Topology optimization of 3D self-supporting structures for additive manufacturing

Abstract

The potential of topology optimization to amplify the benefits of additive manufacturing (AM), by fully exploiting the vast design space that AM allows, is widely recognized. However, existing topology optimization approaches do not consider AM-specific limitations during the design process, resulting in designs that are not self-supporting. This leads to additional effort and costs in postprocessing and use of sacrificial support structures. To overcome this difficulty, this paper presents a topology optimization formulation that includes a simplified AM fabrication model implemented as a layerwise filtering procedure.Unprintable geometries are effectively excluded from the design space, resulting in fully self-supporting optimized designs. The procedure is demonstrated on numerical examples involving compliance minimization, eigenfrequency maximization and compliant mechanism design. Despite the applied restrictions, in suitable orientations fully printable AM-restrained designs matched the performance of reference designs obtained by conventional topology optimization.

An additive manufacturing filter for topology optimization of print-ready designs

“…For clarity we limit the discussion to the 2D case for a rectangular domain discretized by n i ×n j elements, where the vertical direction is the printing direction. The extension to 3D is straightforward but will be discussed elsewhere (Langelaar 2016). Every element in the mesh is associated with a blueprint density variable x (i,j ) , where i and j denote the vertical and horizontal location of the element.…”

Topology Optimization for Additive Manufacturing With Controllable Support Structure Costs

“…In this case, the maximum difference amounted only to 8%, and in fact other part orientations do not result in performance reductions [11]. The examples are however only intended to illustrate the principle, that in general restrictions often reduce performance, and that the presented cost-based formulation offers a way to find a compromise.…”

“…We distinguish two interrelated density values per element: a blueprint density b, expressing the material layout specified by the optimizer, and a printed density p, indicating the actually printable structure. The following subsections summarize the definition of this AM filter and its sensitivity analysis, for a more in-depth discussion the reader is referred to [10,11].…”

“…This approach utilizes a simplified AM fabrication model, that is applied in every TO iteration to transform a blueprint design layout into an as-printed part [10,11]. The AM model is defined in a continuous, differentiable way, and sensitivities of the modeled AM operation can be computed efficiently.…”

Lightweight parametric optimisation method for cellular structures in additive manufactured parts

“…Some authors have analysed the capabilities of different topology optimization techniques, concluding that the designs obtained by these methods usually require post-processing in order to be manufacturable [18]. Other authors have proposed filters to face problems related to overhang angles [19,20], but many other problems should be taken into account to guarantee a printable design. This work focuses on parametric optimisation, which allows controlling the constraints associated with the manufacturing process by the proper definition of the limits of the design variables.…”