Geometry control of deep drawn paperboard parts by influencing the stress-state of semi-finished products

The transition towards sustainable packaging requires reliable forming processes for paperboard, but its anisotropic and hygroscopic nature strongly limits dimensional accuracy in processes such as deep drawing. This study addresses the aforementioned challenge by systematically investigating two complementary strategies: optimizing blank geometry and introducing pretension. A combination of numerical simulations with anisotropic, moisture-dependent plasticity, and experimental validation using a pneumatic press with additively manufactured tools was applied. The base-point method for blank optimization allowed for efficient reduction of flange length deviations and geometric errors by more than 55% in a first iteration and stable convergence within three optimization steps. Pretension strategies, applied either by mechanical pre-stretching or by exploiting hygroexpansion, also reduced anisotropic springback. Hygroexpansion-based pretension proved particularly effective by achieving more homogeneous stress distributions without additional equipment. The results demonstrated that these strategies can reduce springback and increase drawing depth while providing a reproducible approach. Optimized blank geometry ensures a more uniform distribution of blank-holder force, while pretension counteracts anisotropy-induced recovery. Together, these findings provide a pathway toward more accurate and scalable paperboard deep drawing, with relevance for industrial implementation of sustainable three-dimensional packaging.