Views: 70 Author: heyu Publish Time: 03-16-2021 Origin: Site
Among the factors that affect the processing quality and processing capacity of the laser cutting machine, the most important factor is the focus position. Laser cutting uses a focusing lens to focus the high-power laser beam to form a small focus, and then uses the high energy of the focus to treat the steel plate. Melt and vaporize to realize cutting. The positioning of the laser focus is a very critical step. Only when the focus is aligned can a good quality of steel plate cutting be ensured.
With respect to the surface of the processed material, after the laser beam is focused, the focal position is called the focal position. The focus position has an effect on almost all processing parameters such as the width of the slit, the slope, the roughness of the cutting surface, the adhesion state of the slag, and the cutting speed.
This is because the change of the focal position will cause the diameter of the beam irradiated on the surface of the processed material and the angle of incidence of the processed material to change. As a result, the formation state of the slit and the multiple reflection state of the beam in the slit are affected. These cutting phenomena will affect the flow of auxiliary gas and molten metal in the slit.
The figure shows the relationship between the focal position Z of the laser cutting machine and the slit width W on the surface of the processed material.
The state of the focus on the surface of the processed material is set to z=o "zero", the focus position is represented by "+" when moving upward, and "-" when moving downward, and the moving amount is represented by mm. The focal point is at the focal position z=o where the upper slit width W is the smallest. Regardless of whether the focus position is moved up or down, the upper slit width W will become wider.
This change also has the same tendency when processing lenses with different focal lengths are used. The smaller the beam diameter at the focal position and the shorter the focal depth of the lens, the larger the upper slit will vary with the focal position.
The above figure shows the best focus position of the metal laser cutting machine when processing various processing materials.
(1) is the case when the smallest beam diameter z=0 can be obtained on the surface of the processed material. At this time, the maximum energy density can be obtained on the surface of the processed material, and the melting range is relatively narrow, which determines the characteristics of the processing.
(2) is the situation when the focus position is on the "+" side (Z>O). At this time, the laser beam irradiation range on the surface of the processed material becomes wider, and the beam in the slit has a spread angle, which expands the slit width.
(3) When the focal position is on the "-" side (Z<0), the range of the laser beam irradiated on the surface of the processed material becomes wider. The closer to the focal position in the thickness direction, the greater the melting capacity. Afterwards, an inverse slope is generated.
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