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1. Cutting perforation 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. There are two basic methods of perforation for laser cutting machines without punching device:
Blasting perforation-the material is irradiated by continuous laser to form a pit in the center, and then The stream of oxygen coaxial with the laser beam quickly removes the molten material 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 that gradually penetrate deeper, so it takes a few seconds to perforate thick plates. 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 switching of gas type, gas pressure and the control of perforation time.
In the case of pulse perforation, in order to obtain a high-quality cut, 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, it is more realistic to mainly adopt the method of changing the average power of the laser. 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 deformation of small holes (small diameter and thickness) in cutting process
This is because the machine tool (only for high-power 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 concentration in a small area will also scorch the non-processed area, causing deformation of the hole and affecting the 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 laser cutting machines with lower power. Pulse perforation should be used to obtain a better surface finish when processing small holes.
3. The solution to the burrs on the workpiece when laser cutting low carbon steel
According to the work and work of CO2 laser cutting According to the design principle, 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, the focus position test needs to be done, and the adjustment is made according to the offset of the focus; the output power of the laser is not enough, it needs 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, so need Provide high-quality cutting working gas; laser focus deviation, need to do focus position test, adjust according to the focus deviation; machine running time is too long to appear instability, at this time, it needs to be shut down and restarted.
4. When laser cutting stainless steel and aluminum-zinc plate, the workpiece has burrs.
The above cases First, consider the factor of burrs when cutting low-carbon steel, but you cannot simply increase the cutting speed, because increasing the speed will sometimes cause the sheet to be cut through. This situation is particularly prominent when processing aluminum-zinc sheets. At this time, other factors of the machine tool should be considered comprehensively to solve them, such as whether the nozzle should be replaced, and the movement of the guide rail is unstable.
5. Analysis of laser incomplete cutting through state
After analysis, it can be found that the following situations are caused by processing The main unstable conditions: the selection of the laser head nozzle does not match the thickness of the processed plate; 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 cause the laser focus position error to be too large, and the nozzle needs to be re-checked Induction data, especially when cutting aluminum, is most likely to appear.
6. Solutions to abnormal sparks when cutting mild steel
This situation will affect the cutting of parts Processing quality of section finish. At this time, when other parameters are normal, the following conditions should be considered: the loss of the nozzle of the laser head, and 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.
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