Study On Heat Transfer Simulation And Process Of CO₂ Laser Ablation Of PMMA

Acrylic（PMMA）material is widely used in various scenes of production and life,but its integrated processing and molding is the main factor limiting its development.In this paper,the CO₂continuous laser ablation of PMMA material was proposed,and it not only made the machining process more efficient,but also enabled the processing of fine areas with a small heat-affected zone of the processed material.The processing of CO₂continuous laser ablation PMMA sheet involves the interaction between high-energy laser beam and materials,as well as various effects,such as acoustics,thermal,and mechanical effects.The establishment of heat transfer models and the key issuses such as heat transfer mechanism,melting and gasification phenomena during the ablation process,are crucial to improve the quality,accuracy and efficiency of laser ablation.Firstly,the mechanism and theoretical basis of CO₂continuous laser ablation processing were elaborated.Based on the principle of CO₂laser ablation processing,the influence of laser processing parameters on the ablation effect and the effect of the working mode of laser processing on the removal of treatment of the material were clarified.The influence of coupled laser processing parameters and direct writing methods on the ablation process was calculated for the power of CO₂laser ablation of PMMA sheets with certain thickness,laying the feasibility of experimental research.Secondly,based on CO₂ continuous laser ablation of PMMA sheets,numerical simulation was carried out,and the relevant heat transfer model was established on the basis of the Fourier heat transfer model.By establishing suitable boundary conditions and solving using the finite difference method,the following simulation results were obtained:when the laser power density was 67.96 W/mm²,the highest temperature on the surface of the PMMA sheet after ablation exceeds the PMMA melting point of about 490 K,and the laser energy was able to slowly ablate PMMA sheets.When the laser power density was increased to 135.93 W/mm²,the highest temperature on the PMMA surface was exceeded the vaporisation temperature to 650K.At this time,the laser energy could vaporize the sheet in a short time.With the laser power density gradually increased to 203.89 W/mm²,the maximum temperature on the surface of the PMMA sheet was up to 865 K,and the ablation area was removed in large quantities.The ablation results at three power densities are consistent with the simulated results,so the model and simulation results establish the ablation of PMMA panels at these laser parameters,confirm the feasibility of this heat transfer model,and provide guidance on parameter selection for CO2 laser ablation of other materials.Finally,the experimental process and results of the CO₂continuous laser ablation of PMMA sheets were investigated and analysed,and the laser parameters corresponding to a zero defocusing amount were found by studying the radius of the laser spot and the depth of the crater,and the evolution of the defocusing amount with the crater diameter,depth and laser power density was determined.By combining the optimum parameters,the ablation parameters for ideal surface quality were:laser power density of 402.71 W/mm²,laser travel speed of 90 mm/s and laser power of 90W.This process and method can be used for continuous CO₂laser ablation of other non-metallic materials.Other non-metallic materials can be used for reference.