This study investigates the effect of 3D printing speed on the mechanical strength of parts produced with high-speed PLA. Samples were tested according to the ISO 527-1 standard, focusing on tensile strength. The results reveal that increasing the print speed from 30 mm/s to 500 mm/s reduces the mechanical strength of the samples, although the difference is minimal and does not affect the surface quality when the material is appropriately selected. Additionally, the orientation of the samples on the build plate had a significant impact on their strength, with samples printed along the Y-axis exhibiting better tensile performance. Ironing, which smooths the surface at the end of the print, improved the fracture surface consistency and tensile strength, regardless of the print speed. The improvement in tensile strength observed in ironed specimens can be attributed to improved bonding of the layers, reduced porosity, and a reduction in stress concentration points, which ultimately contributed to more uniform stress distribution and less risk of premature failure. Thermal camera images indicated no significant deviations in heat distribution, excluding this factor as a cause for inconsistent fracture points. This study concludes that higher printing speeds offer time and energy savings with minimal impact on mechanical properties, making them suitable for prototyping and decorative elements, although the effects of print speed and orientation should be considered for applications requiring higher strength.

Fused Filament Fabrication (FFF) printing is one of the most all-purpose manufacturing techniques, allowing many complicated parts to be obtained at lower cost. This is especially important in prosthetics, where more complex prostheses, especially of a hand, can cause enormous expense. However, providing the full functionality of a prosthesis often requires combining materials with different properties, such as rigidity and flexibility. The use of such a combination in multi-material printing involves a problem of delamination at the interface between two materials. The research described in this article focused on modifying the structure of the interface to improve adhesion between rigid and flexible materials. Polylactide (PLA), thermoplastic polyurethane (TPU), and acrylonitrile butadiene styrene (ABS) were used. PLA-TPU85, PLA-TPU98, ABS-TPU85, and ABS-TPU98 joints were tested in a three-point bending test. Among the above-mentioned joints, the one called PLA-TPU85 presented the best properties, that is, the ability to transfer forces. Therefore, this joint was selected for further modifications. To improve the adhesion in PLA-TPU85 joint, a sandwich-type structure was designed, and its effectiveness was tested in a shear test. The samples lacking this structure became delaminated during the test, whereas those with the sandwich structure maintained the integrity. Thus, the effectiveness of such a solution was confirmed and applied to the connection of rigid and flexible materials in the final printing of the prosthesis.