# An Optimization Workflow in Design for Additive Manufacturing
## 3 Case Study
The results are represented in Figure 7. In the size optimized model (Figure 7b), the higher value of stress observed on the legend is related to the absence of fillet between the lattice structure and the body and does not depend on the modeling method of the lattice. Nettabb Premium 2020.3 (Autodesk) was used for preliminary process planning, choosing for the best part orientation. Supports too were created inside the software. The Renishaw AM 400 SLM machine was selected, together with the default material configuration for Aluminum AlSi10 Mg-0403 printed with a 25 \(\upmu\)m layer thickness, as suggested by the powders manufacturer [75]. First, the topology optimized model was oriented. Among the proposed orientations, three are reported in Figure 8. The final decision is driven by several considerations. The orientation in Figure 8a has the lowest height, resulting in faster printing time, but presents the highest supported area, requiring more time for supports removal and post-process such as sandblasting to avoid the lower quality of the surface finish in the supported areas; the configuration in Figure 8b has the less supported area, but has the highest support volume and height, resulting in a long build time and high material waste; the configuration in Figure 8c has the lower support volume and a relatively low supported area and build time. Moreover, since the configuration in Figure 8a lays on the platform, the circular functional surfaces on the rod's ends will have the best dimensional and geometrical accuracy. Further milling operations could be needed to comply with the requested tolerances. Figure 8: Part orientation and support generation for the topologically optimized piston rod. (**a–c**) show three possible orientations. Figure 7: FE analyses validation, equivalent Von Mises stress: (**a**) topology optimization, (**b**) size optimization. The same procedure was followed for the orientation of the piston rod with the lattice structure. This time, due to the extreme difficulty of removing the supports between the beams of the lattice, the only orientation that did not present supports in the central part of the model was chosen, as shown in Figure 9.  
Finally, the next step would be to perform the process simulation of the oriented part to assess the printability of the models, the geometrical distortions, and the residual stresses. According to the results, the designer can consider geometrically compensating the part, changing the part orientation, or going back to the modeling phase and remodel the part. The application of the workflow for redesigning the piston rod enabled to obtain two optimized parts and a considerable reduction of the mass, as shown in Table 2.0 The two methods present some drawbacks too. The topology optimized model requires manual remodeling, and it is more prone to failure during the final FE analysis verification, due to human errors during the remodeling phase. The proposed method for the size optimization is in its prototypal stage and it still has a limited choice of unit cells and does not correctly manage the connection between the lattice structure and the adjacent objects. Numerical analyses on the lattice model are computationally demanding but less necessary since the wireframe was previously optimized and the mesh modeling method does not alter the diameter of the beams.