Additively manufactured mesh-type titanium structures for cranial implants: E-PBF vs. L-PBF

• Main Authors: Susanne Lewin, Ingmar Fleps, Jonas Åberg, Stephen J. Ferguson, Håkan Engqvist, Caroline Öhman-Mägi, Benedikt Helgason, Cecilia Persson
• Format: Article
• Language: English
• Published: Elsevier 2021-01-01
• Series: Materials & Design
• Subjects: Additive manufacturing; Electron beam melting; Powder bed fusion; Finite element models; Surface roughness; Cranial implant
• Online Access: http://www.sciencedirect.com/science/article/pii/S0264127520307425

A patient-specific titanium-reinforced calcium phosphate (CaP–Ti) cranial implant has recently shown promising clinical results. Currently, its mesh-type titanium structure is additively manufactured using laser beam powder bed fusion (L-PBF). Nevertheless, an electron-beam (E-PBF) process could potentially be more time efficient. This study aimed to compare the geometrical accuracy and mechanical response of thin titanium structures manufactured by L-PBF (HIPed) and E-PBF (as-printed). Tensile test (ø = 1.2 mm) and implant specimens were manufactured. Measurements by μCT revealed a deviation in cross-sectional area as compared to the designed geometry: 13–35% for E-PBF and below 2% for L-PBF. A superior mechanical strength was obtained for the L-PBF specimens, both in the tensile test and the implant compression tests. The global peak load in the implant test was 457 ± 9 N and 846 ± 40 N for E-PBF and L-PBF, respectively. Numerical simulations demonstrated that geometrical deviation was the main factor in implant performance and enabled quantification of this effect: 34–39% reduction in initial peak force based on geometry, and only 11–16% reduction based on the material input. In summary, the study reveals an uncertainty in accuracy when structures of sizes relevant to mesh-type cranial implants are printed by the E-PBF method.