CAD-integrated modelling of lattice structures for additive manufacturing and property evaluation of generated specimens

Using the rich possibilities of design freedom in additive manufacturing, lattice structures are highly recommended as lightweight components with customizable mechanical properties. Until now, parts with lattice structures are mainly used for illustrative purposes and rarely serve as sections of actually working devices with defined functions. This is because their modelling, dimensioning, and build preparation still remains very complex and time-consuming. To simplify this process for the designer, a CAD-integrated tool is developed. Therein, lattice structures of different shape and size can be created easily, are represented on a parametric level, and displayed as textures. In the design process the topology of the whole structure as well as single lattice elements can be customized individually. It enables the designer to create load carrying components which are fully adapted to their specific function. This subsequently results in lightweight parts, less powder consumption, faster build time, and therefore lower costs during manufacturing. Furthermore, a slicing function for direct export of build job files is implemented. The mechanical properties of the structure are automatically computed by means of FEM. All computations shall be finished in reasonable time to minimize hampering of the designer's workflow. For verification of the mechanical property predictions, tensile tests are performed with Ti-6Al-4V and X3NiCoMoTi18-9-5 steel lattice structures following the design suggestions in draft standard DIN 50099. Results show valid accordance with the computed predictions. Extensive studies were carried out to optimize build parameters for different strut sizes. These parameters are stored in an editable database and are automatically included in the build job files. The resulting tool combines all steps from part design to build file generation on a parametric level within a CAD environment. With this tool even designers without experience in additive manufacturing can integrate AM-specific geometries and functions in their components.