A design, mechanical rating, and load adaptation method for cellular components for additive manufacturing

We present a tool for Design for Additive Manufacturing by internally structuring bulk volumes for lightweight construction. Essential to cost efficient, rapid prototyping is a reliable assessment of mechanical properties without having to build spare samples for testing. Due to its regular nature, our structure allows a beforehand calculation of the mechanical properties like strength and stiffness, even for large geometries with many cells. To improve the mechanical performance of the entire component, the structure of the cells can be adapted in response to a pre-determined load. This adaptation is achieved by locally increasing the diameter of selected struts. Moreover, the mechanical performance of the optimized structure can also be predicted by Finite Element Modeling. The adaptation significantly enhances the load bearing capacity of the product with a low increase in material and production time. For the parameterization of finite element calculations, tests on only a few structured representative specimens are necessary to model the material used in the additive manufacturing process. We have performed the necessary experiments and developed a homogenized material model for a structure made of polyamide 12, which is used in Selective laser sintering and offers specific strength comparable to steel. To prove the viability of the layout and rating method, we structured, manufactured, and tested one life size cantilever chair. The approach presented in this paper can be applied to a large variety of component shapes and many additive manufacturing processes to assess and improve the mechanical capacity of a cellular structure based on how a few cells of a small volume perform.