What problems should be paid attention to when metal laser cutting machine is cutting thick plates

by:Caodahai     2021-09-20
Generally speaking, there is no problem for metal laser cutting to cut metal plates with a thickness of less than 10mm. However, it is not possible to always cut metal plates within this thickness range in the production work, so what should be paid attention to when cutting thick plates The problem? Let's analyze it.  The oxygen purity and pressure in the thickness direction of the plate are difficult to maintain constant. When cutting thick plates with a metal laser cutting machine, the decrease in oxygen purity is also an important factor affecting the quality of the cut. The purity of the oxygen stream has a strong influence on the cutting process. When the purity of the oxygen stream decreases by 0.9%, the iron-oxygen combustion rate will decrease by 10%; when the purity decreases by 5%, the combustion rate will decrease by 37%. The decrease in the combustion rate will greatly reduce the energy input into the kerf during the combustion process and reduce the cutting speed. At the same time, the iron content in the liquid layer of the cutting surface will increase, which will increase the viscosity of the slag and make it difficult to discharge the slag. Severe dross will appear in the lower part, making the quality of the cut unacceptable.   In order to keep the cutting stable, it is required that the purity and pressure of the cutting oxygen flow in the thickness direction of the plate be kept basically constant. In the traditional laser cutting process, common cone nozzles are often used, which can meet the requirements for use in thin plate cutting. However, when cutting thick plates, as the air supply pressure increases, shock waves are easily formed in the nozzle flow field. The shock waves have many harms to the cutting process, reducing the purity of the oxygen flow and affecting the quality of the cut.   The energy that should be released, in fact, cannot ensure that the combustion process continues. On the one hand, because the cutting slit is continuously cooled by the oxygen stream sprayed from the nozzle, the temperature of the cutting front is reduced. On the other hand, the ferrous oxide layer formed by combustion covers the surface of the workpiece and hinders the diffusion of oxygen. When the concentration of oxygen decreases to a certain level, the combustion process will be extinguished. When using a traditional convergent beam for laser cutting, the area of u200bu200bthe laser beam acting on the surface is very small. Due to the high laser power density, not only in the area of u200bu200blaser radiation, the surface temperature of the workpiece has reached the ignition point, but also due to heat conduction, a wider area The area reached the ignition temperature.  The diameter of the surface of the workpiece by the oxygen flow is larger than the diameter of the laser beam. This indicates that not only a strong combustion reaction will occur in the laser radiation area, but also the combustion will also occur at the periphery of the laser spot irradiated by the laser beam. When cutting thick plates, the cutting speed is quite slow, and the speed of iron oxide combustion on the surface of the workpiece is faster than the speed of the cutting head. After the combustion continues for a period of time, the combustion process is extinguished due to the decrease in oxygen concentration.  Only when the cutting head moves to this position, the combustion reaction starts again. The combustion process of the cutting front is carried out periodically, which will cause the temperature fluctuation of the cutting front and the quality of the cut to deteriorate.   Wuhan Gaoneng Laser Equipment Manufacturing Co., Ltd. is a high-tech enterprise integrating Ru0026D, production and sales of professional laser complete sets of equipment. Not only successfully developed laser equipment with advanced technology, but also used self-support import and export rights to promote products to more than forty global products including Hong Kong, South Korea, Vietnam, Malaysia, Thailand, Australia, the United States, Japan, Germany, the Netherlands, Jordan, etc. The country has an advantage in the international market in the same industry.
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