Nozzle | The second particle of vulnerable parts of Fiber Laser Cutting Machine

06, 2019

by oreelaser

In the process of laser cutting, the main factors affecting the cutting quality include laser beam quality, laser power, cutting speed, workpiece thickness, material type and so on. In addition, cutting head nozzle design is also an important factor. Today we will learn more about the relationship between nozzle and cutting quality.

 

The nozzle is mounted in front of the laser cutting head, which helps control the auxiliary gas and protects the focusing lens. The following is a specific relationship between nozzle and cutting quality.

 

1. When the center of the nozzle is different from the laser center, the effect on the cutting quality:

 

  • Affect the cutting part. When the assist gas is injected, the gas volume distribution is uneven, so the cut portion is more likely to have a molten side while the other side has no melted side. In particular, when the thickness of the cut metal sheet exceeds 3 mm, the effect is more serious and sometimes it is impossible to cut.

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  • Affect the quality of sharp corners. Local over-melting may occur when cutting a workpiece having a sharp corner or a small angle. When cutting thick plates, it may not be possible to cut.

 

  • Influence perforation. Especially for thick plates, the instability during the perforation process, the time is not easy to control, and the penetration of the thick plate may cause excessive melting.

 

2. Effect on cutting quality when nozzle diameters are different:

 

The nozzles have different diameters, such as φ1.0 mm, φ1.5 mm, φ2.0 mm, φ2.5 mm, φ3.0 mm. Currently, nozzle apertures are typically used in two sizes: φ 1.5 mm and φ 2 mm.

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≦ 3mm plates

Φ1.5mm is more suitable for plates below 3mm, the cutting surface is thinner; if φ2mm is used, the cutting surface will be thicker and the corners will melt easily.

 

> 3mm plates

Plates with a thickness of more than 3 mm: Due to the high cutting power, the heat dissipation time is longer and the cutting time is relatively increased. Φ1.5mm, the gas diffusion area is small, unstable when used, but basically can be used. Φ2mm, the gas diffusion area is large, the gas flow rate is slow, and the cutting is stable.

 

> 10mm plates

The diameter of φ2.5mm can only be used for thick plate cutting of 10mm or more. 

In summary, the size of the nozzle holes severely affects the quality of the cut and the quality of the perforations. Currently, laser cutting uses nozzles of φ 1.5 mm and φ 2 mm apertures.

 

During the cutting process, the workpiece is held at a constant distance from the nozzle to prevent the splash from rebounding during the cutting process. The diameter of the nozzle determines the shape of the gas stream entering the slit, the gas diffusion region and the gas flow rate, thereby affecting the stability of the melt removal and cutting. The flow rate of the gas entering the slit is large, the speed is fast, the position of the workpiece in the gas flow is appropriate, and the ability to spray the melt is stronger. Therefore, the larger the nozzle aperture is selected, the worse the protection of the focusing mirror is, because the possibility of the bomb is large when the spark of the melt is splashed, so that the life of the lens is shorter.

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Note: When the nozzle is deformed or the nozzle is melted, its effect on the cutting quality is the same as above. Therefore, the nozzle should be placed carefully and should not be damaged to avoid deformation; the melted stain on the nozzle should be cleaned up in time. The quality of the nozzles at the time of manufacture is very accurate and requires the correct installation method. If the conditions are changed during the cutting process due to poor nozzle quality, the nozzle should be replaced in time.

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