Knowledge sharing by Guangdong Shunde Teamwork Model Technology Co., Ltd, whom with over 20 years rapid prototyping experience.
Email: ken@gdtwmx.com
Website: www.gdtwmx.com
In the process of cutting sheet metal using a
Laser Cutting machine, various problems are often encountered. In order to ensure the cutting quality, the following are the seven common problems and the usual solutions:
1. Cutting Perforation Techniques Any kind of thermal cutting technique, except where it is possible to start from the edge of the plate in a few cases, generally must wear a small hole in the plate. Previously in the laser stamping compound machine, a hole was punched out first with a punch, and then laser cutting was started from the small hole. For laser cutting machines without a stamping device there are two basic methods for perforating:
Blasting perforations - The material forms a pit in the center after being irradiated by a continuous laser, and then the molten material is quickly removed by the oxygen flow coaxial with the laser beam to form a hole. The size of the general hole is related to the thickness of the plate. The average diameter of the blasting perforation is half of the plate thickness. Therefore, the thicker blasting perforation of the plate has a large hole diameter and is not round. It is not suitable for use on parts with high processing accuracy. On scrap. In addition, since the pressure of oxygen used for perforation is the same as when cutting, the spatter is large.
Pulse piercing - using high-peak-power pulsed lasers to melt or vaporize small amounts of material, commonly used air or nitrogen as an auxiliary gas, in order to reduce the hole expansion due to exothermal oxidation, the gas pressure is less than the pressure of oxygen when cutting. Each pulsed laser produces only a small particle spray, which is progressively deeper, so that the thick plate piercing time takes several seconds. Once piercing is complete, the auxiliary gas is immediately replaced with oxygen for cutting. In this way, the diameter of the perforation is smaller and the perforation quality is better than the perforation. The laser used for this purpose should not only have a higher output power; more importantly, the temporal and spatial characteristics of the beam, so the general cross-flow CO2 laser cannot adapt to the requirements of laser cutting. In addition, the pulse perforation also requires a more reliable gas control system to achieve gas type, gas pressure switching and perforation time control.
In the case of pulse piercing, in order to obtain high-quality cuts, transition techniques from pulse piercing when the workpiece is at rest to constant speed continuous cutting of the workpiece should be taken into account. Theoretically, the cutting conditions of the acceleration section, such as the focal length, nozzle position, and gas pressure, can be changed. However, it is actually unlikely that the above conditions will be changed due to the short time. In industrial production, the main method to change the laser average power is more realistic. The specific method is to change the pulse width; change the pulse frequency; and simultaneously change the pulse width and frequency. The actual results show that the third kind of effect is the best.
2. Analyze the deformation of the small hole (small diameter and plate thickness) in the cutting process. This is because the machine tool (only for high-power laser cutting machine) does not use the method of blasting perforation when processing small holes, but uses perforation (soft piercing). This way, the laser energy is too concentrated in a very small area and the non-processed area is burned, resulting in hole deformation and affecting the quality of processing. At this time, we should change the way of pulse piercing (soft piercing) to blast piercing (ordinary piercing) in the machining program. For the smaller power laser cutting machine, the opposite is true. In the processing of small holes, pulse perforation should be used to obtain a good surface finish.
3. Workpiece burr solution when laser cutting low-carbon steel According to the CO2 laser cutting work and design principles, the following reasons are the main reasons for the burr caused by the workpiece: the laser focus is not positioned correctly. Need to do focus position test, adjust according to the offset of the focus; laser output power is not enough, need to check whether the laser generator is working properly, if normal, then observe the laser control button output value is correct, and adjust; Line speed is too slow, need to increase the line speed during operation control; the purity of the cutting gas is not enough, need to provide high-quality cutting working gas; laser focus shift, need to do the focus position test, according to the focus of the offset adjustment; The instability caused by the long running time of the machine tool requires a shutdown and restart.
4. When the laser cutting of stainless steel and aluminum zinc plate, the burr produced parts of the above analysis of the appearance of the above conditions, first consider the burr when cutting low carbon steel, but can not simply speed up the cutting speed, because sometimes increase the speed The situation where the plate is not cut is especially prominent when it is used to process aluminum-zinc plates. 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, and the guide rail movement is unstable.
In the process of cutting sheet metal using a laser cutting machine, various problems are often encountered. In order to ensure the cutting quality, the following are the seven common problems and the usual solutions:
5. After analyzing and analyzing the laser incompletely cutting and penetrating state, it can be found that the following situations are the main conditions for processing instability: the selection of the laser head nozzle does not match the processing board thickness; the laser cutting line speed is too fast and requires operation control. Reduce the line speed; In addition, also need special attention is that in the L3030 laser cutting machine cutting more than 5mm carbon steel plate need to replace the 7.5′′ focal length laser lens.
6. Solutions for abnormal sparks when cutting low-carbon steels This condition can affect the quality of the cut surface finish of the part. At this point in the case of other parameters are normal, the following conditions should be considered: Loss of laser head nozzle NOZZEL, the nozzle should be replaced. In the case of no new nozzle replacement, the pressure of the cutting working gas should be increased; the threads of the nozzle and the laser head are loosened. At this point, the cutting should be suspended immediately, check the laser head connection, and re-thread the thread.
7. Selection of puncture point during laser cutting The working principle of the laser beam during laser cutting is: during processing, the material forms a pit in the center after being irradiated by continuous laser, and then the working airflow is coaxial with the laser beam. The molten material is quickly removed to form a hole. The hole is similar to the thread cutting thread hole. The laser beam is used for the contour cutting of the starting point of the processing. Generally, the direction of the laser beam of the flying light path is perpendicular to the tangential direction of the cut contour of the processed part.
Therefore, during the period from the start of the penetration of the steel plate to the cut of the part, the cutting speed of the laser beam will have a large change in the vector direction, that is, a 90° rotation in the vector direction, and a tangent line perpendicular to the cutting profile. The direction is changed to coincide with the tangent of the cutting contour, ie, the angle with the tangent of the contour is 0°. In this way, a relatively rough cutting surface will flow on the cut surface of the material to be processed. This is mainly because the direction of the vector of the laser beam in the movement of the laser beam changes very quickly in a short time. Therefore, we must pay attention to this situation when laser cutting parts. In general, when the design part does not have a roughness requirement on the surface cutting fracture, manual processing may be omitted during the laser cutting programming so that the control software automatically generates a puncture point; however, when the design has a high roughness on the cutting section of the part to be processed. When this is required, it is necessary to notice this problem. It is usually necessary to manually adjust the starting position of the laser beam during the laser cutting program, that is, to manually control the puncture point. The puncture point originally generated by the laser program needs to be moved to a desired and reasonable position in order to achieve the required surface precision of the machined part.
December 15, 2020
