Several major problems of laser cutting thick metal plate

Several major problems of laser cutting thick metal plate

Laser processing, as an advanced material cutting method, has been more and more accepted by the sheet metal producers. With the progress of computer control technology and optical technology, increasingly high expectations for its processing capacity, looking forward to this is not only to cut, it is to cut and sliced expectations. But can give the answer of course can not be separated from the processing machine performance, while the quality of processed materials directly affect the effect of the answer.
Laser processing started earlier in the Europe and the United States and Japan, in the eighties of the last century began by laser processing machine manufacturers of steel production put forward specific quality requirements, and the difference from the ordinary steel but the price is on the high side of laser special steel. And with the laser processing as the main cutting tool is accepted, 25mm the following common steel plate on the laser professional materials as a standard material. However, due to China's development is too fast, too late to adapt to the production of steel, there is a difference between China's steel and imported steel. The main difference is that the content of impurities in steel and the processing of steel surface and transport custody and a series of reasons, resulting in the current situation of Chinese sheet metal cutting.
Today, China's crude steel production is not only the world's first, is more than 50% of global output, developing countries, and even some like Australia, South Korea and other developed countries in order to save costs also used in a large number of board of China, so instead of expecting China steel to adapt to laser cutting as research and put forward to quality processing of inferior materials methods and proposal. Some of these ideas are presented in this paper.
Problems encountered in the processing of medium and heavy plate
1.Carbon steel plate perforation in processing thick plates perforated time accounted for a large proportion, the laser manufacturers have developed a technique for rapid perforation, more representative is high-energy perforation (hole), the advantages of this method is fast (1 second, to t16mm as an example, following the same), but the drawback is that the enormous energy not only affects the processing of small shape, perforation injection of the plate temperature elevated and the impact on the rest of the whole cutting process. With a small power pulse perforation, then a long time (12 seconds), will lead to the cutting efficiency and the unit cost of the increase.
2.Cutting surface quality problem          
Figure 1 and Figure 2 shows a section cutting processing plate often meet, such cutting not only product quality has been questioned, but also with the slag sticking of burn and severe, that reflected not expensive laser processing machine difference to other ways of cutting the value.

3.Stability of whole plate processing          
In the whole process of domestic steel, there will often be a local area of the phenomenon of poor processing. This kind of phenomenon is sometimes very random, even if the machine is in good condition, it will appear. In order to deal with the local fault products and greatly affect the whole work progress, this is not the cause of the processing failure also gives some of the author's analysis and countermeasures.

Solutions of the above problems
1.Peak perforation (HPP) scheme          
As the name suggests is the use of a small duty cycle of the peak pulse laser, combined with the material on the surface of the fuel injection is not fuel to clear the opening edge of the attachment, the reasonable frequency of the control pulse edge cooling edge. Is characterized by relatively deep hole, although a slightly longer time (3 seconds), but penetrated aperture small (about diameter 4mm) and open hole edge without attachments and into the heat is low, to facilitate the next normal cutting, compared to ordinary perforated is to improve the efficiency of 4 times. Figure 3 shows the difference between an ordinary perforation, a HPP perforation, and a high energy punch.

2.Cutting section improvement program          
For the carbon steel, the important factor to improve the cutting section is to control the heat input to the plate and to ensure the full combustion of the laser irradiation. MITSUBISHI motor development K-CUT processing conditions better to complete the mission. Fig. 4 Comparison of the effects of traditional and K-CUT conditions on the same piece of domestic plate. For stainless steel, the important factor to improve the cutting section is the improvement of the beam (improving the depth of focus) and the effective utilization of the auxiliary gas. The bright surface cutting technique is to improve the results obtained by the oscillator and the nozzle. Figure 5 is the effect after improvement. The lower part of the upper part of the section of rough 8 mu and 12 Mu as mechanical processing.

3.Scheme to ensure processing stability          
At present, in order to improve the running speed of the processing machine, the laser machine adopts the structure that is called the flight light path, that is, the material tray does not move and the processing head can move in the whole processing area. In order to compensate for the change of the relative position of the working head and the light source, the manufacturers can also ensure the consistency of the light spot in the range of processing. Although this method has simple structure, it will change the depth of focus, so that in the depth of the depth of the plate is very sensitive to cutting the thick plate will appear to be inadequate (both to keep the light spot and keep the focus depth constant). MITSUBISHI motor using the same length of light path (in the range of light source and the processing of the optical path between the processing head) can avoid the depth of focus changes, so that the spot and the depth of focus are consistent. In addition, the heat gained by the hot plate is controlled, which can solve the stability problem. Figure 6 shows the principle of long path and in the processing area at different points in the processing effect.

Take seriously the problems in the process, study the mechanism and find the solution to the problem. Through the traditional laser technique, a series of exploration and improvement, for more complex plate cutting developed new technology and its application to the ex plus, Rx, XL, etc. series of products, to meet the actual needs of customers in the domestic plate materials processing, thereby greatly improving the production efficiency. We will further efforts to explore new technologies to solve more difficult problems in the processing of the majority of users.

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