Flow properties of polymeric powders for SLS

In order to properly take into account real process conditions relevant to Selective Laser Sintering (SLS), the effect of temperature on the flow properties of polymeric powders was assessed. Shear tests were carried out at temperatures from ambient values to values close to the melting temperature of the polymeric powders. Experiments were performed on two powders with similar chemical compositions but with different melting temperature, very distinct particle shapes and different particle size distributions resulting from different production processes. Experiments indicate that flowability significantly worsens when temperature rises and approaches a value of about 20-30°C lower than the melting point of the polymers. These results are in good agreement with the working temperatures preconized by the SLS machine users. The average intensity of the interparticle forces is calculated from the powder flow properties and the Bond number is considered to verify the suitability of the powder in the SLS process.