Procedural Voronoi Foams for Additive Manufacturing

International audienceMicrostructures at the scale of tens of microns change the physical properties of objects, making them lighter or more flexible. While traditionally difficult to produce, additive manufacturing now lets us physically realize such microstructures at low cost.In this paper we propose to study procedural, aperiodic microstructures inspired by Voronoi open-cell foams. The absence of regularity affords for a simple approach to grade the foam geometry - and thus its mechanical properties - within a target object and its surface. Rather than requiring a global optimization process, the microstructures are directly generated to exhibit a specified elastic behavior. The implicit evaluation is akin to procedural textures in computer graphics, and locally adapts to follow the elasticity field. This allows very detailed structures to be generated in large objects without having to explicitly produce a full representation - mesh or voxels - of the complete object: the structures are added on the fly, just before each object slice is manufactured.We study the elastic behavior of the microstructures and provide a complete description of the procedure generating them. We explain how to determine the geometric parameters of the microstructures from a target elasticity, and evaluate the result on printed samples. Finally, we apply our approach to the fabrication of objects with spatially varying elasticity, including the implicit modeling of a frame following the object surface and seamlessly connecting to the microstructures

Lightweight horse saddletree through reverse engineering and lattice structure design

Additive Manufacturing (AM) is currently making the relevance of lattice structure solutions increasing, allowing the achievement of high performance/mass ratio, where performance stands for energy absorption, stiffness, and/or insulation. This paper undertakes lattice structure for lightweight design of a horse saddletree. Saddletree is the backbone of a horse saddle, and it is composed of different components. In particular, the spring steel reinforcements inside the saddletree make it the heaviest part of the horse saddle, involving also multiple processes of manufacturing and manual assemblies. This paper aims to lightweight an existing saddletree with a Voronoi lattice solution, reducing several manual assemblies. From the methodological point of view, the lightweight design has been based on a multiscale approach, carried out via nTopology (static FEA on the original bulk design, implicit geometrical lattice generation from FEA result maps and Boolean operation among lattice results and bulk design implicit model). The original bulk design has been digitally acquired and modeled through Reverse Engineering techniques, so that a specific customized solution may be improved. A final weight reduction of 76.5% is achieved, providing an example of how topological optimization techniques coupled with AM (in particular Powder Bed Fusion technology) may reduce assembly efforts

Visualisation et fabrication de structures internes complexes

Additive manufacturing enables the fabrication of complex internal structures akinto foams within shapes. These fine scale structures modify the large scale properties of the shape,for instance making it lighter while preserving sufficient rigidity, or creating porosities enablingfluids to traverse.Triangle meshes are not well suited for modeling and visualizing such structures. Instead, severalapproaches have been proposed to model them as implicit solids, described by an indicator functionreturning 1 when a point lies within the solid and 0 outside. Such representations are very compactin memory, however interactive visualization and efficient processing for fabrication can becomedifficult. This stems from the fact that to visualize or fabricate the structure, the function mustbe queried at a high sampling rate. This results in a slow and memory intensive process.In this paper we discuss our approach for dealing with such complex structures in the contextof interactive modeling for additive manufacturing. We describe an algorithm for the progressiverendering of the structures, as well as an efficient slicing procedure for preparing the geometriesfor fabrication.La fabrication additive permet d'intégrer aux objets des structures complexes, ressemblant à des mousses. Ces détails de petite échelle modifient les propriétés à grande échelle de l'objet, par exemple en l'allégeant ou en créant des porosités qui permettent à des fluides de circuler en son sein.Les maillages triangulaires ne sont pas bien adaptés à la modélisation et à la visualisation de ce type de géométries. Des méthodes alternatives ont été proposées, notamment pour les modéliser sous forme de solides implicites, défini par une fonction indicatrice qui renvoie 1 lorsqu'un point est solide et 0 à l'extérieur. Ces représentations sont très compactes en mémoire, cependant leur visualisationinteractive et leur préparation efficace peut devenir coûteuse. Ceci vient du fait que pour visualiser et préparer la structure pour le processus de fabrication, il faut échantilloner la fonction indicatrice avec un pas de discrétisation très fin, ce qui induit de longs temps de calcul et requiert une grande quantité de mémoire. Dans cet article nous discutons d'une approche pour visualiser et modéliserinteractivement ce type de structures, dans le contexte de la fabrication additive.Nous décrivons un algorithme pour l'affichage progressif de structures complexes, ainsi qu'un algorithme de tranchage efficace pour la fabrication additive

State of the Art on Stylized Fabrication

© 2018 The Authors Computer Graphics Forum © 2018 The Eurographics Association and John Wiley & Sons Ltd. Digital fabrication devices are powerful tools for creating tangible reproductions of 3D digital models. Most available printing technologies aim at producing an accurate copy of a tridimensional shape. However, fabrication technologies can also be used to create a stylistic representation of a digital shape. We refer to this class of methods as ‘stylized fabrication methods’. These methods abstract geometric and physical features of a given shape to create an unconventional representation, to produce an optical illusion or to devise a particular interaction with the fabricated model. In this state-of-the-art report, we classify and overview this broad and emerging class of approaches and also propose possible directions for future research

A System for Programming Anisotropic Physical Behaviour in Cloth Fabric

We propose a method to alter the tensile properties of cloth in a user defined and purposeful manner with the help of computer controlled embroidery. Our system is capable of infusing non-uniform stiffening in local regions of the cloth. This has numerous applications in the manufacturing of high performance smart textiles for the medical industry, sports goods, comfort-wear, etc where pressure needs to be redistributed and the cloth needs to deform correctly under a given load. We make three contributions to accomplish this: a decomposition scheme that expresses user-desired stiffness as a density map and a directional map, a novel stitch planning algorithm that produces a series of stitches adhering to the input stiffness maps and an inverse design based optimization driven by a cloth simulator that automatically computes stiffness maps based on user specified performance criteria. We perform multiple tests on physically manufactured cloth samples to show how embroidery affects the resultant fabric to demonstrate the efficacy of our approach