Assessing polymer powder flow for the application of laser sintering

• Adjusting powder flow measurements to the envisaged application is necessary.
• The powder spreader utilises a directly relevant flow profile for laser sintering.
• The flow of PA12, spherical PMMA and PS, and cryomilled TPU powders is tested.
• Defects in the deposited powder layers are qualitatively (visually) assessed.
• The layer density is a quantitative index for assessing powder flow.

A need exists for techniques to assess flow properties of powders intended for laser sintering (LS). Although several powder flow measurement techniques are available, the flowability of a powder is strongly dependent on the nature of the applied flow field and none of the currently availably techniques adopt the flow field of LS. Therefore, this paper proposes a new technique, which mimics the flow in an LS machine, allowing a more appropriate powder flow evaluation for this particular process. The set-up provides qualitative assessment of powder layer smoothness, as well as a quantitative determination of the packing density of the deposited layer. Measurements on PA12, spherical PS and PMMA, and cryogenically milled TPU powders demonstrate the set-up's capability to evaluate powder flow with regard to LS.

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