Arburg plastic freeforming (APF) technology allows for fabricating patient-specific implants (PSIs) in a hospital environment using medical-grade thermoplastic polymers. Among these materials, poly(carbonate-urethane) (PCU) is of great relevance since it is characterised by excellent biocompatibility. This study explores the opportunity to realise a patient-specific cranial plate via APF. First, a Finite Element model (FEM) of the implant under compressive loads is developed and validated using a quasi-isotropic material. Then, this model is used for Finite Element Analysis (FEA) considering Technical Datasheet (TDS) material properties and those measured on 3D-printed specimens, by Three-Point Bending (TPB) tests. Finally, a PCU PSI is fabricated through APF and tested under static loads to validate the consistency of the numerical results. Considering TDS properties, the FEA results indicate that PCU can be used for the manufacturing of this device. Nonetheless, the TPB tests show that the material suffers from a loss of mechanical properties. Using these properties, the displacements calculated via FEA exceed the admissible values for the application. A further decrease in stiffness is observed in the manufactured plate. Overall, findings suggest that PCU can be a viable material to be printed by APF technology for fabricating craniofacial PSIs, with the advantage of minor stress concentration in critical points of the implant if compared with polyetheretheretherketone (PEEK). However, further studies are necessary to effectively represent the effects of 3D printing in the FEMs used for structural validation and design optimisation.

Material Jetting (MJ) 3D printing technology is promising for the fabrication of highly realistic surgical simulators, however, the changes in the mechanical properties of MJ materials after post-printing treatments and over time remain quite unknown. In this study, we investigate the effect of different post-printing processes and aging on the mechanical properties of a white opaque and rigid MJ photopolymer, a white flexible MJ photopolymer and on a combination of them. Tensile and Shore hardness tests were conducted on homogeneous 3D-printed specimens: two different post-printing procedures for support removal (dry and water) and further surface treatment (with glycerol solution) were compared. The specimens were tested within 48 h from printing and after aging (30-180 days) in a controlled environment. All groups of specimens treated with different post-printing processes (dry, water, glycerol) exhibited a statistically significant difference in mechanical properties (i.e. elongation at break, elastic modulus, ultimate tensile strength). Particularly, the treatment with glycerol makes the flexible photopolymer more rigid, but then with aging the initial elongation of the material tends to be restored. For the rigid photopolymer, an increase in deformability was observed as a major effect of aging. The hardness tests on the printed specimens highlighted a significant overestimation of the Shore values declared by the manufacturer. The study findings are useful for guiding the material selection and post-printing processing techniques to manufacture realistic and durable models for surgical training.

Lightweight design is often assumed to be the leading strategy to improve the sustainability of parts produced by additive manufacturing. The present study confutes such an assumption by a cradle-to-gate life cycle assessment of different lightweight strategies applied to a specific case study in the medical field. In particular, a patient-specific finger splint made of polyamide is redesigned by means of generative design, topology optimization and lattice structures. The analysis investigates two markedly different deposition processes, namely Arburg plastic freeforming and fused filament fabrication. The former is carried out on an industrial-grade machine, while a desktop printer is used for the latter. This allows for observing the impact of the redesign in two quite distinct scenarios. Findings demonstrate that, since environmental impacts are mainly driven by building time, the adoption of automated design algorithms can be detrimental to the sustainability of the process. On the other hand, relevant benefits on environmental impacts were achieved by reducing the infill percentage of parts. The results of this work highlight the most relevant aspects which must be considered to limit environmental impacts when designing parts for deposition-based additive manufacturing. This information can be used by designers to drive weight reduction towards sustainability.

This study explores the use of Arburg Plastic Freeforming (APF) technology to produce patient-specific implants (PSIs) using the high-performance polymer polyether–ketone–ketone (PEKK). The APF process allows printing PEKK in an amorphous state, improving toughness and reducing distortion compared to PEEK, with minimal stiffness loss. Three-point bending (TPB) specimens were printed in two orientations and tested to characterise the material. The TPB tests showed minor reductions in mechanical properties, and DSC analysis confirmed the amorphous nature of the printed PEKK. A cranial PSI was also fabricated and subjected to static compression testing. The cranial plate exhibited strong layer adhesion, showing acceptable displacement under loads comparable to those from severe impacts. Finite element analysis (FEA) of the cranial plate was conducted using material properties from technical datasheets and TPB results. FEA results closely matched experimental findings, validating the use of TPB-derived properties for accurate simulation. The findings indicate that APF-printed PEKK is suitable for craniofacial PSIs, offering improved mechanical compatibility and fabrication precision. Further research is needed to evaluate the dynamic impact behaviour and long-term biocompatibility to fully establish clinical applicability.

In injection moulding and additive manufacturing processes, it is common for the final product to exhibit warpage induced by a non-uniform cooling rate after material deposition. Residual stresses can be generated in the built parts, with a volume shrinkage that leads to dimensional inaccuracy and reduced usability. This phenomenon is even amplified in the presence of semi-crystalline polymers, which still need to be more widespread among additive manufacturing processes despite their capacity to show better mechanical properties when compared to amorphous ones. This study evaluates the degree of deformation and subsequently characterises the mechanical properties of a novel modified Polyamide 6 formulation (i.e., RADILON® S X21351 NT) printed through the Arburg Plastic Freeforming process. This new proprietary formulation modified the crystallisation behaviour during cooling. The whole exothermic crystallisation peak was shifted to lower temperatures, allowing the processing envelope of the modified formulation to widen. More specifically, after preliminary polymer characterisation analyses and after evaluating the warpage, a mechanical characterisation was performed using tensile tests on specimens (dry-as-moulded and conditioned) printed with different filling strategies on the build platform (XY-0°; XY- ± 45°; XY-90°; ZX-0°). Measured mechanical properties were ultimately compared to those achieved by applying the injection moulding technique on the same non-modified material. The specimens produced through the Arburg Plastic Freeforming process showed brittle behaviour that was more marked than those obtained by injection moulding. Moreover, the infill direction and water content significantly influenced the mechanical properties of specimens.