SIM-AM 2023


Industrial Challenges in Geometry Optimization for Additive Manufacturing

  • Pauli, Johannes (BMW Group)
  • Möllenhoff, Lin (BMW Group)
  • Geiser, Armin (BMW Group)
  • Bosch, Stefanus (BMW Group)
  • Kostorz, Peter (BMW Group)

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Laser powder bed fusion (LPBF) is considered to be one of, if not the, manufacturing technology with the biggest design freedom. While this holds true, the part geometry does have a big influence on the cost and quality of components manufactured using LPBF. To meet the economic requirements of the automotive industry, it is therefore not enough to optimize a part for mechanical performance only. Instead, the geometry needs to be optimized for manufacturing simultaneously. At BMW an optimization procedure has been developed, that aims to achieve both good mechanical performance as well as a good manufacturability. It involves a topology optimization with the objective to reduce weight, and thus material use, as a first step. Afterwards, the resulting geometry is modified using free-form shape optimization with the Vertex Morphing method [1] to achieve three things: Firstly, the need for support structures, that LPBF requires for large overhangs with too shallow angles, is reduced. In many cases, the design can be changed in a way, that no support structures at all are required. For this, the user defines a printing direction in which the part will be positioned in production. Secondly, the nestability of the component can be optimized. Here, only the production of batches containing the same part multiple times is considered. Again, the user defines in which direction the parts should be nested. The optimization algorithm modifies the shape such that the parts can be placed with smaller spacing between them, while avoiding collisions. These two manufacturability objectives are being optimized under consideration of functional constraints, like weight, stiffness and stresses, that are either kept at a desired level or even further improved. By applying the presented optimization procedure, more parts with less support structure and less material use can be manufactured in the same build volume. This results in lower manufacturing costs, as the labor cost per part is reduced. Selected example parts that are now being used in series production are shown. Without consideration of manufacturing requirements for additive manufacturing in the geometry optimization, these components would not have been economical for series production using LPBF.