Three-dimensional projection-based topology optimization for prescribed-angle self-supporting additively manufactured structures

Johnson, Terrence; Gaynor, Andrew T.

doi:10.1016/j.addma.2018.06.011

Cited by 28 publications

(20 citation statements)

References 25 publications

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“…In (C), the overhang filter is only active in the internal cavities, while the bottom of the crane hook is completely overhanging as it can be supported by easily removable supports provided a 3D implementation. 18,19,27 For the 3D results, the front propagation based filter presented in Reference 27 is utilized. The 3D results presented in this section are obtained with an optimization code based on the portable, extensible toolkit for scientific computing (PETSc).…”

Section: F I G U R E 15mentioning

confidence: 99%

“…Especially, minimizing the need for support structures received considerable attention. Three approaches have emerged: first by enforcing a minimum overhang angle on the surface of the geometry, [13][14][15][16] second by sweeping through the structure layer-by-layer to detect areas that violate the minimum overhang angle, [17][18][19][20][21] and, finally, by modeling a physical aspect of the printing process, accounting for the heating or the self-weight of each layer. 13,[22][23][24] Most of the methods mentioned above focus on completely eliminating all the supports.…”

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confidence: 99%

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Accessibility of support structures in topology optimization for additive manufacturing

Ven

Ayas

Langelaar

et al. 2021

Numerical Meth Engineering

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Additive manufacturing (AM) and topology optimization (TO) have a synergetic relation, as AM can produce complex TO designs, and TO provides high-performance parts that utilize the form freedom provided by AM. Recently, TO has been tailored more toward AM with the inclusion of the minimum allowable overhang angle as a design constraint: resulting designs can be built without any support structures. This work is an extension thereof, by allowing support structures only if they are accessible, such that they can be removed after manufacturing. This is achieved by applying a conventional overhang filter twice, combined with basic operations such as geometry inversion, union, and intersection. The result is an accessibility-aware overhang filter that can be incorporated in TO. Compared with conventional overhang filtered designs, the accessibility filter results in increased part performance and better convergence behavior. Furthermore, a modular filter structure is presented to easily construct the accessibility filter, and its effectiveness is demonstrated on several numerical cases. K E Y W O R D S accessibility of supports, additive manufacturing, overhang, topology design 1 INTRODUCTION The most attractive feature of additive manufacturing (AM) is the unprecedented degree of permitted form freedom. No longer bounded by the design limitations of conventional manufacturing techniques, such as casting or milling, the challenge becomes to find the geometrical layout of the component that truly gives the best performance. 1,2 This is exactly what is provided by topology optimization (TO). Compared with other structural optimization methods, such as size or shape optimization, it exploits maximum design freedom, and is widely recognized as a design approach perfectly suitable for AM. 3,4 Although AM can produce geometrically complex parts created by TO, there are design restrictions that have to be taken into account to prevent an increase in production cost. For example, a design might require a large amount of supports if the angle between a down-facing surface and the base plate is below a material/process specific value, the so called critical overhang angle oh. 5-7 Support structures not only increase the printing cost due to increased material and postprocessing cost, they can even become impossible to remove once the printing is completed. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Section: F I G U R E 15mentioning

confidence: 99%

mentioning

confidence: 99%

Accessibility of support structures in topology optimization for additive manufacturing

Ven

Ayas

Langelaar

et al. 2021

Numerical Meth Engineering

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“…Moreover, for a given mesh, one way to improve the approximation is to include additional points besides the centroids in the definition of i ; cf. Johnson and Gaynor (2018).…”

Section: Overhang Filtermentioning

confidence: 99%

Penalty regulation of overhang in topology optimization for additive manufacturing

Thore

Grundström

Torstenfelt

et al. 2019

Struct Multidisc Optim

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Several filter approaches that introduce additive manufacturing-related overhang constraints in topology optimization exist. However, a drawback of these is that exact satisfaction of overhang constraints produces sharp inward corners resulting in stress singularities. The present paper therefore modifies such filter approaches by a penalty formulation, where the choice of penalty factor regulates how closely the overhang constraint is satisfied. By appropriately choosing certain weight factors in the penalty function, the cost of support structures is also reflected in the formulation in a simple and computationally inexpensive way. The method is demonstrated by parameter studies using the classical MBB beam, using both structured and unstructured meshes.

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“…Moreover, the RAMP model allowed material to grow out of the void, while SIMP did not. However, the numerical stability of SIMP combined with the topological "morphing" capabilities [56] makes the decision of the best material interpolation model somehow unclear. In the scope of this work, the SIMP model was used in the subsequent analysis since it is an industry standard.…”

Section: Comparative Studymentioning

confidence: 99%

“…Moreover, this does not require additional constraints to the optimization problems. Currently, there are two main AM fabrication models, one based on min-max operators [50][51][52], the other being based on area occupation and Heaviside projections [53][54][55][56], which can provide self-supporting designs.…”

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confidence: 99%

Designing Self Supported SLM Structures via Topology Optimization

Barroqueiro

Andrade‐Campos

Valente

2019

JMMP

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The potential of Additive Manufacturing (AM) is high, with a whole new set of manufactured parts with unseen complexity being offered. However, the process has limitations, and for the sake of economic competitiveness, these should also be considered. Therefore, a computational methodology, capable of including the referenced limitations and providing initial solid designs for Selective Laser Melting (SLM) is the subject of the present work. The combination of Topology Optimization (TO) with the simplified fabrication model is the selected methodology. Its formulation, implementation, and integration on the classic TO algorithm is briefly discussed, being capable of addressing the minimum feature size and the overhang constraint limitations. Moreover, the performance and numerical stability of the methodology is evaluated, and numerical variables, such as the accuracy of structural equilibrium equations and the material interpolation model, are considered. A comparative study between these variables is presented. The paper then proposes an enhanced version of the selected methodology, with a better convergence towards a discrete solution.

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Three-dimensional projection-based topology optimization for prescribed-angle self-supporting additively manufactured structures

Cited by 28 publications

References 25 publications

Accessibility of support structures in topology optimization for additive manufacturing

Accessibility of support structures in topology optimization for additive manufacturing

Penalty regulation of overhang in topology optimization for additive manufacturing

Designing Self Supported SLM Structures via Topology Optimization

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