Flexible tooling by 3D extrusion printing for the manufacturing of surgical implants via single-point incremental forming (SPIF)

Single-point incremental forming of surgical prostheses for maxillofacial surgery from metal sheets often involves manual shaping by healthcare personnel using a 3D printed matrix based on computed tomography (CT) or magnetic resonance (MRI) images. To improve quality and automate the process, a hybrid technique combining single-point incremental forming (SPIF) with CNC technology has been proposed, enabling the production of finished prostheses in a single automated operation. In the SPIF process, metallic tooling holds the metal sheet in place, varying geometry according to the shape of the implant. To increase flexibility, use of interchangeable die inserts has been proposed. Inserts, mounted on a metal frame, are 3D printed and can be adapted to different geometries for small-sized implants. This study investigates the influence of key printing parameters on insert robustness, with the aim of identifying parameter settings that yield sufficiently mechanically robust inserts. Specimens made with PLA-based materials (PLA and PLA 3D870) and PETG were tested with different infill densities and printing patterns following the Taguchi methodology. The influence of each parameter on the compressive strength, cost and time was analysed leading to the optimisation of printing settings. Finally, the proposed flexible tooling system was validated through experimental trials. Specimens with spherical cap geometries were successfully manufactured from grade 1 titanium and AISI 304 stainless steel, with varying radii of curvature and drawing depths. The results demonstrated the effectiveness of the flexible tooling, confirming its potential for use in automated manufacturing of prostheses for the medical field.