Mar 19, 2019 | By Thomas

A team of researchers at the Technical University of Denmark (DTU) and Delft University of Technology (TU Delft) has developed a new method for generating stress adapted orthotropic infill for 3D printing.

Topology optimization is recognized as an important design method for exploiting the manufacturing flexibility offered by 3D printing. It optimizes the distribution of a limited amount of material in a prescribed design space, in order to achieve the optimal structural performance.

Previously researchers developed a novel method to design bone-like structure, and even optimize the structure and infill simultaneously. The optimized structures with porous infill have demonstrated remarkable structural performance, regarding stiffness and buckling.

In their latest work, the researchers significantly improved the computational performance, bringing the method one step closer to widespread use in the 3D printing industry. Rather than performing finite element analysis and numerical optimization on the fine structural details, which is computationally intensive, the researchers propose to embed the fine geometric details in a coarse scale analysis via numerical homogenization, then optimize structure on the coarse scale, and finally project optimized results from the coarse scale onto the fine scale. This reduces the computational cost by at least one order of magnitude.

The developed method aligns orthotropic infill patterns with the principal stress directions. A reduction in computational cost of at least one order of magnitude is achieved compared to density-based optimization of shell and infill. This approach also results in 31% stiffness improvement (or similar weight reduction) when dropping conventional isotropic infill in favor of orthotropic stress adapted infill.

Isotropic infill means the material properties of the infill are the same along different directions, e.g., triangular patterns.
Orthotropic infill has material properties that differ along mutually-orthogonal directions, e.g., rectangular patterns.

This work is now published in Computer Methods in Applied Mechanics and Engineering.



Homogenization-based stiffness optimization and projection of 2D coated structures with orthotropic infill


Jeroen P.Groen, Jun Wu, Ole Sigmund


This paper concerns compliance minimization and projection of coated structures with orthotropic infill material in 2D. The purpose of the work is two-fold. First, we introduce an efficient homogenization-based approach to perform topology optimization of coated structures with orthotropic infill material. The design space is relaxed to allow for a composite material description, which means that designs with complex microstructures can be obtained on relatively coarse meshes. Second, a method is presented to project the homogenization-based designs on a fine but realizable scale. A novel method to adaptively refine the lattice structure is presented to allow for a regular spacing of the infill. Numerical experiments show excellent behavior of the projected designs, with structural performance almost identical to the homogenization-based designs. Furthermore, a reduction in computational cost of at least an order of magnitude is achieved, compared to a related approach in which the infill is optimized using a density-based approach.



Posted in 3D Printing Technology



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