Additive manufacturing (AM) has enabled control over heterogeneous materials and structures in ways that were not previously possible, including functionally graded materials (FGM). However, typical computer aided design (CAD) systems — mainly based on boundary representations (B-Rep) — are not built for modeling and representing spatially varying material information, which are the key features for designing FGM parts. While volumetric representations (V-Rep) such as tetrahedral or hexahedral meshes, trivariate splines or subdivision solids can hold the necessary FGM information, they are by default not compatible with existing CAD models. Thus, the capabilities of AM motivate enhancing CAD systems to support volumetric material allocation and distribution.

We present an interactive, intuitive and efficient interaction concept based on grading features and transition functions for augmenting CAD models with smooth volumetric material gradients for multi-material fabrication using our system called GraMMaCAD (Graded Multi-Material CAD). By providing interactive preview modes, the system allows for efficient exploration of the volumetric gradation of the designed FGM part. We fabricated two functional examples that demonstrate the usability of the system and show the ability to quickly augment models with functionally graded material transitions.

This paper recently got accepted at the ASME 2022 International Design Engineering Technical Conferences & Information in Engineering Conference (IDECT-CIE) in St. Louis, Missouri. Authors: Thu Huong Luu, Christian Altenhofen, André Stork, Dieter Fellner (Fraunhofer IDG)

GraMMaCAD provides different preview modes to inspect the material property distribution: (a) Selected CAD faces emitting grading information; (b) Cut plane preview mode; (c) Surface preview mode; (d) Volume preview mode