In-loop additive manufacturing constraints for open-walled microstructures

The derivation and integration of novel in-loop additive manufacturing constraints for open-walled microstructures within a multiscale optimization framework is presented. Problematic fabrication features are discouraged in-loop through the application of an augmented projection filter and two relaxed binary integral constraints, which prohibit the formation of unsupported members, isolated assemblies of overhanging members and slender members during optimization. Through the application of these constraints, it is possible to derive self-supporting, hierarchical structures with varying topology, suitable for fabrication through AM processes. Two classical compliance minimization problems are solved using both the base framework with a prohibitive lower bound constraint applied on member radius to guarantee manufacturability and the base framework with integrated in-loop AM constraints. In both cases, the present work leads to a significant increase in the mechanical performance.