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

本项目旨在通过建模和实验验证，研究不同形状和尺寸的聚合物粉末在激光烧结过程中的流动、相互作用和烧结方式。激光烧结是增材制造技术的一部分，以其在需要定制产品、轻量化和复杂设计的行业中的优势而闻名。在激光烧结中，聚合物粉末床被加热到刚好低于其熔融温度。然后将激光聚焦到床上，扫描最终零件的单层光栅图案。床稍微降低，并施加新的粉末层。然后重复该过程，直到制成部件并且完成增材层过程。粉末的铺展和压实是LS工艺的重要部分，不均匀的粉末层导致高孔隙率和层间较弱的结合，因此导致机械性能差的结构。类似地，颗粒的大小和形状可以改变烧结过程。颗粒之间较大的接触面积导致良好的烧结曲线，并最终导致高密度部件和良好的机械性能。颗粒的表面积、聚合物粘度和表面张力是在对流动和烧结过程建模时将考虑的特征。

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.