Section: New Results

Additive Manufacturing

Iterative Carving for Self-supporting 3D Printed Cavities

Participants: Samuel Hornus and Sylvain Lefebvre.

This work explores the printing of shapes with as little material as possible, mostly with a view toward minimizing fabrication time for large pieces. In particular, it aims at modeling a structure of thin sheets inside a volume in such a way that the sheets and the boundary of the volume can be 3D-printed as is, without internal support.

The work is an adaptation of the technique developed earlier fo other applications in 3D printing and achieved state-of-the-art results. It is available as an Inria technical report [14].

Optimal Discrete Slicing

Participant: Sylvain Lefebvre.

This work is a collaboration with Marc Alexa and Kristian Hildebrand from TU Berlin. We developed a novel algorithm to compute the optimal decomposition of a 3D shape into layers of varying thickness, in a discrete setting. This answers a long standing problem in additive manufacturing. Our approach computes all optimal solutions for any number of slices by formulating the optimization as a dynamic programming problem. We developed efficient algorithms for both computing the geometric errors within each slice (based on volume difference) as well as for the optimizer. Our technique is the first to provide a provably optimal result and outperforms all existing heuristics. The work has been published in ACM TOG [5], presented at SIGGRAPH 2017 and is fully implemented within IceSL, available for public download.

Fabricable Tile Decors

Participants: Sylvain Lefebvre and Jonàs Martínez.

We propose a modeling technique to produce large objects whose surface is composed of user-provided decorative tiles. Such objects are very inefficient to 3D print as they occupy a large volume while in fact using little material. On low end printers they require large amounts of support structures which are difficult to remove. We propose a decomposition of the input shape into sets of planar patches that can print flat and can be later assembled into stable structures. This work is a collaboration with Hong Kong University in the context of the PrePrint3D associated team. It was published in ACM TOG [8] and presented at SIGGRAPH Asia 2017.

Visualizing and Fabricating Complex Internal Structures

Participant: Sylvain Lefebvre.

This work considers efficient display and manufacturing of extremely detailed internal structures described by implicit (procedural) indicator functions [15]. We describe a technique for their progressive rendering when the structures fill an envelope provided as a 3D mesh. We also describe how to efficiently extract slices for additive manufacturing, in a process that is both computationally and memory efficient. This work was presented at the Visual Analytics conference (Moscow, 2017) and is under submission to the Scientific Visualization journal.

Orthotropic k-nearest Foams for Additive Manufacturing

Participants: Jonàs Martínez, Haichuan Song, Jérémie Dumas, Sylvain Lefebvre.

We proposed a novel metamaterial with controllable, freely orientable, orthotropic elastic behavior – orthotropy means that elasticity is controlled independently along three orthogonal axes, which leads to materials that better adapt to uneven, directional load scenarios, and offer a more versatile material design primitive. The fine-scale structures are generated procedurally by a stochastic process, and resemble a foam. This work has been published in ACM TOG [12], and presented at SIGGRAPH 2017.

Color Fused Filament Fabrication

Participants: Haichuan Song, Sylvain Lefebvre.

Traditional filament printers cannot truly reproduce colored objects. The best current techniques rely on a form of dithering exploiting occlusion, that was only demonstrated for shades of two base colors and that behaves differently depending on surface slope. We explored a novel approach for 3D printing colored objects, capable of creating controlled gradients of varying sharpness. Our technique exploits off-the-shelves nozzles that are designed to mix multiple filaments in a small melting chamber, obtaining intermediate colors once the mix is stabilized. The key idea is to divide each input layer into a set of sublayers, each having a different constant color. By locally changing the thickness of the sublayers, we change the color that is perceived at a given location. By optimizing the choice of colors of each sublayer, we further improve quality and allow the use of different numbers of input filaments. We demonstrate our results by building a functional color printer using low cost, off-the-shelves components. Using our tool a user can paint a 3D model and directly produce its physical counterpart, using any material and color available for fused filament fabrication. This work has been submitted and is available at [18].

Anti-aliasing for Fused Filament Deposition

Participants: Haichuan Song, Sylvain Lefebvre.

Layered manufacturing inherently suffers from staircase defects along surfaces that are gently sloped with respect to the build direction. Reducing the slice thickness improves the situation but also largely increases the print time. We proposed a simple yet effective technique to improve the print accuracy for layered manufacturing by filament deposition. It better reproduces the geometry of sloped surfaces without increasing the print time. The key idea is to perform a local anti-aliasing, working at a sub-layer accuracy to produce slightly curved deposition paths and reduce approximation errors. We further split and order paths to minimize defects due to the extruder nozzle shape, avoiding any change to the existing hardware. We apply and analyze our approach on 3D printed examples, showing that our technique greatly improves surface accuracy and silhouette quality while keeping the print time nearly identical. This work has been published in the Computer Aided Design (CAD) journal [19].