Mathematical modeling and investigation of intrinsic interaction mechanisms in CO₂ laser processing of PMMA

The CO₂ laser is capable of efficiently processing high-quality structures on the surface of PMMA (Polymethyl methacrylate). In order to elucidate the intrinsic physical mechanisms underlying the laser processing and to optimize the processing parameters for CO₂ laser machining of PMMA, a mathematical model has been established. This model incorporates the mechanisms of thermal transfer, melting, vaporization phenomena, and the behavior of molten flow within the material under laser irradiation. The dynamics of the interaction between the CO₂ laser and PMMA were systematically explored. Following this, a comprehensive analysis was conducted on the thermodynamic distribution within the material surface processing area, the molten flow characteristics, and the vaporization recoil pressure generated during the process of evaporation ablation. The results indicate that the laser processing of PMMA predominantly occurs via evaporation ablation. It was observed that as the laser power increases, the depth of the ablation pit also gradually increases. However, this increase is accompanied by a corresponding rise in the temperature gradient within the surface layer of the material. When the temperature gradient becomes excessively high, the phenomenon of evaporation ablation introduces vaporization recoil pressure. This results in the accumulation of molten material surrounding the processed pit structure, thereby forming raised structures. Overall, to achieve microstructures with optimal surface quality efficiently during CO₂ laser ablation of PMMA, a laser power setting of 3 W is recommended for irradiation processing. This study elucidates the mechanisms through which laser processing influences the material, providing theoretical guidance for the optimization of laser processing techniques for PMMA.