There are some problems in the processing of medium and thick plates with laser cutting machine. How to solve it? As an advanced material cutting method, laser cutting machine has the advantages of less material waste, obvious cost-effectiveness in large-scale production, strong adaptability to processing objects, and is increasingly accepted by sheet metal manufacturers. Today, China’s crude steel output is not only the first in the world, but also accounts for more than 50% of the global output. This paper will discuss the problems often encountered by laser cutting machine in the processing of medium and thick plates.
1. Carbon steel thick plate perforation
In thick plate processing, perforation time accounts for a large proportion. Various laser manufacturers have developed fast piercing technology, which is more representative of high-energy piercing (sandblasting). The advantage of this method is fast. The disadvantage is that it not only affects the processing of small shapes, but also the huge energy injected in the perforation process will increase the plate temperature, thus affecting the next whole cutting process. When small power pulse is used for drilling, the time is very long (12 seconds), which will reduce the cutting efficiency and increase the unit cost.
2. Quality problem of cutting surface
In the process of processing medium and thick plates, the cutting section is often encountered. Such cutting not only doubts the quality of finished products, but also causes excessive combustion and serious slag adhesion, so it cannot reflect the value of high priced laser processing machines different from other cutting methods.
3. Processing stability of the whole board
In the whole plate processing of household steel, local processing defects often occur. Even if the machine is in good condition, sometimes this phenomenon is random.
How to cut thick plates with laser cutting machine
The solutions for processing medium and thick plates with laser cutting machine are as follows:
1. HPP scheme
The peak pulse laser with small duty cycle and non fuel injection are used on the material surface to remove the attachment at the opening edge, and to control the reasonable frequency of the pulse during cooling and drilling. It is characterized by long sandblasting time (3 seconds), but small pore diameter (about φ 4mm), there is no attachment on the edge of the hole, and the heat input is low, which is convenient for the next conventional cutting and processing, and the efficiency is 4 times higher than that of ordinary piercing.
2. Improvement plan of cutting part
For carbon steel, the important factor to improve the cutting section is to control the heat input to the plate and ensure the complete combustion of the laser irradiated parts. 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 running speed of the laser cutting machine, the laser machine mostly adopts the structure commonly known as the flying light path, that is, the material tray does not move in the whole processing area but the processing head moves. In order to compensate for the change in the relative position between the processing head and the light source, the manufacturer also makes every effort to ensure the consistency of the light spot within the processing range. The use of variable curvature refractors is a common choice. Although the structure of this method is very simple, it will change the focal depth, which makes it difficult to cut the flat plate which is very sensitive to the focal depth. Using an equal length light path (the light propagation path between the light source and the processing head is equal within the machinable range) can avoid the change of focal depth and make the spot and focal depth consistent. In addition, note that the heat input can control the accumulated heat of the board, which can better solve the stability problem.
