As the saying goes, it is the heart of laser equipment and plays a decisive role in laser cutting quality. A good laser should have ideal mode, stable power and other elements. There are many kinds of lasers, which can be defined differently from different angles. According to the excited medium, it can be roughly divided into solid state lasers and gas lasers, which use different solid or gas as the medium respectively. For example, the earlier lasers used ruby as the medium.
At present, the mainstream laser used for laser cutting is carbon dioxide laser, followed by YAG laser. YAG laser has the characteristics of high photoelectric conversion efficiency and small volume, but its application is greatly limited due to its fast loss of energy pump source and high maintenance cost. Carbon dioxide laser is widely used for cutting various materials because it is easy to obtain ideal laser mode and higher energy, stable performance and short downtime.
1： The excitation mode and CO2 laser use electrodes to excite CO2 gas to generate laser, which can be divided into DC excitation and RF excitation according to the installation position of metal electrodes.
2： The laser frequency and laser output are divided into pulse output and continuous output. The laser used for cutting and welding mainly adopts pulse output mode. The pulse frequency mainly affects the cutting speed and notch roughness. To obtain high-speed cutting, high frequency is essential. At present, the frequency of CO2 lasers produced by most manufacturers is within 5000Hz.
3： The beam divergence angle, strictly speaking, does not belong to the laser part, but because the laser mode has a great impact on the far field divergence angle, we will discuss it here. The influence of beam divergence angle on cutting quality is reflected in the width and slope of the incision. The smaller the divergence angle, the narrower the width of the incision, the smaller the slope, and therefore the higher the quality.
4： Laser mode is one of the important indexes to measure laser quality. It can be divided into single mode, basic mode and multi-mode. The fundamental module is TEM-00 module, whose exponents on X and Y axes are both 0, so it is an ideal dot. The TEM-00 mode laser can obtain the beam diameter, and the slit and faster cutting speed can be obtained due to its small light spot in the cutting process. However, multimode is non zero exponent in XY direction, and its beam quality is poor. It is generally used only for welding rather than cutting.
5： Laser power, including peak power, energy stability and other elements. Different power can cut through different thicknesses in the cutting of metal plates. Take the 4KW laser as an example, it can cut 20mm thick carbon steel plate, or 15mm stainless steel, 10mm aluminum alloy; The laser above 5KW can cut 25mm thick carbon steel and 20mm thick stainless steel. Another indicator of power is power stability. Excellent cutting quality must be excellent throughout the incision. Long term production is also a very important test for lasers.
The power of DC excited laser is attenuated due to electrode ablation. In addition, some laser vacuum pumps and turbine pumps use lubricating oil for lubrication, which causes the lubricating oil to pollute the laser resonator and shorten the laser life.
