Laser is the heart of laser equipment and plays a decisive role in the quality of laser cutting. 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. From the excitation medium, it can be roughly divided into solid-state laser and gas laser, which use different solid or gas as the medium respectively. For example, the earliest laser uses Ruby as the medium.
At present, the mainstream laser 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 easy to obtain ideal laser mode and high energy. In addition, it has stable performance and short shutdown time, so it is widely used in the cutting of various materials.
1： Incentive mode. Carbon dioxide laser uses electrode to excite carbon dioxide gas to produce laser. According to the installation position of metal electrode, it can be divided into DC excitation and RF excitation.
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 notch roughness. In order to obtain high-speed cutting, high frequency is essential. At present, the frequency of carbon dioxide laser produced by most manufacturers is within 5000Hz.
3： Beam divergence angle. Strictly speaking, the beam divergence angle does not belong to the laser part, but because the laser mode has a great influence on the far-field divergence angle, I will discuss it here. The narrower the width of the cut and the smaller the angle of divergence, the better the quality of the cut.
4： Laser mode. One of the most important indexes to measure laser quality. It can be divided into single mode, fundamental mode and multimode. The fundamental mode is tem-00 mode, and the exponent on the X and Y axes is 0, so it is an ideal dot. The laser with tem-00 mode can obtain the smallest beam diameter, and the smallest slit and faster cutting speed can be obtained due to the small spot in the cutting process. The multimode is non-zero index in XY direction, and its beam quality is poor. Generally, it is only used for welding rather than cutting.
5： Laser power. Including peak power, energy stability and other factors. Different powers can cut through different thicknesses in the cutting of metal plates. Taking 4kw laser as an example, 20mm thick carbon steel plate, 15mm stainless steel and 10mm aluminum alloy can be cut; 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 cutting throughout. Long term production is also a very important test for lasers. Due to electrode ablation, the power of DC excited laser decreases in long-term working state. In addition, because some laser vacuum pumps and turbine pumps are lubricated with lubricating oil, the lubricating oil pollutes the laser resonator and shortens the service life of the laser.