Numerical methods to predict overheating in SLM lattice structures

Additive manufacture provides significant design flexibility in comparison with traditional manufacturing methods. For example, Selective Laser Melting (SLM) is capable of producing highly complex lattice structures that are not otherwise manufacturable. Such lattice structures enable structural optimisation at a macro level, while reducing associated manufacture time by reducing the component volume. Structural lattices provide a significant commercial opportunity for SLM processing. However, to ensure robust manufacturing outcomes, it is necessary that specific technical constraints be satisfied. In particular, lattice structures typically have high resistance to heat transfer, and consequently may be subject to overheating. Gross overheating may result in visible damage to the lattice network, and rejection of the component. More critical is the possibility for overheating that causes microstructural and fusion defects that are not visually apparent, but will compromise performance and safety in-use. This work provides a useful contribution the available literature by presenting a numerical simulation method to predict overheating in SLM structures. This method can be used prior to manufacture to minimise the risk of overheating and to provide design guidance on how to modify proposed geometry to avoid overheating. The method is calibrated with reference to observed overheating failures in SLM lattice manufactured in aluminium. Computational expense is important to enable the method to be compatible with the early design phase. Opportunities to reduce computational expense are discussed, including symmetry, layer heating simplification and layer concatenation. While all these simplifications reduce the computational expense they are shown to provide simulation data that correctly indicates gross failure of aluminium lattice structures due to overheating.