There are some problems in the processing of medium and heavy plate by laser cutting machine. How to solve them? As an advanced material cutting method, laser cutting machine is more and more accepted by sheet metal producers due to its advantages of less material waste, obvious cost effect in large-scale production and strong adaptability to processing objects. Today, China's crude steel output is not only the first in the world, but also more than 50% of the global output. This paper will talk about the problems often encountered in the laser cutting machine in the processing of medium and thick plates.
1. Perforation of carbon steel thick plate
In the thick plate processing, the perforation time accounts for a large proportion. Various laser manufacturers have developed the technology of rapid perforation, which is more representative of high-energy perforation (hole blasting). The advantage of this method is that it is fast (1 second, take t16mm as an example - the same below). The defect is that it not only affects the processing of small shapes, but also the huge energy injected during the perforation increases the plate temperature, which affects the next whole Cutting process. When using small power pulse to perforate, the time is very long (12 seconds), which will lead to the decrease of cutting efficiency and the increase of unit cost.
2. Cutting surface quality problems
When processing medium and thick plates, cutting sections are often encountered. Such cutting not only questions the quality of the finished products, but also comes with overburning and serious slag sticking, so that it can not reflect the value of high price laser processing machine different from other cutting methods.
3. processing stability of the whole plate
In the whole plate processing of domestic steel, the phenomenon of bad local area processing often occurs. This phenomenon is sometimes random, even when the machine is in good condition.
The solution of laser processing medium thick plate is as follows:
1. HPP scheme
The peak value pulse laser with a small duty cycle and the non fuel injected on the surface of the material are used to remove the attachment on the edge of the opening, and the reasonable frequency of the pulse is controlled while cooling and perforating. It is characterized by a relatively long time (3 seconds) for hole blasting, but the hole diameter is small (about φ 4mm), there is no attachment at the edge of the hole, and the heat input is low, which is convenient for the next normal cutting and processing, and the efficiency is increased by 4 times compared with the ordinary perforation.
2. Improvement plan of cutting section
For carbon steel, the important factor to improve the cutting section is to control the heat input to the plate and ensure the full combustion of the laser irradiated part. For stainless steel, the important factors to improve the cutting section are the improvement of the beam (to improve the focal depth) and the effective use of auxiliary gas. Bright cutting technology is the result of improving the vibration generator and nozzle.
3. Scheme to ensure processing stability
In order to improve the operation speed of the laser cutting machine, the laser machine mostly adopts the structure commonly known as flying light path, that is, the form that the material tray does not move and the machining head moves in the whole machining area. In order to compensate for the change of the relative position between the machining head and the light source, manufacturers also try their best to ensure the consistency of the light spot in the machining range. The use of the curvature variable refractor is a common choice. Although the structure of this method is simple, it will change the focal depth, which makes it difficult to cut the plate which is very sensitive to the focal depth. Using equal length light path (the light propagation path between the light source and the machining head is equal in the machinable range) can avoid the change of focal depth, so that the spot and focal depth are consistent. In addition, the attention to heat input can control the accumulated heat of the plate, which can better solve the stability problem. leapion