以PMMA(有机玻璃)为试件,采用CCD拍摄到CO2激光气化切割前沿的照片。研究焦点位置、切割速度和激光功率对切割前沿形状和前沿深度的影响,并建立激光能量耦合模型。结果表明,由于前沿存在多次反射,使得切割深度增加。正离焦切割时,前沿吸收的总激光功率密度减小,切割深度减小; 负离焦切割时,最大激光功率密度值的位置下移,使得前沿功率密度分布朝着深部推进,切割深度增加,若负离焦量过大,表面光斑直径和光程增加,更深位置的功率密度减小,切割深度减小; 随着激光功率增加、切割速度减小,则前沿弯曲程度减小,被激光直接照射的前沿部位增长,前沿吸收激光功率密度增加,切割深度增加。

Evaporative cutting front shape of PMMA by CO2 lasers is photographed through CCD camera. Effects on cutting front shape and depth by cutting parameters as defocus distance, cutting speed and laser power are discussed. An energy coupling model is built up on the front and kerf shape photographed. The results indicate that multiple reflections are favorable to the increase of depth. When the focal position is above the surface, the absorptive intensity on the front decreases, so the cutting depth decreases. When the focal position is below the surface, the position on the front with the maximum power intensity is downward. The intensity distribution is toward the deeper position, the cutting depth increases. But if the negative focal distance is extremely big, the intensity of the deeper position attenuates sharply with the increase of focal radius and light distances, so the depth deceases. With reducing the cutting speed and increasing the laser power, the curvature decreases, the length of front directly irradiated increases, and thus the cutting depth increases.