Particle Shape and Flow behaviour in Laser Sintering: from modelling to experimental validation

This project proposes to investigate the way the polymeric powders of different shapes and sizes flow, interact and sinter in the Laser Sintering process, through modelling and experimental validation. Laser sintering is part of the additive manufacturing technology, known for its benefits in industries where custom made products, lightweight and complex designs are required. In laser sintering a polymer powder bed is heated to just below its melt temperature. A laser is then focused onto the bed which scans a raster pattern of a single layer of the final part. The bed lowers slightly and a new layer of powder is applied. The process is then repeated until the component is made and the additive layer process is complete.

The spreading and compaction of the powder is an important part of the LS process, a non-uniform layer of powder leads to high porosity and weaker bonding between layers and therefore a structure with poor mechanical performance. Similarly, the size and shape of particles can change the sintering process. Larger contact areas between particles lead to a good sintering profile and ultimately to a high density part and good mechanical properties. Surface area of particles, polymer viscosity and surface tension are characteristics which will be considered when modelling the flow and sintering process.

The main direct beneficiaries of this project are: (i) companies delivering AM products; (ii) AM manufacturers, (iii) powder suppliers and (iv) mill manufacturers.

Companies delivering AM products will directly benefit from the guidelines on how to achieve better sintering product properties which can be further developed according to the research outcomes. The knowledge of how unconventional powders can be used in AM has high potential to broaden the use of AM technologies. Such effect will benefit all four sectors in that (i) could reduce production cost using low-cost powders, (ii) could expand their machine market, (iii) could have new users of certain powders from AM industry and (iv) could supply mills to AM manufacturers or AM users directly.

More specifically, AM manufactures will benefit from the understanding of the flow and sintering behaviour of certain shapes of particles and design and optimise AM machines for such powders. Powder suppliers will then benefit from catering to the new AM processes. Mill manufacturers will benefit from the knowledge about what particle shape and size distribution are required by AM and design milling processes suitable to produce such powders. Therefore, the project research outcomes will provide new impetus to prompt all four sectors to work together in a mutually benefiting "ecosystem".

The project will have also indirect benefits: (1) societal, a wider and more cost effective range of powders in the medical sector will lead to cheaper choices of materials for manufacture custom made implants (e.g. hip replacements) for the older population; (2) environmental, more flexibility in the range of materials leads to better designs, for more complex lightweight structures which ultimately lead to increased efficiency and lower fuel consumption.

The researchers and investigators will also benefit from the technical knowledge, team working and project management skills gained through the project.