熔池光强监测是激光选区熔化(SLM)过程监测的重要方法之一。针对SLM成形过程, 建立了一套熔池光强监测软硬件系统, 通过近红外滤光技术和光电二极管检测电路, 获得成形过程中的熔池光强数据。针对时域信号不能可视化激光作用不同成形位置时的熔池光强变化, 提出了采用映射算法对熔池光强数据进行建模。对变功率下熔池光强进行数据分析与建模, 激光功率120 W熔池温度均值为1 404 ℃时, 二极管信号均值为0.31 V, 标准差为0.04 V, 熔池较稳定; 功率增加到220 W熔池温度为1 727 ℃时, 二极管信号均值增加为0.81 V, 标准差增加为0.22 V, 熔池稳定性变差。表明该熔池光强监测系统可以获得工艺参数对熔池热辐射行为的影响规律, 用于支持SLM成形工艺的研发与优化。

Monitoring on the melt pool light intensity is one important method to process monitoring in selective laser melting(SLM). A melt pool light intensity monitoring system, consisting of hardware and software system, was established for the SLM forming process. By near infrared filter technology and photodiode detection circuit, the data of melt pool light intensity in the forming process were obtained. As the change of the melt pool light intensity in the different forming positions of laser act can′t be visualized by the time domain signal, the mapping algorithm was proposed to model the data of the melt pool. Data analysis and modeling of the melt pool light intensity under the variable power were conducted, when the laser power was 120 W and the melt pool temperature was 1 404 ℃, the mean value of the diode signal was 0.31 V, the standard deviation was 0.04 V, the melt pool was stable; when the power increased to 220 W and the melt pool temperature was 1 727 ℃, the diode signal mean increased to 0.81 V, the standard deviation increased by 0.22 V, the stability of the melt pool deteriorated. The results show that the influence of different process parameters on the thermal radiation behavior of melt pool can be obtained through the melt pool light intensity monitoring system, which can be used to support the development and optimization of SLM forming process.