Topology Optimization

In order to achieve a lightweight construction, it is possible after the FEM simulation by an algorithm to eliminate lightly loaded areas. This creates bionic, light and stiff geometries.

To create the optimization task, objective functions must be set. The case study used a reduction in strain energy to increase stiffness as well as a reduction in volume.

So that the optimization can be influenced accordingly, there is the possibility to deposit geometrical restrictions. Frozen areas (see Figure 9) have been set up in the bearing and load initiation areas to exclude them from optimization. Thus, their subsequent function is still guaranteed. Furthermore, planar symmetries were implemented to avoid asymmetric optimization due to the asymmetric load distribution. In addition, minimum wall thicknesses were implemented to avoid an overdone material reduction in certain areas.

Figure 9 Frozen Areas (in orange)

S.Junk, B.Klerch and U. Hochberg

After optimization, the geometry must be checked for plastic deformation (see Figure 10).

For this purpose, different design proposals are issued. For each optimization loop, a design proposal is generated which differs by a specified factor of volume reduction.

Figure 10: Verification of plastic deformation (in %)

In order to obtain the best possible results, some adjustments were made to the parameters after which the component was re-simulated and optimized. These parameters are particularly the design space, the geometric restrictions and the factor for volume reduction. After selecting the most advantageous solution, the geometry was smoothed using Tosca.smooth and then exported.

3.9 Results

The results for the final geometry of the pelvis module from “Sweaty” (Figure 11) has achieved a weight reduction of 29.2 g (-4.7 %) and a reduction of deformation energy of 2.6 J as seen in Table 2.

Manufacturing Process

Material Yield

Strength [MPA]

Weight [g]

Strain energy [mJ]

Costs [%]

Milling AlZnMgCu1.5 450 617,2 4,3 100

AM AlMgSc 470 588 (-4,7%) 1,7 (-60,5%) 377

Table 2: Results

S.Junk, B.Klerch and U. Hochberg

Figure 11: Final Result

4 CONCLUSION

In order to carry out a process-oriented topology optimization for the SLM process, a few points should be considered. Procedural restrictions such as tolerances and the like are just as important as the anisotropic material properties. For this reason, some questions should be clarified before a topology optimization. In this case study, it was first of all examined with the aid of an ideal shape and the requirements of the tolerances whether the component can principally be manufactured additively. It could be stated that the position of the component has a tremendous influence already in the very early conception phase. On the one hand, production-related restrictions such as the achievable quality change and, on the other, factors relevant to the decision, such as costs and output.

After the restrictions of production and post-processing met the requirements, the additive process could be selected. The process was selected based on the material restrictions. In this way one can conclude that attention should always be paid to the material-process combination and its restrictions.

It has been shown that a design change was necessary because the post processing would otherwise not be possible.

In order to make a decision on topology optimization for additive manufacturing, a quantitative analysis should be carried out. In this case, the potentials of topology optimization and additive manufacturing such as weight and rigidity as well as other factors such as costs have to be assessed sector-specifically. Special attention should be paid to the integral design in particular, since this would be a major encroachment on the overall assembly concept and a holistic functional integration can also have disadvantages. The analysis has shown that the specific potentials of the topology optimization of the pelvis module justify extra effort for the optimization.

In the FE analysis, it has been shown that the component orientation in the building space has a very decisive role in taking into account the anisotropy in the design space.

S.Junk, B.Klerch and U. Hochberg

REFERENCES

[1] Associates, W.: Wohlers report 2017. 3D printing and additive manufacturing state of the industry : annual worldwide progress report. Fort Collins (Colo.): Wohlers Associates 2017

[2] Bikas, H., Stavropoulos, P. a. Chryssolouris, G.: Additive manufacturing methods and modelling approaches: a critical review. The International Journal of Advanced Manufacturing Technology 83 (2016) 1-4, S. 389–405

[3] Sauer, A.: Bionik in der Strukturoptimierung. Praxishandbuch für ressourceneffizienten Leichtbau. Konstruktionspraxis. Würzburg: Vogel Communications Group 2018 [4] Yang, L., Hsu, K., Baughman, B., Godfrey, D., Medina, F., Menon, M. a. Wiener, S.:

Additive Manufacturing of Metals: The Technology, Materials, Design and Production.

Springer Series in Advanced Manufacturing. Cham, s.l.: Springer International Publishing 2017

[5] Klahn, C., Meboldt, M. a. Fontana, F.: Entwicklung und Konstruktion für die Additive Fertigung. Grundlagen und Methoden für den Einsatz in industriellen

Endkundenprodukten. Würzburg: Vogel Business Media 2018

[6] Zaman, U. K. a., Rivette, M., Siadat, A. u. Mousavi, S. M.: Integrated product-process design: Material and manufacturing process selection for additive manufacturing using multi-criteria decision making. Robotics and Computer-Integrated Manufacturing 51 (2018), S. 169–180

[7] Stefan Junk, Benjamin Klerch a. Ulrich Hochberg: Structural Optimization in

Lightweight Design for Additive Manufacturing. (submitted). Procedia CIRP (2019) [8] Zhang, P., Liu, J. a. To, A. C.: Role of anisotropic properties on topology optimization of

additive manufactured load bearing structures. Scripta Materialia 135 (2017), S. 148–152 [9] Hochschule Offenburg Sweaty. https://sweaty.hs-offenburg.de/projekt/, abgerufen am:

04.01.2019

[10] Junk, S., Klerch, B., Nasdala, L. a. Hochberg, U.: Topology optimization for additive manufacturing using a component of a humanoid robot. Procedia CIRP 70 (2018), S. 102–107

[11] Scalmalloy. https://apworks.de/de/scalmalloy/, abgerufen am: 07.01.2019

[12] VDI-Richtlinie 3405 Blatt 3 Additive Fertigungsverfahren Konstruktionsempfehlungen für die Bauteilfertigung mit Laser-Sintern und Laser-Strahlschmelzen (2015)

Functional Lightweight Design for Additive Manufactured Vehicle Liftgate Door Hinge İ. Aydın, E. Akarçay, Ö. F. Gümüş, Ş. Özcan, H. Yelek and C.B. Engin

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