This study investigates how moisture preconditioning and thermal parameters affect the stretchability of paper in 3D forming, with the goal of extending geometric forming limits and enhancing process stability. Multidimensional tensile tests were performed on FibreForm Duo (310 g/m²) using a hemispherical punch. Key variables included water bath dwell time, punch temperature, and contact time, simulating industrial conditions in high-speed packaging. A short duration of water bath immersion (1–3 s) led to rapid moisture uptake (−20%), resulting in significantly improved formability. Compared to unconditioned samples, the maximum stretch increased by up to 3.5 percentage points. The process window identified (3.03 s dwell time; 70 °C punch temperature; 1.08 s contact time to punch) yielded a predicted stretch of 16.5%, representing a notable expansion of the material’s geometric forming capacity. Regression analysis (R² = 0.8946) confirmed the strong statistical significance of all parameters.

In response to increasing sustainability demands, the packaging industry is shifting toward paper-based alternatives to replace polymer packaging. However, achieving complex, three-dimensional geometries comparable to plastics remains challenging due to the limited stretchability of paper. This study investigates advanced preconditioning techniques to enhance the formability of paper materials for deep-draw packaging applications. A custom-built test rig was developed at Syntegon Technology GmbH to systematically evaluate the effects of ultrasound-assisted moistening and segmented radiative heating. Under optimized conditions, 2.67 s moistening, 70.00 °C punch temperature, and 2999 W radiation power, maximum stretchability increased from 13.00% to 26.93%. The results confirm the effectiveness of ultrasound in accelerating moisture uptake and radiation heating in achieving uniform thermal distribution across the paper substrate. Although prototype constraints, such as the absence of inline conditioning and real-time measurement, limit process stability and scalability, the findings provide a strong foundation for developing industrial 3D paper forming processes that support sustainable packaging innovation.

The growing demand for sustainable packaging solutions is driving the development of new paper-based forming processes. Among these, 3D forming of paper has shown particular promise (Groche, P. and Huttel, D. (2015). Paperboard forming - specifics compared to sheet metal forming. BioRes 11). However, limited formability remains a key challenge, restricting potential applications. Since moisture content significantly affects both bending stiffness and stretchability (Franke, W.; Stein, P.; Dörsam, S.; Groche, P. (2018): Formability of paperboard during deep-drawing with local steam application. In: Proceedings of the 21ST international esaform conference on material forming . ESAFORM 2018, Palermo, Italy, 2018: Author(s) (AIP Conference Proceedings), S. 100008), targeted moistening is critical. For high-speed packaging lines with cycle times of 1–3 s, rapid and controlled moistening is required. Previous studies have shown that methods like water baths or sponge applications can improve forming results especially when combined with pressure to ensure even moisture distribution (Stotz, H., Vogt, L., Kasparian, T., Klauser, M., Rauschnabel, J., and Hauptmann, M. (2022). TAPPICon 2022 - advanced development in 3D forming methods for paper packaging . Charlotte, North Carolina, USA, 30 April-4 May 2022. Curran Associates, Inc., Red Hook, NY). However, practical, process-integrated solutions have been lacking. This study investigates a newly developed moistening unit using a porous aluminum interface for one-sided application (Bischoff, B.; Stotz, H.; Klauser, M. (2023). Verfahren und vorrichtung zur herstellung eines verpackungselementes . Angemeldet durch Syntegon Technology GmbH am 05.05.2023. Anmeldenr: 23171862.8. Veröffentlichungsnr.: EP 4 292 805 A1). Experiments with bleached board demonstrated that higher water pressure and longer contact times significantly increased moisture content. Moisture levels of up to 26 % were achieved in just 1–3 s. As a result, formability improved noticeably: the maximum strain increased from 13 % to 19 %, enabling deeper geometries and steeper wall angles – a clear advancement for sustainable packaging design.