Lasers are the heart of laser equipment and play a decisive role in the quality of laser cutting. A good laser should have the ideal mode, stable power and other elements. There are many types of lasers, and they can be defined differently from different angles. Different from the medium of excitation, it can be roughly divided into solid lasers and gas lasers, which use different solids or gases as the medium, for example, the earliest laser uses ruby as the medium. The mainstream laser currently used for laser cutting are CO2 lasers, followed by YAG lasers. 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. The use of carbon dioxide lasers makes it easier to obtain the ideal laser mode and higher energy, coupled with stable performance and short downtime, which is widely used in the cutting of various materials.
Let us talk about some factors that affect the cutting quality of CO2 lasers.
1: Excitation mode. The carbon dioxide laser generates laser light by exciting carbon dioxide gas with an electrode, and can be classified into direct current excitation and radio frequency excitation according to the installation position of the metal electrode.
2: Laser frequency. The laser output is 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 the roughness of the slit. To obtain high-speed cutting, high frequency is indispensable. At present, most manufacturers produce carbon dioxide lasers with frequencies below 5000 Hz.
3: beam divergence angle. From a strict point of view, the beam divergence angle is not part of the laser part, but since the mode of the laser has a great influence on the far-field divergence angle, we will discuss it here. The influence of the beam divergence angle on the cutting quality is reflected in the width and slope of the slit. The smaller the divergence angle, the narrower the slit width, and the smaller the slope, the higher the quality.
4: Laser mode. It is one of the most important indicators for measuring laser quality. Can be divided into single mode, basic mode and multimode. The fundamental mode is both TEM00 mode, and its index on the X and Y axes is 0, so it is an ideal dot. The laser with TEM00 mode can obtain the smallest beam diameter, and the smallest slit and faster cutting speed can be obtained in the cutting process because of its small spot size. The multimode is a non-zero index in the XY direction, and its beam quality is poor, and it is generally used only for welding and not for cutting.
5: Laser power. Including peak power, energy stability and other factors. Different power can be cut through the thickness of the metal sheet. For example, a 4KW laser can cut 20mm thick carbon steel, or 15mm stainless steel, 10mm aluminum alloy; and 5KW or more laser can cut 25mm thick carbon steel, stainless steel up to 20mm. Another indicator of power is power stability, excellent cutting quality, and must be excellent throughout the cut. Long-term production is also a very important test for lasers. DC-excited lasers have attenuated power during long-term operation due to electrode ablation. In addition, since some of the vacuum pumps and turbo pumps of the laser are lubricated with lubricating oil, the lubricating oil contaminates the laser cavity and shortens the life of the laser.
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