IN-OPERANDO BACKSCATTERED ELECTRON SIGNAL ANALYSIS FOR REAL-TIME PROCESS CONTROL IN ELECTRON BEAM POWDER BED FUSION

Abstract

Electron Beam Powder Bed Fusion (EB-PBF) is a promising metal additive manufacturing technology; However, it is not mature enough as Laser based PBF technology due to the challenges of in-situ monitoring application. Traditional optical based monitoring techniques have not been effective as in other metal additive manufacturing technologies. Those limitations are due to the vacuum operation, metallization effect, limited optical accessibility, and radiation. These limitations have limited traditional monitoring reliability for real-time monitoring. Recently, backscattered electrons detectors have been implemented in EB-PBF systems and showed reliability, accuracy, and robustness as an alternative for traditional technologies. However, most of the prior research has focused on pre-melting, post-melting monitoring, and mostly in-melt monitoring for line melts. Leaving the analysis of spot melting, which is one of the EB-PBF strengths, unexplored. This work will be addressing this gap by developing a comprehensive methodology for in-operando signal analysis of spot melts. A design of experiments based on responsive surface methodology is employed to systematically vary beam power and dwell time while controlling spatial distribution, surface conditions, and beam incident angle. By decoupling location and surface effect and adding incident angle effect, a rigorous regression model along with ANOVA analysis has been developed to achieve a very reliable correlation of R^2=96.67% with all of the parameters showing a very strong statistically significant effect (p<0.01). By developing the signal correlation, a validation build was done to simulate the real-life situation to test the reliability of the regression model. The outcomes are expected to be reliable and to improve the understanding of in-melt electron emission behavior.