As-Continuous-As-Possible Ceramics Printing for Shell Models FANCHAO ZHONG, Shandong University YONGLAI XU, Shandong University HAISEN ZHAO, IST Austria, University of Washington and Shandong University LIN LU, Shandong University Fig. 1. Our framework significantly improves fabrication eficiency and product quality of shell models with as-continuous-as-possible ceramics printing. A novel geometric criterion łone-path patchž (OPP) is proposed to decompose the input shell into a minimal number of continuous printing patches with flat and curved paths. Compared with the 195 disconnected printing toolpaths with only flat slicing layers (lef) generated by Ultimaker Cura sofware (diferent colors indicate each connected path, red lines represent the transfer moves), our framework produces 4 continuous deposition paths together with flat and curved slicing layers, realizing much beter printing quality (right) and extremely eficient fabrication process (34.3 mins vs 17.7 mins). We propose a novel computational framework for fabricating thin shell models on an extrusion-based Cartesian 3D printer with the clay material. Extrusion-based ceramics printing involves several inevitable challenges to achieve acceptable print quality, including continuous toolpath with the minimal number of transfer moves, separation of non-model and model structures, etc. Inertia of the extruded material may damage the surface quality during transfer moves. The viscosity also makes support material hard to remove. These challenges even increase for thin shell surfaces, as both sides are of visual signifcance, making it impossible to hide any intermediate structures in the interiors. To conquer these challenges, we adopt a curved layer scheme for ceramics printing. Then we introduce an original criterion łone-path patchž (OPP), for representing a shell surface patch that can be traversed in one path in the context of curved layer printing considering fabrication constraints. We propose a bottom-up OPP merging procedure for decomposing the given shell surface into a minimal number of OPPs and generating the "as-continuous-as-possible" (ACAP) toolpath. Furthermore, we customize the path planning algorithm with a decoupled orientation and support structures computation method. Results demonstrate that our ACAP algorithm prints shell models with both efciency and surface quality. Authors’ addresses: Fanchao Zhong, fanchao98@gmail.com, Shandong University; Yonglai Xu, xyliyrwi@gmail.com, Shandong University; Haisen Zhao, haisen.zhao@ ist.ac.at, IST Austria, University of Washington and Shandong University; Lin Lu, llu@sdu.edu.cn, Shandong University. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for proft or commercial advantage and that copies bear this notice and the full citation on the frst page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specifc permission and/or a fee. Request permissions from permissions@acm.org. © 2022 Association for Computing Machinery. 0730-0301/2022/1-ART $15.00 https://doi.org/10.1145/nnnnnnn.nnnnnnn CCS Concepts: · Computing methodologies → Shape modeling; Graph- ics systems and interfaces; Additional Key Words and Phrases: Toolpath planning, shell models, ceramic printing ACM Reference Format: Fanchao Zhong, Yonglai Xu, Haisen Zhao, and Lin Lu. 2022. As-Continuous- As-Possible Ceramics Printing for Shell Models. ACM Trans. Graph. 1, 1 (January 2022), 15 pages. https://doi.org/10.1145/nnnnnnn.nnnnnnn 1 INTRODUCTION Ceramics printing has been gaining both industrial and academic in- terests in recent years. As a natural material, clay is environmentally friendly and durable; thus, ceramic products are ubiquitous in con- struction, housing, consumer goods, etc. A feasible and cost-efective manufacturing technique for clay is direct ink writing (DIW), an extrusion method using a flament of a highly viscous paste. DIW employs a Cartesian 3D printing framework, the same architecture with fused deposition modeling (FDM), but with a larger opening nozzle that provides more material extrusion efciency for high viscosity clay than thermoplastics [Chen et al. 2019b]. As the most popular clay expression form, shell models like pot- teries have developed since the Stone Age. Possessing featured functionalities like lightweight and efective thermal conductivity, shell models are widely used in oil and gas, aerospace, and craft industries [Bhatt et al. 2020]. In extrusion-based 3D printing, shell models are of high fabrication efciency compared to solid ones. Continuity of the toolpath plays a vital role in the quality of extrusion-based 3D printed objects. The continuity of ceramic 3D printing with clay is even more crucial due to a large amount of semi-liquid pastes during deposition and thus the artifacts caused ACM Transactions on Graphics, Vol. 1, No. 1, Article . Publication date: January 2022. arXiv:2201.02374v2 [cs.GR] 10 Jan 2022