Large-Scale 3D-Printable Bending-Active Formwork with Auxetic Properties

Author

Nakayama, Kazunori and Awaji, Hiroki and Sakai, Yusuke and Yoshikawa, Ryo and Hayashi, Sei and Gondo, Tomoyuki and Kimura, Toshiaki and Mitsuda, Eisuke

Abstract

This study presents an enhanced method for fabricating large-scale bending-active formwork with auxetic properties using pellet-based three-dimensional (3D) printing. Previous work demonstrated the feasibility of constructing auxetic bending-active grid shells using filament-based printing; however, the small printable blocks of approximately 300 mm x 300 mm significantly increased fabrication time and assembly effort. Here, a scalable workflow capable of producing 1 m x 1 m blocks is developed to reduce fabrication time while maintaining structural performance. A continuous single-path printing strategy is adopted to enable rapid block production. In addition, a toolpath design that follows different routes every four layers is implemented to enhance overall stability. Because pellet-based extrusion produces rounded edges that complicate alignment, three joining techniques, namely welding, fusion welding and hot-melt adhesive, are examined. Among these, fusion welding achieves stable bonding under deformation. The methodology integrates computational grid design, material selection, process parameter control and structural evaluation through load-displacement testing. The results show that the proposed system substantially reduces printing time while achieving mechanical behaviour comparable to that of the filament-based approach. Pellet-based 3D printing therefore represents a viable approach for fabricating large-scale bending-active formworks.