Scale-dependent interplay between densification and deposition quality in MEX/M 17-4PH gyroid shell-TPMS

Mechanical performance in metallic TPMS structures fabricated by metal material extrusion (MEX/M) is commonly associated with densification, defect evolution, and microstructural development. However, it remains unclear whether their relative importance remains constant across different geometric configurations or changes as geometric constraints intensify. This study investigates 17–4 PH gyroid Shell-TPMS structures fabricated through filament-based fused filament fabrication (FFF) and rod-based bound metal deposition (BMD). Feedstock characteristics, deposition architecture, defect populations, microstructure, hardness, density-related metrics, and compressive performance were evaluated across multiple configurations. Statistical analysis revealed significant effects of manufacturing condition, geometric configuration, and their interaction on compressive performance (p < 0.001). For moderate-to-thick-wall configurations, BMD exhibited the highest compressive performance, combining macro-porosity below 2 %, hardness values 15–25 % higher than FFF, and a peak stress of 26.63 ± 0.32 MPa. In contrast, a different trend was observed for the ultra-thin configuration (UL = 10 mm, RD = 0.082), where BMD exhibited a peak stress approximately 22 % lower than FFF fabricated with a 0.40 mm nozzle despite the more favorable defect, microstructural, and hardness characteristics associated with the BMD process chain. These results indicate a configuration-dependent interplay between consolidation-related and deposition-related characteristics, with deposition architecture becoming increasingly influential as geometric constraints intensify.