Topology-Optimized 3D Infill Generation Using the Ground Structure Method for Material Extrusion Additive Manufacturing

This paper presents a Ground Structure Method (GSM)-based topology optimization framework to create optimized 3D infill structures tailored to material extrusion additive manufacturing. The infill is considered a closed lattice structure and modeled as a pin-jointed truss. Multiple meshing techniques are investigated to embed the lattice within an arbitrary geometry, producing a skin-lattice structure that serves as both the Finite Element Analysis (FEA) mesh and the infill geometry. A size optimization algorithm based on the Method of Moving Asymptotes (MMA) adjusts strut thicknesses to maximize rigidity. To translate the optimized structure into a printable form, a rasterization-based slicer is introduced, which directly converts the intersections between slicing planes and the FEA mesh into 2D bitmaps, with the contour at each layer mapped to the optimized truss thicknesses. Lastly, an image-to-toolpath process automatically generates the machine files from bitmaps. The method's generality is demonstrated through numerical simulations and printed examples for both 2D and 3D cases. Additionally, experiments show an improvement in stiffness of topology-optimized structures compared to uniform infill structures.