CrossFill: Foam Structures with Graded Density for Continuous Material Extrusion

CrossFill: Foam Structures with Graded Density for Continuous Material Extrusion

Computer Aided Design, 2019

Special issue of Solid and Physical Modeling (SPM) 2019

Tim Kuipers, Jun Wu, and Charlie Wang
Department of Design Engineering, TU Delft
Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong

Various examples of applications of CrossFill. (a) A bicycle saddle with a density specification. A weight of 33 N is added on various locations to show the different response of different density infill. (b) A teddy bear with a density specification. (c) A shoe sole with densities based on a pressure map of a foot. (d) The Stanford bunny painted with a density specification. (e) A medical phantom with an example density distribution for calibrating an MRI scanning procedure.


The fabrication flexibility of 3D printing has sparked a lot of interest in designing structures with spatially graded material properties. In this paper, we propose a new type of density graded structure that is particularly designed for 3D printing systems based on filament extrusion. In order to ensure high-quality fabrication results, extrusion-based 3D printing requires not only that the structures are self-supporting, but also that extrusion toolpaths are continuous and free of self-overlap. The structure proposed in this paper, called CrossFill, complies with these requirements. In particular, CrossFill is a self-supporting foam structure, for which each layer is fabricated by a single, continuous and overlap-free path of material extrusion. Our method for generating CrossFill is based on a space-filling surface that employs spatially varying subdivision levels. Dithering of the subdivision levels is performed to accurately reproduce a prescribed density distribution. We demonstrate the effectiveness of CrossFill on a number of experimental tests and applications.




Cura implementation


title = "CrossFill: Foam Structures with Graded Density for Continuous Material Extrusion",
journal = "Computer-Aided Design",
volume = "114",
pages = "37 - 50",
year = "2019",
issn = "0010-4485",
doi = "",
author = "Tim Kuipers and Jun Wu and Charlie C.L. Wang",
keywords = "Space-filling surface, Graded density, Continuous material extrusion, Functionally graded material, Fused deposition modeling",