Robotic laser directed energy deposition-based additive manufacturing of tubular components with variable overhang angles: Adaptive trajectory planning and characterization

The present work reports on an adaptive trajectory planning to build tubular components with variable overhang angles using a robotic Laser Directed Energy Deposition (LDED) based Additive Manufacturing process without utilizing support structures. The proposed technique uses a non-parallel slicing methodology to build complex components (e.g., bent pipes) and deploys adaptively varying scanning speed and tool orientation. The variation in scanning speed aids in having point-to-point variable layer height enabling non-parallel deposition while changing the tool orientation during deposition permits the manufacturing of support-free bent pipe parts. The bent pipes with 45 degrees and 90 degrees bents were built using an in-house developed LDED system and the built parts are characterized for geometry, density, microstructure, and microhardness. The geometrical analysis indicates a deviation in the range of + 0.5 mm to -0.5 mm, with minimal roundness deviation at different sections. The density analysis of the segments extracted from the bent pipe reveals a density > 98%, with the presence of a few lack of fusion pores and gas pores at isolated locations. The microstructure and microhardness studies show that regions built with higher scanning speeds have a finer grain structure and higher average hardness. The study paves a path to build defect-free and dimensionally stable complex-shaped components with varying overhang angles using LDED.