Intra-layer closed-loop control of build plan during directed energy additive manufacturing of Ti-6Al-4V

The location, timing, and arrangement of depositions paths used to build an additively manufactured component - collectively called the build plan - are known to impact local thermal history, microstructure, thermal distortion, and mechanical properties. In this work, a novel system architecture for intra-layer, closed-loop control of the build plan is introduced and demonstrated for directed-energy deposition of Ti-6Al-4V. The control strategy altered the build plan in real time to ensure that the temperature around the start point of each hatch, prior to deposition, was below a threshold temperature of 415. °C. Potential hatches with an initial temperature above this threshold were temporarily skipped. Compared with open-loop processing, closed-loop control resulted in vertical alignment of columnar prior-β grains, more uniform α-lath widths, and more-uniform microhardness values within the deposited component.