Selective laser sintering of an amorphous polymer - simulations and experiments

Thermal and powder densification modelling of the selective laser sintering of amorphous polycarbonate is reported. Three strategies have been investigated: analytical, adaptive mesh finite difference and fixed mesh finite element. A comparison between the three and experimental results is used to evaluate their ability reliably to predict the behaviour of the physical process. The finite difference and finite element approaches are the only ones that automatically deal with the non-linearities of the physical process that arise from the variation in the thermal properties of the polymer with density during sintering, but the analytical model has some value, provided appropriate mean values are used for thermal properties. Analysis shows that the densification and linear accuracies due to sintering are most sensitive to changes in the activation energy and heat capacity of the polymer, with a second level of sensitivities that includes powder bed density and powder layer thickness. Simulations of the manufacture of hollow cylinders and T-pieces show feature distortions due to excessive depth of sintering at downward facing surfaces in the powder bed. In addition to supporting the modelling, the experiments draw attention to the importance of sintering machine hardware and software controls.