Investigation of a New Approach to Monitor Element Weight Percentage Variation in Compositional Graded Material (CGM) Printing Based on Temperature Contour Measurement

Additive manufacturing (AM) of compositional graded material (CGM) has received increasing attention in recent years. AM enables free tailoring of material element percentage during the manufacturing of the product, to integrate position-determined functions in the built structure. Monitoring the material element weight percentage during fabrication has thus become a critical research issue in CGM-AM for quality control. This paper presented an in-situ sensing method to identify the element weight percentage by monitoring the conductivity variation induced temperature distribution change surrounding the melting pool. The relationship between material conductivity and dimensions of the temperature contour surrounding the melt pool was analytically modeled. To validate the model, thermal images of the melting pools of Cu-Inconel 625 alloy were captured by an infrared camera during Laser Powder Bed Fusion. The thermal images were processed through image segmentation to extract geometric features correlated with the analytical model, i.e., the length, width, and covered area of the contour. All the extracted features at different element weight percentage levels showed trends consistent with the analytical model. Experimental results also quantified the effect of layer accumulation on the contour dimensions and proved the robustness of the presented method.