A nature-inspired build strategy for consistently fabricating intricate objects by wire-arc-based directed energy deposition

In this manuscript, a novel deposition technique termed interrupted metal deposition (IMD) in wire-arc additive manufacturing (IMD-WAAM) was experimentally investigated for the fabrication of thin walls using ER70S-6 wire. A droplet was generated utilizing a conventional MIG welding heat source, with its deposition location precisely controlled via computer-aided process planning (CAPP). The mode of material transfer was globular. The IMD technique was used to fabricate a thin wall intended for subsequent mechanical characterization. Experimental results demonstrate that IMD-WAAM effectively tailors the thermal history of the deposition process through controlled heat input without detrimentally affecting its mechanical properties compared to conventional WAAM. The built-time analysis revealed that the inter-layer cooling time (ILCT) plays a pivotal role in regulating the built time during the metal additive manufacturing process. The average ultimate tensile strength (UTS) measured in the horizontal and build directions were 513.5 MPa and 511.9 MPa, respectively, with an average elongation exceeding 40% in both directions. The mechanical testing and characterization of the thin wall shows that bainite was predominant in the wall made from an IDCT of 5 s, while ferrite and pearlite were revealed in the wall made from an IDCT of 1 s, assisting in improving the hardness of the fabricated part. These findings suggest that IMD-WAAM offers superior mechanical properties and enhanced thermal distribution control, along with tailored microstructures, compared to conventional WAAM, making it a promising approach for the fabrication of thin walls from ER70S-6.