In the laser cutting process, the main factors affecting the cutting quality performance include laser beam quality, laser power, cutting speed, work piece thickness, material type and so on. Besides that the cutting head nozzle design is also an important factor. Today we will learn more about the relationship between nozzles and cutting quality.
The nozzle is typically mounted at the front end of the laser cutting head, which firstly helps to control the auxiliary gas and protects the focusing lens too. The following is the specific relationship between the nozzle and the cutting quality.
1. The effect on the cutting quality when the center of the nozzle is different from the center of the laser:
Affect the cutting section. When the cutting gas is ejected, the gas volume is not uniform, so that the cutting section is more likely to have one side of the melting, and the other side don’t. Especially, when cutting the metal sheet thickness over 3 mm, its effect is more serious, and sometimes it cannot be cut.
Affect the quality of sharp corners. When cutting a work piece with sharp corners or small angles, local over-melting is likely to occur. When cutting thick plates, it may not be possible to cut.
Affect the perforation. Especially for the thick plate, the instability during the perforation, the time is not easy to control, the penetration of the thick plate may cause over-melting.
2. The effect on the cutting quality when the diameter of the nozzle is different:
The nozzle has a different diameter like φ1.0 mm, φ1.5 mm, φ2.0 mm, φ2.5 mm, φ3.0 mm. At present, the nozzle aperture is often used in two sizes: φ1.5 mm and φ2 mm.
φ1.5mm is more suitable for the plate below 3mm,the cutting surface will be thinner; if using φ2mm, the cutting surface will be thicker, and the corners will be easily melted.
Thick plates above 3mm: Due to the high cutting power, the heat dissipation time is longer, and the cutting time also increases relatively. With φ1.5mm, the gas diffusion area is small, so it is not stable when used, but it is basically usable. With φ2mm, the gas diffusion area is large and the gas flow rate is slow, so it is stable when cutting.
The diameter of φ2.5mm can only be used for thick plate cutting of 10mm or more. In summary, the size of the nozzle aperture has a serious impact on the cutting quality and the quality of the perforation. At present, laser cutting uses nozzles of φ1.5 mm and φ2 mm aperture.
The work piece is kept at a stable distance from the nozzle during the cutting process to prevent the splash from rebounding during cutting. The diameter of the nozzle determines the shape of the airflow entering the slit, the gas diffusion area, and the gas flow rate, thereby affecting the removal of the melt and the stability of the cutting. The gas flow into the slit is large, the speed is fast, the position of the workpiece in the airflow is proper, and the ability to spray the melt is stronger. Therefore, the greater the nozzle aperture is selected, the worse the protection of the focusing mirror is, because cutting When the spark of the melt splashes, the chance of the bomb is so great that the life of the lens is shorter.
Note: When the nozzle is deformed or there is melting on the nozzle, its influence on the cutting quality is the same as described above. Therefore, the nozzle should be placed carefully and should not be damaged to avoid deformation; the melt stain on the nozzle should be cleaned up in time. The quality of the nozzles is highly accurate when manufactured and requires the correct method of installation. If the conditions are changed during cutting due to poor nozzle quality, the nozzle should be replaced in time.
If the want to know the other facters which influnt on cutting quality, you can refer to the previous blog on our website.
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