激光直接制造金属零件过程的闭环控制研究

对激光直接制造金属零件过程中熔池温度和熔覆层厚度的变化进行了研究,指出对确定的材料,当激光功率增大到一定值时,熔池内的金属溶液大多已达到了热饱和,温度累积效应并不显著,熔池温度基本保持平稳,而在制造过程中若零件由于工艺不稳定而产生凹凸点,在多次层叠制造后,凹处越凹、凸处越凸,严重影响零件的制造精度。所以通过传感器来直接监测金属零件的熔覆高度,进而通过控制送粉量来保证制造过程中熔覆高度的稳定性比起温度控制来更具有实际意义。提出了熔覆高度的检测方案,并对送粉量的闭环控制系统进行了研究,对送粉量的时间延迟提出了相应的对策。结果表明对熔覆层高度的检测和对送粉量的调节能够提高激光直接制造过程的稳定性和制造精度。

Research about close-loop control system during laser direct manufacturing metallic components

Temperature changes in melt pool and layers' thickness changes during laser direct manufacturing metallic components has been researched. It is proved that to specific material, when laser power is increased to a specific level metallic solute in melt pool will reach to heat saturation, temperature in melt pool remains stable and temperature accumulation effect is not very obvious. It is also found that once concave or protrudent points emerge for process's instability, the situation will deteriorate after multiple layers' cladding, which will seriously influence metal parts' manufacturing accuracy. So by monitoring metal components' cladding height in real time using height sensors, adjusting powder feeding speed accordingly can be more feasible and advantageous than by monitoring temperature in melt pool to gurantee manufacturing accuracy. The scheme of sensoring cladding height is proposed, and close- loop control system of powder feeding speed is developed. It is proved that the way of adjusting powder feeding speed as while as monitoring cladding height of manufactured metallic components can improve laser direct manufacturing process's stability and manufacturing accuracy.