Fast 360{\deg} 3D Metrology for Directed Energy Deposition

Directed Energy Deposition (DED) is a metal additive manufacturing process capable of building and repairing large, complex metal parts from a wide range of alloys. Its flexibility makes it attractive for multiple industrial applications, e.g., in aerospace, automotive and biomedical fields. However, errors or defects introduced at any stage of the printing process can, if undetected, significantly impact the final result, rendering the printed part unusable. Potential in-situ correction methods of printing defects require fast and high-resolution on-the-fly 3D inspection inside the machine, but existing 3D monitoring methods often lack full 360{\deg} 3D coverage, require bulky setups, or are too slow for real-time layer-wise feedback. In this paper, we present a single-shot, multi-view polarized fringe projection profilometry (FPP) system designed for real-time in-situ 3D inspection during DED printing. Multiple camera-projector pairs are arranged around the deposition surface to measure depth from different viewpoints in single-shot, while cross-polarized image filtering suppresses specular reflections caused by varying surface reflectance across different alloys. The final 360{\deg} reconstruction is obtained via joint registration of the captured multi-view measurements. Our prototype has been deployed in a DED system and our first experiments demonstrate a depth precision better than $\delta z < 50\,\mu\mathrm{m}$ on partially reflective and "shiny" metal surfaces, enabling accurate, layer-wise monitoring for closed-loop DED control.