Working principle of laser cutting
Laser cutting replaces the traditional mechanical knife with an invisible beam. It has the characteristics of high precision, fast cutting without cutting pattern restrictions, automatic typesetting to save materials, smooth incision, low processing cost, etc. It will gradually improve or replace the traditional metal cutting process equipment. The mechanical part of the laser cutter head has no contact with the workpiece, and will not scratch the surface of the workpiece during work; the laser cutting speed is fast, the incision is smooth and flat, and generally no subsequent processing is required; the cutting heat affected zone is small, the plate deformation is small, and the cutting seam (0.1mm~0.3mm); the incision has no mechanical stress and no cutting burrs: high processing accuracy, good repeatability, and no damage to the material surface: CNC programming, can process any plane map, can cut a large whole plate, no need to open a mold, economical and time-saving.
Composition of laser cutting equipment
Laser cutting equipment is mainly composed of laser, light guide system, CNC motion system, automatic height adjustment cutting head, working platform and high-pressure gas blowing system. Many parameters affect the laser cutting process, some of which depend on the technical performance of the laser and machine tools, while others are variable. The main parameters of laser cutting are:
Main parameters of laser cutting
1 Light mode
The fundamental mode, also known as the Gaussian mode, is the most ideal mode for cutting, and mainly appears in low-power lasers with a power of less than 1kW. Multimode is a mixture of high-order modes. At the same power, multimode has poor focusing and low cutting ability. The cutting ability and cutting quality of single-mode lasers are better than multimode.
2 Laser power
The laser power required for laser cutting mainly depends on the cutting material, material thickness and cutting speed requirements. Laser power has a great influence on cutting thickness, cutting speed, incision degree, etc. Generally, as the laser power increases, the thickness of the material that can be cut also increases, the cutting speed increases, and the incision degree also increases.
3 Focus position
The focus position has a great influence on the incision width. Generally, the focus is selected to be located about 1/3 of the thickness below the material surface, and the cutting depth is the largest and the incision width is the smallest.
4 Focal moment
When cutting thicker steel plates, a beam with a longer focal moment should be used to obtain a cutting surface with good verticality. The focal depth is large, the spot diameter is also increased, and the power density decreases accordingly, which means the cutting speed is reduced. To maintain a certain cutting speed, the laser power needs to be increased. It is advisable to use a beam with a smaller focal length for cutting thin plates, so that the spot diameter is small, the power density is large, and the cutting speed is fast.
5 Auxiliary gas
Oxygen is often used as the cutting gas for cutting low-carbon steel to utilize the heat of the iron-oxygen combustion reaction to promote the cutting process, and the cutting speed is fast, the incision quality is good, and a slag-free incision can be obtained. Its pressure increases, the kinetic energy increases, and the discharge capacity is enhanced: the size of the cutting gas pressure is determined according to the material, plate thickness, cutting speed and cutting surface quality factors
6 Nozzle structure
The structural shape of the nozzle and the size of the light outlet also affect the quality and efficiency of laser cutting. Different cutting requirements require different nozzles. Commonly used nozzle shapes are: cylindrical, conical, square, etc. Laser cutting generally uses a coaxial (airflow is concentric with the optical axis) blowing method. If the airflow is not coaxial with the optical axis, a large amount of splashing is likely to occur during cutting. To ensure the stability of the cutting process, it is usually necessary to control the distance between the nozzle end face and the workpiece surface, generally 0.5~2.0mm, so that the cutting can proceed smoothly.
