Project seminar


Conformal Microstructure Synthesis in Trimmed Trivariate based V-reps
Q Youn Hong Technion | Sep 22, 2021.  In this talk, we present a microstructure tiling scheme for V-rep models consisting of trimmed trivariates. Trimmed trivariates are formed by hierarchically applying Boolean operations to full tensor-product trivariates. An existing tiling method is employed to tile individual primitive tensor product trivariates in a conformal way, only to handle the intersection of the microstructure tiles with the trimming surfaces of the trivariates. One-to-one and two-to-one bridging tiles are then constructed along the trimmed zones, while tile-clipping is completely avoided. We consider Boolean operation cases of subtraction, intersection and union. The result is a set of, regular in the interior, possibly heterogeneous, trivariates, that defines the whole microstructure arrangement. This result is fully compatible with iso-geometric analysis as well as heterogeneous additive manufacturing. Examples are presented, including of 3D printed heterogeneous microstructures.
The role and the integration of micro-structures for Digital Anatomy 3D printed models
Ido Bitan  Stratasys | Sep 14, 2021.  In order to properly mimic actual human organs through 3D printing, one has to account for various structural behavior characteristics as well as the look and feel of the actual organs. Complex micro-structures which allow to mimic real human tissues are at the backbone of this process. These structures allow users to manipulate the internal core of the printed part and to define the bio-mechanical properties of the target organ. The ability to change material ratios, methods of material deposition and thickness of each layer allows us to reach a wide variety of medical applications according to the measured behavior such as compression values, compliance, tensile strength, isotropic structure and more. During the presentation we will demonstrate how various organs are mimicked through specifically selected micro structures and blending mechanisms.
Application of a new paradigm to microstructured based design. Implementation of the WP1 deliverables in an industrial code
Benjamin Thomas  Hutchinson | June 30, 2021. A first code based on the work done in the Technion about microstructure generation and assembly was developped by Hutchinson. A comparison is made on the possibilities of a commercial CAD software and the proposed code to construct academic but not so simple structures based on elementary tiles with specific acoustic or mechanical properties. This work will end up with a report presenting a workflow on structures that we plan to directly 3D print using the outputs of the program.
The role of Analysis in the design process of micro-structured geometries
Thibaut Hirschler  EPFL | June 16, 2021. The first letter of the project acronym ADAM^2 stands for Analysis. But what does it consists in? We give in this presentation an overview of computer simulation and its role in a design-to-manufacturing cycle. We discuss more specifically the computational design of micro-structured geometries and the challenges arising from this multiscale problem (from an analysis perspective). We present our developed approaches dedicated to ADAM^2 types of structures and discuss what is yet to come in order to build compact and user-friendly ADAM tools for Microstructures.
Precise Hausdorff Distance Computation for Freeform Surfaces Based on Computations with Osculating Toroidal Patches
Sang-Hyun Son  Seoul National University | June 2, 2021. We present an efficient algorithm for computing the precise Hausdorff Distance (HD) between two freeform surfaces. The algorithm is based on a hybrid Bounding Volume Hierarchy (BVH), where osculating toroidal patches (stored in the leaf nodes) provide geometric properties essential for the HD computation in high precision. Intrinsic features from the osculating geometry resolve computational issues in handling the cross-boundary problem for composite surfaces, which leads to the acceleration of HD algorithm with a solution (within machine precision) to the exact HD. The HD computation for general freeform surfaces is discussed, where we focus on the computational issues in handling the local geometry across surface boundaries or around surface corners that appear as the result of gluing multiple patches together in the modeling of generic composite surfaces. We also discuss how to switch from an approximation stage to the final step of computing the precise HD using numerical improvements and confirming the correctness of the HD computation result. The main advantage of our algorithm is in the high precision of HD computation result. As the best cases of the proposed torusbased approach, we also consider the acceleration of HD computation for freeform surfaces of revolution and linear extrusion, where we can support real-time computation even for deformable surfaces. The acceleration is mainly due to a fast biarc approximation to the planar profile curves of the simple surfaces, each generated by rotating or translating a planar curve. We demonstrate the effectiveness of the proposed approach using experimental results.
Geometry and tool motion planning for curvature adapted CNC machining
Oleksii Sliusarenko  BCAM | May 26, 2021. CNC machining is the leading subtractive manufacturing technology. Although it is in use since decades, it is far from fully solved and still a rich source for challenging problems in geometric computing. We demonstrate this at hand of 5-axis machining of freeform surfaces, where the degrees of freedom in selecting and moving the cutting tool allow one to adapt the tool motion optimally to the surface to be produced. We aim at a high-quality surface finish, thereby reducing the need for hard-to-control post-machining processes such as grinding and polishing. Our work is based on a careful geometric analysis of curvature-adapted machining via so-called second order line contact between tool and target surface.On the geometric side, this leads to a new continuous transition between “dual” classical results in surface theory concerning osculating circles of surface curves and osculating cones of tangentially circumscribed developable surfaces. Practically, it serves as an effective basis for tool motion planning. Unlike previous approaches to curvature-adapted machining, we solve locally optimal tool positioning and motion planning within a single optimization framework and achieve curvature adaptation even for convex surfaces. This is possible with a toroidal cutter that contains a negatively curved cutting area. The effectiveness of our approach is verified at hand of digital models, simulations and machined parts, including a comparison to results generated with commercial software.

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