Touch-n-Curl: Designing and Constructing Skeletal Form through 3D Printing Flattened Zipper Assembly

In the realm of digital fabrication, skeletal structures offer lightweight, cost-effective solutions for art installation, rapid fabrication, and large-scale construction. However, existing 3D printing methods for skeletal structures often require support structures, resulting in prolonged print time and excessive material consumption. This paper presents Touch-n-Curl, a design and construction system for rapidly prototyping 3D skeletal curved structures, covering scales from millimeters to meters, by printing 2D zipper assemblies with interlocking mechanisms using conventional 3D printers. This design process is made possible by a computational method that unrolls a 3D model into a 2D branch assembly while minimizing branch intersections, making the fabrication process both efficient and robust. A parametric design tool is developed to support this inverse design workflow, instantly generating 2D zippers and offering a preview of the 3D skeletal assembly. To ensure users can effectively utilize the system, we implement methods such as edge disjoining and tree rectification to accommodate closed mesh imports in addition to opened trees at a wide range of complexity measured by curvature and torsion. The result of this integrated and accessible workflow is evaluated in fabrication speed, mechanical strength, and shape-matching accuracy, and its versatility is showcased through a series of demonstrations.