Numerous sensing modalities have been utilized to monitor metal additive manufacturing, thus assessing process stability and build quality. One common directed energy deposition sensing method is coaxial “melt pool” imaging, wherein a camera mounted coaxially with the laser-focusing optics views the laser-interaction zone via a dichroic mirror. This work demonstrates that coaxial “melt pool” imaging does not always provide reliable, as-solidified, pool geometry measurements. First, coaxially acquired images captured using a charge injection device camera for a range of laser powers, translation speeds, and powder flow rates are compared to optical profilometry-measured true deposition geometries. Furthermore, coaxial “melt pool” images and plume geometries, measured using a bandpass filtered CCD camera, show significant, abrupt “melt pool” geometry changes, which correspond to plume geometry changes. Additionally, interbuild comparisons demonstrate a linear relationship between “melt pool” and plume geometry. The authors conclude that coaxial imaging, as commonly implemented, is an often unreliable melt pool geometry measurement because plume emissions in and around the laser-interaction zone may obscure the melt pool.

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用于基于激光的增材制造的光发射传感-我们实际上要测量什么？

许多传感方式已用于监视金属增材制造，从而评估工艺稳定性和制造质量。一种常见的定向能量沉积感测方法是同轴“熔池”成像，其中与激光聚焦光学系统同轴安装的摄像机通过二向色镜观察激光相互作用区域。这项工作表明，同轴“熔池”成像并不总是能够提供可靠的凝固态几何尺寸测量结果。首先，将使用电荷注入设备的相机针对一系列激光功率，平移速度和粉末流速捕获的同轴采集图像与光学轮廓仪测量的真实沉积几何形状进行比较。此外，使用带通滤波CCD相机测量的同轴“熔池”图像和羽状几何形状显示出显着的，突然的“熔池”几何形状变化，与羽状几何形状变化相对应。此外，内部构造比较显示出“熔池”和羽流几何形状之间的线性关系。作者得出的结论是，通常采用的同轴成像技术通常是不可靠的熔池几何形状测量，因为在激光相互作用区域内和周围的烟流可能会遮盖熔池。