Any kind of thermal cutting technology, except in a few cases, can start from the edge of the board, generally a small hole must be punched in the board. In the laser punching compound machine, a hole was first punched out with a punch, and then the laser was used to cut from the small hole. There are two basic methods of perforating a laser cutting machine without a stamping device:
Cutting perforation
Blast perforation-the material forms a pit in the center after continuous laser irradiation, and then the molten material is quickly removed by the oxygen stream coaxial with the laser beam to form a hole. Generally, the size of the hole is related to the thickness of the plate. The average diameter of the blasting perforation is half the thickness of the plate. Therefore, the blasting perforation of the thicker plate is larger and not round. On waste. In addition, because the oxygen pressure used for perforation is the same as that during cutting, the splash is large.
Pulse perforation——Pulse laser with high peak power is used to melt or vaporize a small amount of material. Air or nitrogen is usually used as auxiliary gas to reduce the expansion of holes due to exothermic oxidation. The gas pressure is lower than the oxygen pressure during cutting. Each pulsed laser produces only small jets of particles, stepping deeper, so thick plate perforations take a few seconds. Once the perforation is complete, the auxiliary gas is replaced with oxygen for cutting. In this way, the diameter of the perforation is small, and the quality of the perforation is better than that of blasting. The laser used for this purpose should not only have a high output power; more importantly, the time and space characteristics of the beam, so the general cross-flow CO2 laser cannot meet the requirements of laser cutting. In addition, pulse perforation also requires a more reliable gas path control system to achieve the switching of gas type, gas pressure, and perforation time.
In the case of pulse perforation, in order to obtain high-quality incisions, the transition technology from pulse perforation when the workpiece is stationary to continuous constant-speed cutting of the workpiece should be paid attention to. In theory, the cutting conditions of the acceleration section, such as the focal length, the nozzle position, and the gas pressure, can usually be changed. However, it is unlikely that the above conditions will be changed due to the short time. In industrial production, it is more realistic to change the average laser power. The specific methods are to change the pulse width; to change the pulse frequency; and to change the pulse width and frequency. The actual results show that the third effect is the best.
Analysis of deformation of small holes (small diameter and plate thickness) during cutting
This is because the machine tool (only for high-power laser cutting machines) does not use blasting perforation when processing small holes, but uses pulse perforation (soft puncture), which makes the laser energy too concentrated in a small area. The non-processed area is also burnt, causing deformation of the hole and affecting the processing quality. At this time, we should change the pulse punching (soft puncture) method to blast punching (common puncture) method in the processing program to solve it. For the small power laser cutting machine, it is just the opposite. In the processing of small holes, the method of pulse perforation should be adopted to obtain better surface finish.
Solutions for burrs on workpieces during laser cutting of low carbon steel
According to the work and design principles of CO2 laser cutting, the following points are analyzed to be the main causes of burrs in the processed parts: the up and down position of the laser focus is incorrect, and a focus position test needs to be performed to adjust according to the focus offset The output power of the laser is not enough, you need to check whether the laser generator is working normally. If it is normal, observe whether the output value of the laser control button is correct and adjust it. The purity of the cutting gas is not enough. It is necessary to provide high-quality cutting working gas. The laser focus shift requires a focus position test, which is adjusted according to the focus shift amount. Instability that occurs when the machine runs for a long time requires shutdown. Restart.
Analysis of burrs in workpieces during laser cutting of stainless steel and aluminum-zinc plate
In the above situation, the factor of burrs when cutting low carbon steel is considered first, but the cutting speed cannot be simply increased, because the increase in speed sometimes leads to the situation that the board does not cut through, which is particularly prominent when processing aluminum-zinc plate. . At this time, other factors of the machine tool should be comprehensively considered, such as whether the nozzle is to be replaced, and the movement of the guide rail is unstable.
