Deriving the Infill Design of Fused Deposition Modelled Parts from Predicted Stress Profiles

The use of Fused Deposition Modelling (FDM) is increasing rapidly in both the commercial and industrial sectors as a means of rapidly prototyping geometrically complex parts. Particular affordances of FDM include the reduction of waste material during manufacture, the use of multiple materials within a single manufacturing process and the ability to manipulate the internal geometry of a part. The latter of which has seen the generation of many 2-dimensional repeating pattern structures such as square, rectilinear and hexagonal, as well as an emerging field of 3-dimensional structures. Although these patterns have provided stiffness and rigidity whilst reducing the production time of FDM prototypes, many do not consider the actual loading conditions of the part in-situ, where it is argued that further significant gains in the performance could be achieved. This includes further reduction in process time and increased part functionality.

Thus, this paper presents initial work into the generation of an infill that is derived from the predicted stress profile for the part. This has been achieved through the post-processing of Finite Element (FE) models to identify the stress profile. Interpolation across these profiles leads to a set of aligned Bézier splines that enable the transmission of force and are also able to be manufactured using FDM. These splines are embedded within the typical slicing procedure of a part ahead of being manufactured on a FDM machine. Initial results from parts designed to support three-point bending loads show a 79% increase in the stiffness of the part alongside a consistent and repeatable mode of failure when compared to the commonly used honeycomb infill design.