Study On The Mechanism And Key Technique Of CO₂ Laser Cutting Nonmetallic Materials Based On Wall Focusing Effects

Laser cutting is one of the most widely used laser processing technology, and its application in industry dates back to the beginning of 1970s. With the improvement of the laser devices and processing technology, it can also be applied to the cutting of the metals such as mild steel and stainless steel and the nonmetallic materials such as wood, FRP, ceramic, quartz and rock. This paper systematically studies the mechanism of evaporation CO₂ laser cutting high absorptive nonmetallic material and its affecting factors, emphasizes the beam transmission and energy absorption of the cutting front and wall, creates a theoretical model of medium and low power level laser cutting nonmetallic material and draws such conclusions as follows:1. The experiment-required PHC-1500 folded quasi-sealed continuous wave lasers is developed, which outputs stable TEMoo mode polarized beam and the optical and machine system equipped well guarantees the cutting precision.2. The die-board and PMMA reflectivity to CO₂ laser is measured by the calorimetric method. The results indicate that the reflectivity to perpendicular polarized beam will increase with the incident angle's growing. The reflectivity to parallel polarized beam is small with the incident angle below 60 degree, and will diminish gradually with the growing of the incident angle, when the incident angle reaches above 60 degree, the reflectivity will increase abruptly with the growing of the incident angle. The theoretical results and calculation results show consistency.3. The evaporation cutting front shape is obtained by high speed photography. With focus position downward, the reducing of the cutting speed and the increasing of laser power, the depth of cutting front will increase and the curvature will increase as well. Due to the thick material, the cutting front will bend, which causes multiple reflections, transmits the light toward the deep position and is favorable for increasing the cutting front depth.4. Based on the cutting front and kerf shape photographed in the experiment, a three-dimensional energy coupling model for evaporative laser cutting nonmetallic material is established through theoretical analysis and the reflective transmission and energy absorption of laser against real bended cutting front and both two walls are analyzed: (1) the front and wall's energy absorption is mainly...