Research

It is now possible to manufacture metallic lattice structures easily with additive manufacturing. Lattice structures can be used to produce high strength low mass parts. However, it does not exist a method to design lattice structures for additive manufacturing. This PhD focuses on lattice structure design methods and manipulation in CAD, CAE and CAM tools to facilitate the wide use of lattice structures in products. The thesis addressed the following research questions:

• Why are lattice structures so little used in part designs?

• What are the information necessary to help designers to design parts containing lattice structures?

• How can lattice structures be created quickly and easily in CAD?The main contributions are:• An evaluation of current CAD tools in terms of human machine interface, CAD file formats, CAE and CAM to design lattice structures was conducted. The results show that current CAD tools and CAD file formats have insufficient performance in the context of design for additive manufacturing. Current CAD tools create and represent lattice structures using surfaces and volumes. This contributes to large file sizes, high RAM consumption, as well as time-consuming creations and operations.

• A new lattice structure design strategy. This method serves as a guideline for designers to integrate lattice structures in additive manufactured parts using the concept of equivalent material. Designers will be able to choose lattice structure patterns and densities.

• A methodology to create equivalent materials is presented. It is solid and does not contain any struts, thus has few surfaces only. With this equivalent material, it will be easier and quicker to conduct FEA due to the small number of surfaces involved. The characteristics of different lattice structure patterns and densities were determined, which are the relative Young’s modulus and relative strength in function of the relative density. This methodology can be applied to all lattice structures.

• The main lattice structure geometrical characteristics were determined. A skeleton model was presented to define lattice structures with points, lines, sections and joints instead of surfaces and volumes. A method is presented to visualise in CAD and slice lattice structures in CAM from the skeleton model.