(564a) Correlating Polyamide Powder Flow Properties to Mechanical and Physical Properties of 3D Printed Parts

Selective Laser Sintering (SLS) is an Additive Manufacturing technique typically used for rapid prototyping and low volume production of functional components. The process employs a laser beam to sinter powdered material, binding it together to create a solid structure. The laser selectively fuses pre-defined areas of a powder bed by scanning cross-sections generated from a 3D digital description of the required part. After each cross-section is scanned, a new layer of material is applied on top, and the process is repeated until the part is complete.

Generating the layers of powder is a precision process and requires a feedstock that can be reliably distributed by the delivery system which is deposited on to the fabrication bed in a consistent manner without agglomerates or voids. Intermittent flow, or agglomerates within the bulk, will cause non-uniform deposition, adversely affecting the efficiency of the process and the properties of the final product. Identifying which powder properties are conducive with the formation of uniform, repeatable layers allows new formulations to be optimised, and suitable raw materials identified, without incurring the significant financial and time overheads associated with running materials through a process to assess compatibility. This approach also helps reduce the occurrence of final products that are out of specification.

This study investigates the relationships between the flow properties of two different grades of Polyamide 12 (PA12) powder and mixtures of, with the mechanical and physical characteristics of the printed parts. The powder bulk properties including flowability were characterised using powder rheology (FT4 Powder Rheometer®, Freeman Technology Ltd, UK). Absolute, or skeletal volume of 3D printed cubes were measured using helium pycnometry (AccuPyc, Micromeritics Instrument Corporation, USA). Tensile specimens were also fabricated, and their mechanical properties were correlated with the initial powder’s flow properties.

By comparing the powder flow properties and the properties of the built parts it was possible to identify strong relationships between various parameters, thereby allowing prediction of final product quality prior to printing. Understanding these relationships helps to identify and develop powders that enhance both process efficiency and the mechanical properties of the final product.