Digital manufacturing of personalized magnesium implants through binder jet additive manufacturing and automated post machining

Abstract

While magnesium (Mg) is a promising material for personalized temporary implants, the lack of a digital manufacturing solution for Mg implants impedes its potential progress. This study introduces a hybrid manufacturing process that integrates binder jet additive manufacturing with automated dry post-machining to enable end-to-end digital manufacturing of personalized Mg implants. Spherical cap-shaped Mg implants were additively manufactured through binder jetting. These implants were placed on graphite flakes during sintering as a potential non-reactive support material, allowing unrestricted shrinkage of 15.2 % to a relative density of 87 %. Microstructural and dimensional analysis revealed consistent interconnected porous microstructures with a shrinkage distortion within ± 0.2 mm of the original digital drawing. High-speed dry milling of the sintered samples, assessed via an orthogonal cutting test, identified the optimized cutting parameters. A three-step machining process for automated 5-axis machining, along with clamping strategies, referencing, and an adaptive plug-in, were successfully implemented. The automated dry machining on binder-jet printed Mg implants resulted in an average roughness of < 1.3 µm with no defects. In summary, this work introduces a robust digital manufacturing solution to advance the transformative landscape of Mg implants and scaffolds.

Keywords

• Sintering
• Binder jet additive manufacturing
• Computer-aided manufacturing
• Orthogonal cutting
• Magnesium implants