Spatial mechanical enhancement strategy enabled by multi-axis material extrusion additive manufacturing

Material extrusion (ME) is one of the most widely used additive manufacturing (AM) methods, but its application is often constrained by the weak interlayer bonding inherent in the layer-by-layer deposition process. To address this limitation, we propose a multi-degree-of-freedom (MDOF) spatial enhancement strategy for material extrusion additive manufacturing. This strategy defines models into core and reinforcement layers at the design stage and utilizes a six-axis printer to achieve spatial anisotropy, significantly improving the overall mechanical properties of printed parts. Mechanical tests reveal that the core layer ratio, the angle between reinforcement and core layer rasters, and the reinforcement layer fill rate have a pronounced impact on tensile, compressive, and bending performance. Scanning electron microscopy (SEM) analysis further elucidates the fracture mechanisms and strengthening effects. The results demonstrate that a core layer ratio of 5:5, a reinforcement angle of 90°, and a fill rate of 90 % yield optimal mechanical performance in standard specimens, while varying these parameters offers insights into potential practical applications. Moreover, the proposed spatial enhancement strategy effectively addresses the issue of low reliability in the mechanical properties along the layer accumulation direction under various operating conditions in traditional ME processes. It expands the applicability of ME process in freeform surfaces and complex structures requiring balanced anisotropic mechanical performance. This strategy holds promise for advancing industrial applications in fields such as aerospace, automotive manufacturing, and biomedical engineering, while demonstrating feasibility for adoption on other multi-axis printing platforms.