The Influence of Auxiliary Gas and Focus Position on Laser Cutting
Views: 84 Author: Summmer Publish Time: 2021-09-21 Origin: Site
The laser cutting machine focuses the laser light emitted from the laser into a high-power density laser beam through the optical path system. The laser beam irradiates the surface of the workpiece to make the workpiece reach the melting point or boiling point. At the same time, the high-pressure gas coaxial with the beam blows away the molten or vaporized metal. As the relative position of the beam and the workpiece moves, the material will eventually form a slit, so as to achieve the purpose of cutting. However, in the process of processing, there are many factors that affect the effect of laser cutting.
When the laser cutting machine cuts carbon steel, it usually uses auxiliary gas. Common auxiliary gases include oxygen, nitrogen and air. What is the difference between these three gases when cutting carbon steel?
First of all, the laser cutting machine uses air as the auxiliary gas and the cost is very low. Air cutting saves the high cost of auxiliary gas, and only needs to consider the electricity cost of the air compressor and the equipment itself. When cutting thin plates, the efficiency of air cutting can be compared with that of nitrogen cutting, and it is an economical and efficient cutting method. But air cutting also has obvious disadvantages when cutting. First, the cutting surface will produce burrs, which require secondary processing to clean up, which is not conducive to the entire product production cycle. Second, the cutting surface will turn black, which will affect the quality of the product. Laser cutting itself has the advantages of efficiency and quality accuracy, but the disadvantages of air cutting have caused many customers to abandon this cutting method.
Secondly, the laser cutting machine chooses oxygen as the auxiliary gas. Oxygen cutting is the most common and traditional cutting method. The advantage of a laser cutting machine using oxygen is mainly reflected in the cost of the gas. For example, there is no need to frequently change the auxiliary gas when cutting carbon steel, which can increase cutting efficiency and facilitate management. But the disadvantage is that after oxygen cutting, an oxide film will remain on the cutting surface. If the product with oxide film is directly welded, the oxide film will naturally peel off after a long time, and the product will form a virtual weld, which affects the welding quality.
Finally, for laser cutting, nitrogen can also be selected as an auxiliary gas. When oxygen is used as an auxiliary gas, an oxide film will be formed on the cutting surface, but the use of nitrogen can prevent the appearance of the oxide film and form a non-oxidized cutting. The surface of the non-oxidized cutting is generally white, which can be directly processed by welding, spraying, etc. The characteristics of strong corrosion resistance also make its application very wide.
Among the factors that affect the processing quality and processing capacity of the laser cutting machine, the focus position is also an important factor, and its specific relationship with processing is as follows.
Relative to the surface of the processed material, after the laser beam is focused, the position of the focal point is called the focal position. The focus position has an impact 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 changes in the focal position will cause changes in the diameter of the beam irradiated on the surface of the processed material and the angle of incidence of the processed material. As a result, the formation state of the slit and the multiple reflection state of the light beam in the slit are affected. These cutting phenomena will affect the flow of auxiliary gas and molten metal in the slit. The state of the focus on the surface of the processed material is set to z=o "zero", the focus position is expressed as "+" when moving upward, "-" when moving downward, and the amount of movement is expressed in 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.
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