Flow properties of polymeric powders for selective laser sintering

The effect of temperature on the flow properties of three different polymeric powders was assessed in order to properly take into account real temperature conditions relevant to Selective Laser Sintering (SLS). Shear tests were carried out at temperatures from ambient conditions to values close to the melting temperature of the polymers. Tested flowability significantly worsens at temperatures 20–30 °C lower than the powder melting point. These results are consistent with the working temperatures identified by SLS machine users, but powder flow properties estimated at finite consolidation cannot be directly used to infer on powder spread-ability. Instead, when the average intensity of the interparticle forces is calculated from the powder flow properties, the derived granular Bond number correlates well with the most suitable process conditions experienced for these powders. In particular, Bond numbers lower than 100 are required for a satisfactory powder layer formation after spreading with the use of a blade.