1. Cutting and perforating technology
Any kind of thermal cutting technology, except for a few cases, which can start from the edge of the board, generally a small hole must be pierced in the board. Previously, a punch was used to punch a hole on a laser punching compound machine, and then a laser was used to start cutting from the small hole. For the metal fiber laser cutting machine without punching device, there are two basic methods for perforating:
Blasting perforation-the material is irradiated by the continuous laser to form a pit in the center, 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 has a larger diameter and is not round. It is not suitable for use on parts with higher processing accuracy. On the waste. In addition, since the oxygen pressure used for perforation is the same as that used for cutting, the splash is larger.
Pulse perforation-a pulse laser with high peak power is used to melt or vaporize a small amount of material. Air or nitrogen is often used as an auxiliary gas to reduce the expansion of the hole due to exothermic oxidation. The gas pressure is lower than the oxygen pressure during cutting. Each pulse laser only produces small particle jets, which gradually penetrate deeper, so it takes a few seconds for the thick plate to perforate. Once the perforation is completed, immediately change the auxiliary gas to oxygen for cutting. In this way, the perforation diameter is smaller, and the perforation quality is better than blast perforation. For this reason, the laser used should not only have a higher 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 needs a more reliable gas path control system to realize the switch of gas type, gas pressure and the control of perforation time.
In the case of pulse perforation, in order to obtain high-quality cuts, the transition technology from pulse perforation when the workpiece is stationary to continuous cutting of the workpiece at constant velocity should be paid attention to. Theoretically speaking, it is usually possible to change the cutting conditions of the acceleration section, such as focal length, nozzle position, gas pressure, etc., but in fact, it is unlikely to change the above conditions due to too short time. In industrial production, the main method of changing the average power of the laser is more realistic. The specific method is to change the pulse width; change the pulse frequency; change the pulse width and frequency at the same time. The actual results show that the third type has the best effect.
2. Analysis of the deformation of the small hole (small diameter and thickness) in the cutting process
This is because the machine tool (only for high-power metal fiber laser cutting machines) does not adopt the method of blasting perforation when processing small holes, but uses the method of pulse perforation (soft puncture), which makes the laser energy too much in a small area. Concentration, the non-processing area is also scorched, resulting in hole deformation and affecting processing quality. At this time, we should change the pulse perforation (soft puncture) method to the blast perforation (ordinary puncture) method in the processing program to solve it. The opposite is true for the metal fiber laser cutting machine with lower power. Pulse perforation should be used in the processing of small holes in order to obtain a better surface finish.
3. The solution to burrs on the workpiece when laser cutting mild steel
According to the working and design principles of CO2 laser cutting, the analysis shows that the following reasons are the main reasons for the burrs of the processed parts: the upper and lower positions of the laser focus are not correct, and the focus position test needs to be performed and adjusted according to the offset of the focus; The output power of the laser is not enough. It is necessary 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 cutting line speed is too slow, and the line speed needs to be increased during operation control; The purity of the cutting gas is not enough, it is necessary to provide high-quality cutting working gas; the laser focus shift, the focus position test needs to be done, and the adjustment is made according to the shift of the focus; the machine running time is too long and the instability occurs, and the machine needs to be shut down at this time Restart.
4. Analysis of burrs on the workpiece during laser cutting of stainless steel and aluminum-zinc plate
For the above situations, first consider the factors of burrs when cutting low-carbon steel, but you cannot simply increase the cutting speed, because increasing the speed sometimes causes the sheet to be cut without penetration. This situation is particularly prominent when processing aluminum-zinc sheets. . At this time, other factors of the machine tool should be taken into consideration to solve the problem, such as whether the nozzle should be replaced or the guide rail movement is unstable.
5. Analysis of the incompletely cut state of the laser
After analysis, it can be found that the following situations are the main reasons for processing instability: the choice of laser head nozzle does not match the processing thickness; the laser cutting line speed is too fast, and the operation control is required to reduce the line speed; the nozzle induction is not allowed to guide When the laser focus position error is too large, it is necessary to re-check the nozzle sensor data, especially when cutting aluminum materials.
6. Solutions to abnormal sparks when cutting mild steel
This situation will affect the processing quality of the cut section finish of the part. At this time, when other parameters are normal, the following conditions should be considered: the loss of the laser head nozzle NOZZEL, the nozzle should be replaced in time. If there is no replacement of a new nozzle, the cutting working gas pressure should be increased; the thread at the connection between the nozzle and the laser head is loose. At this time, the cutting should be suspended immediately, the connection status of the laser head should be checked, and the thread should be reinstalled.
