Taper Angle Suppression For Etched Edge And Efficient Area Removal In Laser Processing Of Surface Pattern

Precise surface pattern is the basic structure to realize the important functions like remote communication,circuit integration and signal acquisition.As the related parts tend to have complex surface shape,weak stiffness,concentrated wiring and wide range of materials,laser processing,with the advantages of non-contact processing,strong flexibility and wide application of materials,has become the mainstream processing method of surface pattern.However,under increasingly stringent requirements for high precision and efficiency,it is urgent to solve the problems including the sloping etching edge caused by Gaussian energy distribution,the low removal efficiency for cross-scale pattern,and the difficulty of achieving both the contour quality and feed rate by single scanning strategy.In view of this,the research of taper angle suppression for etched edge and efficient area removal in laser processing of surface pattern is carried out.The contents are as follows:First,by ANSYS and its APDL language as well as life-death element technique,the accurate loading method of laser heat source is studied,and the ablation cross-section of metal by moving pulsed laser is simulated.The results show that the profile by vertical laser etching is highly similar to that of laser energy distribution,while the one by oblique laser etching is obviously asymmetric.In view of the time-consuming calculation and poor flexibility of FEM,the analytical calculation model of ablation cross-section is developed,and the typical etching cross-section and its cause are analyzed.The experimental results show that the prediction errors of the microgroove's depth and width are 3.3% and 11.2% respectively,and the sensitivity of groove width to scanning speed is poor.Next,to solve the problem of sloping etching edge,the technology of taper angle suppression in laser milling,preliminary etching then sidewall trimming,is proposed.The calculation model of laser ablation cross-section is developed to the condition of oblique incidence.When the incident angle is less than 40°,the prediction errors of the microgroove's depth,width and sidewall taper angle are 3.8%,3.8% and 6.7%,respectively.Based on the target of vertical sidewall and the premise of etching depth control,an orderly planning method for the beam-workpiece relative pose,laser fluence and scanning speed for the sidewall trimming is established.Two types of processed microgrooves are basically unchanged in depth and width while the taper angle decreases from 34 ° and 49 ° to 2 ° and 3 ° respectively,whose suppression degree is more than 90%.Then,to improve the processing efficiency by using the laser characteristics,a laser parameter planning method that defocus with energy compensation under the etching depth constraint is proposed.The calculation model of ablation cross-section by defocusing laser processing and the parametric characterization method of the sputter profile are established.Considering the factors of defocus and sputter,the laser energy compensation method under the etching depth constraint is established.The results show that the width of processed microgroove increases by 64.5% while the depth is guaranteed.The average prediction error of sputter height is 8.6% while the original accuracy of the modified ablation cross-section calculation model is retained.In addition,after energy compensation,the etched area is changed from almost no depth to the state meeting the requirements.Last,considering the limitation of single scanning strategy,a laser dual scanning strategies that contour-parallel scanning in outer region and direction-parallel scanning in inner region is proposed.The partition criterion with the equidistant offset curve of the pattern contour being the boundary is established considering the driving ability of the machine tool.The estimation of scanning path interval for area removal by laser milling is also studied.For the contour curve that is non first-order continuous,methods of eliminate self intersection and redundant intersecting segments of curves are developed.The experiments show that the pattern contour is smooth and the overburning in the pattern center is reduced from 23?m to 1?m.Combining with defocus and energy compensation,the processing time is reduced by 28.6% compared with that by contour-parallel scanning strategy.The research is integrated into the software of precise laser processing of surface pattern,and patterns on the inner and outer surfaces of various thin-walled curved parts are prepared.The research results can provide reference for manufacturing high-tech products based on surface functional pattern,and for laser processing technology innovation.