Abstract
Although additive manufacturing (AM) allows for a large design freedom, there are some manufacturing limitations that have to be taken into consideration. One of the most restricting design rules is the minimum allowable overhang angle. To make topology optimization suitable for AM, several algorithms have been published to enforce a minimum overhang angle. In this work, the layer-by-layer overhang filter proposed by Langelaar (Struct Multidiscip Optim 55(3):871–883, 2017), and the continuous, front propagation-based, overhang filter proposed by van de Ven et al. (Struct Multidiscipl Optim 57(5):2075–2091, 2018) are compared in detail. First, it is shown that the discrete layer-by-layer filter can be formulated in a continuous setting using front propagation. Then, a comparison is made in which the advantages and disadvantages of both methods are highlighted. Finally, the continuous overhang filter is improved by incorporating complementary aspects of the layer-by-layer filter: continuation of the overhang filter and a parameter that had to be user-defined are no longer required. An implementation of the improved continuous overhang filter is provided.
Highlights
Additive manufacturing (AM) is widely recognized for its capability to manufacture complex components
This study investigates the differences and similarities between the discrete, layer-bylayer methods presented in Langelaar (2016, 2017), and the continuous, front propagation method presented in van de Ven et al (2018)
Because the continuous filter is described in a continuous setting, it can be readily used in unstructured meshes while the maximum overhang angle can be adjusted independent of the mesh by modifying the speed function
Summary
Additive manufacturing (AM) is widely recognized for its capability to manufacture complex components. As the resulting designs of topology optimization (TO) are frequently geometrically complex, the combination of both methods has received significant interest. This interest is even further increased with the advent of metal AM, which opens the possibility to realize optimal functional components with high strength and toughness. The focus of this study is on the methods in the first category: the filters that follow the printing sequence. Most methods in this category are presented as discrete filters, defined on a discretized geometry. It is shown that the discrete method can be formulated with front propagation discretized on a structured grid (Section 3). For clarity this paper focuses on 2D formulations, but the principles apply to the 3D case as well
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