Selecting Assist Gases for Laser Cutting Machine

Selecting Assist Gases for Laser Cutting Machine

Fiber Laser cutting is a widely used heat treatment process in industrial manufacturing. Laser cutting machines are able to quickly engrave and cut metal sheets, and can achieve a high-quality surface finish even when processing particularly complex shapes.

In this encyclopedia article, we will explore the laser cutting process, technology and its assist gases, including nitrogen, oxygen and compressed air, to help you understand how it works and its benefits.

What is fiber laser cutting?

Laser cutting is a production process that uses a high-powered laser to cut materials, which is guided through optics by a computer numerical control (CNC) system. This production process is widely used in various industries such as automotive, aerospace, electronics and medical, and can be used to cut a variety of materials such as metals, plastics, ceramics, wood, fabrics and paper.

Laser cutting uses a focused laser beam to melt the material in a localized area, and produces the cutting effect with the help of a coaxial jet. The laser beam itself is not affected by the gas, which is responsible for effectively burning, melting or vaporizing the material, and the gas is responsible for blowing away any debris generated in the process, thereby ensuring a high-quality cut edge.

Laser cutting can also be used for welding and etching. Advantages of laser cutting include high precision and accuracy, less contamination, and easier clamping of the workpiece. Fiber lasers, in particular, are known for their ability to cut with precision. A key advantage of fiber lasers is their ability to provide consistent beam quality over long distances, so they can cut evenly across a wide range of material types and thicknesses. This consistency helps improve the quality of cut edges and minimizes the need for secondary operations.

How does a laser cutter work?

A laser cutter works by directing a high-powered laser beam through optics and onto the material to be cut. The laser beam is focused by a lens and projected onto the material, causing the local material temperature to rise rapidly and melt or vaporize. A coaxial gas stream is then used to blow away the molten material, completing the material removal and creating the cutting effect. The gas stream also helps cool the material and prevent it from warping or twisting. Laser cutters are controlled by a computer numerical control (CNC) system to ensure precision and accuracy during the cutting process.

What is assist gas in fiber laser cutting?

Assist gas is used in laser cutting to improve the quality and efficiency of the cutting process. The assist gas helps purge the molten material and prevents it from re-solidifying on the surface of the material. It also helps cool the material and prevent it from distorting or deforming. Nitrogen, oxygen and compressed air are the most commonly used assist gases in laser cutting.

1. Using Nitrogen in Laser Cutting

Nitrogen is the most widely used assist gas in laser cutting, thanks to its inert nature. It is used to ensure high-quality performance of the laser, especially when high-quality cutting is required. Nitrogen removes oxygen from the air, preventing it from reacting with the hot metal, and obtaining a perfect, bright cut without affecting the color of the material (depending on the purity of the nitrogen used). Nitrogen is an inert gas, which allows the laser to operate in an oxygen-free environment and prevents oxidation of the cut edge. Nitrogen also plays an important role in reducing costs, increasing cutting speeds, increasing productivity, improving control performance and achieving efficient processing. Optional "plug-and-play" solutions provide nitrogen on demand.

2. Using Oxygen in Laser Cutting

Laser cutting uses oxygen as an assist gas for materials that are difficult to process by other methods. Oxygen is a highly reactive gas that multiplies the power of the laser beam and causes an exothermic reaction, which allows the cutting of thicker materials. Oxygen reacts with the material being cut, promoting melting and vaporization through chemical reactions. Depending on the material, oxygen can also be used to increase cutting speed and reduce the cost of the cutting process. However, oxygen can cause oxidation and form a carbonized layer on the cut edge, which can result in poor surface quality of the product, and the oxidized surface can also affect the adhesion of coatings or paints. In addition, oxygen reacts strongly and very thin slices cannot be obtained.

3. Using compressed air in laser cutting

Compressed air can also be used as an auxiliary gas in laser cutting, and it can also increase the speed and economic benefits of laser cutting. However, due to the 21% oxygen content in air, it is not possible to process parts with clean cuts when using compressed air as an auxiliary gas for laser cutting (usually, these parts need to be deburred before entering the next process, which requires additional labor). This cut quality is sufficient for parts that will be painted or welded later, because the color of the cut edge is not important.

What is the purity of the auxiliary gas generally?

The purity of the assist gas depends on the customer's requirements for the final product, but it is important to consider the following:

 If air is used, we cannot change the purity of the air, so it will contain 78% nitrogen and 21% oxygen.

 If oxygen is used, the purity is usually higher than 99.5%.

 If nitrogen is used, the purity will depend on the material being cut, whether the material is further processed, and the importance of the cut edge color.

Remember that by reducing the purity of the nitrogen, you can significantly reduce costs.