermore, there is minimal deformation of the part, ensuring high cutting precision.
A cutting speed comparison between laser cutting and other cutting methods for low carbon steel sheets is shown in the table below.
Comparison of cutting speed of various cutting methods:
| Cutting method | Laser cut | plasma cutting | Oxyacetylene cutting | Water jet cutting |
| Cutting speed | Very fast | Fast | Slow | Very slowly |
- High cutting speed: for example, a 2500W laser can cut a 1mm thick cold-rolled carbon steel plate at a speed of 16-19 meters per minute.
- Non-contact cutting: Laser cutting is a non-contact process, meaning there is no physical contact between the nozzle and the workpiece, which eliminates the need to worry about tool wear.
1. Laser cutting accounts for 39% of the laser equipment market
The laser market grew in 2020, but the growth rate slowed compared to the previous two years. The sales revenue of laser equipment in the market (including imports) across all sectors was 69.2 billion yuan, representing a year-on-year increase of 5.17%.
Due to the uncertain global economic trend, the total sales revenue of China's laser equipment market is projected to be 74.0 billion yuan in 2021, with a year-on-year increase of 6.94%.
In the industrial laser equipment market, laser cutting is the most widely used application, accounting for 39% of the market. Marking and welding come second and third, accounting for 19% and 12% of the market, respectively.
2. Moving towards high power, high precision and large format
In recent years, domestic laser cutting machine technology has experienced significant advancements and is now moving towards greater power, greater precision and larger format capabilities.
In line with China's push towards smart production, the industrial sector is undergoing a transformation from traditional processing to high-quality production. As a result, the market scale of China's laser cutting industry is expected to continue its rapid growth trajectory.
3. Application of compressed air in laser cutting
Laser cutting machines are capable of meeting the cutting requirements of a wide variety of materials and complex shapes. Along with a high-energy laser, auxiliary gases are also required to complete the cutting process.
Commonly used auxiliary gases for laser cutting include oxygen (O2), nitrogen (N2), and compressed air. Compressed air is the most affordable and affordable option compared to oxygen and nitrogen. It is often used as an auxiliary gas for laser cutting.
The quality of compressed air has a direct impact on the quality of metal laser cutting. Factors such as size and gas pressure stability can affect the cutting result.
When selecting the size of the air compressor used to support the laser cutting machine, it is important to take into consideration the design of the laser cutting head, the required auxiliary gas pressure, and the size of the nozzle to ensure the best combination between the air compressor and laser cutting machine.
4. Comparison of laser cutting with different auxiliary gases
When performing laser cutting, the choice of cutting gas depends on the type of material to be cut. The selection of cutting gas and its pressure can significantly impact the quality of the laser cutting process.
The most commonly used auxiliary gases for laser cutting include oxygen (O2), nitrogen (N2), compressed air, and in some cases argon (Ar).
Cutting gas can be categorized into high pressure gas and low pressure gas based on its pressure.
The main functions of laser cutting auxiliary gases include supporting combustion and heat dissipation, removing molten residue generated during cutting, preventing molten residue from returning to the nozzle, and protecting the focusing lens.
The choice of laser cutting process and auxiliary gas depends on the material to be cut and the power of the laser cutting machine.
The following is a summary of the characteristics, uses and scope of application of different types of auxiliary gases:
(1) Oxygen (O 2 )
Oxygen is mainly used to cut carbon steel materials. The heat generated by the chemical reaction between oxygen and iron increases the endothermic fusion of the metal, thus improving cutting efficiency and allowing the cutting of thicker materials. This significantly increases the processing capacity of laser cutting machines.
However, the presence of oxygen results in the formation of an oxide film on the cutting surface, causing a quenching effect on the surrounding material and increasing its hardness. This may affect subsequent processing.
The cutting surface of oxygen-cut carbon steel plates is normally black or dark yellow. These plates are usually cut with low-pressure oxygen and then drilled.
(2) N nitrogen (N 2 )
When nitrogen is used as an auxiliary gas in cutting, it creates a protective atmosphere around the molten metal, preventing oxidation and preventing the formation of an oxide film. This results in an oxidation-free cut.
However, nitrogen does not react with the metal, leading to a lack of heat of reaction and weaker cutting ability compared to oxygen. Furthermore, nitrogen consumption during nitrogen cutting is several times greater than that of oxygen, resulting in higher cutting costs.
The benefits of non-oxidative cutting include direct welding, coating and strong corrosion resistance. The cutting surface is white.
Nitrogen is typically used to cut stainless steel, galvanized plates, aluminum plates and aluminum alloys, brass and other materials. Low pressure drilling and high pressure cutting methods can be used.
Gas flow has a significant impact on cutting during nitrogen cutting. To ensure optimal cutting, it is important to maintain sufficient gas flow and at the same time ensure cutting gas pressure.
(3) Compressed air
Compressed air can be easily obtained and is much cheaper than oxygen and nitrogen as it can be supplied directly by an air compressor.
Although air only contains about 20% oxygen, leading to lower cutting efficiency compared to oxygen cutting, its cutting capacity is similar to that of nitrogen and slightly higher than that of nitrogen cutting.
The cutting surface of air cutting is yellow.
When there is no strict requirement on the surface color of the cut material, using compressed air for cutting is the most economical and practical option compared to using nitrogen.
(4) Argon (Air)
Argon is an inert gas commonly used in laser cutting to prevent oxidation and nitrification. It can also be used in welding processes. However, it should be noted that the cost of argon is higher compared to nitrogen, making it less economical for typical laser cutting applications.
Argon cutting is mainly used to cut titanium and titanium alloys, and the end face of the kerf produced by argon cutting is white in color.
Currently, the market price of liquid nitrogen is approximately 1,400 yuan per ton. When using liquid nitrogen for laser cutting, Dewar cans are required, with a typical can containing 120 kg. The cost of 1kg of liquid nitrogen is more than 3 yuan.
Let's calculate it at 1,400 yuan/ton.
120×1.4=168 yuan, and the specific gravity of nitrogen in the standard state is 1.25kg/m 3 so the maximum use of liquid nitrogen in a Dewar tank is about 120/1.25=96Nm 3 which is converted to nitrogen cost per nm: 168/96 = 1.75 yuan /Nm 3 .
If a domestic brand air compressor is used to supply 16 bar compressed air, delivering 1.27 m 3 per minute, the full load input power of this type of air compressor is 13.4 kW.
If the industrial electricity tariff is calculated as 1.0 yuan/kWh, the air cost per m 3 is 13.4×1.0/ (1.27×60) =0.176 yuan/m 3 .
If the actual consumption of 0.5m3 gas per minute and the laser cutting machine works 8 hours a day, the daily cost saved by using air cutting compared to nitrogen cutting is: (1.75-0.176 )x8x60x0.5 = 378 yuan.
If the laser cutting machine works 300 days a year, the gas cost saved in one year will be: 378 × 300 = 113,400 yuan.
It is clear that using compressed air instead of nitrogen for cutting is a more economical and practical option. In recent years, laser cutting technology has undergone significant advancements, with a focus on high power, high precision and large format capabilities.
As China moves towards smart production, the industrial sector is undergoing a transformation from traditional processing to high-quality production.
The laser cutting market in China is expected to continue its rapid growth, offering broad market opportunities for laser air compressors.
