为实现不等壁厚复杂零件的激光增材制造,设计开发了一种基于自适应镜的可变圆光斑激光熔覆光学系统。系统由反射式抛物准直镜、反射式自适应镜和反射式抛物聚焦镜等组成。通过气压比例阀调节自适应镜腔内气压,改变自适应镜表面曲率半径,使光束以不同程度的会聚角或发散角入射到反射式抛物聚焦镜,从而改变作用在工件表面的激光光斑大小。建立了基于自适应镜变斑光学系统的物理模型,通过Matlab和Zemax软件仿真分析了自适应镜焦距的变化范围、反射式抛物准直镜与反射式抛物聚焦镜的焦距和位置,以及光纤激光光源参数等对系统变斑特性的影响。采用6 kW光纤激光器,按照变光斑、变功率、等速度、等功率密度的方案进行激光熔覆工艺实验,实现了壁厚由3 mm渐变到8 mm的椭圆形工件的激光熔覆增材制造。

In order to realize the laser additive manufacturing of complex parts with unequal wall thickness, a variable circular spot laser cladding optical system based on adaptive mirror is proposed. The system consists of reflective parabolic collimating mirror, reflective adaptive mirror and reflective parabolic focusing mirror. The air pressure proportional valve is used to adjust the gas pressure in the adaptive mirror cavity, to change the radius of curvature of the adaptive mirror surface, and make the beam incident on the reflective parabolic focusing mirror at different convergence angles or divergence angles, so as to change the spot size acting on the surface of the workpiece. Physical model is established based on adaptive mirror variable spot optical system, and using Matlab and Zemax softwares, the effects of the range of the adaptive mirror focal length, the focal length and position of the reflective parabolic collimating mirror and the reflective parabolic focusing mirror, and the parameters of the fiber laser source on the variable spot characteristics of the system are analyzed. A 6 kW fiber laser is used to carry out cladding experiment according to the scheme of variable spot, variable power, constant speed and constant power density, and an elliptical workpiece with a wall thickness of 3-8 mm is realized.