Investigating intermediate shapes for multi-stage forming of cranial implants

Abstract

Single Point Incremental Forming (SPIF), a numerically controlled sheet forming technique, excels in adaptability and cost reduction for small-scale production and customized parts. This study explores multi-stage SPIF, focusing on applications in the medical domain, particularly the fabrication of personalized medical implants. Addressing critical challenges related to formability and accuracy, this study emphasizes the significance of multi-stage forming and the importance of the design of intermediate shapes. Forming a cranial implant using one intermediate stage is studied, preliminary in pure Zinc as a cost-effective alternative for heated Ti. The intermediate shape is generated using automatic geometry adaptations such as translating and scaling the CAD model. Nine different experiments are conducted and compared in terms of final geometric accuracy and thickness distributions. The study shows that the proposed intermediate shapes for multi-stage forming significantly improve the geometric accuracy from 1.08 mm mean absolute deviation in traditional single stage forming to 0.41–0.59 mm. However, the used intermediate shapes have a strong but varying effect on thickness distributions throughout the part, showing the importance and sensitivity of the exact intermediate geometry. These insights provide a valuable understanding of the process, shaping the pathway for enhanced utilization of SPIF and setting the stage for future improvements.