This paper presents a novel approach to numerical modelling of selective laser melting (SLM) processes characterized by melting and solidification of the deposited particulate material. The approach is based entirely on two homogeneous methods, such as cellular automata and Lattice Boltzmann. The model components operate in the common domain allowing for linking them into a more complex holistic numerical model with the possibility to complete full-scale calculations eliminating complicated interfaces. Several physical events, occurring in sequence or simultaneously, are currently considered including powder bed deposition, laser energy absorption and heating of the powder bed by the moving laser beam leading to powder melting, fluid flow in the melted pool, flow through partly or not melted materials and solidification. The possibilities and benefits of the proposed solution are demonstrated through a series of benchmark cases, as well as model verifications. The presented case studies deal mainly with melting and solidification of the powder bed including the free surface flow, wettability, and surface tension. An example of process simulation shows that the approach is generic and can be applied to different multi-material SLM processes, where energy transfer including solid–liquid phase transformation is essential, by integrating the developed models within the proposed framework.

This paper presents an original model of powder bed generation developed within the frame of an integrated modelling approach for studying the interaction of physical mechanisms in additive layer manufacturing (ALM) of orthopaedic implants. The model is based on cellular automata (CA) approach and describes the relationship between moving particles of different sizes during deposition on a surface in three dimensions. The surface is defined by the horizontal two-dimensional CA on which particles fall and irreversibly stick to a growing deposit. The model allows for consideration of different restructuring cases when particles are allowed to rotate as often as necessary until achievement of a local minimum position. Changes in the packing density of the powder bed have been investigated numerically depending on technological parameters, such as particle size distribution, deposition rate and sequence of powder deposition. The model has been developed with the aim of merging to the finite element (FE)-based integrated model and is applicable to a different ranges of materials including metals and also non-metals.

A laser beam heating model (LBHM) is an important part of a platform for numerical modelling of a multi-material selective laser melting process. The LBHM is utilised as a ray-tracing algorithm that is widely applied for rendering in different applications, mainly for visualisation and very recently for laser heating models in selective laser melting. The model presented in this paper was further extended to transparent and translucent materials, including materials where transparency is dependent on the material temperature. In addition to reflection and surface absorption, commonly considered in such models, phenomena such as refraction, scattering and volume absorption were also implemented. Considering associated energy transfer, the model represents a laser beam as a stream of moving particles, i.e. photons of the same energy. When the photons meet a boundary between materials, they are reflected, absorbed or transmitted according to geometric and thermal interfacial characteristics. This paper describes the LBHM in detail, its verification and validation, and also presents several simulation examples of the entire selective laser melting process with implemented LBHM.