In Bone Tissue Engineering (BTE), autologous bone-regenerative cells are combined with a scaffold for large bone defect treatment (LBDT). Microporous, polylactic acid (PLA) scaffolds showed good healing results in small animals. However, transfer to large animal models is not easily achieved simply by upscaling the design. Increasing diffusion distances have a negative impact on cell survival and nutrition supply, leading to cell death and ultimately implant failure. Here, a novel scaffold architecture was designed to meet all requirements for an advanced bone substitute. Biofunctional, porous subunits in a load-bearing, compression-resistant frame structure characterize this approach. An open, macro- and microporous internal architecture (100 µm–2 mm pores) optimizes conditions for oxygen and nutrient supply to the implant’s inner areas by diffusion. A prototype was 3D-printed applying Fused Filament Fabrication using PLA. After incubation with Saos-2 (Sarcoma osteogenic) cells for 14 days, cell morphology, cell distribution, cell survival (fluorescence microscopy and LDH-based cytotoxicity assay), metabolic activity (MTT test), and osteogenic gene expression were determined. The adherent cells showed colonization properties, proliferation potential, and osteogenic differentiation. The innovative design, with its porous structure, is a promising matrix for cell settlement and proliferation. The modular design allows easy upscaling and offers a solution for LBDT.

The filament drive is a key part of the extrusion assembly of a Fused Filament Fabrication printer. This investigation examines the maximum feed force and the slip of different driving rollers using a filament made of polylactic-acid (PLA) on a test stand. The test stand systematically varies the main feed process parameters: feed velocity, pinch force between the rollers, and feed force. The maximum feed force has a characteristic dependency on the pinch force combined with a feed-velocity-dependency, which is influenced by the outer diameter of the driving roller. The slip was found to increase linearly with the feed force. The slip decreases with increasing pinch force and is nearly constant for pinch forces above 77 N—172 N, depending on the driving roller tooth geometry and outer diameter. A model derived from contact mechanics was used for phenomenological modeling of the slip in relation to pinch force and feed velocity. An exponential ansatz provided good modeling of the slip at a constant pinch force. The model of the slip combined with the extrusion forces in the liquefier can be used to estimate the material flow in the future, thus leading to increased precision of the parts in a magnitude of systems.