Purpose -The holistic numerical model based on cellular automata (CA) and Lattice Boltzmann methods (LBM) is being developed as part of an integrated modelling approach applied to study the interaction of different physical mechanisms in laser assisted additive layer manufacturing (ALM) of orthopaedic implants. Several physical events occuring in sequence or simultaneously are considered in the holistic model. They include a powder bed deposition, laser energy absorption and heating of the

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... r bed by the moving laser beam leading to powder melting or sintering, fluid flow in the melted pool, flow through partly or not melted material and solidification. Design/methodology/approach -The mentioned physical events are accompanied by heat transfer in solid and liquid phases including interface heat transfer at the boundaries. The sintering/melting model is being developed using LBM as an independent numerical method for hydrodynamic simulations originated from lattice-gas cellular automata (LGCA). It is going to be coupled with the CA based model of powder bed generation. Findings -The entire laser assisted ALM process has been analised and divided on several stages considering the relevant physical phenomema. The entire holistic model consisting of four interrelated submodels has currently been developed to a different extent. The submodels include the CA based model of powder bed generation, the LBM-CA based model of heat exchange and transfer, the thermal solid-liquid interface model and the mechanical solid-liquid interface model for continuous liquid flow. Practical implications -The results obtained can be used to explain the interaction of the different physical mechanisms in ALM, which is intensively developing field of advanced manufacturing of metal, non-metal and composite structural parts for instance in bio-engineering among others. The proposed holistic model is considered to be a part of the integrated modelling approach being developed as a numerical tool for investigation of the co-operative relashionships between multiphysical phenomena occurred in sequence or simultaneousely during heating of the powder bed by the moving high energy heat source leading to selective powder sintering or melting, fluid flow in the melted pool and through partly (or not) melted material and also to solidification. The model is compatible with the earlier developed CA based model for generation of the powder bed allowing for decrease of the numerical noise. Originality/value -The present results are original and new for the study of the complex relathionships between multifysical phenomena occurring during ALM process based on selective laser sintering or melting (SLS/SLM) including fluid flow and heat transfer among others identified as crucial for obtaining the desirable properties. Nomenclature Roman letters c = specific heat e = phase space variable {ei, i = 1,...,b} = set of discrete velocities F = external force f(x,v,t) = particles distribution function