System for lightweight design through additive manufacturing
Data di pubblicazione
Data di priorità
Politecnico di Milano
Department of Civil and Environmental Engineering
Matteo Bruggi, Ingrid Paoletti (ABC)
A novel approach based on multiscale topology optimization to design stiff and robust components using a limited amount of material, simultaneously defining i) boundaries of the element and ii) internal arrangements of circular/spherical holes with graded radius that can be effectively 3D-printed.
The methodology allows generating optimal 2D or 3D components (any object subject to loads and constraints, e.g. mechanical parts, structural components, elements of the building envelope, design pieces, industrial design objects, …) that are especially conceived for fabrication with Additive Manufacturing (AM) techniques working by layers such as Fused Deposition Modelling (FDM). Indeed, circular/spherical holes in Hexagonal Close-Packed (HCP) arrangements allow defining an isotropic/transversely isotropic graded microstructure that can be effectively printed without the need for extended supports to be added during the printing process. Benefits of the proposed methodology are expected also for other AM techniques, such as metal printing. Due to the static indeterminacy of the microstructure, robust results are found (more than one load path arises in the optimal design). An efficient algorithm is coded that takes design domain and boundary conditions as input to write an output file containing the printable geometry for AM. Also, when boundaries of a hollow component are prescribed i), the algorithm can be used to equip it with an optimal microstructure ii).
Campo di applicazione
•Generation and fabrication of mechanical components: printing of original parts / lightened spares with optimized performance and robustness towards load variations (automotive and aerospace industries)
•Generation and fabrication of massive structural components or massive technological components with structural function that need for lightening (building industry)
•Generation and fabrication of design pieces through the definition of the optimal shape of the boundaries within a given design domain, along with an internal microstructure conceived for 3d-printing
•In general, solution to fabrication issues / printing issues encountered in the additive manufacturing of complex hollow objects, through the definition of an optimal perforated microstructure against critical overhangs and deformability/sagging issues.
The distinctive feature of the proposed multiscale approach is the adoption of a graded porous microstructure made of circular/spherical holes, packed in the HCP (Hexagonal Close-Packed) arrangement. This gives the following advantage over existing multi-scale approaches:
•The microstructure is conceived for 3D-printing: circular/spherical holes are not extensively affected by overhang issues (they do not call for extended additional printing supports).
•The geometry of the graded microstructure is easy to compute, digitally handle and pass to the 3D-printer through an efficient and fast algorithm: once the reference dimension of the unit cell is defined, centers and radii of circles/spheres are the only parameters involved in the description of the geometry.
•The microstructure is isotropic (2D) or transversely isotropic with low degree of anisotropy (3D): a few independent parameters are needed to describe the homogenized constitutive tensor; expressions giving tensor components as functions of the material density are available or can be easily derived; a lightening of the full material is performed introducing a minimal anisotropy; robustness towards variation in the loads is expected.
•The microstructure is porous: the smooth geometry of the holes mitigates stress concentrations related to geometrical singularities (such as sharp corners and intersections found in some lattices); the microstructure is expected less prone to buckling with respect to some truss lattices.
•The microstructure may be easily scaled depending on the printing technology by acting on the reference dimension of the unit cell (that can be straightforwardly related to the thickness of the deposed layer of material).
•The approach works both in 2D (plates) and 3D (solids).
Stadio di sviluppo